The expression pattern of SEPT7 correlates with sperm morphology

A novel indel within the bovine SEPT7 gene is associated with ovary length

The ovary can generate oocytes and secrete female hormones and thus is of great significance to animal fertility. In turn, the functioning of this organ has an effect on the profit margins of the livestock breeding industry. As the development-regulating gene and target gene of miR-202, SEPT7 might play an important role in ovarian growth. Therefore, we hypothesized that SEPT7 is related to ovarian traits owing to the regulation of gonad-specific miR-202. To further investigate the connection between bovine SEPT7 and ovarian development, we analyzed data from 408 samples. After genotyping and analyzing three selected loci, we found that two out of the three loci (L1 and L5) were polymorphic, of which the minimum allelic frequencies were 0.417 (L1) and 0.094 (L5). Moreover, one novel indel L1 of SEPT7 was associated with ovarian length (p < 0.05). More specifically, individuals with II and ID genotypes have longer ovaries than those with the DD genotype. Our work shows that SEPT7 can be selected as a testing marker gene for animal fertility. Our findings contribute to improving the prospects of the cattle industry and the wider use of genetic techniques in breeding.

Morphological and Molecular Bases of Male Infertility: A Closer Look at Sperm Flagellum

Infertility is a major health problem worldwide without an effective therapy or cure. It is estimated to affect 8-12% of couples in the reproductive age group, equally affecting both genders. There is no single cause of infertility, and its knowledge is still far from complete, with about 30% of infertile couples having no cause identified (named idiopathic infertility). Among male causes of infertility, asthenozoospermia (i.e., reduced sperm motility) is one of the most observed, being estimated that more than 20% of infertile men have this condition. In recent years, many researchers have focused on possible factors leading to asthenozoospermia, revealing the existence of many cellular and molecular players. So far, more than 4000 genes are thought to be involved in sperm production and as regulators of different aspects of sperm development, maturation, and function, and all can potentially cause male infertility if mutated. In this review, we aim to give a brief overview of the typical sperm flagellum morphology and compile some of the most relevant information regarding the genetic factors involved in male infertility, with a focus on sperm immotility and on genes related to sperm flagellum development, structure, or function.

Septin7 is indispensable for proper skeletal muscle architecture and function

Today septins are considered as the fourth component of the cytoskeleton, with the Septin7 isoform playing a critical role in the formation of higher-order structures. While its importance has already been confirmed in several intracellular processes of different organs, very little is known about its role in skeletal muscle. Here, using Septin7 conditional knockdown (KD) mouse model, the C2C12 cell line, and enzymatically isolated adult muscle fibers, the organization and localization of septin filaments are revealed, and an ontogenesis-dependent expression of Septin7 is demonstrated. KD mice displayed a characteristic hunchback phenotype with skeletal deformities, reduction in in vivo and in vitro force generation, and disorganized mitochondrial networks. Furthermore, knockout of Septin7 in C2C12 cells resulted in complete loss of cell division while KD cells provided evidence that Septin7 is essential for proper myotube differentiation. These and the transient increase in Septin7 expression following muscle injury suggest that it may be involved in muscle regeneration and development.

Differential expression analysis and identification of sex-related genes by gonad transcriptome sequencing in estradiol-treated and non-treated Ussuri catfish Pseudobagrus ussuriensis

