Worm Breeder's Gazette 12(3): 69 (June 15, 1992)
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.
Mutations in lin-19 and lin-23 cause hyperplastic growth in multiple tissue types. Homozygous lin-19 or lin-23 progeny from heterozygous parents proceed through embryogenesis normally. The onset of blast cell proliferation is not accelerated. However, once blast cells start to proliferate they produce an excess of cells. The exact division pattern is different from larva to larva. In mutants homozygous for lin-23 ,all larval blast cells, except germ cells, are affected and produce on average about two times the number of descendents. In mutants homozygous for lin-19 ,only those blast cell divisions which occur after L1 stage, including germ cells, are abnormal, producing on average four times the normal number. Homozygous lin-19 and lin-23 hermaphrodites are sterile and die prematurely in L4 stage or as adults.
The lin-19 gene has been mapped to chromosome III between unc-69 and vab-7 [ unc-69 (1/16) lin-19 (15/16) vab-7 ].Cosmids spanning the region of interest were microinjected with rol-6 DNA to rescue the lin-19 phenotype. Two overlapping cosmids, W01G9 and W04F9 ,rescued lin-19 .The lin-19 gene has been further mapped to a region smaller than 7.8 kb. A cDNA which maps to this region has been obtained and is being sequenced.
The lin-23 gene has been mapped to chromosome II between lin-4 and dpy-10 [ lin-4 (10/17) lin-23 (7/17) dpy-10 ].Again, cosmids spanning the region of interest were microinjected with rol-6 DNA to rescue the lin-23 phenotype. Two overlapping cosmids, F58F12 and T25H2 ,rescued lin-23 .Subcloning the cosmids to delineate the position of lin-23 is now underway.
Stable rescued lines of homozygous lin-19 and lin-23 produced a high proportion of inviable eggs. Because inviable eggs are not observed from heterozygotes containing the stable arrays, the eggs are inviable from a lack of lin-19 or lin-23 product rather than from an excess of lin-19 or lin-23 product from the cosmid arrays. Evidently, both maternal lin-19 and lin-23 product are required for embryogenic development. The majority of inviable eggs from rescued lin-19 homozygotes arrest with many cells in a disorganized mass, although other arrest phenotypes are also obtained, from less than 60 cells to the three fold stage. The various arrest phenotypes are perhaps due to differential amounts of message from the array. A detailed study of arrested eggs from rescued lin-23 homozygotes has not been made yet.