The transition from mitotic to meiotic cell cycles is essential for haploid gamete formation and fertility. Stimulated by retinoic acid gene 8 ( Stra8 ) is an essential gatekeeper of meiotic initiation in vertebrates; yet, the molecular role of STRA8 remains principally unknown. Here we demonstrate that STRA8 functions as a suppressor of autophagy during spermatogenesis in mice. Stra8 -deficient germ cells fail to enter meiosis and present aberrant upregulation of autophagy-lysosome genes, commensurate with autophagy activation. Biochemical assays show that ectopic expression of STRA8 alone is sufficient to inhibit both autophagy induction and maturation. Studies also revealed that, Nr1d1 , a nuclear hormone receptor gene, is upregulated in Stra8 -deficient testes and that STRA8 binds to the Nr1d1 promoter, indicating that Nr1d1 is a direct target of STRA8 transcriptional repression. In addition, it was found that NR1D1 binds to the promoter of Ulk1 , a gene essential for autophagy initiation, and that Nr1d1 is required for the upregulated Ulk1 expression in Stra8 -deficient testes. Furthermore, both genetic deletion of Nr1d1 and pharmacologic inhibition of NR1D1 by its synthetic antagonist SR8278 exhibit rescuing effects on the meiotic initiation defects observed in Stra8 -deficient male germ cells. Together, the data suggest a novel link between STRA8-mediated autophagy suppression and meiotic initiation. Author summary Meiotic initiation is a key feature of sexual reproduction that launches an intricate chromosomal program involving DNA double strand breaks (DSBs), homolog pairing, cohesion, synapsis, and recombination. Vertebrate gene Stra8 is an essential gatekeeper of meiotic initiation. However, the molecular role of STRA8 and its target genes remain elusive. Using mouse spermatogenesis as a model, we report that STRA8 suppresses autophagy by repressing the transcription of a nuclear hormone receptor gene Nr1d1 , and in turn, silencing the expression of Ulk1 , a gene essential for autophagy initiation. Given that autophagy is critical for protein and cellular organelle recycling and for preventing genomic instability, our study suggests that this newly demonstrated function of STRA8, as a suppressor of autophagy, may be an important mechanistic feature of its role in meiotic initiation.
【초록키워드】 ectopic expression, Genetic, Transcription, autophagy, Protein, DNA, cells, mice, male, Recombination, Fertility, molecular, retinoic acid, genomic, expression, Critical, function, Target genes, cellular, sexual reproduction, target gene, germ cells, hormone receptor, haploid gamete, cell cycles, double strand, Activation, maturation, transition, upregulation, organelle, spermatogenesis, vertebrates, meiosis, promoter, homolog, suppressor, cohesion, DSBs, Nr1d1, STRA8, synapsis, Ulk1, nuclear, Effect, Genes, Cell, transcriptional, bind, addition, inhibit, required, demonstrated, upregulated, chromosomal, suppresse, turn, mitotic, double strand break, meiotic, Vertebrate, 【제목키워드】 expression, suppresse,