Investigation of Causes of Meiotic Arrest in the Sertoli Cell-Specific Androgen Receptor Knockout Testes

Undergraduate #98
Discipline: Biological Sciences
Subcategory: Genetics

Nadia Harerimana - College of the Atlantic
Co-Author(s): Travis Kent, The Jackson Laboratory, Bar Harbor, ME; Mary Ann Handel, The Jackson Laboratory, Bar Harbor, ME

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Androgen receptor (AR) action in Sertoli cells is required for germ cells to complete meiosis and is crucial for male fertility. The Sertoli cell-specific AR knockout (SCARKO) mouse model exhibits spermatogenic arrest, with germ cells failing to exit meiotic prophase I. Previous studies on the SCARKO mouse model have shown that germ cells of these mice do not complete meiosis and there is also a progressive loss of germ cells. To investigate the cellular mechanisms by which absence of AR signaling in Sertoli cells causes these phenotypes, these experiments took advantage of synchronized spermatogenesis in SCARKO testis to enrich for pachytene cells in meiotic prophase I. Using immunocytological analysis of meiotic chromosome spreads, I quantified the expression of γ-H2AFX, a phosphorylated histone, and the testis-specific histone H1t, which is synthesized in mid-late pachytene spermatocytes. The results show no major difference between SCARKO and wild-type (WT) spermatocytes in the expression of γ-H2AFX or testis-specific histone H1T. In addition, to assess which germ cell-types undergo apoptosis in SCARKO testes, I used a TUNEL assay to detect apoptotic cells at various time points during pachynema. I observed a higher number of apoptotic spermatocytes in SCARKO testis compared to WT testes beginning zygotene. Although apoptosis in germ cells of SCARKO testis is detected in zygotene stages, the surviving SCARKO spermatocytes appear to progress through late pachytene stage in the same manner as WT controls.

Nadia Harerimana,College of the Atlantic,ERN .docx

Funder Acknowledgement(s): This study was supported, in part, by a grant from NIH awarded to Mary Ann Handel and the Maine INBRE fellowship.

Faculty Advisor: Mary Ann Handel, Maryann.handel@jax.org

Role: In this research, I particularly studied the timing apoptosis in the Sertoli cell-specific androgen receptor knockout testes. I used a TUNEL assay to detect apoptotic cells at various time points during pachynema. I observed a higher number of apoptotic spermatocytes in SCARKO testis compared to WT testes beginning zygotene.