1. 	Lysing and Spreading a Nucleus from a Biopsied Blastomere
<ol>
<li>Cell lysis buffer for spreading cells (0.2% Tween20 in 0.01 M HCl, pH 2.0) should be prepared 24 hours in advance and stored at -20&deg;C. Prepare 100 mL and filter 20 mL into a 30 mL sterile universal container using a sterile 20 mL syringe and syringe filter. Dispense 1 mL aliquots into 10-15 1.7 mL sterile microcentrifuge tubes, close and label the tubes prior to freezing. It is recommended to have two different batches is use, the new batch and the previous batch, which has been tested and can be used if the new batch is unsatisfactory.</li>
<li>Defrost the lysis buffer at room temperature 30 minutes before the biopsy procedure. For practical purposes the working temperature will be between room temperature and hand temperature.</li>
<li>Score a small circle (approximately 5 mm diameter) on the underside of an amine-coated slide (e.g. Genetix) using a diamond pen and pre-label the slide with the case number, unique slide number, and biopsy date. Use a separate slide for each blastomere in numerical order, and label with the embryo number. Slides should be labeled with a hard pencil such as 4H, and "blotted" with a latex glove to remove any graphite dust.</li>
<li>Place a small volume of lysis buffer within the circle.</li>
<li>Transfer the biopsied blastomere into the lysis buffer. If necessary add lysis buffer within the circle until the cell begins to lyse; the cell should lyse completely and the cytoplasm disperse before the buffer dries.</li>
<li>Observe the nucleus to ensure that it remains within the circle and is not lost; if the cell does not have a nucleus or has multiple nuclei, biopsy another cell.</li>
<li>Leave the slide to air-dry at room temperature.</li>
</ol>
2. 	In Situ Hybridization of a Single Blastomere Nucleus
<ol>
<li>Prepare an ethanol series (70, 90 and 100%) made up in sterile distilled water.</li>
<li>Turn on and set the hot block (e.g. Hybaid Omnislide or Vysis Hybrite) to 75&deg;C.</li>
<li>Defrost probes, vortex, and centrifuge. The reagents should be witnessed and verified to be correct before making up the probe mixture. Pipette volumes as specified by the manufacturer to make up the probe mixture in a 0.65 mL sterile microcentrifuge tube and vortex and centrifuge before use. The total volume of probe mixture should be sufficient to allow 2 &mu;L per nucleus to be tested and rounded up to the nearest 10 &mu;L to allow a safety margin.</li>
<li>Pre-wash the slides in coplin jars using phosphate-buffered saline (PBS) (pH 7.0: 0.14 M NaCl, 3 mM KCl, 10 mM Na2HPO4, 2 mM KH2PO4) for 5 min at room temperature.</li>
<li>Rinse the slides twice in sterile distilled water.</li>
<li>Dehydrate the slides with the ethanol series (70, 90, and 100%) for 2 min each at room temperature and air-dry. Ensure slides are fully immersed and if any graphite dust floats to the surface, soak up with a clean tissue.</li>
<li>Record the position of the nucleus within the circle by visualizing with a phase contrast microscope.</li>
<li>Dehydrate with 100% ethanol for 2 min at room temperature and air-dry.</li>
<li>Apply 2 &mu;L of probe mixture, and cover with a 9 x 9 mm coverslip (one quarter of an 18 x 18 mm no.1 coverslip).</li>
<li>Seal the edges of the coverslip with rubber cement (e.g. Cow Gum; Cow Proofing).</li>
<li>Codenature the slides on a hot block at 75&deg;C for 5 min, and then hybridize the slides overnight (16-20 h) in a humidified chamber at 37&deg;C. Probe mixes that consist entirely of centromere probes (i.e. for sex-linked cases) will give a satisfactory result after 60 min of hybridization.</li>
<li>Prepare a water bath with sufficient coplin jars and heat to 71&deg;C.</li>
<li>Prepare a 0.4x standard saline citrate (SSC) stringent wash solution (pH 7.0 at 71&deg;C, 0.06 M NaCl, 6 mM C6H5Na3O7.2H2O) and heat in the water bath.</li>
<li>Dispense 50 mL of stringent wash per coplin jar required and check that the temperature is 71&deg;C immediately prior to use using a clean thermometer.</li>
<li>Carefully remove the rubber cement from each slide and rinse off the coverslip using 4x SSC/0.05% Tween20 (pH 7.0) at room temperature.</li>
<li>Wash the slides in the 0.4x SSC stringent wash at 71&deg;C for 5 min. Wash no more than 6 slides per coplin jar.</li>
<li>Wash the slides in 4x SSC/0.05% Tween20 at room temperature for 2 min.</li>
<li>If the probe mix contains indirectly labelled probe(s), drain the slides of excess liquid and apply 20 &mu;L of fluorescently conjugated antibody under a 20 x 20 mm square of Parafilm.</li>
<li>Incubate in a humidified chamber at 37&deg;C for 15 min.</li>
<li>Remove the Parafilm and wash once in 4x SSC/0.05% Tween20 at room temperature for 2 min.</li>
<li>Wash twice for 2 min in PBS at room temperature and drain the slides.</li>
<li>Apply 6 &mu;L of DAPI/Vectashield (160 ng of 4',6-diamidino-2-phenylindole dihydrochloride in 1 mL of Vectashield mounting medium, Vector Laboratories) to a 22 x 22 mm no. 0 coverslip and invert the slide over the coverslip.</li>
<li>Blot and seal the edges of the coverslip with clear nail varnish.</li>
</ol>
3. 	Analysis using a Fluorescence Microscope Suitably Equipped with Appropriate Filters for the Probes Used.
<ol>
<li>Score signals by direct visualization using a fluorescence microscope and single band-pass filters for each fluorochrome in the assay. Each nucleus should be scored by two analysts. A general guideline should lead to scoring of a single signal where two closely spaced signals are less than one domain (signal-width) apart; however, judgment based on experience needs to be exercised to interpret signals of varying size, intensity, and separation.</li>
<li>Use imaging software (e.g. Isis, MetaSystems, Altlussheim, Germany; CytoVision, Genetix) to capture an image of the nucleus for confirmation of the visual diagnosis, and for image archiving as part of a laboratory quality assurance plan.</li>
</ol>
4. Representative Results:
Metaphase and interphase nuclei from cultured peripheral blood lymphocytes should be examined to confirm that the selected probes are specific for the translocation chromosomes, informative for the breakpoints (the subtelomere probes should hybridize only to the translocated segments and the centromere probe(s) to the centric segment(s)) and the signals in interphase nuclei should be bright and discrete. Scoring the number of signals for each probe in 100 interphase nuclei from each partner is recommended to assess the efficiency of the assay. In this case 2 signals were scored in 95%-99% of nuclei for each probe. Figure 1 shows a metaphase and interphase nucleus from a preparation for a reciprocal translocation between the short arms of chromosomes 5 and 9.
Signals in interphase nuclei from embryo blastomeres should be bright and discrete and scored using separate band pass filters for the colors used. Figure 2 shows a blastomere nucleus with a normal signal pattern (2 copies for all the loci tested) consistent with a normal or balanced chromosome complement for chromosome 5 and 9, and a nucleus with an abnormal signal pattern consistent with an unbalanced product of the translocation that has monosomy (one copy) for the translocated segment of chromosome 5 and trisomy (3 copies) for the translocated segment of chromosome 9.
<img src="/files/ftp_upload/2570/2570fig1.jpg" alt="Figure 1" /> 
Figure 1. A metaphase spread and an interphase nucleus prepared from cultured peripheral blood lymphocytes from a carrier of a reciprocal translocation between the short arms of chromosomes 5 and 9 with breakpoints at 5p14.3 and 9p24.1: 46,XY,t(5;9)(p14.3;p24.1).ish t(5;9)(5ptel48-,9ptel30+;9ptel30-,5ptel48+,9cen+). FISH probes were selected for both translocated segments (5p14.3&rarr;5pter, red Cytocell subtelomere5ptel48 TexasRed ; 9p24.1&rarr;9pter, green Cytocell subtelomere 9ptel30 FITC) and the centric segment of chromosome 9 (9p24.1&rarr;9qter, blue Abbott CEP 9 alpha satellite SpectrumAqua).
<img src="/files/ftp_upload/2570/2570fig2.jpg" alt="Figure 2" /> 
Figure 2. Signals in interphase blastomere nuclei from day-3 embryos captured using a different filter for each fluorochrome and merged to form a composite image. (A) Two signals for each probe indicating two copies of each locus, which is consistent with a normal or balanced complement for the translocation chromosomes. (B) One red signal, three green signals and two blue signals indicating one copy of the translocated segment of chromosome 5, three copies of the translocated segment of chromosome 9 and two copies of the centric segment of chromosome 9, which is consistent with adjacent-1 segregation of the translocation resulting in an unbalanced product with monosomy for 5p14.3&rarr;5pter and trisomy for 9p24.1&rarr;9pter.

