Essential role for SUN5 in anchoring sperm head to the tail

Novel homozygous missense variants in SUN5 and DNAH10 associated with male infertility and oligoasthenoteratozoospermia

Genetic variants are known causes of male infertility and oligoasthenoteratozoospermia (OAT), as shown by knockout mouse models and patients with infertility. However, most OAT cases lack a definitive genetic diagnosis. Peripheral blood and semen samples were collected from a patient with OAT. Semen analysis, Papanicolaou staining, transmission electron microscopy, whole-exome sequencing (WES), Sanger sequencing, and in silico analyses, such as conservative analysis and conformational analyses, were used to investigate the genetic causes of OAT. Semen analysis revealed a notable reduction in sperm count and motility, and defects in sperm morphology. Light and electron microscopy showed numerous defects in the head-to-tail coupling apparatus of the sperm, and a small number of structural defects in the sperm flagella. WES identified two novel homozygous missense variants SUN5: c.G703A/p.A235T and DNAH10: c.A1436G/p.Q479R. The p.A235T and p.Q479R variants were predicted to generate aberrant SUN5 and DNAH10 proteins using in silico analysis. Here, we report the identification of two novel deleterious variants of SUN5 and DNAH10 associated with OAT, expanding the mutant spectrum of male infertility.

CD38hi macrophages promote fibrotic transition following acute kidney injury by modulating NAD+ metabolism

Acute kidney injury (AKI) encompasses a spectrum of conditions, varying from mild and self-limiting to severe cases that can lead to chronic kidney disease (CKD). Macrophages are crucial in the progression from AKI to CKD, yet the diversity of macrophage subsets complicates the identification of key functional types. We established a detailed single-cell atlas of mononuclear macrophages from the onset of AKI through its progression to CKD. Our results indicate that a macrophage subset with high CD38 expression is closely linked to renal fibrosis following AKI in both mouse model and AKI patients. These CD38hi macrophages, derived from resident macrophages via Csf1 signaling, secrete the NAD-depleting enzyme CD38, inducing senescence in renal tubular cells and promoting chronic inflammation and renal fibrosis. Knocking out CD38 in macrophages elevated renal NAD levels, reducing senescence and fibrotic responses. Furthermore, we initiated a dosing regimen for a CD38 inhibitor, demonstrating its potential to reduce fibrosis post-AKI, suggesting that targeting CD38hi macrophages-mediated NAD+ metabolism could be a promising therapy to halt AKI to CKD progression.

TEX38 localizes ZDHHC19 to the plasma membrane and regulates sperm head morphogenesis in mice

Sperm morphogenesis is a tightly regulated differentiation process, disruption of which leads to sperm malfunction and male infertility. Here, we show that Tex38 knockout (KO) male mice are infertile. Tex38 KO spermatids exhibit excess retention of residual cytoplasm around the head, resulting in abnormal sperm morphology with backward head bending. TEX38 interacts and colocalizes with ZDHHC19, a testis-enriched acyltransferase catalyzing protein S-palmitoylation, at the plasma membrane of spermatids. ZDHHC19 and TEX38 are each downregulated in mouse testes lacking the other protein. TEX38 stabilizes and localizes ZDHHC19 to the plasma membrane of cultured cells and vice versa, consolidating their interdependence. Mice deficient in ZDHHC19 or harboring a C142S mutation that disables the palmitoyltransferase activity of ZDHHC19 display phenotypes resembling those of Tex38 KO mice. Strikingly, ZDHHC19 palmitoylates ARRDC5, an arrestin family protein regulating sperm differentiation. Overall, our findings indicate that TEX38 forms a stable complex with ZDHHC19 at the plasma membrane of spermatids, which governs downstream S-palmitoylation of proteins essential for morphological transformation of spermatids.

