Christopher B. Geyer, Ph.D.
Associate Professor
Society for the Study of Reproduction New Investigator Award 2017
East Carolina University Scholar 2017
office: ECHI 4112
phone: 252-744-3433
email: geyerc@ecu.edu
B.S., Virginia Polytechnic Institute and State University
Ph.D., The University of Texas Health Science Center at San Antonio
Postdoctoral Fellow, National Institute of Environmental Health Sciences
Research
Research
My laboratory uses mouse spermatogenesis as a model system to investigate mechanisms involved in regulating cellular differentiation. Spermatogenesis begins in the neonatal mouse testis with the segregation of prospermatogonia into distinct undifferentiated and differentiating populations. A proportion of undifferentiated spermatogonia retain stem cell potential (as foundational spermatogonial stem cells, or SSCs), and the remainder becomes progenitor spermatogonia that proliferate and differentiate in response to retinoic acid (RA). This initial fate decision is critical, as imbalances cause spermatogenic defects that can lead to human testicular cancer or infertility. It is currently unknown how mammalian spermatogonial fate decisions are regulated; however, they are critical for maintaining tissue homeostasis, as imbalances cause spermatogenesis defects that can lead to human testicular cancer or infertility. A great deal of effort has been exerted to understand how the SSC population is maintained. In contrast, little is known about the essential program of differentiation initiated by RA that precedes meiosis, and the pathways and proteins involved are poorly defined. A primary reason for this gap in knowledge is there are few reported changes in steady state mRNA levels during differentiation, preventing identification of the full complement of involved gene products to inform focused studies.
To better understand neonatal germ cell differentiation at the onset of spermatogenesis, we are currently using transgenic and knockout mice along with pharmacologic interventions to: 1 – define the requisite molecular signaling pathways downstream of RA; 2 – determine the role of RA in translational regulation during spermatogonial differentiation and meiotic initiation; and 3 – define how RA responsiveness regulates spermatogonial fate during both the formation of the foundational SSC pool at the beginning of spermatogenesis and adult steady-state spermatogenesis.
Selected Publications
Peart NJ, Johnson TA, Lee S, Sears MJ, Yang F, Quesnel-Vallieres M, Feng H, Recinos Y, Barash Y, Zhang C, Hermann BP, Wang PJ, Geyer CB, and Carstens RP. 2022. The germ cell-specific RNA binding protein RBM46 is essential for spermatogonial differentiation in mice. PLoS Genet, accepted for publication September 15.
Lester WC, Johnson TA, Hale B, Serra ND, Elgart B, Wang R, Geyer CB, and Sperry AO. 2021. Aurora A kinase (AURKA) is required for male germline maintenance and regulates sperm motility in the mouse. Biol Reprod. 105(6): 1603-1616. PMID: 34518881.
Menon DU, Kirsanov O, Geyer CB, and Magnuson T. 2021. Mammalian SWI/SNF chromatin remodeler is essential for reductional meiosis in males. Nat Comm 12(1): 6581. PMID: 34772938.
Jones SL, Styles J, and Geyer CB. 2021. A new translation and reader’s guide to the first detailed description of the first wave of spermatogenesis in the mouse. Mol Reprod Dev 88(7): 473-478. PMID: 34096665.
Cheng K, Chen IC, Cheng CE, Mutoji K, Hale BJ, Hermann BP, Geyer CB, Oatley JM, and McCarrey JR. 2020. Unique epigenetic programming distinguishes regenerative spermatogonial stem cells in the developing mouse testis. iScience 23(10): 101596. PMID: 33083754.
Kirsanov, O., Renegar, R.H., Busada, J.T., Serra, N.D., Harrington, E.V., Johnson, T.A., and Geyer CB. 2020. The rapamycin analog Everolimus reversibly impairs male germ cell differentiation and fertility in the mouse. Biol Reprod 103(5): 1132-1143. PMID: 32716476.
