Testis-expressed protein 33 is not essential for spermiogenesis and fertility in mice

Abstract

Gene expression analyses have revealed that there are >2,300 testis-enriched genes in mice, and gene knockout models have shown that a number of them are responsible for male fertility. However, the functions of numerous genes have yet to be clarified. The aim of the present study was to identify the expression pattern of testis-expressed protein 33 (TEX33) in mice and explore the role of TEX33 in male reproduction. Reverse transcription-polymerase chain reaction and western blot assays were used to investigate the mRNA and protein levels of TEX33 in mouse testes during the first wave of spermatogenesis. Immunofluorescence analysis was also performed to identify the cellular and structural localization of TEX33 protein in the testes. Tex33 knockout mice were generated by CRISPR/Cas9 gene-editing. Histological analysis with hematoxylin and eosin or periodic acid-Schiff (PAS) staining, computer-assisted sperm analysis (CASA) and fertility testing, were also carried out to evaluate the effect of TEX33 on mouse spermiogenesis and male reproduction. The results showed that Tex33 mRNA and protein were exclusively expressed in mouse testes and were first detected on postnatal days 21–28 (spermiogenesis phase); their expression then remained into adulthood. Immunofluorescence analysis revealed that TEX33 protein was located in the spermatids and sperm within the seminiferous tubules of the mouse testes, and exhibited specific localization to the acrosome, flagellum and manchette during spermiogenesis. These results suggested that TEX33 may play a role in mouse spermiogenesis. However, Tex33 knockout mice presented no detectable difference in testis-to-body weight ratios when compared with wild-type mice. PAS staining and CASA revealed that spermatogenesis and sperm quality were normal in mice lacking Tex33 . In addition, fertility testing suggested that the Tex33 knockout mice had normal reproductive functions. In summary, the findings of the present study indicate that TEX33 is associated with spermiogenesis but is not essential for sperm development and male fertility.

Scrutinizing the human TEX genes in the context of human male infertility

“…TEX33 expression peaks during meiosis, suggesting that TEX33 might be required to progress beyond the spermatogonial stage. However, Tex33 was previously reported as being dispensable for fertility in mice, as Tex33 knockout mice are fertile and exhibit normal testicular histology 28,29 . The authors attribute this finding, standing in contrast to the high expression in germ cells, to gene redundancy, assuming that lack of functional Tex33 can be compensated by other genes in mice 29 .…”

“…However, Tex33 was previously reported as being dispensable for fertility in mice, as Tex33 knockout mice are fertile and exhibit normal testicular histology. 28,29 The authors attribute this finding, standing in contrast to the high expression in germ cells, to gene redundancy, assuming that lack of functional Tex33 can be compensated by other genes in mice. 29 As the functional domains of TEX33 are not known yet, the compensating genes are yet to be determined.…”

Integrated single cell transcriptome sequencing analysis reveals species‐specific genes and molecular pathways for pig spermiogenesis

“…Closely related to the maturation of spermatids, spermiogenesis reflects the rapid morphological changes of spermatids (from round to elongated to mature), which is also fundamental to the downstream spermiation process and implied in male fertility issues (Torres‐Flores et al., 2023; Xia et al., 2021; Zhang et al., 2023). Possibly driven by sperm competition, accelerated molecular evolution of genes occurs in spermiogenesis (Murat et al., 2023), whereas spermatogonia, spermatocytes, and somatic cells show relatively similar patterns of constraint and molecular innovation to somatic cell types in other organs.…”

“…Closely related to the maturation of spermatids, spermiogenesis reflects the rapid morphological changes of spermatids (from round to elongated to mature), which is also fundamental to the downstream spermiation process and implied in male fertility issues (Torres-Flores et al, 2023;Xia et al, 2021;Zhang et al, 2023).…”

Endocrine disorders and fertility and pregnancy: An update

“…It has been demonstrated with such genes as ADAD1 and ADAD2 (271), Kindlin-2 (272), Wip 1 (273), and Crybb2 (274). At the same time, the lack of influence on fertility of a dozen or so genes, which are expressed within the testes, has been confirmed (275)(276)(277)(278)(279).…”