Identification of key genes and variants associated with boar sperm freezability using whole genome resequencing

Cryopreservation induces various cryodamages to the structural or functional aspects of boar sperm, resulting in the deterioration of sperm quality. The extent of cryodamages varies significantly among different individual boars. In our study, 50 boars with either good sperm freezability (GSF) or poor sperm freezability (PSF) were selected from a population of 402 boars. These two groups exhibited significant differences in sperm quality, acrosome integrity, mitochondrial membrane potential, and plasma membrane integrity. Subsequent whole-genome resequencing and FST analysis of GSF and PSF boars uncovered genetic differentiation among 5632 genes. Spermatogenesis, sperm structure, and lipid composition were identified as the potential factors, and 35 genes, such as RNF8, PACRG, CADM1, SPAG16, PPP3CA and MFF, were identified as key candidate genes associated with sperm freezability. Furthermore, by using MassARRAY genotyping and a general linear model, nine variants, including seven single nucleotide polymorphisms (SNPs) and two insertion variants, were found to be significantly correlated with sperm freezability. These variants, located within the candidate genes, represent potential molecular markers for sperm freezability. Our research contributes novel insights into the genetic mechanisms underlying freezability differences in boar sperm and identifies candidate genes and key molecular markers that could be applied in boar breeding practices.

Loss of CCDC188 causes male infertility with defects in the sperm head-neck connection in mice†

Acephalic spermatozoa syndrome represents a rare genetic and reproductive disease, which is defined as semen composed of mostly headless spermatozoa. The connecting piece in the neck region, also known as the head-to-tail coupling apparatus, plays a crucial role in the tight linkage between the sperm head and tail. Dysfunction of this structure can lead to separation of sperm heads and tails, and male infertility. Using the mouse as an experimental model, several proteins have been identified as associated with the head-to-tail coupling apparatus and disruption of these proteins causes acephalic spermatozoa. However, the molecular mechanism underlying this morphologic anomaly and head-to-tail coupling apparatus remains elusive. In this study, we focused on coiled-coil domain containing 188 (Ccdc188), which shows testis-enriched expression. To elucidate the physiological role of CCDC188, we generated a knockout mouse line using the CRISPR/Cas9 system. Ccdc188 knockout male mice were sterile, indicating that CCDC188 is indispensable for male fertility. Most Ccdc188-null spermatozoa were acephalic. Transmission electron microscopy revealed that while the sperm head-to-tail coupling apparatus could assemble properly without CCDC188, the head-to-tail coupling apparatus failed to attach to the nucleus during spermiogenesis, leading to sperm head and neck separation. In addition, we found almost all of the spermatozoa in the cauda epididymis lacked a mitochondrial sheath. Taken together, we demonstrated that CCDC188 plays a crucial role in forming a tight sperm head-neck junction.

CEP44 and CCDC15 label the spermatozoa proximal and atypical distal centrioles

The centrosome is a conserved characteristic of eukaryotic and human cells but is highly specialized in reproductive cells. The spermatozoan centrosome includes a slightly modified proximal centriole, an atypical distal centriole, and specialized pericentriolar material, including striated columns and capitellum. We investigated the localization of canonical centriolar proteins CEP44 and CCDC15 in human spermatozoa. We found that CEP44 localizes mainly at the proximal centriole and distal centriole bases relative to centrin. CCDC15 colocalizes with centrin in both the proximal centriole and distal centriole. These findings further our understanding of the spermatozoan centrosome composition.

CCDC113 stabilizes sperm axoneme and head-tail coupling apparatus to ensure male fertility

The structural integrity of the sperm is crucial for male fertility, defects in sperm head-tail linkage and flagellar axoneme are associated with acephalic spermatozoa syndrome (ASS) and the multiple morphological abnormalities of the sperm flagella (MMAF). Notably, impaired head-tail coupling apparatus (HTCA) often accompanies defects in the flagellum structure, however, the molecular mechanisms underlying this phenomenon remain elusive. Here, we identified an evolutionarily conserved coiled-coil domain-containing (CCDC) protein, CCDC113, and found the disruption of CCDC113 produced spermatozoa with disorganized sperm flagella and HTCA, which caused male infertility. Further analysis revealed that CCDC113 could bind to CFAP57 and CFAP91, and function as an adaptor protein for the connection of radial spokes, nexin-dynein regulatory complex (N-DRC), and doublet microtubules (DMTs) in the sperm axoneme. Moreover, CCDC113 was identified as a structural component of HTCA, collaborating with SUN5 and CENTLEIN to connect sperm head to tail during spermiogenesis. Together, our studies reveal that CCDC113 serve as a critical hub for sperm axoneme and HTCA stabilization in mice, providing insights into the potential pathogenesis of infertility associated with human CCDC113 mutations.

