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Feinbaum RL, & Ambros VR (1991). NEW ALLELES OF LIN-4 presented in International C. elegans Meeting. Unpublished information; cite only with author permission.
Based on the phenotype of the single lin-4 allele, (e912), it has been proposed that lin-4 acts at the top of the heterochronic regulatory pathway and controls the activity of lin-14. In order to further understand the role of lin-4 in the temporal control of development we have begun to isolate new alleles of this gene by non- complementation and to identify the null phenotype. Because no new alleles of lin-4 have been identified in numerous general screens for egl or vul animals (where they might have been expected to turn up) and no deficiency of the lin4 locus existed, our first non- complementation screen was aimed at isolating a deficiency of the lin- 4 locus. Wild type N2 males were mutagenized with gamma rays, mated by lin-4(e912)dpy-101mncl; lin-14(nl 79ts) hermaphrodites and the Fl hermaphrodite progeny were screened at 20 C for non-dpy lin-4 like animals. Out of 7,000 Fl hermaphrodites screened, one lin-4 deletion mutant (maDf4) was identified. maDf4 is homozygous inviable and fails to complement lin-4 as well bli-2, clr-l, and unc-85 that map to the left of lin-4. maDf4 does not delete spe-3, a gene that maps only 0.1 mu to the right of lin4. However, Southern blot analysis has shown that maDf4 deletes a 5kb EcoRI fragment (see Lee et al.) that rescues the lin4 mutant phenotype, suggesting that maDf4 does not retain functional lin-4 sequences. Based on analysis using a dissecting microscope, the phenotype of lin4(e912) dpy-l OlmaDf4 animals is indistinguishable from that of lin4(e912)11in4(e912) animals (with the exception of an enhanced sterility of lin4(e912) dpy-lOlmaDf4 animals). These data suggest that the original lin-4(e912) allele is not a gain- of-function allele and indicates that lin4(e912)1null is fertile and viable. Since lin-4(e912)1maDf4 is not significantly different from lin-4(e912)11in-4(e912), lin-4(e912) is probably null or close to null. Encouraged that we knew the expected phenotype of lin4(e912)11in4( null) we have intiated a new series of non-complementation screens to identify EMS induced lin-4 alleles. Out of 8,000 Fl hermaphrodites screened so far we have identified one new lin4 allele, (mal 61). mal 61 looks phenotypically similar to e912 but Southern blot analysis has confirmed that it is in fact a new allele of lin4.