Worm Breeder's Gazette 14(2): 37 (February 1, 1996)
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.
Division of Biological Sciences, University of Missouri, Columbia, MO 65211
The commitment to non-dauer development is made prior to the L1 molt
(Swanson and Riddle, Dev. Bio. 84: 27) when amphid neurons detect a
favorable ratio of food to pheromone in the environment. Our lab has
previously described the cloning of genes involved in the regulation of
this developmental decision. Three of these genes encode components of
a TGF-ß regulated signalling pathway: daf-7 = a novel TGF-ß ligand (Lim,
et al., WM93: 15), daf-1= a type-1 TGF-ß-like receptor (Georgi et al.,
Cell 61: 635), and daf-4 = a type-2 BMP/dpp-like receptor (Estevez, M.
et al., Nature 365: 644). Mutations in any one of these three genes
results in constitutive dauer larva formation (Daf-c). Additional
phenotypes associated with mutations in the daf-4 gene are small body
size (Sma) and male tail defects (Mab). Mutations in the daf-8 gene are
Daf-c, and all four genes have been placed at the same step in an
ordered genetic pathway. Here we describe the cloning of the daf-8
gene.
Three transposon alleles of daf-8 were generated. A region
flanking a novel Tc1 insertion site was cloned and used to confirm the
genomic position of the fragment in the daf-8 region. Overlapping
cosmids in this area have been restriction mapped and the areas
corresponding to the Tc1 flanking sequence cloned. Approximately 3 kb
of genomic sequence has been determined and the largest open reading
frame encodes a MAD/dwarfin homolog. So far, DAF-8 is most similar to
the Drosophila MAD protein (~70%). The MAD protein was isolated in a
genetic screen for enhancers of dpp (Raferty et al., Genetics 139: 241)
and is believed to be a downstream effector for dpp signalling (Sekelsky
et al., Genetics 139: 1347). Mutants in sma-2, -3, and -4 encoding the
dwarfin protein family (Savage et al., WBG 13.5, 74 ) are Sma and Mab,
but not Daf-c. The daf-8 mutants are Daf-c, but not Sma or Mab.
The DWARFINS are believed to be cytoplasmic proteins, but
nothing is known about how they function in the cell. Since the sma and
daf-8 mutants all exhibit aspects of the daf-4 phenotype, it is
possible that these proteins all act downstream of the daf-4 receptor,
but at different developmental time points and/or in completely
different cells. Further experiments are in progress to address these
questions.