CCDC28A deficiency causes head-tail coupling defects and immotility in murine spermatozoa

Male infertility presents a substantial challenge in reproductive medicine, often attributed to impaired sperm motility. The present study investigates the role of CCDC28A, a protein expressed specifically in male germ cells, whose paralog CCDC28B has been implicated in ciliogenesis. We identify unique expression patterns for CCDC28A and CCDC28B within the mouse testes, where CCDC28A is expressed in germ cells, whereas CCDC28B is expressed in supporting somatic cells. Through knockout mouse models and histological analyses, we reveal that CCDC28A deficiency results in diminished sperm motility and structural aberrations in sperm tails, notably affecting the head-tail coupling apparatus (HTCA), thereby causing male infertility. Fine structural analyses by transmission electron microscopy reveal disruptions at the capitulum-basal plate junction of the HTCA in the CCDC28A mutants. This results in the bending of the head within the neck region, often accompanied by thickening of the tail midpiece. Our discovery demonstrates that CCDC28A plays an essential role in male fertility and sperm tail morphogenesis through the formation of HTCA.

Novel variations in TENT5D lead to teratozoospermia in infertile patients

PURPOSE

Teratozoospermia is the main pathogenic factor of male infertility. However, the genetic etiology of teratozoospermia is largely unknown. This study aims to clarify the relationship between novel variations in TENT5D and teratozoospermia in infertile patients.

MATERIALS AND METHODS

Two infertile patients were enrolled. Routine semen analysis of patients and normal controls was conducted with the WHO guidelines. Whole-exome sequencing (WES) was conducted to identify pathogenic variants in the two patients. Morphology and ultrastructure analysis of spermatozoa in the two patients was determined by Papanicolaou staining, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The functional effect of the identified variants was analyzed by immunofluorescence staining and western blotting. The expression of TENT5D in different germ cells was detected by immunofluorescence staining.

RESULTS

Two new hemizygous variations, c.101C > T (p.P34L) and c.125A > T (p.D42V), in TENT5D were detected in two patients with male infertility. Morphology analysis showed abnormalities in spermatozoa morphology in the two patients, including multiple heads, headless, multiple tails, coiled, and/or bent flagella. Ultrastructure analysis showed that most of the spermatozoa exhibited missing or irregularly arranged '9+2' structures. Further functional experiments confirmed the abrogated TENT5D protein expression in patients. In addition, both p.P34L and p.D42V substitutions resulted in a conformational change of the TENT5D protein. We precisely analyzed the subcellular localization of TENT5D in germ cells in humans and mice. And we found that TENT5D was predominantly detected in the head and flagellum of elongating spermatids and epididymal spermatozoa.

CONCLUSIONS

Our results showed further evidence of a relationship between TENT5D mutation and human male infertility, providing new genetic insight for use in the diagnosis and treatment of male infertility.

SUN5, a testis-specific nuclear membrane protein, participates in recruitment and export of nuclear mRNA in spermatogenesis

SUN5, a testis-specific gene, is associated with acephalic spermatozoa syndrome (ASS). Here, we demonstrate that SUN5 is involved in mRNA export. In Sun5-knockout mice ( Sun5 -/-), poly(A) + RNA accumulates in the nuclei of germ cells, leading to reduced sperm counts, decreased sperm motility and disrupted sperm head-to-tail junctions. Additionally, in the GC-2 germ cell line with RNA interference of Sun5, heterogeneous nuclear ribonucleoproteins (hnRNPs) and poly (A) + RNA (mainly mRNA) are retained in the nucleus. Further mechanistic studies reveal that SUN5 interacts with Nxf1 (nuclear RNA export factor 1) and nucleoporin 93 (Nup93). Interference with Nup93 inhibits mRNA export. Treatment with leptomycin B to block the CRM1 pathway indicates that Sun5 regulates mRNA export through an Nxf1-dependent pathway. In Sun5 -/- mice, the binding of Nxf1 and Nup93 decreases due to loss of Sun5 function, and the process of submitting Nxf1-binding mRNPs to Nup93 is inhibited, resulting in abnormal spermatogenesis. Together, these data may elucidate a novel pathway for mRNA export in male germ cells.