The Ussuri catfish (Pseudobagrus ussuriensis) has an XX/XY sex determination system but its sex determination gene(s) remain unknown. To better understand the molecular sex determination mechanism, transcriptome analysis was conducted to obtain sex-related gene expression profiles. Transcriptome analyses were made of male and female developing/differentiating gonads by high-throughput RNA sequencing, including gonads from fish given an estradiol-induced sex reversal treatment. A total of 81,569 unigenes were assembled and 39,904 were significantly matched to known unique proteins by comparison with public databases. Twenty specifically expressed and 142 differentially expressed sex-related genes were extracted from annotated data by comparing the treatment groups. These genes are involved in spermatogenesis (e.g., Dnali1, nectin3, klhl10, mybl1, Katnal1, Eno4, Mns1, Spag6, Tsga10, Septin7), oogenesis (e.g., Lagr5, Fmn2, Npm2, zar1, Fbxo5, Fbxo43, Prdx4, Nrip1, Lfng, Atrip), gonadal development/differentiation (e.g., Cxcr4b, Hmgb2, Cftr, Ch25h, brip1, Prdm9, Tdrd1, Star, dmrt1, Tut4, Hsd17b12a, gdf9, dnd, arf1, Spata22), and estradiol response (e.g., Mmp14, Lhcgr, vtg1, vtg2, esr2b, Piwil1, Aifm1, Hsf1, gdf9). Dmrt1 and gdf9 may play an essential role in sex determination in P. ussuriensis. The expression patterns of six random genes were validated by quantitative real-time PCR, which confirmed the reliability and accuracy of the RNA-seq results. These data provide a valuable resource for future studies of gene expression and for understanding the molecular mechanism of sex determination/differentiation and gonadal development/differentiation (including hormone-induced sexual reversal) in Ussuri catfish. This has the potential to assist in producing monosex Ussuri catfish to increase aquacultural productivity.

ACTN4 Mediates SEPT14 Mutation-Induced Sperm Head Defects

Septins (SEPTs) are highly conserved GTP-binding proteins and the fourth component of the cytoskeleton. Polymerized SEPTs participate in the modulation of various cellular processes, such as cytokinesis, cell polarity, and membrane dynamics, through their interactions with microtubules, actin, and other cellular components. The main objective of this study was to dissect the molecular pathological mechanism of SEPT14 mutation-induced sperm head defects. To identify SEPT14 interactors, co-immunoprecipitation (co-IP) and nano-liquid chromatography-mass spectrometry/mass spectrometry were applied. Immunostaining showed that SEPT14 was significantly localized to the manchette structure. The SEPT14 interactors were identified and classified as (1) SEPT-, (2) microtubule-, (3) actin-, and (4) sperm structure-related proteins. One interactor, ACTN4, an actin-holding protein, was selected for further study. Co-IP experiments showed that SEPT14 interacts with ACTN4 in a male germ cell line. SEPT14 also co-localized with ACTN4 in the perinuclear and manchette regions of the sperm head in early elongating spermatids. In the cell model, mutated SEPT14 disturbed the localization pattern of ACTN4. In a clinical aspect, sperm with mutant SEPT14, SEPT14^A123T (p.Ala123Thr), and SEPT14^I333T (p.Ile333Thr), have mislocalized and fragmented ACTN4 signals. Sperm head defects in donors with SEPT14 mutations are caused by disruption of the functions of ACTN4 and actin during sperm head formation.

Association of single nucleotide polymorphism c.673C>A/p.Gln225Lys in SEPT12 gene with spermatogenesis failure in male idiopathic infertility in Northeast China

Male infertility is a complex multifactorial disease affecting approximately 10% of couples who want to have children. Some cases of infertility can be explained by genetic factors. Septins are members of the GTPase superfamily, which are involved in diverse biological processes including morphogenesis, compartmentalization, cytokinesis, and apoptosis. The septin 12 gene, SEPT12, is expressed exclusively in post-meiotic male germ cells and is considered as a critical gene for spermatogenesis. In this study, we evaluated 200 patients with non-obstructive azoospermia and detected mutations of 25 spermatogenesis-associated genes by targeted exome sequencing. We report a missense SEPT12 variant, c.673C>A/p.Gln225Lys, in an infertile man with non-obstructive azoospermia. The variation was located inside the GTPase domain and had a SIFT score of 0.02 (<0.50) and was considered to be 'probably damaging' by PolyPhen. This case may provide clues to help establish the relationship between SEPT12 gene alterations and some cases of idiopathic male infertility. The role of this variant should thus be investigated further.

