Constitutive activation of NOTCH1 signaling in Sertoli cells causes gonocyte exit from quiescence

• Published in: Developmental biology Vol. 377; no. 1; pp. 188 - 201
• Main Authors: Garcia, Thomas Xavier, DeFalco, Tony, Capel, Blanche, Hofmann, Marie-Claude
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2013
• Subjects: adults; Aging; Animals; Apoptosis; Cell Cycle - genetics; Cell Differentiation; Cell Proliferation; cellular microenvironment; CYP26B1; Cytochrome P-450 Enzyme System - metabolism; fetal development; Fetus - cytology; GDNF; Gene Expression Regulation, Developmental; genes; germ cells; Glial Cell Line-Derived Neurotrophic Factor - metabolism; Gonocyte; green fluorescent protein; Integrases - metabolism; Male; Mice; Mitosis; mutants; Notch signaling; Organ Specificity; Phenotype; Receptor, Notch1 - metabolism; Retinoic Acid 4-Hydroxylase; Sertoli cell; Sertoli cells; Sertoli Cells - cytology; Sertoli Cells - metabolism; Signal Transduction - genetics; spermatogenesis; Spermatogonia - cytology; Spermatogonia - metabolism; stem cells; Testis development; Testis development; Sertoli cell; CYP26B1; GDNF; Notch signaling; Gonocyte
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2013.01.031

Notch signaling components have long been detected in Sertoli and germ cells in the developing and mature testis. However, the role of this pathway in testis development and spermatogenesis remains unknown. Using reporter mice expressing green fluorescent protein following Notch receptor activation, we found that Notch signaling was active in Sertoli cells at various fetal, neonatal, and adult stages. Since Notch signaling specifies stem cell fate in many developing and mature organ systems, we hypothesized that maintenance and differentiation of gonocytes and/or spermatogonial stem cells would be modulated through this pathway in Sertoli cells. To this end, we generated mutant mice constitutively expressing the active, intracellular domain of NOTCH1 (NICD1) in Sertoli cells. We found that mutant Sertoli cells were morphologically normal before and after birth, but presented a number of functional changes that drastically affected gonocyte numbers and physiology. We observed aberrant exit of gonocytes from mitotic arrest, migration toward cord periphery, and premature differentiation before birth. These events, presumably unsupported by the cellular microenvironment, were followed by gonocyte apoptosis and near complete disappearance of the gonocytes by day 2 after birth. Molecular analysis demonstrated that these effects are correlated with a dysregulation of Sertoli-expressed genes that are required for germ cell maintenance, such as Cyp26b1 and Gdnf. Taken together, our results demonstrate that Notch signaling is active in Sertoli cells throughout development and that proper regulation of Notch signaling in Sertoli cells is required for the maintenance of gonocytes in an undifferentiated state during fetal development. ► Using Notch reporter mice, we show that Notch signaling is active in Sertoli cells. ► Mutant mice constitutively over-expressing NICD1 in Sertoli cells are sterile. ► Gonocytes start dying at E15.5 due to premature differentiation. ► Factors required for proper gonocyte maintenance are dysregulated in the mutant. ► Excess or improperly-timed Notch activation impairs fetal gonocyte maintenance.