Development of functional spermatozoa in mammalian spermiogenesis

Infertility is a global health problem affecting one in six couples, with 50% of cases attributed to male infertility. Spermatozoa are male gametes, specialized cells that can be divided into two parts: the head and the flagellum. The head contains a vesicle called the acrosome that undergoes exocytosis and the flagellum is a motility apparatus that propels the spermatozoa forward and can be divided into two components, axonemes and accessory structures. For spermatozoa to fertilize oocytes, the acrosome and flagellum must be formed correctly. In this Review, we describe comprehensively how functional spermatozoa develop in mammals during spermiogenesis, including the formation of acrosomes, axonemes and accessory structures by focusing on analyses of mouse models.

SUN5 interacts with nuclear membrane LaminB1 and cytoskeletal GTPase Septin12 mediating the sperm head-and-tail junction

Acephalic spermatozoa syndrome (ASS) is a severe teratospermia with decaudated, decapitated, and malformed sperm, resulting in male infertility. Nuclear envelope protein SUN5 localizes to the junction between the sperm head and tail. Mutations in the SUN5 gene have been identified most frequently (33-47%) in ASS cases, and its molecular mechanism of action is yet to be explored. In the present study, we generated Sun5 knockout mice, which presented the phenotype of ASS. Nuclear membrane protein LaminB1 and cytoskeletal GTPases Septin12 and Septin2 were identified as potential partners for interacting with SUN5 by immunoprecipitation-mass spectrometry in mouse testis. Further studies demonstrated that SUN5 connected the nucleus by interacting with LaminB1 and connected the proximal centriole by interacting with Septin12. The binding between SUN5 and Septin12 promoted their aggregation together in the sperm neck. The disruption of the LaminB1/SUN5/Septin12 complex by Sun5 deficiency caused separation of the Septin12-proximal centriole from the nucleus, leading to the breakage of the head-to-tail junction. Collectively, these data provide new insights into the pathogenesis of ASS caused by SUN5 deficiency.

Genetic mutation of Cep76 results in male infertility due to abnormal sperm tail composition

The transition zone is a specialised gate at the base of cilia/flagella, which separates the ciliary compartment from the cytoplasm and strictly regulates protein entry. We identified a potential new regulator of the male germ cell transition zone, CEP76. We demonstrated that CEP76 was involved in the selective entry and incorporation of key proteins required for sperm function and fertility into the ciliary compartment and ultimately the sperm tail. In the mutant, sperm tails were shorter and immotile as a consequence of deficits in essential sperm motility proteins including DNAH2 and AKAP4, which accumulated at the sperm neck in the mutant. Severe annulus, fibrous sheath, and outer dense fibre abnormalities were also detected in sperm lacking CEP76. Finally, we identified that CEP76 dictates annulus positioning and structure. This study suggests CEP76 as a male germ cell transition zone protein and adds further evidence to the hypothesis that the spermatid transition zone and annulus are part of the same functional structure.

Coiled-coil domain containing 159 is required for spermatid head and tail assembly in mice†

The centrosome is critical for maintaining the sperm head-tail connection and the formation of flagellar microtubules. In this study, we found that in mouse testes, CCDC159 (coiled-coil domain-containing protein 159) is specifically localized to the head-tail coupling apparatus (HTCA) of spermatids, a structure that ensures sperm head-tail tight conjunction. CCDC159 contains a C-terminal coiled-coil domain that functions as the centrosomal localization signal. Gene knockout (KO) of Ccdc159 in mice resulted in acephalic spermatozoa, abnormal flagella, and male infertility. To explore the mechanism behind CCDC159 regulating spermatogenesis, we identified CCDC159-binding proteins using a yeast two-hybrid screen and speculated that CCDC159 participates in HTCA assembly by regulating protein phosphatase PP1 activity. Further RNA-sequencing analyses of Ccdc159 KO testes revealed numerous genes involved in male gamete generation that were downregulated. Together, our results show that CCDC159 in spermatids is a novel centrosomal protein anchoring the sperm head to the tail. Considering the limitation of KO mouse model in clarifying the biological function of CCDC159 in spermatogenesis, a gene-rescue experiment will be performed in the future.