The role of septin 7 in physiology and pathological disease: A systematic review of current status

Septins are a conserved family of cytoskeletal GTPases present in different organisms, including yeast, drosophila, Caenorhabditis elegans and humans. In humans, septins are involved in various cellular processes, including exocytosis, apoptosis, leukemogenesis, carcinogenesis and neurodegeneration. Septin 7 is unique out of 13 human septins. Mammalian septin 6, septin 7, septin 2 and septin 9 coisolate together in complexes to form the core unit for the generation of the septin filaments. Physiological septin filaments are hetero-oligomeric complexes consisting of core septin hexamers and octamers. Furthermore, septin 7 plays a crucial role in cytokinesis and mitosis. Septin 7 is localized to the filopodia and branches of developing hippocampal neurons, and is the most abundant septin in the adult rat forebrain as well as a structural component of the human and mouse sperm annuli. Septin 7 is crucial to the spine morphogenesis and dendrite growth in neurons, and is also a structural constituent of the annulus in human and mouse sperm. It can suppress growth of some tumours such as glioma and papillary thyroid carcinoma. However, the molecular mechanisms of involvement of septin 7 in human disease, especially in the development of cancer, remain unclear. This review focuses on the structure, function and mechanism of septin 7 in vivo, and summarizes the role of septin 7 in cell proliferation, cytokinesis, nervous and reproductive systems, as well as the underlying molecular events linking septin 7 to various diseases, such as Alzheimer's disease, schizophrenia, neuropsychiatric systemic lupus erythematosus, tumour and so on.

SEPT12 phosphorylation results in loss of the septin ring/sperm annulus, defective sperm motility and poor male fertility

Septins are critical for numerous cellular processes through the formation of heteromeric filaments and rings indicating the importance of structural regulators in septin assembly. Several posttranslational modifications (PTMs) mediate the dynamics of septin filaments in yeast. However, little is known about the role of PTMs in regulating mammalian septin assembly, and the in vivo significance of PTMs on mammalian septin assembly and function remains unknown. Here, we showed that SEPT12 was phosphorylated on Ser198 using mass spectrometry, and we generated SEPT12 phosphomimetic knock-in (KI) mice to study its biological significance. The homozygous KI mice displayed poor male fertility due to deformed sperm with defective motility and loss of annulus, a septin-based ring structure. Immunohistochemistry of KI testicular sections suggested that SEPT12 phosphorylation inhibits septin ring assembly during annulus biogenesis. We also observed that SEPT12 was phosphorylated via PKA, and its phosphorylation interfered with SEPT12 polymerization into complexes and filaments. Collectively, our data indicate that SEPT12 phosphorylation inhibits SEPT12 filament formation, leading to loss of the sperm annulus/septin ring and poor male fertility. Thus, we provide the first in vivo genetic evidence characterizing importance of septin phosphorylation in the assembly, cellular function and physiological significance of septins.

Major regulatory mechanisms involved in sperm motility

The genetic bases and molecular mechanisms involved in the assembly and function of the flagellum components as well as in the regulation of the flagellar movement are not fully understood, especially in humans. There are several causes for sperm immotility, of which some can be avoided and corrected, whereas other are related to genetic defects and deserve full investigation to give a diagnosis to patients. This review was performed after an extensive literature search on the online databases PubMed, ScienceDirect, and Web of Science. Here, we review the involvement of regulatory pathways responsible for sperm motility, indicating possible causes for sperm immotility. These included the calcium pathway, the cAMP-dependent protein kinase pathway, the importance of kinases and phosphatases, the function of reactive oxygen species, and how the regulation of cell volume and osmolarity are also fundamental components. We then discuss main gene defects associated with specific morphological abnormalities. Finally, we slightly discuss some preventive and treatments approaches to avoid development of conditions that are associated with unspecified sperm immotility. We believe that in the near future, with the development of more powerful techniques, the genetic causes of sperm immotility and the regulatory mechanisms of sperm motility will be better understand, thus enabling to perform a full diagnosis and uncover new therapies.

