UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy-en-Josas, France.
UMR 7592 Institut Jacques Monod, Université Paris Diderot/CNRS, Paris, France.
PLoS Genet. 2019 Feb 8;15(2):e1007909. doi: 10.1371/journal.pgen.1007909. eCollection 2019 Feb.
Gonad differentiation is a crucial step conditioning the future fertility of individuals and most of the master genes involved in this process have been investigated in detail. However, transcriptomic analyses of developing gonads from different animal models have revealed that hundreds of genes present sexually dimorphic expression patterns. DMXL2 was one of these genes and its function in mammalian gonads was unknown. We therefore investigated the phenotypes of total and gonad-specific Dmxl2 knockout mouse lines. The total loss-of-function of Dmxl2 was lethal in neonates, with death occurring within 12 hours of birth. Dmxl2-knockout neonates were weak and did not feed. They also presented defects of olfactory information transmission and severe hypoglycemia, suggesting that their premature death might be due to global neuronal and/or metabolic deficiencies. Dmxl2 expression in the gonads increased after birth, during follicle formation in females and spermatogenesis in males. DMXL2 was detected in both the supporting and germinal cells of both sexes. As Dmxl2 loss-of-function was lethal, only limited investigations of the gonads of Dmxl2 KO pups were possible. They revealed no major defects at birth. The gonadal function of Dmxl2 was then assessed by conditional deletions of the gene in gonadal supporting cells, germinal cells, or both. Conditional Dmxl2 ablation in the gonads did not impair fertility in males or females. By contrast, male mice with Dmxl2 deletions, either throughout the testes or exclusively in germ cells, presented a subtle testicular phenotype during the first wave of spermatogenesis that was clearly detectable at puberty. Indeed, Dmxl2 loss-of-function throughout the testes or in germ cells only, led to sperm counts more than 60% lower than normal and defective seminiferous tubule architecture. Transcriptomic and immunohistochemichal analyses on these abnormal testes revealed a deregulation of Sertoli cell phagocytic activity related to germ cell apoptosis augmentation. In conclusion, we show that Dmxl2 exerts its principal function in the testes at the onset of puberty, although its absence does not compromise male fertility in mice.
性腺分化是决定个体未来生育能力的关键步骤，涉及这一过程的大多数主调控基因已被详细研究。然而，不同动物模型的发育性腺的转录组分析表明，数以百计的基因呈现出有性二态表达模式。DMXL2 就是其中之一，但其在哺乳动物性腺中的功能尚不清楚。因此，我们研究了 DMXL2 基因敲除的总缺失和性腺特异性缺失小鼠的表型。DMXL2 的完全功能缺失在新生鼠中是致命的，出生后 12 小时内死亡。DMXL2 基因敲除的新生鼠虚弱且无法进食。它们还存在嗅觉信息传递缺陷和严重低血糖，表明其过早死亡可能是由于全身神经元和/或代谢缺陷所致。DMXL2 在出生后，在雌性的卵泡形成和雄性的精子发生过程中，在性腺中的表达增加。DMXL2 在两性的支持细胞和生殖细胞中均有表达。由于 DMXL2 基因缺失是致命的，因此仅对 DMXL2 KO 幼鼠的性腺进行了有限的研究。出生时未发现明显缺陷。随后通过条件性删除基因在性腺支持细胞、生殖细胞或两者中对 DMXL2 的性腺功能进行了评估。在性腺中条件性删除 DMXL2 并不影响雄性或雌性的生育能力。相反，在整个睾丸或仅在生殖细胞中删除 DMXL2 的雄性小鼠，在第一次精子发生过程中出现了轻微的睾丸表型，在青春期时可明显检测到。事实上，在整个睾丸或仅在生殖细胞中缺失 DMXL2，会导致精子计数比正常水平低 60%以上，并且生精小管结构受损。对这些异常睾丸进行的转录组和免疫组织化学分析显示，与精子细胞凋亡增加相关的支持细胞吞噬活性失调。总之，我们表明，DMXL2 在青春期开始时在睾丸中发挥其主要功能，尽管其缺失并不影响雄性小鼠的生育能力。