Genetic Causes of Qualitative Sperm Defects: A Narrative Review of Clinical Evidence

Several genes are implicated in spermatogenesis and fertility regulation, and these genes are presently being analysed in clinical practice due to their involvement in male factor infertility (MFI). However, there are still few genetic analyses that are currently recommended for use in clinical practice. In this manuscript, we reviewed the genetic causes of qualitative sperm defects. We distinguished between alterations causing reduced sperm motility (asthenozoospermia) and alterations causing changes in the typical morphology of sperm (teratozoospermia). In detail, the genetic causes of reduced sperm motility may be found in the alteration of genes associated with sperm mitochondrial DNA, mitochondrial proteins, ion transport and channels, and flagellar proteins. On the other hand, the genetic causes of changes in typical sperm morphology are related to conditions with a strong genetic basis, such as macrozoospermia, globozoospermia, and acephalic spermatozoa syndrome. We tried to distinguish alterations approved for routine clinical application from those still unsupported by adequate clinical studies. The most important aspect of the study was related to the correct identification of subjects to be tested and the correct application of genetic tests based on clear clinical data. The correct application of available genetic tests in a scenario where reduced sperm motility and changes in sperm morphology have been observed enables the delivery of a defined diagnosis and plays an important role in clinical decision-making. Finally, clarifying the genetic causes of MFI might, in future, contribute to reducing the proportion of so-called idiopathic MFI, which might indeed be defined as a subtype of MFI whose cause has not yet been revealed.

BAG5 regulates HSPA8-mediated protein folding required for sperm head-tail coupling apparatus assembly

Teratozoospermia is a significant cause of male infertility, but the pathogenic mechanism of acephalic spermatozoa syndrome (ASS), one of the most severe teratozoospermia, remains elusive. We previously reported Spermatogenesis Associated 6 (SPATA6) as the component of the sperm head-tail coupling apparatus (HTCA) required for normal assembly of the sperm head-tail conjunction, but the underlying molecular mechanism has not been explored. Here, we find that the co-chaperone protein BAG5, expressed in step 9-16 spermatids, is essential for sperm HTCA assembly. BAG5-deficient male mice show abnormal assembly of HTCA, leading to ASS and male infertility, phenocopying SPATA6-deficient mice. In vivo and in vitro experiments demonstrate that SPATA6, cargo transport-related myosin proteins (MYO5A and MYL6) and dynein proteins (DYNLT1, DCTN1, and DNAL1) are misfolded upon BAG5 depletion. Mechanistically, we find that BAG5 forms a complex with HSPA8 and promotes the folding of SPATA6 by enhancing HSPA8's affinity for substrate proteins. Collectively, our findings reveal a novel protein-regulated network in sperm formation in which BAG5 governs the assembly of the HTCA by activating the protein-folding function of HSPA8.

Molecular characterization of SPATA6 and association of its SNPs with testicular size in sheep

The testis is an important organ for maintaining fertility in males, and testis size is positively correlated with ejaculate volume, sperm motility, thus fertility. Spermatogenesis-associated 6 (SPATA6) is an evolutionarily conserved testis-specific gene reported in many species. However, the effect of SPATA6 expression levels on testicular development and the effect of single nucleotide polymorphisms (SNPs) on testis and epididymis phenotype in sheep have not been studied. The purpose of the research was to investigate the expression profile of SPATA6 and its effect on testicular development and to confirm the effect of SNPs on the testis and epididymis phenotype. In this study, we detected a 1245bp coding sequence (CDS) of SPATA6 and encoded 414 amino acids. The expression levels of SPATA6 were significantly higher in the testis than in other tissues and gradually increased with testis development. Moreover, the expression level in the large testis was significantly higher than that in the small testis at six months. A total of 11 SNPs were detected in the coding region of SPATA6 by cDNA-pooling sequencing and improved multiplex ligation detection reaction (iMLDR) methods. Correlation analysis showed that SNP2 (c. 3631C > G) significantly affected left epididymis weight (LEW) and right epididymis weight (REW), and SNP10 (c. 937 A > G) significantly affected REW. And the combined genotype of SNP1 (c. 4245 G > A) and SNP2 significantly affected REW. The current study concluded that SPATA6 plays an important role in testicular development and the SNPs significantly associated with the epididymis phenotype can provide molecular markers for the early selection of high-fertility Hu sheep.

