Worm Breeder's Gazette 15(4): 41 (October 1, 1998)
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.
Max-Planck Institut für Entwicklungsbiologie, Abt. Zellbiologie, Spemannstrasse 35, 72076 Tübingen, Germany.
In Pristionchus pacificus, seven of the twelve ventral epidermal cells die of programmed cell death during late embryogenesis. Ppa-lin-39(tu29) mutant animals are vulvaless and egg-laying defective because P(1-11).p undergo programmed cell death (Eizinger & Sommer, Science 278, 452-455). In contrast, Ppa-lin-39; Ppa-ced-3 double mutants have a functional vulva and they are egg-laying positive (see previous WBG article). This observation can be used to isolate cell death mutants in a Ppa-lin-39 suppressor screen. In a mutagenesis screen in a Ppa-lin-39 mutant background (egg-laying defective), suppressors can be identified by the reappearance of eggs (egg-laying positive). Such a screen can be performed to isolate general cell death defective mutations, but also to isolate genes that affect the programmed death of only certain cells. Such "specific" cell death genes might be involved in the regulation of the cell death in the ventral epidermal region but not in the regulation of the death of other cells that die in wild-type animals. Such genes might act like a local "killer" signal which activates the cell death machinery in P(1-4,9-11).p. As egg-laying screens are not very labour intensive, one can perform large-scale screens and thus, one might be able to saturate for potential "specific cell death" genes. To look for the existence of such a killer signal in the P. pacificus ventral epidermis, we have carried out a suppressor screen in the Ppa-lin-39(tu29) mutant background. We have EMS-mutagenized approximately 60 000 gametes and have isolated 16 suppressors that are egg-laying positive. Nomarski observation indicated that in all 16 suppressors all 12 Pn.p cells are present. P(1-4).p and P(8,9).p have an epidermal fate, P(5-7).p form the vulva and P11.p and sometimes P10.p differentiate in the pre-anal region. After outcrossing, these suppressors keep the cell death defective phenotype. Genetic complementation tests revealed, that all 16 suppressors are allelic to Ppa-ced-3. This has been confirmed by identifying molecular lesions in the Ppa-ced-3 gene in five alleles. Thus, the Ppa-lin-39 suppressor screen indicates a strong bias towards the isolation of Ppa-ced-3 alleles. In addition, there is no indication that a killer signal acts to specifically induce the cell death of P(1-4,9-11).p and thus, no "specific cell death" genes have been identified.