Worm Breeder's Gazette 12(2): 45 (January 1, 1992)

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.

The Synthetic Multivulva Gene lin-9 Encodes A Novel Protein

Greg Beitel, Bob Horvitz

HHMI, Dept. Biology, MIT, Cambridge, MA 02139, USA (617) 253-5820

The synthetic Multivulva (syn Muv) phenotype results from combining mutations in two classes of genes (A and B); single mutants in either class alone have an apparently wild-type vulval phenotype as double mutants carrying two mutations from the same class (Ferguson and Horvitz, Genetics 123:109-121,1989). The two classes seem likely to specify functionally redundant pathways.

lin-9 is a class B gene represented by three alleles: n112 , n942 ,and n943 .In combination with a class A mutation, all three cause a syn Muv phenotype; however, n942 and n943 also cause a recessive sterile phenotype that is independent of class A mutations. We have reported that an 8 kb genomic fragment rescues the lin-9 ( n112 ); lin-15 ( n433 )syn Muv phenotype (WBG 11#2 pg 29). We have now identified a smaller genomic fragment of 5.2 kb that rescues the syn Muv phenotype of lin-9 ( n112 ); lin-15 ( n433 ),and both the syn Muv and sterile phenotypes of lin-9 ( n942 ); lin-8 ( n111 )and lin-9 ( n943 ); lin-8 ( n111 ).Smaller clones fail to rescue both the syn Muv and sterile phenotypes. Any subclones or constructs that disrupt the open reading frame of the putative lin-9 transcript (see below) eliminate rescuing activity, suggesting that this open reading frame is the lin-9 gene. We plan to sequence lin-9 mutant alleles to confirm this point. Also, we have not been able to separate the activity that rescues the syn Muv phenotype from that which rescues the sterile phenotype, suggesting that lin-9 functions similarly both in the undefined process required for fertility and in vulval development.

The 8 kb fragment was used to probe cDNA libraries made by Stuart Kim and Bob Barstead. From 400,000 plaques screened from the Kim library, we recovered six positive phage clones representing two incomplete cDNAs and one genomic fragment. From 350,000 plaques screened from the Barstead library, we recovered 22 positives representing 18 unique clones. Comparing the sequences of the 5' and 3' ends of the Barstead cDNAs with the genomic sequence of the cosmid ZK637 determined by the MRC group (WBG 11 #5 pg 13), seven are misligation products, eight are very incomplete and three are nearly full length lin-9 cDNAs. The two longest cDNAs begin with partial SL1 trans-spliced leader sequences, suggesting that we have full length cDNAs. These cDNAs, excluding the poly-A tails, are 2,314 and 2,305 nt long. These sizes are consistent with the ~2.4 kb transcript seen on Northern blots. The transcript contains an open reading frame of 642 aa that shows no significant similarity to proteins in the GenBank or SwissProt databases. The sequence of the open reading frame is not very informative, with the possible exception that the C-terminal region is relatively hydrophobic and may have several transmembrane domains.

To investigate the expression pattern of lin-9 ,we have constructed lin-9 -lacZgene fusions and epitope-tagged versions of lin-9 .Preliminary experiments with the lin-9 -lacZfusions have produced staining only in the heads and tails of animals. Further experiments with additional lin-9 -lacZfusion constructs and with the epitope-tagged constructs are in progress.