NRG1 and KITL Signal Downstream of Retinoic Acid in the Germline to Support Soma-Free Syncytial Growth of Differentiating Spermatogonia.
Defined culture systems supporting spermatogonial differentiation will provide experimental platforms to study spermatogenesis. However, germline-intrinsic signaling mechanisms sufficient to support spermatogonial differentiation without somatic cells remain largely undefined. Here, we analyzed EGF superfamily receptor and ligand diversity in rat testis cells, and delineated germline-intrinsic signalingviaan ERBB3 co-transducer, ERBB2, as essential for retinoic acid-induced syncytial growth by differentiating spermatogonia. Like the ERBB2/3 agonist NRG1, we found KIT Ligand (KITL) robustly supported spermatogonial differentiation without serum or somatic cells. ERBB2 inhibitors failed to disrupt KITL-dependent spermatogonial development, and, KITL prevented ERBB3-deficient spermatogonial degeneration upon differentiation. Thus, we report NRG1 and KITL activate alternative pathways downstream of retinoic acid signaling in the germline that are essential for stem cells to undergo pre-meiotic steps of spermatogenesis in culture. Robust serum/soma-free spermatogonial differentiation opens new doors to study mammalian germ cell biology in culture, which will facilitate the discovery of spermatogenic factors that can drive meiotic progressionin vitro.
Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
Karen M
KM
Chapman
Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
Gerardo A
GA
Medrano
Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
Jaideep
J
Chaudhary
Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA ; Cecil H. & Ida Green Center for Reproductive Biology Sciences, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
F Kent
FK
Hamra
differentiating spermatogonia; gametogenesis; germline; in vitro spermatogenesis; progenitor cells; spermatogenesis; spermatogonial stem cells