Worm Breeder's Gazette 9(3): 45
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.
As part of our continuing analysis of essential genes on the left third of LG I, we have been testing our sDp2-rescued lethals for complementation with previously defined genes in the region. To our surprise, we have found lethal alleles of two genes which were not known to be essential genes. We have recovered an EMS-induced lethal allele of bli-4 and both EMS and gamma radiation-induced lethal alleles of him-l.The lethal allele of bli-4, h42, maps half way between dpy and unc-13. The phenotype of bli-4(e937)/bli-4(h42) is blistered, whereas bli-4 (h42) is a recessive lethal mutation. h42 also fails to complement let-77 (s90) which maps to the left of dpy-14. h42 may be a small deficiency of bli-4 and let-77, however, since we use a low dose of EMS (0.012 M), it is unlikely that h42 is a deficiency. It seems more likely that bli-4 and let-77 are really the same gene. Complementation between e937 and s90 is being done. Both the EMS- (h134) and gamma-induced (h55) recessive lethal alleles of him-l map 0.5 map units to the left of (or above?) dpy-S, exactly where the original (and only) allele (e879) was mapped [Hodgkin, Horvitz and Brenner (1979) Genetics 91: 67-94]. The lethal alleles have a similar late larval or sterile adult phenotype. e879 produces about 20% males by X nondisjunction and reduces recombination on the X-chromosome specifically. Worms carrying h134 in trans to e879 are very sick and produce 10 - 20% males. e879 is slightly semidominant with e879/+ giving 1 - 2% male progeny. Our lethal alleles also behave semidominantly: h134/+ produces about 1% males and +(sDp2)/h134/h134 produces 1 - 2 % males. Interestingly, sDf4, which deletes him-l, also has a mild Him phenotype. It is surprising that a gene which was thought to affect only the X-chromosome would have lethal alleles. One hypothesis is that the wild type him-l gene product is required for proper pairing, recombination and segregation of all chromosomes at meiosis. e879 may be a weak hypomorphic allele which can take care of the autosomes but can't manage the X. Our lethals could be loss of function alleles which do not allow meiosis to proceed at all, leading to sterility. We will use sup-7 [Waterston ( 1981) Genetics 97: 307-325] to try to determine if these are amber alleles. To update the last newsletter note about gamma-induced sDp2 lethals - - None of the lethals fails to complement more than one complementation group. If any of them are deficiencies, they must be small. It may be that sDp2 is not very good at rescuing deficiencies. We are currently analyzing a set of gamma-induced lethals balanced over szT1 (I;X). end-body i