Two studies in the nematode Caenorhabditis elegans: Part I. Gon-4: An organ-specific cell cycle regulator. Part II. Prolyl-4-hydroxylase: A critical enzyme required for morphology and viability.

摘要

This thesis uses Caenorhabditis elegans to study two aspects of animal development: Organogenesis and Structure.; The gon-4 gene is required for gonadogenesis in C. elegans. Normally, two somatic gonadal precursor cells, Z1 and Z4, and their descendants follow a reproducible pattern of cell divisions with respect to timing, plane of division and subsequent fates. By contrast, in gon-4 mutants, the somatic gonadal lineages are severely defective: Z1 and Z4 divisions occur much later than normal; subsequent cell divisions are delayed or absent. Development of the germ line and vulva is also aberrant. The adult gonads of gon-4 mutants exhibit a variable phenotype with respect to size, shape and extent of differentiation; normal somatic gonadal structures are never observed. The lineages of non-gonadal tissues (except the vulva) and the timing of development (e.g. molts) appear unaffected in gon-4 mutants. The gon-4 alleles are predicted to be strong loss-of-function or null alleles by both genetic and molecular criteria. We conclude that gon-4 is a gonad-specific cell lineage regulator and suggest that it is part of a genetic program common to the regulation of gonadogenesis. We have cloned gon-4 and analyzed its products. gon-40 produces a single transcript that encodes a novel, acidic, nuclear protein. A GON-4::GFP fusion protein that rescues a gon-4 mutant to fertility is present in somatic gonadal precursor cells, suggesting that gon-4 acts cell-autonomously.; Part II demonstrates the role of prolyl 4-hydroxylase in C. elegans . The C. elegans genome possesses two genes, dpy-18 and phy-2, that encode α-subunits of the enzyme prolyl 4-hydroxylase. We have generated deletions within each gene to eliminate prolyl 4-hydroxylase activity from the animal. The dpy-18 mutant has an aberrant body morphology, consistent with a role of prolyl 4-hydroxylase in formation of the body cuticle. The phy-2 mutant is phenotypically wild-type. However, the dpy-18; phy-2 double mutant is not viable, suggesting an essential role for prolyl 4-hydroxylase that is normally accomplished by either dpy-18 or phy-2. The effects of the double mutation were mimicked by small-molecule inhibitors of prolyl 4-hydroxylase suggesting that C. elegans can serve as a model system for the discovery of new inhibitors.