Worm Breeder's Gazette 11(2): 108

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.

More on lin-15

R.K. Herman and E.M. Hedgecock

Recessive mutations in lin-15 lead to a multivulva (Muv) phenotype 
as a consequence of the expression of 1  or 2  fates by all members of 
the vulval equivalence group, P(3-8).p.  (In wild-type hermaphrodites, 
P3.p, P4.p and P8.p express 3  fates, and P(5-7).p express 2 , 1  and 
2  fates, respectively, and generate the vulva.) Because laser 
ablation of the anchor cell in lin-15 animals does not abolish the Muv 
phenotype,it has been proposed that the site of action of lin-15 is 
within the P(3-8).p cells themselves (Ferguson, Sternberg and Horvitz 
1987).
Duplication-loss-at-P1 mosaics: We have extended the result--
reported by RKH in the last issue of the WBG--that mosaics in which 
lin-15(+) is present among the descendants of AB, which includes P(3-8)
.p, but absent from descendants of P1 tend, unexpectedly, to be Muv.  
Zygotes of genotype unc-93: lin-15 
sup-10; cf)[unc-3(+)  
sup-10(+)] in which the duplication is lost at P1 
are non-Unc-93 non-Unc-3 and give all Unc-3 
geny.  Among 33 such animals, 23 had 1-3 
ventral protrusions at positions distinct from the vulva.  The P(3-8).
p cell lineages of four duplication-loss-at-P1 mosaics were followed.  
One was lin-15-like, one was wild-type and two were intermediate; in 
both of the latter animals, P(3-7).p gave essentially 1  or 2  lineage 
patterns, and P8.p was 3 .  Thus in three of the four animals, both P3.
p and P4.p displayed the lin-15 phenotype.  The nearest common 
ancestor of these cells is AB.p.  The non-Osm (ascertained by dye 
filling of amphid and phasmid neurons) non-Unc-3 phenotypes of all 
three animals indicated that the duplication was in fact present among 
the descendants of AB.p.  Thus lin-15 must be cell nonautonomous.
Duplication-loss-at-AB mosaics: loss of lin-15(+) by AB also 
produces a Muv phenotype.  For these mosaics unc-3 
sup-10(n983): were used; 
sup-10(n983) confers the rubber band phenotype and is recessive to sup-
10(+) (Greenwald and Horvitz 1986).  Duplication loss at AB or AB.p 
results in an Unc-3 non-rubber band animal that yields wild-type 
progeny.  Each of nine such animals was Muv (2-4 ventral protrusions).
The focus of lin-15 action is thus found among descendants of both 
P1 and (more strongly) AB.  We suggest that hyp7, which derives from 
both P1 and AB, may be the relevant tissue (see accompanying abstract).
An alternative possibility would involve an interaction between the 
gonad and the P(3-8).p cells.  We hope soon to test our prediction 
that the Muv phenotype observed in many loss-at-P1 mosaics is not 
dependent on the presence of gonadal cells, particularly an anchor 
cell.