Ovol2, a zinc finger transcription factor, is dispensable for spermatogenesis in mice
Ovol2, a mouse homolog of Drosophila ovo, was identified as a zinc finger transcription factor predominantly expressed in testis. However, the function of Ovol2 in postnatal male germ cell development remains enigmatic. Here, we firstly examined the mRNA and protein levels of Ovol2 in developing mouse testes by RT-qPCR and western blot and found that both mRNA and protein of Ovol2 are continually expressed in postnatal developing testes from postnatal day 0 (P0) testes to adult testes (P56) and exhibits its higher level at adult testis. Further testicular immuno-staining revealed that OVOL2 is highly expressed in the spermatogonia, spermatocytes and round spermatids. Interestingly, our conditional ovol2 knockout mouse model show that loss of ovol2 in embryonic germ cells does not affect fecundity in mice. Our data also show that Ovol1 may have compensated for the loss of Ovol2 functions in germ cells. Overall, our data indicate that ovol2 is dispensable for germ cell development and spermatogenesis.
KeywordsOvol2 Spermatogenesis Fertility Knockout mice
To investigate the fertility of Vasa-cKO mice, we bred the Vasa-cKO males with fertility-proven WT females for at least 5 months. Unexpectedly, Vasa-cKO breeding pairs can produce comparable litter size to WT breeding pairs (data not shown), which indicated that Vasa-cKO male mice are completely fertile. Consistent with this fertile phenotype, testis gross morphology and weights are comparable between Vasa-cKO and WT control mice (Fig. 2f-g). Histological analyses further revealed that Vasa-cKO testes display normal spermatogenesis (Fig. 2h). To further confirm the Vasa-Cre recombined deletion efficiency in DNA level, we detected the delete allele of Ovol2 in the offspring derived from Vasa-cKO male breeding pairs by PCR-based DNA analyses. As we expected, all of pups are contained Ovol2 delete allele (Additional file 1: Figure S2). Together, these data indicate that Ovol2 is not essential for spermatogenesis and male germ cell development in mice despite its high expression in testis.
Ovol1, another Drosophila ovo mouse homologue, was confirmed to express in overlapping tissues with Ovol2, such as skin, kidney and testis. Ablation of Ovol1 in mice led to abnormal male germ cell development and male infertility, and Ovol1 is essential for spermatogenesis . Thus, we analyzed the expression levels of Ovol1 in adult WT and Vasa-cKO testes by RT-qPCR. Interestingly, both Ovol1 mRNA and protein levels were significantly increased in Vasa-cKO testes compared with those of WT testes (Fig. 2i-k). Therefore, these data suggest that Ovol1 may have compensated for the loss of Ovol2 functions in germ cells, which leads to normal phenotype in Vasa-Cre;Ovol2lox/lox mice. However, it is worthwhile pointing out that other transcription factors need to be elucidated in future, which may contribute to the compensation of OVOL2 loss-of -function in male germ cells. Overall, in this study, we report that Ovol2 is dispensable for testicular germ cell development and spermatogenesis in mice, and provide a molecular therapeutic clue for human male infertility caused by genetic mutation.
Both mRNA and protein of Ovol2 are continually expressed in postnatal developing testes from postnatal day 0 (P0) testes to adult testes (P56) and exhibits its highest level at adult testis. Ovol2 is dispensable for testicular germ cell development and spermatogenesis in mice. Ovol1 may have compensated for the loss of Ovol2 functions in germ cells, which leads to normal phenotype in Ovol2 conditional mutation mice.
Available of data and materials
The data and materials for supporting the conclusion of this short communication are included within the article.
Ethics and approval
All the animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of Tongji Medical College, Huazhong University of Science and Technology, and the mice were housed in the specific pathogen-free facility of Huazhong University of Science and Technology. All experiments with mice were conducted ethically according to the Guide for the Care and Use of Laboratory Animal guidelines.
SY conceived and designed the study. JZ, JD, WQ, CC, and YW performed all bench experiments. JD and SY wrote the manuscript. SY and YT. supervised the project. All authors read and approved the final manuscript.
This work supported by grants from National Natural Science Foundation of China (31671551 to S.Y.), the Science Technology and Innovation Commission of Shenzhen Municipality (JCYJ20170244 to S.Y.), Natural Science Foundation of Hubei Province (2017CFA069 to S.Y.).
Consent for publication
The authors declare that they have no completing interests.
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