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Comments on Antebi A et al. (1995) International C. elegans Meeting "daf-12, A HETEROCHRONIC GENE THAT CONTROLS CONTINUOUS AND DAUER DEVELOPMENT" (0)
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Antebi A, & Hedgecock EM (1995). daf-12, A HETEROCHRONIC GENE THAT CONTROLS CONTINUOUS AND DAUER DEVELOPMENT presented in International C. elegans Meeting. Unpublished information; cite only with author permission.
Heterochronic genes control the temporal program of larval development. Mutations can advance or delay the maturation of individual tissues. We have identified two heterochronic loci, daf-12 and mig-8, that control gonadal development. These mutations prevent or delay the cell migrations that determine the reflexed shape of the mature gonad (Mig phenotype). daf-12 also regulates hypodermal development. In mutant animals, the seam cells repeat the L1 molt division pattern at the L2 molt. During the L4 intermolt, seam cells often fail to make the larval/adult fate switch, and repeat their stem-cell like division pattern, resulting in gaps in the lateral alae (Lin phenotype). daf-12 also controls the choice between continuous versus dauer development. Depending upon allele, these mutants are defective in dauer formation (Daf-d phenotype), or form dauers constitutively under non-inducing conditions (Daf-c). daf-12 lies at the convergence of dauer and heterochronic pathways. In the dauer pathway, daf-12 integrates inputs from neurosensory and BMP signaling pathways to implement dauer or continuous development (Riddle et al. 1981; Estevez et al 1993; Thomas et al., 1993). In the heterochronic pathway (Ambros, 1989), daf-12 appears to act downstream of lin-14 (and its negative regulator lin-4), but upstream of lin-28 and lin-29. Like lin-14 and lin-28, daf-12 phenotypes are suppressed by dauer development. The various daf-12 phenotypes (Mig, Lin, Daf) are expressed by L3. Experiments with a heat-sensitive allele are consistent with a requirement for daf-12 by L2. daf-12 is a complex locus with six distinct classes of alleles which express either one, two or all three phenotypes. daf-12(+) encodes a nuclear hormone receptor (D. Riddle, P. Larsen, W.Yeh p.c.), suggesting that the temporal program of larval development is coordinated hormonally in nematodes.