Septins belong to a family of polymerizing GTP-binding proteins that are required for many cellular functions, such as membrane compartmentalization, vesicular trafficking, mitosis, and cytoskeletal remodeling. One family member, septin12, is expressed specifically in the testis. In this study, we found septin12 expressed in multiple subcellular compartments during terminal differentiation of mouse germ cells. In humans, the testicular tissues of men with either hypospermatogenesis or maturation arrest had lower levels of SEPTIN12 transcripts than normal men. In addition, increased numbers of spermatozoa with abnormal head, neck, and tail morphologies lacked SEPT12 immunostaining signals, as compared with normal spermatozoa. To elucidate the role of septin12, we generated 129 embryonic stem cells containing a septin12 mutant allele with a deletion in the exons that encode the N-terminal GTP-binding domain. Most chimeras derived from the targeted embryonic stem cells were infertile, and the few fertile chimeras only produced offspring with a C57BL/6 background. Semen analysis of the infertile chimeras showed a decreased sperm count, decreased sperm motility, and spermatozoa with defects involving all subcellular compartments. The testicular phenotypes included maturation arrest of germ cells at the spermatid stage, sloughing of round spermatids, and increased apoptosis of germ cells. Electron microscopic examination of spermatozoa showed misshapen nuclei, disorganized mitochondria, and broken acrosomes. Our data indicate that Septin12 expression levels are critical for mammalian spermiogenesis.

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Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF) and are associated with congenital bilateral absence of the vas deferens (CBAVD), which is the major cause of infertility in male patients with CF. However, most Taiwanese patients with CBAVD do not carry major CFTR mutations. Some patients have a single copy deletion of the solute carrier family 9 isoform 3 (SLC9A3) gene. SLC9A3 is a Na+/H+ exchanger, and depleted Slc9a3 in male mice causes infertility due to the abnormal dilated lumen of the rete testis and efferent ductules. Furthermore, SLC9A3 interacts with CFTR in the pancreatic duct and functions as a genetic modifier of CF. However, SLC9A3 function and its relation to CFTR expression in the male reproductive tract in vivo remain elusive. In the present study, we found that CFTR expression was dramatically decreased in the epididymis and vas deferens of Slc9a3 knockout mice. Adult Slc9a3-/- mice showed not only significantly decreased epididymis and vas deferens weight but also increased testis weight. Furthermore, Slc9a3-/- mice developed obstructive azoospermia because of abnormal abundant secretions and calcification in the lumen of the reproductive tract. Ultrastructural analysis of the epithelium in Slc9a3–/–epididymis and vas deferens displayed disorganized and reduced number of stereocilia and numerous secretory apparatuses. Our data revealed that interdependence between SLC9A3 and CFTR is critical for maintaining a precise microenvironment in the epithelial cytoarchitecture of the male reproductive tract. The Slc9a3-deficient mice with impaired male excurrent ducts in this study provide proof for our clinical findings that some Taiwanese of CBAVD carry SLC9A3 deletion but without major CFTR mutations.

The d-galactose (d-gal)-injected animal model, which is typically established by administering consecutive subcutaneous d-gal injections to animals for approximately six or eight weeks, has been frequently used for aging research. In addition, this animal model has been demonstrated to accelerate aging in the brain, kidneys, liver and blood cells. However, studies on aging in male reproductive organs that have used this animal model remain few. Therefore, the current study aimed to optimize a model of male reproductive aging by administering d-gal injections to male mice and to determine the possible mechanism expediting senescence processes during spermatogenesis. In this study, C57Bl/6 mice were randomized into five groups (each containing 8–10 mice according to the daily intraperitoneal injection of vehicle control or 100 or 200 mg/kg dosages of d-gal for a period of six or eight weeks). First, mice subjected to d-gal injections for six or eight weeks demonstrated considerably decreased superoxide dismutase activity in the serum and testis lysates compared to those in the control group. The lipid peroxidation in testis also increased in the d-gal-injected groups. Furthermore, the d-gal-injected groups exhibited a decreased ratio of testis weight/body weight and sperm count compared to the control group. The percentages of both immotile sperm and abnormal sperm increased considerably in the d-gal-injected groups compared to those of the control group. To determine the genes influenced by the d-gal injection during murine spermatogenesis, a c-DNA microarray was conducted to compare testicular RNA samples between the treated groups and the control group. The d-gal-injected groups exhibited RNA transcripts of nine spermatogenesis-related genes (Cycl2, Hk1, Pltp, Utp3, Cabyr, Zpbp2, Speer2, Csnka2ip and Katnb1) that were up- or down-regulated by at least two-fold compared to the control group. Several of these genes are critical for forming sperm-head morphologies or maintaining nuclear integration (e.g., cylicin, basic protein of sperm head cytoskeleton 2 (Cylc2), casein kinase 2, alpha prime interacting protein (Csnka2ip) and katanin p80 (WD40-containing) subunit B1 (Katnb1)). These results indicate that d-gal-injected mice are suitable for investigating male reproductive aging.

The main objective of this study was to evaluate the potential genetic effects of SEPT14 on male infertility through sequencing the SEPT14 coding region. To address this research gap, 254 men with sperm abnormalities and 116 normozoospermic men were recruited, and the whole-coding regions of SEPT14 were sequenced. Two heterozygous mutations, p.Ala123Thr (3/254 vs. 0/116) and p.Ile333Thr (3/254 vs. 0/116), were identified in these cases. A high percentage of defective sperm heads was found in sperm with mutated SEPT14. Both mutations are highly evolutionarily conserved among vertebrates. The results of a fine morphological and chromatin structural analysis indicated severely malformed sperm heads with abnormal chromatin packaging through transmission electron microscopy and Toluidine blue staining. Compared with controls, high DNA fragmentation was demonstrated in sperm from cases carrying SEPT14 mutations using the comet assay. In addition, these two mutations in SEPT14 affected its polymerization ability in vitro. These data revels that the two SEPT14 missense mutations impaired sperm head morphology and induced DNA damage. Our study suggests that genetic variant of SEPT14 is one of the effects for human sperm formation and male fertility.