SEPT12/SPAG4/LAMINB1 complexes are required for maintaining the integrity of the nuclear envelope in postmeiotic male germ cells

Male infertility affects approximately 50% of all infertile couples. The male-related causes of intracytoplasmic sperm injection failure include the absence of sperm, immotile or immature sperm, and sperm with structural defects such as those caused by premature chromosomal condensation and DNA damage. Our previous studies based on a knockout mice model indicated that SEPT12 proteins are critical for the terminal morphological formation of sperm. SEPT12 mutations in men result in teratozospermia and oligozospermia. In addition, the spermatozoa exhibit morphological defects of the head and tail, premature chromosomal condensation, and nuclear damage. However, the molecular functions of SEPT12 during spermatogenesis remain unclear. To determine the molecular functions of SEPT12, we applied a yeast 2-hybrid system to identify SEPT12 interactors. Seven proteins that interact with SEPT12 were identified: SEPT family proteins (SEPT4 and SEPT6), nuclear or nuclear membrane proteins (protamine 2, sperm-associated antigen 4, and NDC1 transmembrane nucleoproine), and sperm-related structural proteins (pericentriolar material 1 and obscurin-like 1). Sperm-associated antigen 4 (SPAG4; also known as SUN4) belongs to the SUN family of proteins and acts as a linker protein between nucleoskeleton and cytoskeleton proteins and localizes in the nuclear membrane. We determined that SEPT12 interacts with SPAG4 in a male germ cell line through coimmunoprecipitation. During human spermiogenesis, SEPT12 is colocalized with SPAG4 near the nuclear periphery in round spermatids and in the centrosome region in elongating spermatids. Furthermore, we observed that SEPT12/SPAG4/LAMINB1 formed complexes and were coexpressed in the nuclear periphery of round spermatids. In addition, mutated SEPT12, which was screened from an infertile man, affected the integration of these nuclear envelope complexes through coimmunoprecipitation. This was the first study that suggested that SEPT proteins link to the SUN/LAMIN complexes during the formation of nuclear envelopes and are involved in the development of postmeiotic germ cells.

Relationship between absence of annulus and asthenozoospermia in Iranian men

PURPOSE

To find a relationship between absence of annulus and asthenozoospermia in Iranian men.

METHODS

In the present study, semen samples from 100 asthenozoospermic and 20 normozospermic patients were analyzed for sperm concentration and motility. Spermatozoa were immunostained for the two septin subunits Sept4 and Sept7. The absence of the annulus structure was confirmed by transmission electron microscopy and western blot analysis for septin 4. DNA sequencing for all coding exons of SEPT12 was performed for a patient using peripheral blood sample.

RESULTS

Specific antibodies for SEPT4 and SEPT7 consistently labeled the annuli in spermatozoa from all of the 20 normozospermic men, while in one of 100 patients with asthenozoospermia, 75% of sperms lacking septin 4 or septin 7 proteins at the annulus. It was shown that the structural defect in annulus formation is not caused by point mutation of SEPT12 gene.

CONCLUSIONS

In conclusion, the results of this study demonstrated that the frequency of the absence of annulus in asthenozoospermic sample of Iranian population has a low frequency and could not be assume as a diagnostic marker for classifying asthenozoospermic patients.

Comparative expression analysis of Septin 14 in testes of infertile men with normal spermatogenesis and spermatogenic failure

BACKGROUND

Septins are an evolutionary conserved group of GTP-binding and filament-forming proteins that have diverse cellular roles. An increasing body of data implicates the septin family in the pathogenesis of diverse states including cancers, neurodegeneration, and male infertility.

OBJECTIVE

The objective of the study was to evaluate the expression pattern of Septin14 in testis tissue of men with and without spermatogenic failure.

MATERIALS AND METHODS

The samples retrieved accessible random between infertile men who underwent diagnostic testicular biopsy in Royan institute. 10 infertile men with obstructive azoospermia and normal spermatogenesis and 20 infertile men with non-obstructive azoospermia were recruited for real-time reverse transcription (RT)-PCR analysis of the testicular tissue. Total RNA was extracted with trizol reagent.