Hale, B.J., R.F. Fernandez, S.Q. Kim, V.D. Diaz, S.N. Jackson, L. Liu, J.T. Brenna, B.P. Hermann, C.B. Geyer, and J.M. Ellis. 2019. Acyl-CoA synthetase 6 enriches seminiferous tubules with the ω-3 fatty acid docosahexaenoic acid and is required for male fertility in the mouse. J. Biol. Chem. 294(39): 14394-14405. PMID: 31399511.
Jones, S.L., K . Harris, and C.B. Geyer. 2019. A new translation and reader’s guide to Victor von Ebner’s classical description of spermatogenesis. Mol. Reprod. Dev. 86(11): 1462-1484. PMID: 31642147.
Velte, E.K., B.A. Niedenberger, N.D. Serra, A. Singh, L. Roa-DeLaCruz, B.P. Hermann, and C.B. Geyer. 2019. Differential RA responsiveness directs formation of functionally distinct spermatogonial populations at the initiation of spermatogenesis in the mouse. Development. 146(12). PMID: 31023878.
Hermann, B.P., K. Cheng, A. Singh, L. Roa-De La Cruz, K.N. Mutoji, I.C. Chen, H. Gildersleeve, J.D. Lehle, M. Mayo, B. Westernströer, N.C. Law, M.J. Oatley, E.K. Velte, B.A. Niedenberger, D. Fritze, S. Silber, C.B. Geyer, J.M. Oatley, and J.R. McCarrey. 2018. The mammalian spermatogenesis single-cell transcriptome, from spermatogonial stem cells to spermatids. Cell Rep. 25(6): 1650-1667. PMID: 30404016.
Serra, N., E.K. Velte, B.A. Niedenberger, O. Kirsanov, and C.B. Geyer. 2018. The mTORC1 component RPTOR is required for maintenance of the foundational spermatogonial stem cell pool in mice. Biol. Reprod. [Epub ahead of print]. PMID 30202948.
Niedenberger, B.A., K. Cook, V. Baena, N.D. Serra, E.K. Velte, J.E. Agno, K.A. Litwa, M. Terasaki, B.P. Hermann, M.M. Matzuk, and C.B. Geyer. 2018. Dynamic cytoplasmic projections connect mammalian spermatogonia in vivo. Development. 145(15). PMID: 29980567.
Sertoli, E. and C.B. Geyer. 2018. The Structure of seminiferous tubules and the development of [spermatids] in rats. Biol. Reprod. (99)3: 482-503. PMID: 29961830.
Niedenberger, B.A. and C.B. Geyer. 2018. Advanced immunostaining approaches to study early male germ cell development. Stem Cell Res. 27: 162-168. PMID: 29475796.
Geyer, C.B. 2017. A historical perspective on some “new” discoveries on spermatogenesis from the laboratory of Enrico Sertoli in 1878. Biol. Reprod. 99(3): 671. PMID: 30060065.
Serra, N.D., E.K. Velte, B.A. Niedenberger, O. Kirsanov, C.B. Geyer. 2017. Cell-autonomous requirement for mammalian target of rapamycin (Mtor) in spermatogonial proliferation and differentiation in the mouse. Biol. Reprod. 96(4): 816-828.
Mutoji, K., A. Singh, T. Nguyen, H. Gildersleeve, A.V. Kaucher, M.J. Oatley, J.M. Oatley, E.K. Velte, C.B. Geyer, K. Cheng, J.R. McCarrey, and B.P Hermann. 2016. TSPAN8 expression distinguishes spermatogonial stem cells in the prepubertal mouse testis. Biol. Reprod. 95(6): 117.
Busada, J.T., E.K. Velte, N. Serra, K. Cook, B.A. Niedenberger, W.D. Willis, E.H. Goulding, E.M. Eddy, and C.B. Geyer. 2016. Rhox13 is required for a quantitatively normal first wave of spermatogenesis in mice. Reproduction 152: 379-88.
Busada, J.T. and C.B. Geyer. 2015. The role of retinoic acid (RA) in spermatogonial differentiation. Biol. Reprod. 94: 10.
