<i>Cracd</i> Marks the First Wave of Meiosis during Spermatogenesis and Is Mis-Expressed in Azoospermia Mice

• Main Authors: Paige L. Snider, Olga Simmons, Simon J. Conway
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Journal of Developmental Biology
• Subjects: <i>Cracd</i>; mouse testis development; spermatogonia; differentiation; gene expression; meiosis
• Online Access: https://www.mdpi.com/2221-3759/8/3/21

Testicular development starts in utero and maturation continues postnatally, requiring a cascade of gene activation and differentiation into different cell types, with each cell type having its own specific function. As we had previously reported that the <i>Capping protein inhibiting regulator of actin (Cracd)</i> gene was expressed in the adult mouse testis, herein we examine when and where the β-catenin associated <i>Cracd</i> is initially expressed during postnatal testis development. Significantly, <i>Cracd</i> mRNA is present in both the immature postnatal and adult testis in round spermatid cells, with highest level of expression occurring during the first wave of meiosis and spermatogenesis. In the juvenile testes, <i>Cracd</i> is initially expressed within the innermost region but as maturation occurs, <i>Cracd</i> mRNA switches to a more peripheral location. Thereafter, <i>Cracd</i> is downregulated to maintenance levels in the haploid male germ cell lineage. As <i>Cracd</i> mRNA was expressed within developing round spermatids, we tested its effectiveness as a biomarker of non-obstructive azoospermia using transgenic knockout mice models. Meaningfully, <i>Cracd</i> expression was absent in <i>Deleted in azoospermia like (Dazl)</i> null testis, which exhibit a dramatic germ cell loss. Moreover, <i>Cracd</i> was abnormally regulated and ectopically mis-expressed in <i>Polypyrimidine tract binding protein-2 (Ptbp2)</i> conditional germ cell restricted knockout testis, which exhibit a block during spermatid differentiation and a reduction in the number of late stage spermatocytes coincident with reduced β-catenin expression. Combined, these data suggest that <i>Cracd</i> is a useful first wave of spermatogenesis biomarker of azoospermia phenotypes, even prior to an overt phenotype being evident.