Histone deacetylases (HDACs) are an ancient class of enzymes that have
been conserved throughout evolution and are found in diverse organisms such as
animals, plants, fungi, eubacteria and archaebacteria. In C. elegans, twelve
HDACs have been identified so far. These HDACs have been grouped into four
different classes (Class I, II, III and IV) based on their cofactor requirements and
sequence homologies. hda-1 is one of the three Class I HDACs in C. elegans and
plays a role in the morphogenesis of several organs including the vulva. This thesis focuses on the role of hda-1 in vulval morphogenesis. The hermaphrodite vulva has twenty-two cells which can be further divided into seven different cell types: VulAs, VulBls, VulB2s, VulCs and VulDs (secondary great granddaughters), YulEs and VulFs (primary great granddaughters). The analysis of expression pattern of hda-1 revealed that hda-1 is expressed in the progeny of
both the primary and secondary vulval precursor cells (VPCs). To examine hda-1 mutant phenotype in detail, I examined the expression pattern of five different vulval cell-type specific markers (cdh-3, zmp-1, ceh-2, egl-17 and daf-6) in hda-1 animals. The results revealed that hda-1 is necessary for proper differentiation of multiple vulval cell types. To study the evolutionary conservation of hda-1 function, I examined the role of hda-1 ortholog in C. briggsae. C. briggsae is a close relative of C. elegans and has almost identical vulval morphology. Knocking down Cbr-hda-1 in C. briggsae animals resulted in defective vulval phenotype. Consistent with this
result, the expression of two cell- fate specific markers (C. briggsae orthologs of zmp-1 and egl-17) was found to be altered in Cbr-hda-1 RNAi treated animals. Thus, hda-1 function in the vulva appears to be conserved in these two species. To identify the hda-1 targets in vulval morphogenesis in C. elegans, microarray approach was taken. Two genes fos-1 and lin-29 were identified as putative targets and were examined in some detail. Among the targets identified
(these still need to be validated), I focused on fos-1 and lin-29 for detailed
investigation. The RNAi-mediated knockdown of hda-1 caused alterations in the
expression pattern ofthefos-1 transcript,fos-1b. To examine interaction between
fos-1 and lin-29, I used double RNAi approach and examinedfos-1 (RNAi), lin-
29 (RNAi), hda-1 (cw2) animals. It was found that fewer animals exhibit defects
in vulval morphology in these animals as compared to fos-1 (RNAi), hda-1 (cw2)
animals. While this suggests a possible interaction between lin-29 and hda-1 in
the vulva, these results need to be validated by doing additional experiments. In summary, the work described in this thesis demonstrates that hda-1 plays an important role in vulval morphogenesis and regulates the expression of several important genes. Also, the function of hda-1 in C. elegans and C. briggsae
is evolutionarily conserved. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21729 |
| Date | 09 1900 |
| Creators | Joshi, Katyayani |
| Contributors | Gupta, Bhaqwati, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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