Worm Breeder's Gazette 10(1): 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.
Temperature sensitive period for the M lineage defect Many of the cells that are affected in lin-12 mutants require cell- cell interactions for the specification of their fates. The temperature sensitive periods (TSPs) for lin-12 activity for the hermaphrodite cells Z1.aaa/Z4.ppp and P(3-8).p coincide with the times their fates are determined in wild-type, implying that lin-12 acts or is synthesized at those times. The M lineage progeny M(d/v)(l/r)pa are also affected in lin-12 mutant hermaphrodites (see Table 1). Unlike the other groups of cells affected by lin-12 mutations, laser ablation experiments have not demonstrated cell interaction among M lineage progeny (C. Kenyon, J. Thomas, personal communication). During the course of studying non-null revertants of lin-12(d) alleles, we identified an allele that is t.s. for the M lineage defect: at 20 C, 2/31 hermaphrodites have ventral coelomocytes (cc), whereas at 25 C, 17/25 hermaphrodites have ventral cc. To determine the TSP for lin-12 activity in the M lineage, hermaphrodites grown at 20 C or at 25 C were staged according to the number of M cell progeny, shifted to the appropriate temperature, and subsequently scored for the presence of ventral cc. The data in Table 2 demonstrate the TSP for lin-12 activity in the M lineage is when the lineally-homologous M. (d/v)(l/r)pa are born, suggesting that their fates are not determined before this time. The question of whether cell-cell interactions are important for the specification of their fates awaits genetic mosaic analysis, which is in progress. [See Figure 1] [See Figure 2] lin-12(0) hermaphrodites are essentially sterile. Tim Schedl isolated q269, a weakly fertile mutation, which we subsequently demonstrated is an allele of lin-12. Tim observed that, in adult hermaphrodites, the proximal as well as the distal arms contained undifferentiated cells that are morphologically similar to germ cells: in the 'loop' region, the germ line differentiated into sperm and a few oocytes. Other recessive lin-12 alleles, including an amber lin- 12(0) mutant, all show the same germ line phenotype. We thank Tim for sending us q269 and for helping us identify the lin-12(0) germ line phenotype.