<ol>
	<li>Scriven, P. N., Handyside, A. H., Ogilvie, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosome+translocations:+segregation+modes+and+strategies+for+preimplantation+genetic+diagnosis.">Chromosome translocations: segregation modes and strategies for preimplantation genetic diagnosis.</a> Prenat. Diagn. 18, 1437-1449 (1998).</li><li>Mackie Ogilvie, C., Scriven, P. N., Harper, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preimplantation+genetic+diagnosis+for+chromosome+rearrangements.">Preimplantation genetic diagnosis for chromosome rearrangements.</a> Preimplantation Genetic Diagnosis. , 194-201 (2009).</li><li>Harper, J. C., Coonen, E., Ramaekers, F. C. S., Delhanty, J. D. A., Handyside, A. H., Winston, R. M. L., Hopman, A. H. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+the+sex+of+human+preimplantation+embryos+in+two+hours+using+an+improved+spreading+method+and+fluorescent+in+situ+hybridisation+using+directly+labelled+probes.">Identification of the sex of human preimplantation embryos in two hours using an improved spreading method and fluorescent in situ hybridisation using directly labelled probes.</a> Hum. Reprod. 9, 721-724 (1994).</li><li>Mackie Ogilvie, C., Scriven, P. N., Harper, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preimplantation+genetic+diagnosis+for+sex-linked+diseases+and+sex-selection+for+non-medical+reasons.">Preimplantation genetic diagnosis for sex-linked diseases and sex-selection for non-medical reasons.</a> Preimplantation Genetic Diagnosis. , 230-235 (2009).</li><li>Munn&#233;, S., Lee, A., Rosenwaks, Z., Grifo, J., Cohen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnosis+of+major+chromosome+aneuploidies+in+human+preimplantation+embryos.">Diagnosis of major chromosome aneuploidies in human preimplantation embryos.</a> Hum. Reprod. 8, 2185-2192 (1993).</li><li>Mackie Ogilvie, C., Scriven, P. N., Harper, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preimplantation+genetic+diagnosis+for+infertility+(preimplantation+genetic+screening).">Preimplantation genetic diagnosis for infertility (preimplantation genetic screening).</a> Preimplantation Genetic Diagnosis. , 203-229 (2009).</li><li>Scriven, P. N., Bossuyt, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnostic+accuracy:+theoretical+models+for+preimplantation+genetic+testing+of+a+single+nucleus+using+the+fluorescence+in+situ+hybridization+technique.+Hum+Reprod.">Diagnostic accuracy: theoretical models for preimplantation genetic testing of a single nucleus using the fluorescence in situ hybridization technique. Hum Reprod.</a> Cytogenetics. 5, 394-400 (2010).</li><li>Coonen, E., Dumoulin, J. C., Ramaekers, F. C., Hopman, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimal+preparation+of+preimplantation+embryo+interphase+nuclei+for+analysis+by+fluorescence+in-situ+hybridization.">Optimal preparation of preimplantation embryo interphase nuclei for analysis by fluorescence in-situ hybridization.</a> Hum. Reprod. 9, 533-537 (1994).</li><li>Dozortsev, D. I., McGinnis, K. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+fixation+technique+for+fluorescence+in+situ+hybridization+for+preimplantation+genetic+diagnosis.">An improved fixation technique for fluorescence in situ hybridization for preimplantation genetic diagnosis.</a> Fertil. Steril. 76, 186-188 (2001).</li><li>Hsu, L. Y., Benn, P. A., Tannenbaum, H. L., Perlis, T., Carlson, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosomal+polymorphisms+of+1,+9,+16,+and+Y+in+4+major+ethnic+groups:+a+large+prenatal+study.">Chromosomal polymorphisms of 1, 9, 16, and Y in 4 major ethnic groups: a large prenatal study.</a> Am. J. Med. Genet. 26, 95-101 (1987).</li><li>Shim, S. H., Pan, A., Huang, X. L., Tonk, V. S., Varma, S. K., Milunsky, J. M., Wyandt, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FISH+variants+with+D15Z1.">FISH variants with D15Z1.</a> J. Assoc. Genet. Technol. 29, 146-151 (2003).</li><li>Knight, S. J., Flint, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perfect+endings:+a+review+of+subtelomeric+probes+and+their+use+in+clinical+diagnosis.">Perfect endings: a review of subtelomeric probes and their use in clinical diagnosis.</a> J. Med. Genet. 37, 401-409 (2000).</li><li>Thornhill, A. R., de Die-Smulders, C. E., Geraedts, J. P., Harper, J. C., Harton, G. L., Lavery, S. A., Moutou, C., Robinson, M. D., Schmutzler, A. G., Scriven, P. N., Sermon, K. D., Wilton, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ESHRE+PGD+Consortium+(PGS)+ESHRE+PGD+Consortium+'Best+practice+guidelines+for+clinical+preimplantation+genetic+diagnosis+(PGD)+and+preimplantation+genetic+screening+(PGS)'.">ESHRE PGD Consortium (PGS) ESHRE PGD Consortium 'Best practice guidelines for clinical preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS)'.</a> Hum. Reprod. 20, 35-48 (2005).</li><li>Munn&#233;, S., Wells, D., Cohen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Technology+requirements+for+preimplantation+genetic+diagnosis+to+improve+assisted+reproduction+outcomes.">Technology requirements for preimplantation genetic diagnosis to improve assisted reproduction outcomes.</a> Fertil. Steril. 94, 408-430 (2010).</li><li>Wilton, L., Williamson, R., McBain, J., Edgar, D., Voullaire, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Birth+of+a+healthy+infant+after+preimplantation+confirmation+of+euploidy+by+comparative+genomic+hybridization.">Birth of a healthy infant after preimplantation confirmation of euploidy by comparative genomic hybridization.</a> N. Engl. J. Med. 345, 1537-1541 (2001).</li><li>Wells, D., Alfarawati, S., Fragouli, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+comprehensive+chromosomal+screening+for+embryo+assessment:+microarrays+and+CGH.">Use of comprehensive chromosomal screening for embryo assessment: microarrays and CGH.</a> Mol. Hum. Reprod. 14, 703-710 (2008).</li><li>Handyside, A. H., Harton, G. L., Mariani, B., Thornhill, A. R., Affara, N., Shaw, M. A., Griffin, D. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Karyomapping,+a+universal+method+for+genome+wide+analysis+of+genetic+disease+based+on+mapping+crossovers+between+parental+haplotypes.">Karyomapping, a universal method for genome wide analysis of genetic disease based on mapping crossovers between parental haplotypes.</a> J. Med. Genet. 47, 651-658 (2010).</li></ol>

