Worm Breeder's Gazette 10(2): 73
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.
Collagen genes in C. elegans represent a large multigene family with 50-150 members. Sequencing analysis indicates that collagen genes of C. elegans share a common gene structure. Although they share the common gene structure the members of the gene family exhibit a wide range of sequence similarity, ranging from 50% to 99.5%. Unlike most other large multigene families, most members of the collagen gene family are dispersed in the C. elegans genome. Thus, collagen genes of C. elegans are of interest for studying mechanisms involved in molecular evolution. Genomic Southern hybridization experiments indicate that genes near to each other have greater sequence similarity than do those more distant. The sequences of two genes separated by 1.5 kb, col-12 and col-13, have been determined. Only 5 nucleotide changes are observed in the 951 nucleotides of the coding region (99.5 % identity). Amino acid sequence comparisons reveal that the coding regions are identical except for 2 amino acids at the amino terminus. The intron sequences ( 52 nucleotides) are identical, however, the 5' and 3' untranslated regions are strikingly different from each other (less than 50% identity). To determine when these two genes are expressed Northern blot hybridization experiments have been done with col-12 and col-13 specific probes from the 3' untranslated region. The col-12 specific probe hybridizes to a 1.2 kb transcript and the col-13 probe hybridizes to a 1.3 kb transcript. Both of the transcripts are detected at similar levels in L4 and adult molt RNAs, but are not found in embryo and dauer molt RNAs. The size difference in the transcripts is likely to be due to the difference in the length of the 3' untranslated regions, since a consensus poly(A) addition signal for col-12 is identified 87 nucleotides downstream from the translational termination codon but no poly(A) addition signal for col-13 has been identified. However, several possible poly(A) addition signals that differ by 2 nucleotides from the consensus signal are located 150-200 nucleotides downstream from the termination codon in col-13. The results show that both of these genes are expressed at the same developmental stages. It is interesting that the 5' flanking regions of these genes are divergent yet they display the same mode of regulation during development. These data suggest that col-12 and col-13 are derived from a gene duplication and that the coding regions have been conserved by gene conversion. It is an unusual observation that gene conversion has maintained sequence similarity only from the translational start codon to the termination codon.