Worm Breeder's Gazette 10(1): 110
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.
mab-9(e1245) males have highly abnormal tails, with internal structures (spicules, gubernaculum) missing, constipation and defective tail morphogenesis. A small percentage of mab-9 hermaphrodites are also constipated. As reported at the worm meeting this May, analysis of the tail lineages of mab-9 males indicated that the primary defect was in the B lineage, which appears partially transformed towards a Y-like lineage (see figure). Ventral and lateral hypodermal lineages are wild-type. Observations on mab-9 hermaphrodites suggested that an analogous B-to-Y transformation was also occurring. Such transformations could account for the gross mutant phenotypes observed. nDf3 (Greenwald & Horvitz, 1980) does not complement e1245. Of 5 e1245/nDf3 males lineaged, 2 showed a virtually complete transformation of B to Y, including the division of the most posterior daughter in L3 (see figure). The other 3 worms had lineage patterns typical of e1245 homozygotes. No new lineage defects were seen; the terminal phenotype of the deficiency heterozygote is within the observed range of e1245. Therefore e1245 is not null, but it is probably close. Analysis of the U and F lineages up to the L3 moult in 3 mab-9 males revealed that the divisions of F.lv and F.rv at about 1.5h after their formation (i.e., at 30.5h) does not occur. Variable divisions of the dorsal and ventral daughters of F.l and F.r occur at around 34h, synchronously with the divisions of U.la and U.ra (if they occur). Thus, F appears to execute a U-like lineage; whether this is a primary or secondary effect of the mab-9 mutation is not clear. The lineage defect in e1245 males is suppressed by one or two copies of the amber suppressor sup-5(e1464). The B lineage in mab-9;sup-5 males is wild- type as far as late L3: good spicules are made. However tail morphogenesis is not perfect, and the spicules are slightly protruding (even at 15 C), probably due to incomplete suppression. Other amber suppressors are being tested. In lin-12(0) males, Y is transformed into the neuron DA9 (Greenwald et al. 1983). If B is being transformed into Y in mab-9, one might predict a further transformation in the double mutant, or at least some reduction in cell proliferation. To test this prediction, the strain e1245:lin-12(n137n720)unc-32(e189);e1490 was constructed. Males of this strain are very ill (most die before or during L1), but partial lineages from two worms showed no such interaction: B still executes a Y-like lineage. This is confirmed by spot checks of several worms of this genotype and of an analogous strain using lin-12( n676n909). This negative result may indicate that B is not being transformed into Y in mab-9, but alternative explanations are possible. For instance, it could be argued that the wildtype role of lin-12 is not to specify Y-ness but to control a more basic decision (e.g., blast cell/neuron). The information necessary to execute a Y lineage would therefore be extant in the double mutant, and could be used by the transformed B cell. To clarify the nature of the null phenotype of mab-9, I am currently screening for more alleles of the locus.