Suppressors of
let-60 Dominant Negative Mutations Trent Gu and Min Han Department of MCD Biology, University of Colorado, Boulder The gene
let-60 ras plays a key role in a genetic pathway that specifies the vulva cell fate. Loss of function (lf) mutations of
let-60 cause Vul (and therefore is egg laying defective), in which all of the VPCs take on the hyperdermal cell fate. Hyperactive mutations or gain of function (gf) of
let-60 cause Muv, in which more than three VPCs are differentiated to become vulva cells. Ras is used to transmit cell growth signals in many organisms from yeast to human. Studying the role of
let-60 ras pathway in C. elegans will help in understanding the Ras signal transduction pathway in other organisms. How the
lef-60 ras pathway is negatively controlled is not well understood. For example, we don't know how the kinases downstream of
let-60 ras are kept inactive. To isolate the negative regulators downstream of
let-60 ras, we have screened and isolated suppressors that revert the Vul phenotype caused by a
let-60 ras dominant-negative (dn) mutation. Seven different genes are identified from fourteen recessive extragenic suppressors. The preliminary mapping and complementation results of nine recessive extragenic suppressors are shown below The suppression of
let-60 (dn) by
ku105 is not allele specific since
ku105 can suppress three different
let-60 (dn) alleles:
sy94,
syl01,and
syl00.
ku105 homozygous suppress
let-60(dn) better than
ku105/Df, indicating that
ku105 is possibly a recessive antimorph. Since previous genetic study suggests that the
let-60 ras (dn) mutation decreases the pathway's activity (thus leading to the vulvaless phenotype), potential suppressors are expected to increase or restore the normal activity of the pathway.