passaging and scoring the caenorhabditis elegans p0 generation for germline gfp expression

Epigenetic Inheritance and ChIP in &lt;em&gt;Caenorhabditis elegans&lt;/em&gt;

Epigenetic inheritance allows the transmission of gene regulatory information across generations and can therefore allow the environment or experiences of parents to affect their progeny. In C. elegans, germline gene silencing initiated by exogenous double-stranded RNA (dsRNA) can be inherited for multiple generations in progeny not exposed to the original trigger1,2,3,4. This process, termed RNA interference (RNAi) inheritance, is one of several related epigenetic silencing phenomena in C. elegans, including piRNA-initiated multigenerational silencing2,5, paramutation/RNAe (RNA-induced epigenetic silencing)6,7,8, and multicopy array-initiated silencing9, which have overlapping but distinct requirements for small RNA and chromatin regulation machinery. In C. elegans exogenous RNAi, dsRNA is processed into small interfering RNAs (siRNAs) that act in a complex with primary Argonaute proteins to recognize their target mRNA. This targeting leads to the amplification of secondary siRNAs that associate with secondary Argonautes to silence target mRNA through both cytoplasmic and nuclear silencing pathways. For germline-expressed RNAi targets, the nuclear secondary Argonaute HRDE-1 and additional nuclear RNAi factors target nascent transcripts, resulting in transcriptional repression and recruitment of histone methyltransferases to deposit repressive chromatin marks, including H3K9me310. Histone H3K9me3 promotes the establishment of heritable silencing of germline-expressed green fluorescent protein (GFP) transgenes by RNAi inheritance11,12.
The goal of this protocol is to use a transgene expressing a GFP-histone fusion protein in the germline as a reporter for RNAi inheritance and to assay changes in histone modifications at the reporter transgene locus using chromatin immunoprecipitation and quantitative polymerase chain reaction (ChIP-qPCR). This protocol describes a standardized plate-based RNAi feeding approach to initiate reporter silencing. It also provides a detailed timeline for passaging animals between generations by isolating in utero embryos from gravid adults by alkaline hypochlorite treatment (&#39;bleaching&#39;). Methods and representative data for monitoring the frequency of GFP silencing in a subset of the population by fluorescence microscopy and for histone H3K9me3 ChIP-qPCR are also described. Reporter-based RNAi inheritance assays provide a highly tractable system to functionally dissect the roles of genetic and environmental factors in epigenetic regulation13,14, and genetic screens using such reporters have identified both genes that are required for2,3,15 and genes that negatively regulate16,17 the duration of transgenerational epigenetic inheritance.

Author Spotlight: RNAi Inheritance and ChIP in C. elegans 

Analysis of Transgenerational Epigenetic Inheritance in C. elegans Using a Fluorescent Reporter and Chromatin Immunoprecipitation (ChIP)

Research in our lab examines how chromatin-associated proteins, histone modifications, and small RNA pathway factors work together in the context of development and transgenerational epigenetic inheritance. The RNA inheritance assay, using a GFP reporter, has become a very powerful tool. This protocol describes how to standardize the preparation, scoring, and passaging of worms, and the preparation of ChIP samples, which can help to generate reproducible results.One of the experimental challenges when studying germline-expressed transgenes is isolating the effects in the animal's germline. We're currently using whole animals for ChIP, but in the future we would like to develop assays to examine chromatin, specifically in the germline. Our laboratory is interested in histone methylation and proteins that recognize these marks.Going forward, we would like to investigate the interplay between these chromatin readers and small RNA pathways in the context of RNAi inheritance at transgenes and the regulation of endogenous sequences.

Watch this Scientific Journal Video about Passaging and Scoring the Caenorhabditis elegans P0 Generation for Germline GFP Expression at JoVE.com

Passaging and Scoring the Caenorhabditis elegans P0 Generation for Germline GFP Expression  

Passaging and Scoring the Caenorhabditis elegans P0 Generation for Germline GFP Expression