No conflicts of interest declared.

The application of fluorescence in situ hybridization (FISH) to a single embryo cell (blastomere) presents special challenges both in practicalities and in interpretation of the signal pattern. The biopsied cell needs to be spread within a pre-defined area on the slide in order to facilitate its localization following FISH; extreme care needs to be taken in ensuring that the cell is lysed, that the cytoplasm has been dispersed, and that the nucleus is visible and intact; and, as the diagnosis depends on the results from this single cell, stringent scoring and interpretation guidelines should be applied. However, in experienced hands, FISH is a robust technique for pre-implantation genetic diagnosis (PGD) in clinical practice. The principle of PGD by FISH is that target-specific DNA probes labelled with different fluorochromes or haptens can be used to detect the copy number of specific loci, and thereby to detect chromosome imbalance associated with meiotic segregation of chromosome rearrangements (1), including Robertsonian translocations, reciprocal translocations, inversions, and complex rearrangements (2). FISH can also be used to select female embryos in families with X-linked disease, for which there is no mutation-specific test (3, 4). More controversially, FISH has also been used to screen for sporadic chromosome aneuploidy in order to try and improve the efficiency of assisted reproduction (5, 6); however, the predictive value of this test using FSIH is likely to be unacceptably low in most people's hands and it is not recommended for routine clinical use (7). This article concentrates on the technical aspects and the limitations of FISH applied to clinical single-cell diagnosis.
Methods of spreading and fixing single blastomeres include methanol/acetic acid (5, 8), Tween/HCl (9), and a combination of Tween/HCl and methanol/acetic acid (10). Variations include hypotonic treatment of cells prior to spreading and/or pepsin and paraformaldehyde treatment after fixation. The method should be appropriately validated for the laboratory (14). The Tween/HCl method is described in detail in this article. The Tween/HCl method is technically simple and highly reproducible in different laboratories. This method can be used to prepare single nuclei for the FISH diagnosis of sex determination and chromosome rearrangements with acceptable diagnostic accuracy (7).
Probe mixes can combine directly labelled and indirectly labelled probes, and probes from different manufacturers. Probes for known polymorphic chromosome regions (11, 12), or those known to cross-hybridize significantly with other chromosomes (13) should be avoided, although can be used if shown to be specific and suitable for PGD by prior testing on both reproductive partners. Available fluorochromes/haptens and strategies for discriminating probes include the following: Texas Red (TR), fluorescein isothiocyanate (FITC), SpectrumGreen (Vysis), SpectrumOrange (Vysis), SpectrumAqua, biotinylated probes detected with TR-avidin, FITC-avidin, or Cy-5 streptavidin (visualized using a FarRed filter), a mix of red and green probes to produce a yellow signal, a second round of hybridization and a third color created by sequential capturing of SpectrumOrange using a TexasRed and a SpectrumGold filter).
A probe set containing three probes, specific for the centromere regions of the X and Y chromosomes and one autosome, is recommended for sex determination (14); the autosomal probe is used to establish ploidy and thereby to differentiate between trisomy X (2n, 47,XXX) and triploidy (3n, 69,XXX), and between tetrasomy X (48,XXXX) and tetraploidy (4n, 92,XXXX). A typical probe set applied in this setting is the Abbott AneuVysion mix containing alpha-satellite X, Y, and 18; this probe set has been demonstrated to have a very low polymorphism rate, and therefore pre-treatment work-up of the reproductive partners is not required (14).
The probe mix for any specific rearrangement should: Ideally contain probes at least sufficient to detect all the expected products of the rearrangement with chromosome imbalance. If this is not possible, probe mixes where the undetected unbalanced products have been assessed to be non-viable in a recognizable pregnancy and are likely to have very low prevalence may be acceptable (14). Be tested on cultured lymphocyte metaphases from both reproductive partners. At least ten metaphase spreads should be examined for probe specificity, polymorphisms and cross-hybridization, and, for the chromosome rearrangement carrier, to ensure that the probes hybridize as expected to the different segments of the rearrangement. In addition, at least 100 interphase nuclei from these preparations should be scored to assess signal specificity, brightness, and discreteness (14).
Commercial PGS probe sets are available (e.g. Abbott MultiVysion PB or PGT), targeting the chromosomes most frequently found to be aneuploid in products of conception, and comprising a single probe per chromosome targeted. Typically the nucleus may have a second hybridization with probes for additional chromosomes providing an assay for chromosomes 13, 15, 16, 18, 21, 22, and XY (14). The predictive value of this test using the spreading and FISH technique described here is likely to be unacceptably low in most people's hands and it is not recommended for routine clinical use (7, 15).
Techniques such as comparative genomic hybridization (CGH) applied to single cells are able to test for the copy number of every chromosome (Wilton et al. 2001), and the use of single nucleotide polymorphisms (SNP) arrays and quantitative analysis (Wells et al. 2008) or "karyomapping" genotyping (Handyside et al. 2009) are promising alternative techniques to detect chromosome aneuploidy. However, the resolution limit and accuracy for segment imbalance remain uncertain and it is likely that FISH will continue to be the technique of choice for chromosome rearrangements involving small segments.

