Chuan Shen et al. (2005) International Worm Meeting "Hypoxia signaling and regulation of the hypoxia-inducible factor (HIF-1) in C. elegans"

Chuan Shen, Kelly Gillette, Sara McMaken, Jo Anne Powell-Coffman

[International Worm Meeting, 2005]

The C. elegans hif-1 gene is orthologous to the mammalian hypoxia inducible factor alpha units, transcription factors that play critical roles in oxygen homeostasis, development, and tumorgenesis [1-3]. Mutants lacking hif-1 function are viable in normoxic conditions, but they cannot adapt to hypoxia [2]. Oxygen-dependent degradation of HIF-1 protein is regulated by the evolutionarily conserved EGL-9/ VHL-1 pathway [3]. To better understand the role of HIF-1 in hypoxia response and to obtain a molecular description of HIF-1 function, we compared mRNA expression patterns in wild-type, hif-1-deficient, and vhl-1-deficient worms under normoxia and hypoxia using full-genome microarrays. We identified 110 hypoxia-regulated gene expression changes in wild-type worms, 63 of which require hif-1 function. This establishes that C. elegans HIF-1 has a central role in transcriptional response to hypoxia [4]. We designed genetic strategies to identify genes that regulate HIF-1 function (rhy genes: regulators of hypoxia-inducible factor). The microarray data allows us to diagnose mutant phenotypes at a molecular level and prioritize mutants for further study. rhy-1 is a potential negative regulator of HIF-1. In C. elegans carrying a loss-of-function mutation in rhy-1 or in worms treated with rhy-1 RNAi, HIF-1 target genes are over-expressed. In contrast, genes that are induced by hypoxia independent of hif-1 function are not misexpressed in rhy-1 mutants. This indicates that rhy-1 acts specifically to negatively regulate HIF-1 transcriptional activity. We are in the process of further characterizing the mechanisms by which RHY-1 regulates HIF-1 function, and we are working towards molecular characterization of additional rhy genes. 1. Semenza G. (2000) J Appl Physiol, 88: 1474-1480 2. Jiang et al. (2001) Proc Natl Acad Sci USA, 98(14): 7916-21 3. Epstein et al. (2001) Cell, 107(1): 43-54 4. Shen et al. (2005) JBC in press

Sara Vassalli et al. (2006) European Worm Meeting "Identification of Genes required for Anchor Cell Attachment and Invasion during Vulval Development"

ALEX HAJNAL, Sara Vassalli

[European Worm Meeting, 2006]

Sara Vassalli and Alex Hajnal. During vulval development in the hermaphrodite, three out of six equivalent vulval precursor cells (the VPCs P3.p to P8.p) are induced by a signal from the gonadal anchor cell (AC). The LIN-3 EGF growth factor produced by the AC activates the EGFR/RAS/MAPK pathway in the VPCs to specify the primary cell fate. Prior to vulval induction, the gonad is separated from the VPCs by two basal laminas covering each tissue such that the position of the AC relative to the VPCs is variable when the animal moves. At the time of vulval induction in the early L3 stage, however, the AC attaches to the basal side of the future primary cell P6.p. After the first round of vulval cell divisions (Pn.px stage), the basal laminas separating the gonad from the vulval cells start to dissolve precisely under the AC. After the second round of divisions (Pn.pxx stage), the basal laminas between the AC and the four primary vulval cells are interrupted, and the AC invades the vulval tissue.. While the mechanism of vulval induction is well studied, less is known about genes regulating the attachment of the AC to P6.p and the following invasion step. To study these two processes, we performed a forward genetic screen for mutants with defects in AC positioning and/or invasion. Since worms with an abnormal or missing connection between the gonad and the vulva usually display a protruding vulva (Pvl) phenotype, we first screened for animals with a Pvl phenotype and then examined them for defects in the positioning or invasion of the AC. Among 5300 F1 clones, we identified 8 sterile mutants with a misplaced AC and 2 mutants, in which the AC is normally positioned but fails to dissolve the basal laminas and invade the vulval tissue. Details about the cloning and analysis of the genes identified in this screen will be presented at the meeting.