Identification of novel genes expressed during mammalian spermatogenesis: analysis of their functions and implication for fertility

• Autores: Yan Huang
• Directores de la Tesis: Ignasi Roig Navarro (dir. tes.)
• Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2022
• Idioma: inglés
• Tribunal Calificador de la Tesis: Jesús Page Utrilla (presid.), Aurora Ruiz-Herrera Moreno (secret.), Tatiana García Muse (voc.)
• Programa de doctorado: Programa de Doctorado en Biología Celular por la Universidad Autónoma de Barcelona
• Materias:
  • Ciencias de la vida
    • Biología celular
    • Biología molecular
• Enlaces
  • Tesis en acceso abierto en: TESEO
• Resumen

  • Meiosis is a specialized cell division, generating haploid gametes during gametogenesis for successful reproduction. Meiotic failure leads to infertility in mammals. In humans, infertility has become a major social health issue with many unknown genetic causes. Thus, in this work, we aimed to identify novel meiotic genes required for mammalian gametogenesis for better clinically relevant diagnosis and therapeutics. This work builds on the finding of several unannotated transcripts detected in 14 dpp mouse testis that we predicted to be novel genes. To test this hypothesis, we performed a sequential screen and eventually identified two novel meiotic prophase-specific genes Bend2 and Usp44. Then, we went through characterizing their localization in meiocytes using our in-house polyclonal antibodies and analyzing mutant mice focusing on fertility and meiotic major events (synapsis and recombination). On one hand, BEND2 is a BEN domain-containing protein likely involved in chromatin and transcriptional regulation. BEND2 is highly expressed in nuclei from spermatogonia until early pachytene during spermatogenesis, independently of either DSB formation or completion of recombination. The deletion of BEND2 leads to a significant loss of primordial follicles in adult females with reduced fertility but has minor effects on spermatogenesis, despite increased apoptosis. BEND2 deficient meiocytes exhibited normal synapsis and considerably increased ¿H2AX during late prophase. A subtle change of RPA and RAD51 foci numbers and altered meiotic progression in Bend2 mutant spermatocytes and a reduced CO number in Bend2 mutant oocytes were also found. These results indicate BEND2 is required for female fertility but not male¿s and the BEND2 mutation leads to insufficient DSB repair during prophase. On the other hand, USP44 is a deubiquitinating enzyme that localizes at synapsed chromosome axes during meiotic prophase, in a SPO11- and DMC1-dependent manner. In the absence of USP44, meiosis was arrested in most seminiferous tubules. Spermatocytes exhibited extensive defects in homolog pairing and synapsis, substantial ¿H2AX signals persisted in zygotene-like cells with accumulations of RPA and RAD51 foci, and only a minority of spermatocytes progressed to the diplotene stage. These results suggest that USP44 is essential for homolog pairing, synapsis, and DSB repair as well as male fertility. In conclusion, our results confirm our approach is valid for identifying novel genes involved in mammalian gametogenesis. Using this strategy, we successfully identified two novel meiotic genes essential for mammalian fertility, thus providing new insights into understanding, diagnosing, and treating human infertility.