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Comments on Nicole Fielenbach et al. (2001) International C. elegans Meeting "dre-1, a new heterochronic gene affecting gonadal and extragonadal developmental age" (0)
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Nicole Fielenbach, & Adam Antebi (2001). dre-1, a new heterochronic gene affecting gonadal and extragonadal developmental age presented in International C. elegans Meeting. Unpublished information; cite only with author permission.
The daf-12 nuclear hormone receptor specifies L3 options of dauer formation and reproductive growth, and couples dauer and heterochronic pathways. Genetic analysis suggests that daf-12 is necessary for dauer diapause, but only partly required for the promotion of reproductive growth. As evidence, candidate null mutants of daf-12 have completely penetrant dauer defective phenotypes, but impenetrant delayed heterochronic phenotypes starting in the third larval stage. In contrast, recessive gain-of-function alleles are dauer defective and display penetrant heterochrony in gonadal and extragonadal tissues. In a simple model, receptors of the gain-of-function alleles interfere with a redundant activity from another locus. If so, then screens for mutants that enhance the heterochronic phenotypes of daf-12 null alleles should reveal this activity. We identified one locus, dre-1 ( d af-12 re dundant function 1 ) in genome-wide genetic screens. Another locus, lin-46 , we found taking a candidate gene approach. Both loci interact with daf-12 in a stage and tissue-specific manner. dre-1 on its own displays an impenetrant heterochronic delay of adult programs in the seam and gonad. In dre-1daf-12 double mutants, the gonadal phenotype is dramatically enhanced. Notably, distal tip cells fail their L3 dorsal movements and instead migrate into head and tail, similar to daf-12 gain-of-function alleles. dre-1 maps to the center of chromosome V. We are currently positionally cloning dre-1 . lin-46 was first identified by Moss and Ambros, and has impenetrant delayed L3 and Adult seam phenotypes. daf-12 null mutants also show impenetrant L3 seam phenotypes. Double mutants display synergistic and penetrant heterochronic defects in the seam, but not the somatic gonad. In summary, dre-1 and lin-46 act in parallel to daf-12 to regulate third and later stage programs in gonadal and extragonadal tissues. Conceivably, the DAF-12 nuclear receptor may serve to coordinate heterochronic circuits in different tissues by a hormonal mechanism.