RESULTS

Comparison of the mRNA level of septin14 revealed that in tissues with partial (n=10) or complete spermatogenesis (n=10), the expression of septin 14 was significantly higher than sertoli cell only tissues.

CONCLUSION

The testicular tissues of men with hypospermatogenesis, maturation arrest and sertoli cell only had lower levels of septin 14 transcripts than normal men. These data indicates that Septin 14 expression level is critical for human spermatogenesis.

Septin 7 is required for orderly meiosis in mouse oocytes

Septin 7 is a conserved GTP-binding protein. In this study, we examined the localization and functions of Septin 7 during mouse oocyte meiotic maturation. Immunofluorescent analysis showed that intrinsic Septin 7 localized to the spindles from the pro-MI stage to the MII stage. Knockdown of Septin 7 by siRNA microinjection caused abnormal spindles and affected extrusion of the first polar body. Septin 7 mRNA tagged with myc was injected into GV stage oocytes to overexpress Septin 7. Overexpressed Myc-Septin 7 localized to the spindle and beneath the plasma membrane displaying long filaments. Fluorescence intensity of spindle α-tubulin in myc-Septin 7-injected oocytes was weaker than that of the control group, demonstrating that Septin 7 may influence recruitment of α-tubulin to spindles. MII oocytes injected with myc-Septin 7 exhibited abnormal chromosome alignment, and parthenogenetic activation failed to allow extrusion of the second polar body, suggesting that overexpression of Septin 7 may affect extrusion of the polar body by disturbing the alignment of chromosomes and regulating α-tubulin recruitment to spindles. In summary, Septin 7 may regulate meiotic cell cycle progression by affecting microtubule cytoskeletal dynamics in mouse oocytes.

The role of the septin family in spermiogenesis

SEPTINS (FULL NAME: Septin; symbol name: SEPT) belong to a family of polymerizing GTP-binding proteins that are required for many cellular functions, including membrane compartmentalization, vesicle trafficking, mitosis and cytoskeletal remodeling. Two of the 14 family members in the mammalian species, Septin12 and 14 are expressed specifically in the testis. In the mouse, knockout of Septin4 and Septin12 leads to male sterility with distinctive sperm pathology (defective annulus or bent neck). In humans, sperm with abnormal expression patterns of SEPT4, 7 and 12 are more prevalent in infertile men. How septin filament is assembled/dissembled and how the SEPT-related complex regulates spermatogenesis still await further investigation.

Membrane-associated RING-CH 10 (MARCH10 protein) is a microtubule-associated E3 ubiquitin ligase of the spermatid flagella

Spermiogenesis is a complex and dynamic process of the metamorphosis of spermatids into spermatozoa. There is a great deal that is still unknown regarding the regulatory mechanisms for the formation of the sperm flagellum. In this study, we determined that the membrane-associated RING-CH 10 (March10) gene is predominantly expressed in rat testis. We isolated two March10 isoforms encoding MARCH10a and MARCH10b, which are generated by alternative splicing. MARCH10a is a long RING finger protein, and MARCH10b is a short RING finger-less protein. Immunohistochemical staining revealed that the MARCH10 proteins are specifically expressed in elongating and elongated spermatids, and the expression is absent in epididymal spermatozoa. MARCH10 immunoreactivity was observed in the cytoplasmic lobes as well as the principal piece and annulus of the flagella. When overexpressed in COS7 cells, MARCH10a was localized along the microtubules, whereas MARCH10b was distributed throughout the cytoplasm. An in vitro microtubule cosedimentation assay showed that MARCH10a is directly associated with microtubules. An in vitro ubiquitination assay demonstrated that the RING finger domain of MARCH10a exhibits an E3 ubiquitin ligase activity along with the E2 ubiquitin-conjugating enzyme UBE2B. Moreover, MARCH10a undergoes proteasomal degradation by autoubiquitination in transfected COS7 cells, but this activity was abolished upon microtubule disassembly. These results suggest that MARCH10 is involved in spermiogenesis by regulating the formation and maintenance of the flagella in developing spermatids.