Worm Breeder's Gazette 7(2): 30
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 cloned a small family of developmentally-regulated genes from C. elegans. The timing of expression and abundance and size of the mRNA suggest that these genes code for the recently-identified yolk proteins. The genes were cloned by selecting the most abundantly- expressed sequences from a C. elegans cDNA library in pACYC184. At least 40 such clones, selected solely on that basis, are members of a single family of related genes. Like the yolk proteins, these genes are expressed abundantly in adult hermaphrodites but apparently not at all in adult males or in larvae. Thus they appear to be controlled at the level of transcription. The gene family containing five genes, based on genomic Southern blots. Genomic clones have been selected from John Karn's lambda1059 libraries. So far we have isolated four genes from the lambda libraries. All four are between 5 and 6 kb in length and all hybridize to a single RNA species about 4.7 kb in length on Northern blots of adult hermaphrodite RNA. This is approximately the right length to code for the largest of the yolk proteins. One of the genes has been analyzed in more detail. It is 5.1 kb long and contains only two or three small (0.1-0.3 kb) introns. There are two sub-families based on cross-hybridization and restriction maps. Two of the genes are so similar that they hybridize nearly as well to each other as each does to itself. Furthermore, of the eight restriction sites found within each of these genes, six are found at homologous sites within the other gene (including one within an intron). The other sub-family, is composed of three genes. Two of these genes have been cloned and are linked in tandem, with only about 2 kb of DNA between the 3' end of one and the 5' end of the other. C. elegans Bergerac has an extra 1.7 kb of DNA between these two genes and we are now in the process of mapping the location of the genes on the chromosome using this heterogeneity. These two genes are so closely related to one another that we have found no restriction site differences between them. The members of one sub-family also cross-hybridize to the members of the other sub-family but the hybridizations are much weaker than within a sub-family. Nevertheless some restriction sites appear to be shared between the two sub-families.