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Identification and characterization of factors functioning with EGL-38 PAX to regulate lin-48 in Caenorhabditis elegans

Tseng, Rong-Jeng

Abstract Details

2008, Doctor of Philosophy, Ohio State University, Molecular, Cellular, and Developmental Biology.

Pax genes are important in organogenesis during animal development. These genes affect the development of a range of different cell types, and promote cell proliferation and cell survival. Different functions are mediated through the regulation of different target genes, suggesting that cellular context plays an important role in Pax protein function. Pax proteins may function in a combinatorial manner with other proteins acting through separate enhancers. In C. elegans, genetic studies have shown that the Pax2/5/8 gene egl-38 functions in the development of several different cells and organ types including the egg-laying system, the hindgut, and the development of male mating spicules.

lin-48 is a direct target for EGL-38 in hindgut cells. To identify additional genes important for lin-48 expression, I have performed a genetic screen for altered lin-48::gfp expression pattern and identified mutant candidates that might mediate the response to EGL-38. Two major categories of mutant candidates were isolated. One category of mutants has reduced lin-48::gfp expression in the hindgut, which is a phenocopy of egl-38. The other category showed enhanced and ectopic GFP expression. The two categories represent candidates for positive and negative regulatory factors, respectively. Most mutants in both categories have pleiotropic mutant phenotypes but exhibit moderate to low penetrance for all defects. In addition, the newly isolated egl-38(gu22) allele was compared to previously described alleles to extend the analysis of each allele for a range of functions. Each egl-38 allele disrupts certain functions of egl-38 but they cannot be ordered into an allelic series. Instead, the alleles exhibit cell or tissue preferential defects compared to each other.

In many organisms, repetitive DNA serves as a trigger for gene silencing. However, some gene expression is observed from repetitive genomic regions such as heterochromatin, suggesting mechanisms exist to modulate the silencing effects. In this work, I identified mutations in two genes important for expression of repetitive sequences: lex-1 and tam-1. Here I show that lex-1 encodes a protein containing an ATPase domain and a bromodomain. LEX-1 is similar to the yeast Yta7 protein, which maintains boundaries between silenced and active chromatin. tam-1 has previously been shown to encode a RING finger/B-box protein that modulates gene expression from repetitive DNA. I found that lex-1, like tam-1, acts as a class B synthetic multivulva (synMuv) gene. However, since lex-1 and tam-1 mutants have normal P granule localization, it suggests they act through a mechanism distinct from other class B synMuvs. I observed intragenic (interallelic) complementation with lex-1 and a genetic interaction between lex-1 and tam-1, data consistent with the idea that the gene products function in the same biological process, perhaps as part of a protein complex. I propose that LEX-1 and TAM-1 function together to influence chromatin structure and to promote expression from repetitive sequences.

Helen M. Chamberlin (Advisor)
Amanda A. Simcox (Committee Chair)
138 p.

Recommended Citations

Citations

  • Tseng, R.-J. (2008). Identification and characterization of factors functioning with EGL-38 PAX to regulate lin-48 in Caenorhabditis elegans [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213384889

    APA Style (7th edition)

  • Tseng, Rong-Jeng. Identification and characterization of factors functioning with EGL-38 PAX to regulate lin-48 in Caenorhabditis elegans. 2008. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1213384889.

    MLA Style (8th edition)

  • Tseng, Rong-Jeng. "Identification and characterization of factors functioning with EGL-38 PAX to regulate lin-48 in Caenorhabditis elegans." Doctoral dissertation, Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213384889

    Chicago Manual of Style (17th edition)