A framework for identifying fertility gene targets for mammalian pest control

Fertility-targeted gene drives have been proposed as an ethical genetic approach for managing wild populations of vertebrate pests for public health and conservation benefit. This manuscript introduces a framework to identify and evaluate target gene suitability based on biological gene function, gene expression and results from mouse knockout models. This framework identified 16 genes essential for male fertility and 12 genes important for female fertility that may be feasible targets for mammalian gene drives and other non-drive genetic pest control technology. Further, a comparative genomics analysis demonstrates the conservation of the identified genes across several globally significant invasive mammals. In addition to providing important considerations for identifying candidate genes, our framework and the genes identified in this study may have utility in developing additional pest control tools such as wildlife contraceptives.

Identification of CFAP52 as a novel diagnostic target of male infertility with defects of sperm head-tail connection and flagella development

Male infertility is a worldwide population health concern. Asthenoteratozoospermia is a common cause of male infertility, but its etiology remains incompletely understood. No evidence indicates the relevance of CFAP52 mutations to human male infertility. Our whole-exome sequencing identified compound heterozygous mutations in CFAP52 recessively cosegregating with male infertility status in a non-consanguineous Chinese family. Spermatozoa of CFAP52-mutant patient mainly exhibited abnormal head-tail connection and deformed flagella. Cfap52-knockout mice resembled the human infertile phenotype, showing a mixed acephalic spermatozoa syndrome (ASS) and multiple morphological abnormalities of the sperm flagella (MMAF) phenotype. The ultrastructural analyses further revealed a failure of connecting piece formation and a serious disorder of '9+2' axoneme structure. CFAP52 interacts with a head-tail coupling regulator SPATA6 and is essential for its stability. Expression of microtubule inner proteins and radial spoke proteins were reduced after the CFAP52 deficiency. Moreover, CFAP52-associated male infertility in humans and mice could be overcome by intracytoplasmic sperm injection (ICSI). The study reveals a prominent role for CFAP52 in sperm development, suggesting that CFAP52 might be a novel diagnostic target for male infertility with defects of sperm head-tail connection and flagella development.

ARRDC5 deficiency impairs spermatogenesis by affecting SUN5 and NDC1

Sperm with normal morphology and motility are essential for successful fertilization, and the strong attachment of the sperm head-tail coupling apparatus to the nuclear envelope during spermatogenesis is required to ensure the integrity of sperm for capacitation and fertilization. Here, we report that Arrdc5 is associated with spermatogenesis. The Arrdc5 knockout mouse model showed male infertility characterized by a high bent-head rate and reduced motility in sperm, which led to capacitation defects and subsequent fertilization failure. Through mass spectrometry, we found that ARRDC5 affects spermatogenesis by affecting NDC1 and SUN5. We further found that ARRDC5 might affect the vesicle-trafficking protein SEC22A-mediated transport and localization of NDC1, SUN5 and other head-tail coupling apparatus-related proteins that are responsible for initiating the attachment of the sperm head and tail. We finally performed intracytoplasmic sperm injection as a way to explore therapeutic strategies. Our findings demonstrate the essential role and the underlying molecular mechanism of ARRDC5 in anchoring the sperm head to the tail during spermatogenesis.