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		<th>Material Name</th>
		<th>Type</th>
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		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
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<tr>
<td>Hydrochloric Acid, 2.5L</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>101254H</td>
<td>&nbsp;</td>
<tr>
<td>Sodium Chloride, 5Kg</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>443827W</td>
<td>&nbsp;</td>
<tr>
<td>Potassium Chloride, 250g</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>26764.232</td>
<td>&nbsp;</td>
<tr>
<td>di-Sodium Hydrogen Orthophosphate Anhydrous, 500g</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>102494C</td>
<td>&nbsp;</td>
<tr>
<td>Potassium Dihydrogen Orthophosphate, 500g</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>10203 4B</td>
<td>&nbsp;</td>
<tr>
<td>Sodium Hydroxide Pellets, 500g</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>28245.265</td>
<td>&nbsp;</td>
<tr>
<td>Tween20, 500mL</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>663684B</td>
<td>&nbsp;</td>
<tr>
<td>Ethanol, 2.5L</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>8.18760.2500</td>
<td>Duty Paid</td>
</tr>
<tr>
<td>Tri-Sodium Citrate, 5Kg</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>27833.363</td>
<td>&nbsp;</td>
<tr>
<td>Cow Gum, 250mL</td>
<td>&nbsp;</td>
<td>Cow Proofings Ltd.</td>
<td>No longer available</td>
<td>Old stocks can still be found in art shops</td>
</tr>
<tr>
<td>DAPI/Antifade ES, 0.125&mu;g/mL, 500ul</td>
<td>&nbsp;</td>
<td>Cytocell</td>
<td>DES500L</td>
<td>150&mu;l vial rec&#x2019;d with each Cytocell TEL Probe</td>
</tr>
<tr>
<td>Nail Varnish, 12mL</td>
<td>&nbsp;</td>
<td>Boots</td>
<td>10088316001</td>
<td>&nbsp;</td>
<tr>
<td>Amine-coated Slides, 25</td>
<td>&nbsp;</td>
<td>Genetix</td>
<td>K2615</td>
<td>&nbsp;</td>
<tr>
<td>DAPI, 0.1mL</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>D-9542</td>
<td>&nbsp;</td>
<tr>
<td>Vectashield, 10mL</td>
<td>&nbsp;</td>
<td>Vector Laboratories</td>
<td>H1000</td>
<td>&nbsp;</td>
<tr>
<td>Texas-Red-avidin, 0.001mL</td>
<td>&nbsp;</td>
<td>Vector Laboratories</td>
<td>A-2016</td>
<td>&nbsp;</td>
<tr>
<td>FITC-avidin, 0.001mL</td>
<td>&nbsp;</td>
<td>Vector Laboratories</td>
<td>A-2011</td>
<td>&nbsp;</td>
<tr>
<td>Cy-5 Streptavidin, 0.001mL</td>
<td>&nbsp;</td>
<td>GE Healthcare</td>
<td>PA45001</td>
<td>&nbsp;</td>
<tr>
<td>Microcentrifuge Tubes, 1.75mL, box of 500</td>
<td>&nbsp;</td>
<td>Thistle Scientific</td>
<td>AX-MCT-175-C</td>
<td>&nbsp;</td>
<tr>
<td>Microcentrifuge Tubes, 0.6mL, box of 1000</td>
<td>&nbsp;</td>
<td>Thistle Scientific</td>
<td>AX-MCT-060-C-CS</td>
<td>&nbsp;</td>
<tr>
<td>30ml Universal Containers, box of 400</td>
<td>&nbsp;</td>
<td>Sterilin</td>
<td>128B</td>
<td>Available from NHS Supply Chain, Cat No. KCP053</td>
</tr>
<tr>
<td>Hot Block</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Spirit Burner Spirit Burner Socket Spirit Burner Wick</td>
<td>&nbsp;</td>
<td>VWR VWR VWR</td>
<td>451-0107 451-3112 451-3111</td>
<td>&nbsp;</td>
<tr>
<td>Plugged Glass Pipettes</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>PMK-300-052R</td>
<td>&nbsp;</td>
<tr>
<td>Dissecting Microscope</td>
<td>&nbsp;</td>
<td>Wild Heerbrugg</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Tissues, 100boxes</td>
<td>&nbsp;</td>
<td>NHS SUPPLY CHAIN</td>
<td>MJT058</td>
<td>&nbsp;</td>
<tr>
<td>Metal Culture Trays</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Plastic Melamine Trays</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>682-009</td>
<td>&nbsp;</td>
<tr>
<td>Oven</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Mouth Pipette Mouthpiece</td>
<td>&nbsp;</td>
<td>Scientific Laboratory Supplies</td>
<td>HAE3700 </td>
<td>&nbsp;</td>
<tr>
<td>Tubing</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Syringe Filter, 0.2&mu;m pore size, 25mm diameter</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>FDM-340-010U</td>
<td>&nbsp;</td>
<tr>
<td>Diamond Pen</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>818-0021</td>
<td>&nbsp;</td>
<tr>
<td>Hot Block for Slides</td>
<td>&nbsp;</td>
<td>Thermo Hybaid</td>
<td>HBOSBB</td>
<td>&nbsp;</td>
<tr>
<td>Hybridization Chamber</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Tissue Roll</td>
<td>&nbsp;</td>
<td>NHS SUPPLY CHAIN</td>
<td>MJT004</td>
<td>&nbsp;</td>
<tr>
<td>Schieferdecker Jar</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>631-9313</td>
<td>&nbsp;</td>
<tr>
<td>Coplin Jar</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>631-9331</td>
<td>&nbsp;</td>
<tr>
<td>Forceps, Fine</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>232-2123</td>
<td>&nbsp;</td>
<tr>
<td>Forceps, Blunt</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>232-2113</td>
<td>&nbsp;</td>
<tr>
<td>1000mL Beaker</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>213-1642</td>
<td>&nbsp;</td>
<tr>
<td>Phase Contrast Microscope</td>
<td>&nbsp;</td>
<td>Nikon</td>
<td>E200</td>
<td>&nbsp;</td>
<tr>
<td>Fibre-free Blotting Cards, box of 100</td>
<td>&nbsp;</td>
<td>Fisher Scientific (Raymond Lamb)</td>
<td>SDE1</td>
<td>&nbsp;</td>
<tr>
<td>Blue-Frosted Microscope Slides, box of 100</td>
<td>&nbsp;</td>
<td>Scientific Laboratory Supplies</td>
<td>MIC3022</td>
<td>&nbsp;</td>
<tr>
<td>Coverslips, 18x18mm, No. 1, box of 200</td>
<td>&nbsp;</td>
<td>Scientific Laboratory Supplies</td>
<td>MIC3110</td>
<td>&nbsp;</td>
<tr>
<td> Coverslips, 22x22mm, No. 0, box of 200</td>
<td>&nbsp;</td>
<td>Scientific Laboratory Supplies</td>
<td>MIC3104</td>
<td>&nbsp;</td>
<tr>
<td>Coverslips, 22x50mm, No. 0, box of 100</td>
<td>&nbsp;</td>
<td>Scientific Laboratory Supplies</td>
<td>MIC3206</td>
<td>&nbsp;</td>
<tr>
<td>1mL Syringe, box of 100</td>
<td>&nbsp;</td>
<td>NHS Supply Chain</td>
<td>FWC045</td>
<td>&nbsp;</td>
<tr>
<td>1mL Pipette Tip, 10racks of 1000</td>
<td>&nbsp;</td>
<td>Thistle Scientific</td>
<td>AX-T-1000-C-L-R</td>
<td>&nbsp;</td>
<tr>
<td>Incubator</td>
<td>&nbsp;</td>
<td>LEEC</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Waterbath</td>
<td>&nbsp;</td>
<td>Grant</td>
<td>W22</td>
<td>&nbsp;</td>
<tr>
<td>Alcohol Thermometer</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Various sources available</td>
</tr>
<tr>
<td>pH Meter</td>
<td>&nbsp;</td>
<td>Jenway</td>
<td>3305</td>
<td>&nbsp;</td>
<tr>
<td>pH Electrode</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>662-1759</td>
<td>BNC Plug to fit Jenway pH meter 3305</td>
</tr>
<tr>
<td>Heated Stirrer</td>
<td>&nbsp;</td>
<td>Bibby</td>
<td>HC502</td>
<td>&nbsp;</td>
<tr>
<td>1mL Pasteur Pipettes, box of 500</td>
<td>&nbsp;</td>
<td>Scientific Laboratory Supplies</td>
<td>PIP4202</td>
<td>&nbsp;</td>
<tr>
<td>Parafilm, 50mm x 75m</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>291-1214</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

