office: ECHI 4112
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
My laboratory uses mouse spermatogenesis as a model system to investigate mechanisms involved in regulating cellular differentiation. In the mouse, prospermatogonia proliferate for a short period following sex determination in the fetal testis, and then become quiescent from 14.5 dpc until 1-2 dpp. Then, in response to an undefined signal(s), they move from a central position to the periphery of the testis cords and resume mitosis as spermatogonia. Completion of both tasks is required for their continued survival.
Spermatogonia are then flanked by Sertoli cells within the cord and myoid cells outside the cord, and then respond to paracrine signals from these somatic cells to either become stem cells (As) or differentiate (A1-4) to ultimately enter meiosis. The first wave of spermatogenesis does not rely upon stem cell function, but rather on these spermatogonia that differentiate from the founder pool of prospermatogonia. These developmental transitions are critical for establishment of spermatogenesis, but the underlying pathways and proteins involved are poorly defined.
To better understand neonatal germ cell differentiation at the onset of spermatogenesis, we are currently investigating: 1 – the molecular mechanisms downstream of retinoic acid (RA) signaling, 2 – translation regulation during the prospermatogonia-to-spermatogonia transition, and 3 – the role of reproductive homeobox gene 13 (RHOX13) in male fertility.
Keiser, J.T., P.M. Jobst, A.S. Garst, J.T. Boone, C.B. Geyer, C. Phelps, D.L. Ayares, and R.L. Page. 2001. Preimplantation screening for transgenesis using an embryonic specific promoter and green fluorescent protein. Cloning 3: 23-30.
Geyer, C.B., C.M. Kiefer, T. Yang, and J.R. McCarrey. 2004. Ontogeny of a demethylation domain and its relationship to activation of tissue-specific transcription. Biol. Reprod. 71: 837-844.
McCarrey, J.R., C.B. Geyer, and H. Yoshioka. 2005. Epigenetic regulation of testis-specific gene expression. Ann. N.Y. Acad. Sci. 1061: 226-242.
Yoshioka, H., C.B. Geyer, J.L. Hornecker, K.T. Patel, and J.R. McCarrey. 2007. In vivo analysis of developmentally and evolutionarily dynamic protein-DNA interactions regulating transcription of the Pgk2 gene during mammalian spermatogenesis. Mol. Cell Biol. 27: 7871-7885.
Geyer, C.B. and E.M. Eddy. 2008. Identification and characterization of Rhox13, a novel X-linked mouse homeobox gene. Gene 423: 194-200.
Geyer, C.B., A.I. Inselman, J. Sunman, S. Bornstein, M.A. Handel, and E.M. Eddy. 2009. A missense mutation in the Capza3 gene and disruption of F-actin organization in spermatids of repro32 infertile male mice. Dev. Biol. 330: 142-152.
Danshina, P.V., C.B. Geyer, Q. Dai, E.H. Goulding, W.D. Willi, G.B. Kitto, J.R. McCarrey, E.M. Eddy, and D.A. O’Brien. 2009. Phosphoglycerate kinase 2 (PGK2) is essential for sperm function and male fertility in mice. Biol. Reprod. 82: 136-145
Geyer, C.B., R. Saba, Y. Kato, A.J. Anderson, V.K. Chappell, Y. Saga, and E.M. Eddy. 2010. Rhox13 is translated in premeiotic germ cells in male and female mice and translation is regulated by NANOS2 in the male. Biol. Reprod. 86: 127.
Overcash, R.F., V.A. Chappell, T. Green, C.B. Geyer, A.S. Asch, and M.J. Ruiz-Echevarria. 2013. Androgen signaling promotes translation of TMEFF2 in prostate cancer cells via phosphorylation of the α subunit of the translation initiation factor 2 (eIF2α).PLoS One 8: e55257.
Niedenberger, B.A., V.K. Chappell, E.P. Kaye, R.H. Renegar, and C.B. Geyer. 2013. Nuclear localization of the actin binding protein Palladin in Sertoli cells. Mol. Reprod. Dev. 80: 403-413.
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.
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.
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 (accepted for publication).