Two alleles of the gene un-32, el 926 and
u282, have been isolated by Kenyon and Hedgecock (l) and Chalfie and Au (2) respectively. A third allele,
bx46, was isolated in our lab in a screen for Mab (male abnormal) mutations. The phenotype of a
lin-32 mutant is loss of both V-rays and Trays in the male. We do not believe that any of the three alleles of
lin-32 is a null, because none are completely expressive, and because strong alleles of
lin-32, which are also touch insensitive, are rare (2). We have scored over 6,000 chromosomes in a non- complementation screen using the touchinsensitivity of 11282 allele, but no new allele of
lin-32 has yet been isolated. This suggests to us that the null allele of
lin-32 could be lethal in heterozygous combination with
u282 allele. We are in the process of creating deficiencies that uncover
lin-32 to test this hypothesis. Lineage analysis has been done on
lin-32(
el926) by Kenyon and Hedgecock (1). They found that
lin-32(
el926) caused the Q, postdeirid, and ray neuroblast cells to adopt certain hypodermal fates, and suggested that
lin-32 functioned in a switch between certain hypoderrnal and neuronal cell fates. Mutations in two genes,
lin-22 and
mab-21, have the opposite effects. In
lin-22 males, Vl-VS cells produce up to 10 pairs of ectopic rays (3); in
mab-21 males, T.apapa cells produce one pair of ectopic rays. We constructed
lin-22(
mu2);1in- 32
(u282) and
mab-21(bxS3);1in-32
(u282) double mutants and found that
lin-32 was epistatic to
lin-22 and
mab-21 in blocking the formation of ectopic rays. Therefore,
lin-32 appears to act downstream of
lin-22 and
mab-21. Interestingly, we found that
lin-32 mutation may also affect certain hypodennal cell fates; it may transform the ectopic Rn. p cells generated in the
lin-22 mutant from non-alae producing cells to body seam cells and thereby produce almost intact alae in the
lin22; 1in-32 double mutant. We are currently in the process of cloning the
lin-32 gene. We are identifying Tcl-polymorphic loci closely linked to
lin-32, in preparation for attempting transformation rescue.