fish for pre-implantation genetic diagnosis

Pre-implantation genetic diagnosis (PGD) is an established alternative to pre-natal diagnosis, and involves selecting pre-implantation embryos from a cohort generated by assisted reproduction technology (ART). This selection may be required because of familial monogenic disease (e.g. cystic fibrosis), or because one partner carries a chromosome rearrangement (e.g. a two-way reciprocal translocation). PGD is available for couples who have had previous affected children, and/or in the case of chromosome rearrangements, recurrent miscarriages, or infertility. Oocytes aspirated following ovarian stimulation are fertilized by in vitro immersion in semen (IVF) or by intracytoplasmic injection of an individual spermatozoon (ICSI). Pre-implantation cleavage-stage embryos are biopsied, usually by the removal of a single cell on day 3 post-fertilization, and the biopsied cell is tested to establish the genetic status of the embryo. Fluorescence in situ hybridization (FISH) on the fixed nuclei of biopsied cells with target-specific DNA probes is the technique of choice to detect chromosome imbalance associated with chromosome rearrangements, and to select female embryos in families with X-linked disease for which there is no mutation-specific test. FISH has also been used to screen embryos for spontaneous chromosome aneuploidy (also known as PGS or PGD-AS) in order to try and improve the efficiency of assisted reproduction; however, the predictive value of this test using the spreading and FISH technique described here is likely to be unacceptably low in most people's hands and it is not recommended for routine clinical use. We describe the selection of suitable probes for single-cell FISH, spreading techniques for blastomere nuclei, and in situ hybridization and signal scoring, applied to PGD in a clinical setting.

