These studies will identify and characterize key components of the intrinsic genetic program that controls development and function of male germ cells. The approaches currently being applied are to identify genes expressed specifically in male germ cells, use the gene knockout approach to define the roles of the proteins they encode, employ yeast two-hybrid assays and deletion mutagenesis to identify protein-protein interactions essential for development of the male gamete, and prepare antisera to determine the temporal-spatial distribution of specific gene products. Many genes are expressed only in male germ cells and selected genes are being studied that encode proteins whose functions are essential for novel aspects of gamete development and/or function. (1) Initiation and progression of meiosis in male germ cells: Retinoic acid regulates entry into meiosis, but the timing of entry differs between male and female germ cells. We have identified a novel homeobox transcription factor RHOX13 and hypothesize that retinoic acid signaling involves activation of its gene. The Rhox13 gene is transcribed in male and female germ cells beginning on embryonic day E13.5. Translation of RHOX13 occurs in the E13.5 ovary and coincides with the entry of female germ cells into meiosis. Translation of RHOX13 begins on postnatal day P4 and proceeds male germ cells entry into meiosis. We hypothesize that the RNA-binding protein NANOS2 binds to the 3'UTR of the Rhox13 transcript to suppress its translation. Current studies are testing this hypothesis. (2) Regulation of meiotic progression in spermatogenesis: The mechanisms regulating transition from prophase I to metaphase I of meiosis during spermatogenesis are uncertain. Previous studies have suggested that proteins other than or in addition to CDK1 and Cyclin B1 may regulate this process during spermatogenesis. Conditional gene targeting approaches are being used to determine if these proteins are essential for the progression of meiosis in male germ cells. (3) The role of novel scaffold proteins and glycolytic enzymes in sperm motility: The flagellum is one of the most complex of all cell organelles and many of its proteins are encoded by genes expressed during post-meiotic haploid phase of spermatogenesis. We have used a variety of approaches to identify components of the fibrous sheath, a key cytoskeletal component of the sperm flagellum. These included structural proteins, signal transduction anchoring proteins, and glycolytic enzymes, most of which are encoded by genes only expressed in male germ cells. This led us to hypothesize thatmammalian sperm require ATP produced by glycolysis for motility and the fibrous sheath is an essential scaffold for the glycolytic enzymes. This hypothesis has been confirmed using gene targeting and current studies are determining how the different glycolytic enzymes and structural components of the fibrous sheath are assembled and how their functions are regulated.

Project Start
Project End
Budget Start
Budget End
Support Year
25
Fiscal Year
2011
Total Cost
$2,062,113
Indirect Cost
City
State
Country
Zip Code
Chen, Liang-Yu; Brown, Paula R; Willis, William B et al. (2014) Peritubular myoid cells participate in male mouse spermatogonial stem cell maintenance. Endocrinology 155:4964-74
Chaffee, Blake R; Shang, Fu; Chang, Min-Lee et al. (2014) Nuclear removal during terminal lens fiber cell differentiation requires CDK1 activity: appropriating mitosis-related nuclear disassembly. Development 141:3388-98
Brown, Paula R; Odet, Fanny; Bortner, Carl D et al. (2014) Reporter mice express green fluorescent protein at initiation of meiosis in spermatocytes. Genesis 52:976-84
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Eddy, Edward M; Chen, Liang-Yu (2013) Location, location, location: how does a spermatogonium know it is a spermatogonial stem cell (SSC)? Biol Reprod 88:132
Odet, Fanny; Gabel, Scott; London, Robert E et al. (2013) Glycolysis and mitochondrial respiration in mouse LDHC-null sperm. Biol Reprod 88:95
Xie, Fang; Eddy, Edward M; Conti, Marco (2013) Analysis of signaling pathways controlling flagellar movements in mammalian spermatozoa. Methods Enzymol 524:91-104
Arao, Yukitomo; Hamilton, Katherine J; Goulding, Eugenia H et al. (2012) Transactivating function (AF) 2-mediated AF-1 activity of estrogen receptor ? is crucial to maintain male reproductive tract function. Proc Natl Acad Sci U S A 109:21140-5
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Geyer, Christopher B; Saba, Rie; Kato, Yuzuru et al. (2012) Rhox13 is translated in premeiotic germ cells in male and female mice and is regulated by NANOS2 in the male. Biol Reprod 86:127

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