The testis-specific expressed gene Spata34 is not required for fertility in mice

Testis-specific knockout of Kdm2a reveals nonessential roles in male fertility but partially compromises spermatogenesis

Lysine-specific histone demethylase 2 (Kdm2a) is a regulatory factor of histone modifications that participates in gametogenesis and embryonic development. The mis-regulation of Kdm2a can lead to aberrant gene expression, thereby contributing to abnormal cell proliferation, differentiation, apoptosis, and tumorigenesis. However, due to the potential confounding effects that are secondary to the loss of Kdm2a function from the soma in existing whole-animal mutants, the in vivo function of Kdm2a in spermatogenesis for male fertility remains unknown. Herein, we focus on exploring the spatiotemporal expression profile and biological functions of Kdm2a in the spermatogenesis and fertility of male mice. A testis-specific knockout Kdm2a model (Kdm2a cKO) was established by using the Stra8-Cre/loxP recombinase system to explore the roles of Kdm2a in male fertility. Our results showed that Kdm2a was ubiquitously expressed and dynamically distributed in multiple tissues and cell types in the testis of mice. Surprisingly, Kdm2a-deficient adult males were completely fertile and comparable with their control (Kdm2aflox/flox) counterparts. Despite the significantly reduced total number of sperm and density of seminiferous tubules in Kdm2a cKO testis accompanied by the degeneration of spermatogenesis, the fertilization ability and embryonic developmental competence of the Kdm2a cKO were comparable with those of their control littermates, suggesting that Kdm2a disruption did not markedly affect male fertility, at least during younger ages. Furthermore, Kdm2a homozygous mutants exhibited a lower total number and motility of sperm than the control group and showed notably affected serum 17β-estradiol concentration. Interestingly, the transcriptome sequencing revealed that the loss of Kdm2a remarkably upregulated the expression level of Kdm2b. This effect, in turn, may induce compensative effects in the case of Kdm2a deficiency to maintain normal male reproduction. Together, our results reveal that Kdm2a shows spatiotemporal expression during testicular development and that its loss is insufficient to compromise the production of spermatozoa completely. The homologous Kdm2b gene might compensate for the loss of Kdm2a. Our work provides a novel Kdm2a cKO mouse allowing for the efficient deletion of Kdm2a in a testis-specific manner, and further investigated the biological function of Kdm2a and the compensatory effects of Kdm2b. Our study will advance our understanding of underlying mechanisms in spermatogenesis and male fertility.

Inactivation of testis-specific gene C4orf46 is dispensable for spermatogenesis and fertility in mouse

Several genes have been reported to be involved in spermatogenesis but their functional importance in male fertility is yet needed to be elucidated. Therefore, in current research, we focused to explore the in vivo role of evolutionary conserved and testis-specifically expressed, C4orf46, gene in male mouse fertility and spermatogenesis. The expression profile of C4orf46 is specific to testes and expressed in testes from 7 days of postpartum to onward. Thus, we generated the C4orf46 knockout mice by utilizing CRISPR/Cas9 genome editing technology and examined gene function in spermatogenesis and fertility. Surprisingly, C4orf46 knockout mice were completely fertile, displayed normal testes morphology, however, higher sperm contents were observed in knockout mice compared to wild type (WT) littermates. Subsequently, intact testis histology and architecture of seminiferous tubules were observed in C4orf46 knockout and WT mice. Similarly, sperm morphology and swimming velocity of C4orf46 knockout mice were comparable with the WT littermates. Furthermore, all type of germ cells ranging from spermatogonia to mature spermatozoa were observed in the testes and epididymis sections of C4orf46 knockout mice suggesting that disruption of C4orf46 did not impact spermatogenesis. Moreover, meiotic prophase I progression was normal, and each type of cell population was comparable between knockout and WT mice. Overall, finding from this research indicates that C4orf46 is not an essential gene for fertility in mice. This study will help researchers to avoid the repetition and duplication of efforts, and to explore the genes that are indispensable for spermatogenesis and male fertility.

Spermatogenesis is normal in Tex33 knockout mice

Testis expressed gene 33 (Tex33) is a recently reported testis-specific gene and it is evolutionarily conserved in vertebrates. The Tex33 expression is found in cytoplasm of round spermatids in Mus musculus. However, the in vivo function of Tex33 remains unknown. In this study, we made a 62bp in frame deletion on Exon2 of Tex33 gene by CRISPR/Cas9 in C57B/L6 mouse, which cause frame shift mutation of Tex33 gene. Tex33^-/-adult male were fertile, and there is no significant change on litter size compared with male wildtype (Tex33^+/+) adult. Besides, no overt differences were found in testis/body weight ratios, testicular/epididymal tissue morphology, sperm counts, sperm morphology and spermatozoa motility in adult Tex33^-/-male mice (N = 3), in comparison with Tex33^+/+ adult (N = 3). TUNEL assay also indicates the germ cells apoptosis ratio was not significantly changed in adult Tex33^-/- adult male mouse testis (N = 3), compared with adult Tex33^+/+ male (N = 3). Importantly, the first wave of elongating spermatids formation happens in 5w old mice. We find that the first wave of spermiogenesis is not disrupted in both 5-week-old Tex33^+/+ and Tex33^-/-male mouse testes and three hallmarks of spermatogenesis, PLZF,γ-H2AX and TNP1, are all detectable in seminiferous tubule. All results indicate that Tex33 is a redundant gene to spermatogenesis. This study can help other researchers avoid repetitive works on redundant genes.

Evolutionarily conserved and testis-specific gene, 4930524B15Rik, is not essential for mouse spermatogenesis and fertility

Thousands of genes are involved in spermatogenesis, however, the functional roles of most these genes for male fertility remain to be discovered. This research focused to explore the function of evolutionarily conserved and testis-specific expressed gene 4930524B15Rik, which is known as C5orf47 in human. We generated 4930524B15Rik knockout mice by CRISPR/Cas9 technology and found 4930524B15Rik^-/- mice were fertile. Furthermore, no averted abnormalities were observed in testis morphology, epididymal sperm contents and sperm morphology in 4930524B15Rik knockout mice. Subsequently, histological analysis of testicular tissue revealed intact structure of seminiferous tubules along with the presence of all types of germ cells in 4930524B15Rik^-/- mice similar to wild type. Additionally, cytological analysis of spermatocytes displayed no significant differences in the prophase I progression of meiosis, further indicating that 4930524B15Rik have no essential function in mammalian spermatogenesis. Altogether, these results indicated that 4930524B15Rik is dispensable for fertility of male mice and these findings will help researchers to avoid future research overlap and to focus on genes that are crucial for spermatogenesis and reproduction.