Watch this Scientific Journal Video about FISH for Pre-implantation Genetic Diagnosis at JoVE.com

FISH for Pre-implantation Genetic Diagnosis

This article describes the selection of suitable probes for single-cell FISH, spreading techniques for blastomere nuclei, and in situ hybridization and signal scoring, applied to pre-implantation genetic diagnosis (PGD) in a clinical setting.

Pre-implantation genetic diagnosis (PGD) is an established alternative to pre-natal diagnosis, and involves selecting pre-implantation embryos from a ...

fish-for-pre-implantation-genetic-diagnosis

Research

JoVE Journal

Medicine

36.7K Views.  Guy’s & St Thomas’ Centre for Preimplantation Genetic Diagnosis. This article describes the selection of suitable probes for single-cell FISH, spreading techniques for blastomere nuclei, and in situ hybridization and signal scoring, applied to pre-implantation genetic diagnosis (PGD) in a clinical setting.

Video: FISH for Pre-implantation Genetic Diagnosis

Microinjection of CRISPR/Cas9 Protein into Channel Catfish, Ictalurus punctatus, Embryos for Gene Editing

The complete genome of the channel catfish, Ictalurus punctatus, has been sequenced, leading to greater opportunities for studying channel catfish gene function. Gene knockout has been used to study these gene functions in vivo. The clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (CRISPR/Cas9) system is a powerful tool used to edit genomic DNA sequences to alter gene function. While the traditional approach has been to introduce CRISPR/Cas9 mRNA into the single cell embryos through microinjection, this can be a slow and inefficient process in catfish. Here, a detailed protocol for microinjection of channel catfish embryos with CRISPR/Cas9 protein is described. Briefly, eggs and sperm were collected and then artificial fertilization performed. Fertilized eggs were transferred to a Petri dish containing Holtfreter's solution. Injection volume was calibrated and then guide RNAs/Cas9 targeting the toll/interleukin 1 receptor domain-containing adapter molecule (TICAM 1) gene and rhamnose binding lectin (RBL) gene were microinjected into the yolk of one-cell embryos. The gene knockout was successful as indels were confirmed by DNA sequencing. The predicted protein sequence alterations due to these mutations included frameshift and truncated protein due to premature stop codons.

Microinjection of CRISPR/Cas9 Protein into Channel Catfish, Ictalurus punctatus, Embryos for Gene Editing

A simple and efficient microinjection protocol for gene editing in channel catfish embryos using the CRISPR/Cas9 system is presented. In this protocol, guide RNAs and Cas9 protein were microinjected into the yolk of one-cell embryos. This protocol has been validated by knocking out two channel catfish immune-related genes.

The complete genome of the channel catfish, Ictalurus punctatus, has been sequenced, leading to greater opportunities for studying channel catfish gene ...

Genetics

Efficient Production and Identification of CRISPR/Cas9-generated Gene Knockouts in the Model System Danio rerio

Characterization of the clustered, regularly interspaced, short, palindromic repeat (CRISPR) system of Streptococcus pyogenes has enabled the development of a customizable platform to rapidly generate gene modifications in a wide variety of organisms, including zebrafish. CRISPR-based genome editing uses a single guide RNA (sgRNA) to target a CRISPR-associated (Cas) endonuclease to a genomic DNA (gDNA) target of interest, where the Cas endonuclease generates a double-strand break (DSB). Repair of DSBs by error-prone mechanisms lead to insertions and/or deletions (indels). This can cause frameshift mutations that often introduce a premature stop codon within the coding sequence, thus creating a protein-null allele. CRISPR-based genome engineering requires only a few molecular components and is easily introduced into zebrafish embryos by microinjection. This protocol describes the methods used to generate CRISPR reagents for zebrafish microinjection and to identify fish exhibiting germline transmission of CRISPR-modified genes. These methods include in vitro transcription of sgRNAs, microinjection of CRISPR reagents, identification of indels induced at the target site using a PCR-based method called a heteroduplex mobility assay (HMA), and characterization of the indels using both a low throughput and a powerful next-generation sequencing (NGS)-based approach that can analyze multiple PCR products collected from heterozygous fish. This protocol is streamlined to minimize both the number of fish required and the types of equipment needed to perform the analyses. Furthermore, this protocol is designed to be amenable for use by laboratory personal of all levels of experience including undergraduates, enabling this powerful tool to be economically employed by any research group interested in performing CRISPR-based genomic modification in zebrafish.

Efficient Production and Identification of CRISPR/Cas9-generated Gene Knockouts in the Model System Danio rerio

Targeted genome editing in the model system Danio rerio (zebrafish) has been greatly facilitated by the emergence of CRISPR-based approaches. Herein, we describe a streamlined, robust protocol for generation and identification of CRISPR-derived nonsense alleles that incorporates the heteroduplex mobility assay and identification of mutations using next-generation sequencing.

Characterization of the clustered, regularly interspaced, short, palindromic repeat (CRISPR) system of Streptococcus pyogenes has enabled the development ...

Microinjection for Transgenesis and Genome Editing in Threespine Sticklebacks

The threespine stickleback fish has emerged as a powerful system to study the genetic basis of a wide variety of morphological, physiological, and behavioral phenotypes. The remarkably diverse phenotypes that have evolved as marine populations adapt to countless freshwater environments, combined with the ability to cross marine and freshwater forms, provide a rare vertebrate system in which genetics can be used to map genomic regions controlling evolved traits. Excellent genomic resources are now available, facilitating molecular genetic dissection of evolved changes. While mapping experiments generate lists of interesting candidate genes, functional genetic manipulations are required to test the roles of these genes. Gene regulation can be studied with transgenic reporter plasmids and BACs integrated into the genome using the Tol2 transposase system. Functions of specific candidate genes and cis-regulatory elements can be assessed by inducing targeted mutations with TALEN and CRISPR/Cas9 genome editing reagents. All methods require introducing nucleic acids into fertilized one-cell stickleback embryos, a task made challenging by the thick chorion of stickleback embryos and the relatively small and thin blastomere. Here, a detailed protocol for microinjection of nucleic acids into stickleback embryos is described for transgenic and genome editing applications to study gene expression and function, as well as techniques to assess the success of transgenesis and recover stable lines.

