Worm Breeder's Gazette 13(2): 84 (February 1, 1994)

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.

Identifying mutations in the bli-4 gene, a member of the K ex2 -likegene family.

Colin Thacker, Martin Srayko, Ann Rose Department of Medical Genetics, University of British Columbia, Vancouver, B C, V6 T lZ3

Figure 1

We are studying the role of two genes that encode serine endoproteases that belong to the K ex2 -likefamily of prohormone convertases. These two genes include bli-4 and one identified as a sequenced cDNA designated cm1 O b9 (Waterston et al., 1992, Nature Genet 1:114-123). Genetic analysis of bli-4 has enabled us to group mutant alleles into three classes (Peters et al, 1991, Genetics 129:95-102). The first mutant class includes the only viable mutation e937 which results in the blistering of the adult cuticle. Class II mutants include 11 lethal alleles which arrest development in late embryogenesis prior to hatching. These 11 alleles fail to complement e937 .Class III mutants comprise 2 lethal alleles that complement e937 yet fail to complement the class II lethal alleles. Class III animals predominantly arrest as early L1 larvae, although some lethality in late embryogenesis is also observed. The bli-4 gene was originally cloned in our laboratory by Ken Peters. The gene encodes at least three different proteins with extensive sequence similarity to the K ex2 -likefamily of serine endopeptidases. The three isoforms are produced by alternative splicing at the 3'-end of the gene as depicted in the figure of the gene structure below:

So far we have been able to identify molecular lesions in three bli-4 alleles, e937 and two class II lethals. The e937 mutation is a 3.2kb deletion that removes the exon unique to blisterin A (Peters and Rose, W.B G. 11:28, 1991) resulting in the complete abrogation of expression of this product as demonstrated by northern analysis. Presumably, blisterin A is required for the production or maintenance of the adult cuticle. The class II mutant, h1 O10is a spontaneous allele isolated in a precomplementation screen for bli-4 alleles in a mut-6 background. The Tc1 insertion has been sequenced and found to reside in exon 9, 3' of the protease domain. A second class II lethal allele, q508 was found to contain a 366bp deletion that removes the splice acceptor and 33 nucleotides from exon 12. q508 was isolated by Lisa Kadyk in Judith Kimble's laboratory. Both of the lesions identified in the class II lethal alleles occur within the first 12 exons that are common to all of the bli-4 transcripts These results suggest that all of the class II alleles contain mutations either within this common region or in regulatory elements that control the expression of the gene, resulting in the loss of activity of all isoforms. We believe that the class III mutants are the result of mutations within the exons unique to either or both blisterin B and C, suggesting that these alternate isoforms have an essential function for early nematode development. We are currently attempting to identify the molecular lesions in the remaining class II and III lethal alleles using PCR-heteroduplexing and direct sequencing of PCR products.

We have also initiated studies on a second gene which was originally identified by the random cDNA sequencing project (Waterston et al., 1992, Nature Genet. 1:114-123). The cDNA cm1 O b9 has been mapped to the YAC clone Y51C6 in a region of chromosome III that is actively being sequenced by the genome sequencing group. Although the sequence of the gene that encodes cm1 O b9 is not on the current ACEDB, we anticipate that it will be available in the next update. We have sequenced most of the cDNA and have determined that it represents a partial clone which does not include the protease domain. However, the sequence generated suggests that the cDNA encodes a product that most closely resembles Drosophila and vertebrate furin, a member of the K ex2 -likefamily. We are in the process of characterizing this gene in more detail by isolating cDNA clones that are more complete at the 5'-end.

We would like to take this opportunity to thank Patty Wohldmann for forwarding cm1 O b9 to us, and especially Lisa Kadyk in Judith Kimble's lab for the q508 allele.

This work was supported by grants from the MRC (Canada) and the B.C. Health Foundation.