Deficiency of the Tmem232 Gene Causes Male Infertility with Morphological Abnormalities of the Sperm Flagellum in Mice

The axoneme and accessory structures of flagella are critical for sperm motility and male fertilization. Sperm production needs precise and highly ordered gene expression to initiate and sustain the many cellular processes that result in mature spermatozoa. Here, we identified a testis enriched gene transmembrane protein 232 (Tmem232), which is essential for the structural integrity of the spermatozoa flagella axoneme. Tmem232 knockout mice were generated for in vivo analyses of its functions in spermatogenesis. Phenotypic analysis showed that deletion of Tmem232 in mice causes male-specific infertility. Transmission electron microscopy together with scanning electron microscopy were applied to analyze the spermatozoa flagella and it was observed that the lack of TMEM232 caused failure of the cytoplasm removal and the absence of the 7th outer microtubule doublet with its corresponding outer dense fiber (ODF). Co-IP assays further identified that TMEM232 interacts with ODF family protein ODF1, which is essential to maintain sperm motility. In conclusion, our findings indicate that TMEM232 is a critical protein for male fertility and sperm motility by regulating sperm cytoplasm removal and maintaining axoneme integrity.

Overexpression of ODF1 in Gastrointestinal Tract Neuroendocrine Neoplasms: a Novel Potential Immunohistochemical Biomarker for Well-differentiated Neuroendocrine Tumors

Gastrointestinal tract neuroendocrine neoplasms (NENs) are a group of rare heterogeneous tumors with different prognoses. The 2019 WHO classification of digestive system tumors defines the classification of NENs as neuroendocrine tumors (NETs G1-G3) and neuroendocrine carcinomas (NECs). We investigated outer dense fiber of sperm tails 1 (ODF1) expression in 137 gastrointestinal tract NENs including 53 NETs G1, 29 NETs G2, 3 NETs G3, and 52 NECs. Twenty adenocarcinomas and 6 squamous cell carcinomas also were included in the study. The results showed that ODF1 was positive in 83 of 85 (97.6%) primary gastrointestinal tract NETs, including 9 of 10 (90%) gastric, 19 of 19 (100%) small bowel, 10 of 11 (90.9%) colorectal, and 45 of 45 (100%) appendiceal neoplasms. There was a significantly statistical difference in the rates of ODF1 positivity in NETs (83/85, 97.6%) vs NECs (25/52, 48.1%, P < 0.001). ODF1 showed diffuse staining in NETs G1 (53/53, 100%) and NETs G2 (28/29, 96.6%), > 50% staining in NETs G3 (2/3, 66.7%), and focal staining (< 50%) in NECs (23/52, 44.2%) but 2 cases (2/52) showed > 50% staining. ODF1 showed no expression in all 20 adenocarcinomas and 6 squamous cell carcinomas. In conclusion, ODF1 was firstly identified as a novel marker for NENs, especially for NETs in the gastrointestinal tract. The expression mechanism and clinical significance of ODF1 in NENs needed further study.

ODF1, sperm flagelar protein is expressed in kidney collecting ducts of rats

ODF1 has been described as an exclusively expressed testicular protein and is located in the outer dense fibers along the sperm tail. ODF1 has been involved in the sperm motility and in the development of the flagellum, but the function of ODF1 is not already clear. Other ODF proteins, such as ODF2 have been characterized in other tissues like the basal body of the kidney primary cilium, but so far only the mRNA of ODF1 has been described in other tissues. These observations let us to hypothesize that the expression of the protein ODF1 could not be limited to the testis. Therefore, in the present work we proposed to evaluate if the ODF1 protein could also be present in tissues other than the testis. Here we demonstrated through western blot, immunofluorescence, and RT-PCR techniques that the protein and mRNA of ODF1 have been identified in the rat kidney. Finally, the presence of ODF1 in kidney has also been confirmed through proteomic analysis using mass spectrometry. The results derived from these different complementary approaches indicate that, to our knowledge and for the first time, ODF1 is demonstrated to be present in an additional organ different to testis. This results raise new questions about potential other functions and locations of the ODF1 protein.

CCDC42 Localizes to Manchette, HTCA and Tail and Interacts With ODF1 and ODF2 in the Formation of the Male Germ Cell Cytoskeleton

Terminal differentiation of male germ cells into functional spermatozoa requires shaping and condensation of the nucleus as well as the formation of sperm-specific structures. A transient microtubular structure, the manchette, is mandatory for sperm head shaping and the development of the connecting piece and the sperm tail. The connecting piece or head-to-tail coupling apparatus (HTCA) mediates the tight linkage of sperm head and tail causing decapitation and infertility when faulty. Using mice as the experimental model, several proteins have already been identified affecting the linkage complex, manchette or tail formation when missing. However, our current knowledge is far too rudimentary to even draft an interacting protein network. Depletion of the major outer dense fiber protein 1 (ODF1) mainly caused decapitation and male infertility but validated binding partners collaborating in the formation of sperm-specific structures are largely unknown. Amongst all candidate proteins affecting the HTCA when missing, the structural protein CCDC42 attracted our attention. The coiled-coil domain containing 42 (CCDC42) is important for HTCA and sperm tail formation but is otherwise largely uncharacterized. We show here that CCDC42 is expressed in spermatids and localizes to the manchette, the connecting piece and the tail. Beyond that, we show that CCDC42 is not restricted to male germ cells but is also expressed in somatic cells in which it localizes to the centrosome. Although centrosomal and sperm tail location seems to be irrespective of ODF1 we asked whether both proteins may form an interacting network in the male germ cell. We additionally considered ODF2, a prevalent protein involved in the formation of spermatid-specific cytoskeletal structures, as a putative binding partner. Our data depict for the first time the subcellular location of CCDC42 in spermatids and deepen our knowledge about the composition of the spermatid/sperm-specific structures. The presence of CCDC42 in the centrosome of somatic cells together with the obvious restricted male-specific phenotype when missing strongly argues for a compensatory function by other still unknown proteins most likely of the same family.

Genetic contribution of SUN5 mutations to acephalic spermatozoa in Fujian China

Acephalic spermatozoa is an extremely rare disease associated with primary infertility. A recent study showed that genetic alterations in the SUN5 gene lead to this disease, and SUN5 mutations could explain the disease in about half of the patients. Therefore, in the present study, to re-visit the genetic contribution of SUN5 mutations to acephalic spermatozoa, we recruited 15 unrelated affected individuals and screened the SUN5 gene for mutations by whole-exome sequencing (WES) and Sanger sequencing. Five of the 15 (33.33%) subjects were found to carry the same homozygous mutation in the SUN5 gene c.381delA (p.V128Sfs*7). Neither homozygous nor compound heterozygous mutations in SUN5 were found in the other 10 patients. The c.381delA mutation resulted in the truncation of the SUN5 protein and decreased the expression and altered the distribution of the outer dense fiber 1 (ODF1) protein. Thus, in our study SUN5 mutations accounted for only one-third of the patients in our cohort, which is lower than the percentage reported previously. Thus, our study suggests that the contribution of SUN5 mutations to acephalic spermatozoa might not be as high as described previously. These results will help in the genetic counseling of patients with acephalic spermatozoa.