Transgenic manipulations and genome editing are critical for functionally testing the roles of genes and cis-regulatory elements. Here a detailed microinjection protocol for the generation of genomic modifications (including Tol2-mediated fluorescent reporter transgene constructs, TALENs, and CRISPRs) is presented for the emergent model fish, the threespine stickleback.

The threespine stickleback fish has emerged as a powerful system to study the genetic basis of a wide variety of morphological, physiological, and ...

Developmental Biology

High-throughput DNA Extraction and Genotyping of 3dpf Zebrafish Larvae by Fin Clipping

Zebrafish (Danio rerio) possess orthologues for 84% of the genes known to be associated with human diseases. In addition, these animals have a short generation time, are easy to handle, display a high reproductive rate, low cost, and are easily amenable to genetic manipulations by microinjection of DNA in embryos. Recent advances in gene editing tools are enabling precise introduction of mutations and transgenes in zebrafish. Disease modeling in zebrafish often leads to larval phenotypes and early death which can be challenging to interpret if genotypes are unknown. This early identification of genotypes is also needed in experiments requiring sample pooling, such as in gene expression or mass spectrometry studies. However, extensive genotypic screening is limited by traditional methods, which in most labs are performed only on adult zebrafish or in postmortem larvae. We addressed this problem by adapting a method for the isolation of PCR-ready genomic DNA from live zebrafish larvae that can be achieved as early as 72 h post-fertilization (hpf). This time and cost-effective technique, improved from a previously published genotyping protocol, allows the identification of genotypes from microscopic fin biopsies. The fins quickly regenerate as the larvae develop. Researchers are then able to select and raise the desired genotypes to adulthood by utilizing this high-throughput PCR-based genotyping procedure.

Zebrafish have been used as reliable genetic model organisms in biomedical research, especially with the advent of gene-editing technologies. When larval phenotypes are expected, DNA extraction and genotype identification can be challenging. Here, we describe an efficient genotyping procedure for zebrafish larvae, by tail clipping, as early as 72-h post-fertilization.

Zebrafish (Danio rerio) possess orthologues for 84% of the genes known to be associated with human diseases. In addition, these animals have a short ...

Manipulation of Gene Function in Mexican Cavefish

Cave animals provide a compelling system for investigating the evolutionary mechanisms and genetic bases underlying changes in numerous complex traits, including eye degeneration, albinism, sleep loss, hyperphagia, and sensory processing. Species of cavefish from around the world display a convergent evolution of morphological and behavioral traits due to shared environmental pressures between different cave systems. Diverse cave species have been studied in the laboratory setting. The Mexican tetra, Astyanax mexicanus, with sighted and blind forms, has provided unique insights into biological and molecular processes underlying the evolution of complex traits and is well-poised as an emerging model system. While candidate genes regulating the evolution of diverse biological processes have been identified in A. mexicanus, the ability to validate a role for individual genes has been limited. The application of transgenesis and gene-editing technology has the potential to overcome this significant impediment and to investigate the mechanisms underlying the evolution of complex traits. Here, we describe a different methodology for manipulating gene expression in A. mexicanus. Approaches include the use of morpholinos, Tol2 transgenesis, and gene-editing systems, commonly used in zebrafish and other fish models, to manipulate gene function in A. mexicanus. These protocols include detailed descriptions of timed breeding procedures, the collection of fertilized eggs, injections, and the selection of genetically modified animals. These methodological approaches will allow for the investigation of the genetic and neural mechanisms underlying the evolution of diverse traits in A. mexicanus.&#160;

We describe approaches for the manipulation of genes in the evolutionary model system Astyanax mexicanus. Three different techniques are described: Tol2-mediated transgenesis, targeted manipulation of the genome using CRISPR/Cas9, and knockdown of expression using morpholinos. These tools should facilitate the direct investigation of genes underlying the variation between surface- and cave-dwelling forms.

Cave animals provide a compelling system for investigating the evolutionary mechanisms and genetic bases underlying changes in numerous complex traits, ...

Visualization of Cellular Electrical Activity in Zebrafish Early Embryos and Tumors

Bioelectricity, endogenous electrical signaling mediated by ion channels and pumps located on the cell membrane, plays important roles in signaling processes of excitable neuronal and muscular cells and many other biological processes, such as embryonic developmental patterning. However, there is a need for in vivo electrical activity monitoring in vertebrate embryogenesis. The advances of genetically encoded fluorescent voltage indicators (GEVIs) have made it possible to provide a solution for this challenge. Here, we describe how to create a transgenic voltage indicator zebrafish using the established voltage indicator, ASAP1 (Accelerated Sensor of Action Potentials 1), as an example. The Tol2 kit and a ubiquitous zebrafish promoter, ubi, were chosen in this study. We also explain&#160;the processes of Gateway site-specific cloning, Tol2 transposon-based zebrafish transgenesis, and the imaging process for early-stage fish embryos and fish tumors using regular epifluorescent microscopes. Using this fish line, we found that there are cellular electric voltage changes during zebrafish embryogenesis, and fish larval movement. Furthermore, it was observed that in a few zebrafish malignant peripheral nerve sheath tumors, the tumor cells were generally polarized compared to the surrounding normal tissues.

Here, we show the process of creating a cellular electric voltage reporter zebrafish line to visualize embryonic development, movement, and fish tumor cells in vivo.

Bioelectricity, endogenous electrical signaling mediated by ion channels and pumps located on the cell membrane, plays important roles in signaling ...