Busada, J.T., B.A. Niedenberger, E.K. Velte, B.D. Keiper, and C.B. Geyer. 2015. Mammalian target of rapamycin complex 1 (mTORC1) is required for mouse spermatogonial differentiation in vivo. Dev. Biol. 407: 90-102.
Niedenberger, B.A., J.T. Busada, and C.B. Geyer. 2015. Marker expression reveals heterogeneity of spermatogonia in the neonatal mouse testis. Reproduction 149: 329-338.
Hermann, B.P., K.N. Mutoji, E.K. Velte, D. Ko, J.M. Oatle, C.B. Geyer, and J.R. McCarrey. 2015. Transcriptional and translational heterogeneity among neonatal mouse spermatogonia. Biol. Reprod. 92: 54.
Busada, J.T., V.A. Chappell, B.A. Niedenberger, E.P. Kaye, B.D. Keiper, C.A. Hogarth, and C.B. Geyer. 2014. Retinoic acid regulates Kit translation during spermatogonial differentiation in the mouse. Dev. Biol. 397: 140-149.
Niedenberger, B.A., V.A. Chappell, C.A. Otey, and C.B. Geyer. 2014. Actin dynamics regulate subcellular localization of the F-actin binding protein PALLD in mouse Sertoli cells. Reproduction 148: 333-341.
Busada, J.T., E.P Kaye, R.H. Renegar, and C.B. Geyer. 2014. Retinoic acid induces multiple hallmarks of the prospermatogonia-to-spermatogonia transition in the neonatal mouse. Biol. Reprod. 90: 64.
Chappell, V.A., J.T. Busada, B.D. Keiper, and C.B. Geyer. 2013. Translational activation of developmental mRNAs during neonatal testis development. Biol. Reprod. 89: 61.
View PubMed Publications for further listings
Current Funding
“Challenging the role of retinoic acid in meiotic initiation” (NIH R21 HD105963); Christopher Geyer, Principal Investigator; National Institute of Child Health and Human Development; 2/22/2022-2/28/2024.
“The Role of Retinoid Exposure in Specification of the Foundational SSC Pool” (NIH R01 1R01HD090083); Christopher Geyer, Principal Investigator; National Institute of Child Health and Human Development; 3/26/2017-2/28/2023.
Staff and Students
Location ECHI 4400
| Name | Title | |
|---|---|---|
| Bryan Niedenberger, M.S. | Research Technician | niedenbergerb@ecu.edu |
| Emma Gilbert | Graduate Student | gilbertem21@students.ecu.edu |
| Molly Alexander, M.S. | Graduate Student | alexandermo22@students.ecu.edu |
| Jasmine Jenkins | Master’s student | jenkinsja18@students.ecu.edu |
| Will Miller | Master’s student | millerw15@students.ecu.edu |
| Alexander Fisher | Undergraduate student | fishera21@students.ecu.edu |
Former Students and Post-Doctoral Fellows
| Name | Title | Location |
|---|---|---|
| Vesna Chappell, Ph.D. | Biologist | Reproductive Endocrinology Group, National Institute of Environmental Health Science, Research Triangle Park, NC |
| Jonathan Busada, Ph.D. | Assistant Professor | Department of Microbiology, Immunology, and Cell Biology, West Virginia University School of Medicine, Morgantown, WV |
| Ellen (Velte) Harrington, Ph.D. | Technical Sales Specialist | Bioprocess Engineering Services LTD, United Kingdom |
| Taylor Johnson, Ph.D. | Teaching Assistant Professor | Department of Anatomy and Cell Biology, Brody School of Medicine at East Carolina University, Greenville, NC |
| Nicholas Serra | Postdoctoral Research Fellow | Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA |
| Oleksandr “Sasha” Kirsanov, Ph.D. | IRTA Postdoctoral Fellow | Placental Cell Biology Group, National Institute of Environmental Health Sciences, Research Triangle Park, NC |
| Benjamin Hale, Ph.D. | Grant writing specialist | Eva Garland Consulting, LLC, Research Triangle Park, NC |