Mammalian spermatogenesis is supported by a robust stem cell system that exquisitely balances self renewal with differentiation. Spermatogonial stem cells (SSCs) and their progenitors lie on the basal side of the Sertoli cell tight junctions and therefore outside the blood-testis barrier making them readily accessible targets for contraceptive intervention. Cells that manifest stem cell properties reside within a population of cells referred to as undifferentiated spermatogonia (Aundiff)- Different cells within the Aundiff population contribute to the stem cell pool during steady state spermatogenesis than during regeneration. Our proposed studies address the regulation of local signaling within the stem cell niche as well as germ cell intrinsic factors that regulate stem cell self-renewal, proliferation and differentiation. We propose that heparin sulfate proteoglycans (HSPGs) within the extracellular matrix (ECM) and on the surface of SSCs regulate the bioavailability of glial cell line-derived neurotrophic factor (GDNF), a critical signaling molecule expressed by Sertoli cells that is required for stem cell self-renewal. Using a combination of live cell imaging of fluorescently labeled SSCs in seminiferous tubule explants, germ cell transplantation and gerietic analysis in vivo, we will test the hypothesis that GDNF regulates SSC self-renewal by acting as a chemoattractant to sequester SSCs from inductive differentiation signals. In preliminary studies we have established a critical role for LIN28A, a highly-conserved RNA binding protein and regulator of the let-7 class of miRNAs that is expressed in Aundif1 in regulating the size of the Aundiff compartment. We propose experiments to distinguish between a role for LIN28A in proliferation and differentiation of Aund/Yf spermatogonia. Lastly, to discover additional regulators of SSC self-renewal, we will use high-throughput sequencing of RNA (RNAseq) isolated from polysomes of SSCs, Sertoli cells and peritubular myoid cells obtained from testis that are blocked in the transition from Aal to A1 spermatogonia under conditions of steady-state and regenerative SSC self-renewal.
There is an unmet need throughout the world for more contraceptive options for men. This proposal is focused on discovering the basic mechanisms used to regulate spermatogonial stem cell self-renewal and differentiation. We seek to discover both extrinsic and intrinsic regulators of SSCs with the belief that these will lead to novel targets of contraceptive intervention and a better understanding of the consequences of contraceptive regimens currently under consideration.
|Griswold, Michael D (2016) Spermatogenesis: The Commitment to Meiosis. Physiol Rev 96:1-17|
|Kocarnik, Beverly M; Boyko, Edward J; Matsumoto, Alvin M et al. (2016) Baseline estradiol concentration in community-dwelling Japanese American men is not associated with intra-abdominal fat accumulation over 10 years. Obes Res Clin Pract 10:624-632|
|Arnold, Samuel L; Stevison, Faith; Isoherranen, Nina (2016) Impact of Sample Matrix on Accuracy of Peptide Quantification: Assessment of Calibrator and Internal Standard Selection and Method Validation. Anal Chem 88:746-53|
|Chao, Jing; Rubinow, Katya B; Kratz, Mario et al. (2016) Short-Term Estrogen Withdrawal Increases Adiposity in Healthy Men. J Clin Endocrinol Metab 101:3724-3731|
|Chen, Yao; Ma, Li; Hogarth, Cathryn et al. (2016) Retinoid signaling controls spermatogonial differentiation by regulating expression of replication-dependent core histone genes. Development 143:1502-11|
|Roth, M Y; Page, S T; Bremner, W J (2016) Male hormonal contraception: looking back and moving forward. Andrology 4:4-12|
|Lee, Ada P; Roth, Mara Y; Nya-Ngatchou, Jean-Jacques et al. (2016) Testicular fine-needle aspiration for the assessment of intratesticular hormone concentrations. Asian J Androl 18:21-4|
|Roth, Mara Y; Amory, John K (2016) Beyond the Condom: Frontiers in Male Contraception. Semin Reprod Med 34:183-90|
|Amory, John K (2016) Male contraception. Fertil Steril 106:1303-1309|
|Kent, Travis; Arnold, Samuel L; Fasnacht, Rachael et al. (2016) ALDH Enzyme Expression Is Independent of the Spermatogenic Cycle, and Their Inhibition Causes Misregulation of Murine Spermatogenic Processes. Biol Reprod 94:12|
Showing the most recent 10 out of 112 publications