Begin preparing the agarose pads by placing a drop of melted 1%agarose onto the vinyl record using a glass Pasteur pipet. Orient a glass slide so that the lines on the record are horizontal or vertical, and place the slide quickly onto the agarose drop for 30 seconds. Remove the glass slide from the record and add approximately five microliters of freshly prepared five millimolar levamisole under the stereoscope.Gently flick the tube containing worms and transfer 5 to 10 microliters onto the agarose pad to mount the worms. Estimate the number of worms as they are being added so that there are approximately 40 worms per replicate. Line up the worms in rows using an eyelash pick, and place a glass coverslip onto the slide.Isolate the embryos from the remaining worms using the bleaching protocol and plate 250 embryos onto 35 millimeter NGM plates seeded with OP50-1 bacteria. Under the fluorescent stereoscope, use a GFP filter set and count and record the number of GFP positive and GFP negative worms on the slides for each replicate using a tally counter. The manual scoring of the nuclear GFP signal in the germline for each generation showed that the silencing of the transgene was fully penetrant in the scored P0 and F1 worms treated with GFP RNAi.In the F2 generation, the proportion of the population exhibiting inheritance of GFP silencing was approximately 50%By the F5 generation, the majority of the population did not show the inheritance of silencing. By the F10 generation, all the worms expressed GFP and no inheritance was detected.

passaging-scoring-caenorhabditis-elegans-p0-generation-for-germline

Research

JoVE Journal

Genetics

369 Views.  University of Toronto. Begin preparing the agarose pads by placing a drop of melted 1%agarose onto the vinyl record using a glass Pasteur pipet. Orient a glass slide so that the lines on the record are horizontal or vertical, and place the slide quickly onto the agarose drop for 30 seconds. Remove the glass slide from the record and add approximately five microliters of freshly prepared five millimolar levamisole under the stereoscope.Gently flick the tube containing worms and transfer 5 to 10 microliters on...

Video: Passaging and Scoring the Caenorhabditis elegans P0 Generation for Germline GFP Expression  

Transgenerational epigenetic inheritance (TEI) allows the transmission of information through the germline without changing the genome sequence, through factors such as non-coding RNAs and chromatin modifications. The phenomenon of RNA interference (RNAi) inheritance in the nematode Caenorhabditis elegans is an effective model to investigate TEI that takes advantage of this model organism's short life cycle, self-propagation, and transparency. In RNAi inheritance, exposure of animals to RNAi leads to gene silencing and altered chromatin signatures at the target locus that persist for multiple generations in the absence of the initial trigger. This protocol describes the analysis of RNAi inheritance in C. elegans using a germline-expressed nuclear green fluorescent protein (GFP) reporter. Reporter silencing is initiated by feeding the animals bacteria expressing double-stranded RNA targeting GFP. At each generation, animals are passaged to maintain synchronized development, and reporter gene silencing is determined by microscopy. At select generations, populations are collected and processed for chromatin immunoprecipitation (ChIP)-quantitative polymerase chain reaction (qPCR) to measure histone modification enrichment at the GFP reporter locus. This protocol for studying RNAi inheritance can be easily modified and combined with other analyses to further investigate TEI factors in small RNA and chromatin pathways.

This protocol describes an RNA interference and ChIP assay to study the epigenetic inheritance of RNAi-induced silencing and associated chromatin modifications in C. elegans.

Transgenerational epigenetic inheritance (TEI) allows the transmission of information through the germline without changing the genome sequence, through ...

Bleaching and Plating Caenorhabditis elegans P0 Generation Embryos onto RNAi-NGM plates

Bleaching and Plating Caenorhabditis elegans P0 Generation Embryos onto RNAi-NGM plates  

Prepare animals for the RNAi inheritance assay by picking three or four gravid Caenorhabditis elegans adults under the 35 millimeter standard NGM plates seeded with OP50-1 bacteria. After four days, wash the gravid adult worms off the plates into 1.5 milliliter tubes using 800 microliters of M9 buffer supplemented with Triton X-100. Repeat the wash and pull the worms into one tube.After centrifuging the worms at 1, 000 G for 1.5 to two minutes, aspirate the supernatant leaving 100 microliters without disturbing the worm pellet. To each tube containing the worm pellet, add 650 microliters of double distilled water. To isolate the C.elegans embryos from the collected population, add 250 microliters of the freshly prepared bleaching solution and start a timer.Every one to two minutes, vortex the tubes thoroughly. After five minutes, monitor the degradation of adult worms under the stereoscope. Continue vortexing until the worms are completely dissolved and only embryos remain.This generally takes six to seven minutes. Immediately centrifuge the tubes at 1, 000 G for 1.5 minutes and aspirate the supernatant, leaving approximately 50 to 100 microliters of the supernatant with the embryos. Add one milliliter of M9 buffer supplemented with Triton X-100 to the embryos and vortex.Centrifuge the suspension and repeat the wash two times. After the final wash, aspirate the supernatant and leave approximately 100 microliters in the tube. Vortex the tubes with isolated embryos and pipette two microliters from each tube twice onto a labeled glass slide.Count the embryos using a tally counter to estimate the concentration of embryos per microliter. To start a semi-synchronized population growth, transfer approximately 250 embryos onto each RNAi NGM plate containing E.coli HT115 bacteria with GFP or control RNAi vectors. Allow the liquid to absorb.Incubate the P naught generation treated with RNAi for four days at 21 degrees Celsius.

