Sexual dimorphism is a fundamental feature of virtually all animals, affecting many tissues and cell types in the body. In the nematode Caenorhabditis elegans, the activity of a single gene, tra-1, is necessary and sufficient to dictate whether the entire body develops as male or female. If tra-1 is active, all tissues differentiate as female, whereas if tra-1 is inactive, all tissues differentiate as male. Thus tra-1 is an ideal candidate for study of sexual differentiation. In addition, C. elegans is an ideal organism for such studies because the two sexes differ extensively, development can be analyzed at the single cell level, and powerful molecular and genetic tools exist. In this project I want to answer two basic questions: first, what controls the activity of tra-1, and second, when tra-1 is active, what genes does it, in turn, control to cause female sexual differentiation. Elegant genetic studies have shown that a series of negative regulators converts the X chromosome to autosome ratio of the embryo into an 'on' or 'off' state of tra-1. How is this accomplished? Molecular and genetic studies of tra-1 revealed that control of its activity requires a short domain of the TRA-1 protein. To identify regulators that bind this domain and inactivate TRA-1, we are performing a yeast two-hybrid screen. We will identify proteins that bind to the critical domain of TRA-1 and test their function in vivo. Using this portion of TRA-1 as a 'bait', we have already identified several promising candidate regulators which we propose to study further. These experiments will complete the link between upstream regulators and tra-1. How does tra-1 direct sexual differentiation? To find out, I propose to study genes that are regulated by tra-1, using two approaches. The first is to study mab-3, a gene whose properties (a sexual regulator acting downstream of tra-1) suggest it is a tra-1 target. mab-3 has been localized to a short chromosomal interval by transformation rescue, and will be cloned. mab-3 will be tested for transcriptional regulation by tra-1, and its role in regulating yolk protein expression in the intestine will be studied. The second approach is to identify new genes that are controlled by tra-1, using a representational difference analysis (RDA) PCR method. I will identify sex-specific mRNAs from the two sexes. From this screen, I will select a small number of genes for further study, concentrating on those that appear to be directly regulated by tra-1. These experiments will ultimately reveal in molecular detail how tra-1 controls sexual differentiation.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM053099-03
Application #
2750048
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1996-08-01
Project End
2001-07-31
Budget Start
1998-08-01
Budget End
1999-07-31
Support Year
3
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of Minnesota Twin Cities
Department
Genetics
Type
Schools of Medicine
DUNS #
168559177
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
Weinberg, Peter; Berkseth, Matthew; Zarkower, David et al. (2018) Sexually Dimorphic unc-6/Netrin Expression Controls Sex-Specific Maintenance of Synaptic Connectivity. Curr Biol 28:623-629.e3
Zhang, Teng; Zarkower, David (2017) DMRT proteins and coordination of mammalian spermatogenesis. Stem Cell Res 24:195-202
Kroetz, Mary B; Zarkower, David (2015) Cell-Specific mRNA Profiling of the Caenorhabditis elegans Somatic Gonadal Precursor Cells Identifies Suites of Sex-Biased and Gonad-Enriched Transcripts. G3 (Bethesda) 5:2831-41
Murphy, Mark W; Lee, John K; Rojo, Sandra et al. (2015) An ancient protein-DNA interaction underlying metazoan sex determination. Nat Struct Mol Biol 22:442-51
Berkseth, Matt; Ikegami, Kohta; Arur, Swathi et al. (2013) TRA-1 ChIP-seq reveals regulators of sexual differentiation and multilevel feedback in nematode sex determination. Proc Natl Acad Sci U S A 110:16033-8
Chong, Tracy; Collins 3rd, James J; Brubacher, John L et al. (2013) A sex-specific transcription factor controls male identity in a simultaneous hermaphrodite. Nat Commun 4:1814
Gamble, Tony; Zarkower, David (2012) Sex determination. Curr Biol 22:R257-62
Matson, Clinton K; Zarkower, David (2012) Sex and the singular DM domain: insights into sexual regulation, evolution and plasticity. Nat Rev Genet 13:163-74
Arur, Swathi; Ohmachi, Mitsue; Berkseth, Matt et al. (2011) MPK-1 ERK controls membrane organization in C. elegans oogenesis via a sex-determination module. Dev Cell 20:677-88
Kalis, Andrea K; Murphy, Mark W; Zarkower, David (2010) EGL-5/ABD-B plays an instructive role in male cell fate determination in the C. elegans somatic gonad. Dev Biol 344:827-35

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