Worm Breeder's Gazette 8(3): 65
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We have continued to look at transcription of the actin genes during C. elegans development both in wild-type worms and revertants of actin mutants. We now have gene-specific probes for all four genes. Using these probes in conjunction with improved Northern sensitivity we have determined the post-embryonic pattern of actin gene transcription. Some of these results contradict results reported in an earlier Newsletter. In wild-type worms all four actin genes are transcribed and the level of transcription does not appear to fluctuate during post- embryonic development. Three size classes of transcripts of 1450, 1550 and 1650 nucleotides are made from the four genes. The 1450 size class is comprised of transcripts from genes 1 and 2; the 1550 and 1650 size classes are comprised of gene 3 and gene 4 transcripts respectively. We have not extensively quantitated the abundance of the transcripts from each gene but it appears that gene 1, 3 and 4 transcripts are comparable in abundance. Gene 2 transcripts are clearly the least abundant. We have started to look at embryonic and tissue-specific transcription using in situ hybridization to whole worms. Preliminary results have failed to localize transcripts from any of the genes to a specific tissue or embryonic stage. As a control we have localized a yolk protein gene probe (provided by Tom Blumenthal) to the intestinal cells of appropriately staged worms under the same hybridization conditions. We are working on improving the resolution of the in situ hybridizations. We have analyzed the post-embryonic transcription of the actin genes in three revertants of actin mutants in which reversion was accompanied by rearrangement in the actin gene cluster. As reported before, the three revertants have transcriptional patterns that differ from those seen in wild-type worms. Although we have identified the transcripts in each case, a correlation between the physical arrangement of the genes and the effect on transcription is not straightforward. For example, RW2458, which has a 500 bp insertion in the gene 1 region, has a detectable gene 1 transcript although greatly reduced in abundance. This transcript is identical in size to the wild-type transcript. This revertant also has an additional actin transcript about 600 nucleotides long. As we have not yet precisely localized the point of the insertion event relative to the coding region of the gene, it is difficult to interpret these results. We are currently cloning the rearranged regions from the revertants in order to define the exact structure of the rearrangements in the hope that it will allow us to say something more profound about the developmental regulation of these genes.