Screening Sperm for the Rapid Isolation of Germline Edits in Zebrafish

The advent of targeted CRISPR-Cas nuclease technologies has revolutionized the ability to perform precise genome editing in both established and emerging model systems. CRISPR-Cas genome editing systems use a synthetic guide RNA (sgRNA) to target a CRISPR-associated (Cas) endonuclease to specific genomic DNA loci, where the Cas endonuclease generates a double-strand break. The repair of double-strand breaks by intrinsic error-prone mechanisms leads to insertions and/or deletions, disrupting the locus. Alternatively, the inclusion of double-stranded DNA donors or single-stranded DNA oligonucleotides in this process can elicit the inclusion of precise genome edits ranging from single nucleotide polymorphisms to small immunological tags or even large fluorescent protein constructs. However, a major bottleneck in this procedure can be finding and isolating the desired edit in the germline. This protocol outlines a robust method for screening and isolating germline mutations at specific loci in Danio rerio (zebrafish); however, these principles may be adaptable in any model where in vivo sperm collection is possible.

CRISPR-Cas technologies have revolutionized the field of genome editing. However, finding and isolating the desired germline edit remains a major bottleneck. Therefore, this protocol describes a robust method for quickly screening F0 CRISPR-injected zebrafish sperm for germline edits using standard PCR, restriction digest, and gel electrophoresis techniques.

The advent of targeted CRISPR-Cas nuclease technologies has revolutionized the ability to perform precise genome editing in both established and emerging ...

A Reverse Genetic Approach to Test Functional Redundancy During Embryogenesis

Gene function during embryogenesis is typically defined by loss-of-function experiments, for example by targeted mutagenesis (knockout) in the mouse. In the zebrafish model, effective reverse genetic techniques have been developed using microinjection of gene-specific antisense morpholinos. Morpholinos target an mRNA through specific base-pairing and block gene function transiently by inhibiting translation or splicing for several days during embryogenesis (knockdown). However, in vertebrates such as mouse or zebrafish, some gene functions can be obscured by these approaches due to the presence of another gene that compensates for the loss. This is especially true for gene families containing sister genes that are co-expressed in the same developing tissues. In zebrafish, functional compensation can be tested in a relatively high-throughput manner, by co-injection of morpholinos that target knockdown of both genes simultaneously. Likewise, using morpholinos, a genetic interaction between any two genes can be demonstrated by knockdown of both genes together at sub-threshold levels. For example, morpholinos can be titrated such that neither individual knockdown generates a phenotype. If, under these conditions, co-injection of both morpholinos causes a phenotype, a genetic interaction is shown. Here we demonstrate how to show functional redundancy in the context of two related GATA transcription factors. GATA factors are essential for specification of cardiac progenitors, but this is revealed only by the loss of both Gata5 and Gata6. We show how to carry out microinjection experiments, validate the morpholinos, and evaluate the compensated phenotype for cardiogenesis.

Gene function can be obscured in loss-of-function experiments if there is compensation by another gene. The zebrafish model provides a relatively high-throughput means to reveal such functional redundancy in living embryos.

Gene function during embryogenesis is typically defined by loss-of-function experiments, for example by targeted mutagenesis (knockout) in the mouse. In ...

Biology

Gene Trapping Using Gal4 in Zebrafish

Large clutch size and external development of optically transparent embryos make zebrafish an exceptional vertebrate model system for in vivo insertional mutagenesis using fluorescent reporters to tag expression of mutated genes. Several laboratories have constructed and tested enhancer- and gene-trap vectors in zebrafish, using fluorescent proteins, Gal4- and lexA- based transcriptional activators as reporters 1-7. These vectors had two potential drawbacks: suboptimal stringency (e.g. lack of ability to differentiate between enhancer- and gene-trap events) and low mutagenicity (e.g. integrations into genes rarely produced null alleles). Gene Breaking Transposon (GBTs) were developed to address these drawbacks 8-10. We have modified one of the first GBT vectors, GBT-R15, for use with Gal4-VP16 as the primary gene trap reporter and added UAS:eGFP as the secondary reporter for direct detection of gene trap events. Application of Gal4-VP16 as the primary gene trap reporter provides two main advantages. First, it increases sensitivity for genes expressed at low expression levels. Second, it enables researchers to use gene trap lines as Gal4 drivers to direct expression of other transgenes in very specific tissues. This is especially pertinent for genes with non-essential or redundant functions, where gene trap integration may not result in overt phenotypes. The disadvantage of using Gal4-VP16 as the primary gene trap reporter is that genes coding for proteins with N-terminal signal sequences are not amenable to trapping, as the resulting Gal4-VP16 fusion proteins are unlikely to be able to enter the nucleus and activate transcription. Importantly, the use of Gal4-VP16 does not pre-select for nuclear proteins: we recovered gene trap mutations in genes encoding proteins which function in the nucleus, the cytoplasm and the plasma membrane.

This protocol describes the method of gene trap insertional mutagenesis using Gal4-VP16 as the primary reporter and GFP/RFP as secondary reporters in zebrafish. Approximately one in ten high-expressing F0 fish yield gene trap progeny co-expressing GFP and RFP. The screening procedure can be readily scaled to adapt to the size of the laboratory performing the insertional mutagenesis screen.

Large clutch size and external development of optically transparent embryos make zebrafish an exceptional vertebrate model system for in vivo insertional ...

Rapid and Efficient Zebrafish Genotyping Using PCR with High-resolution Melt Analysis

Zebrafish is a powerful vertebrate model system for studying development, modeling disease, and performing drug screening. Recently a variety of genetic tools have been introduced, including multiple strategies for inducing mutations and generating transgenic lines. However, large-scale screening is limited by traditional genotyping methods, which are time-consuming and labor-intensive. Here we describe a technique to analyze zebrafish genotypes by PCR combined with high-resolution melting analysis (HRMA).&#160;This approach is rapid, sensitive, and inexpensive, with lower risk of contamination artifacts.&#160;Genotyping by PCR with HRMA can be used for embryos or adult fish, including in high-throughput screening protocols.

PCR combined with high-resolution melt analysis (HRMA) is demonstrated as a rapid and efficient method to genotype zebrafish.

Zebrafish is a powerful vertebrate model system for studying development, modeling disease, and performing drug screening. Recently a variety of genetic ...