Collection of F1 Generation Caenorhabditis elegans for Chromatin Immunoprecipitation (ChIP)

Collection of F1 Generation Caenorhabditis elegans for Chromatin Immunoprecipitation (ChIP)  

Begin by plating approximately 3, 500 C.elgans F1 generation embryos on 14 plates and allow them to grow to the young adult stage for three days at 21 degrees Celsius. Wash and collect the C.elgans into 1.5-milliliter tubes using PBS/TX. Centrifuge at 1000 G for two minutes, aspirate, and pull the worms from one strain into one tube.Repeat three washes with PBS/TX. Next, aspirate the supernatant leaving one milliliter in the tube and invert to mix. After counting the number of C.elgans worms in three microliters three times, calculate the concentration of worms and transfer a volume corresponding to 3000 worms to a new tube for formaldehyde cross-linking.

Formaldehyde Crosslinking of the F1 Generation of Caenorhabditis elegans for ChIP

Formaldehyde Crosslinking of the F1 Generation of Caenorhabditis elegans for ChIP  

Begin by adding formaldehyde to a 1.8%final concentration to the tube containing the worms and rotating the tube at room temperature for six minutes. Then immediately freeze the tubes in liquid nitrogen, and store the samples at 80 degrees Celsius. To proceed thaw the formaldehyde cross-link sample in a room temperature water bath for three minutes, and rotate the samples for 16 minutes at room temperature.At 1.25 molar glycine to a 125 millimolar final concentration, and rotate for five minutes at room temperature. Following this step, keep the samples on ice, or at four degrees, and use ice cold buffers until the magnetic bead elution. After centrifuging the sample at 1000 g for three minutes, wash it three times with one milliliter of PBSTX.Then wash it two times with one milliliter of Resuspension Buffer. After the last wash, leave enough Buffer to ensure the total volume is at least three times the pellet volume and a minimum of 100 microliters.

Sonication of Formaldehyde-Crosslinked Caenorhabditis elegans and Chromatin Immunoprecipitation

Sonication of Formaldehyde-Crosslinked Caenorhabditis elegans and Chromatin Immunoprecipitation  

Begin by mixing and aliquoting 90 to 120 microliters of the formaldehyde crosslinked C.Elegans samples into a polystyrene sonication tube. Add an equal volume of resuspension buffer containing 2X detergents. Sonicate in a water bath sonicator for seven minutes.Gently mix the sample by pipetting and repeat the sonication for an additional seven minutes. Once done, transfer the sonicated lysate to a 1.5 milliliter tube. Add a half volume of resuspension buffer without detergents.After centrifugation at 13, 000 G for 15 minutes at four degrees Celsius, divide the lysate supernatant into four parts. Store the input lysate part at minus 20 degrees Celsius in a 1.5 milliliter tube. Add 0.5 micrograms of anti-H3K9 trimethylation, anti-histone H3 or IgG to the appropriate immunoprecipitation or IP sample.Incubate the reaction at four degrees Celsius overnight with rotation. The following day, aliquot the nine microliters of protein G coated magnetic beads per IP sample in a 1.5 milliliter tube. After two washes with one milliliter of FA-150, resuspend the magnetic beads in the FA-150 buffer.Once done, add 7.5 microliters of the magnetic bead suspension to each IP antibody mix before incubating the tubes at four degrees Celsius for two hours with rotation. Next, wash the magnetic beads seven times using at least 200 microliters of each buffer solution. Incubate each wash at four degrees Celsius for five minutes with rotation before collecting the beads on a magnetic stand to aspirate the wash.After aspirating the last wash of the buffer, resuspend the magnetic beads in 50 microliters of chromatin IP elution buffer, and transfer it to a 1.5 milliliter tube. After eluting the sample in a ThermoMixer, collect the beads on a magnetic stand and transfer the supernatant to a new tube. Repeat the elution with another 50 microliters of chromatin immunoprecipitation elution buffer.Once done, pull a total of 100 microliters of supernatant before proceeding with reverse cross-linking and DNA elution.