A missense mutation in Ehd1 associated with defective spermatogenesis and male infertility

Normal function of the C-terminal Eps15 homology domain-containing protein 1 (EHD1) has previously been associated with endocytic vesicle trafficking, shaping of intracellular membranes, and ciliogenesis. We recently identified an autosomal recessive missense mutation c.1192C>T (p.R398W) of EHD1 in patients who had low molecular weight proteinuria (0.7-2.1 g/d) and high-frequency hearing loss. It was already known from Ehd1 knockout mice that inactivation of Ehd1 can lead to male infertility. However, the exact role of the EHD1 protein and its p.R398W mutant during spermatogenesis remained still unclear. Here, we report the testicular phenotype of a knockin mouse model carrying the p.R398W mutation in the EHD1 protein. Male homozygous knockin mice were infertile, whereas the mutation had no effect on female fertility. Testes and epididymes were significantly reduced in size and weight. The testicular epithelium appeared profoundly damaged and had a disorganized architecture. The composition of developing cell types was altered. Malformed acrosomes covered underdeveloped and misshaped sperm heads. In the sperm tail, midpieces were largely missing indicating disturbed assembly of the sperm tail. Defective structures, i.e., nuclei, acrosomes, and sperm tail midpieces, were observed in large vacuoles scattered throughout the epithelium. Interestingly, cilia formation itself did not appear to be affected, as the axoneme and other parts of the sperm tails except the midpieces appeared to be intact. In wildtype mice, EHD1 co-localized with acrosomal granules on round spermatids, suggesting a role of the EHD1 protein during acrosomal development. Wildtype EHD1 also co-localized with the VPS35 component of the retromer complex, whereas the p.R398W mutant did not. The testicular pathologies appeared very early during the first spermatogenic wave in young mice (starting at 14 dpp) and tubular destruction worsened with age. Taken together, EHD1 plays an important and probably multifaceted role in spermatogenesis in mice. Therefore, EHD1 may also be a hitherto underestimated infertility gene in humans.

A framework for identifying fertility gene targets for mammalian pest control

Fertility-targeted gene drives have been proposed as an ethical genetic approach for managing wild populations of vertebrate pests for public health and conservation benefit.This manuscript introduces a framework to identify and evaluate target gene suitability based on biological gene function, gene expression, and results from mouse knockout models.This framework identified 16 genes essential for male fertility and 12 genes important for female fertility that may be feasible targets for mammalian gene drives and other non-drive genetic pest control technology. Further, a comparative genomics analysis demonstrates the conservation of the identified genes across several globally significant invasive mammals.In addition to providing important considerations for identifying candidate genes, our framework and the genes identified in this study may have utility in developing additional pest control tools such as wildlife contraceptives.

Molecular genetic mechanisms of teratozoospermia

In recent years, the incidence of teratospermia has been increasing, and it has become a very important factor leading to male infertility. The research on the molecular mechanism of teratospermia is also progressing rapidly. This article briefly summarizes the clinical incidence of teratozoospermia, and makes a retrospective summary of related studies reported in recent years. Specifically discussing the relationship between gene status and spermatozoa, the review aims to provide the basis for the genetic diagnosis and gene therapy of teratozoospermia.

Murine fertility and spermatogenesis are independent of the testis-specific Spdye4a gene

BACKGROUND

While many testis-enriched genes have been identified as important regulators of the spermatogenic process, the specific roles played by several of these genes and their functional importance has yet to be fully clarified.

METHODS

We employed a CRISPR/Cas9 approach to introduce a 5 bp in-frame deletion within the Spdye4a gene (Exon 2) of C57BL/6 mice (Spdye4a^-/-). Fertility and sperm counts were evaluated. Testes tissues and cell suspensions were analyzed via histological and immunofluorescence staining. mRNA and protein levels of candidate genes were assessed through qPCR and Western blotting. In vitro fertilization was used to assess the ability of sperm cells to bind to egg cells.

RESULTS

Spdye4a^-/- mice did not exhibit any reduction in fertility, and exhibited comparable sperm counts, morphology and motility to those of wildtype littermates. Functionally, Spdye4a^-/- sperm exhibited normal sperm-egg binding activity in vitro. Furthermore, the testes of Spdye4a^-/- mice exhibited a full range of germ cells from spermatogonia to mature spermatozoa. No differences in the progression of meiotic prophase I were observed when comparing Spdye4a^-/- and wildtype mice, indicating that the loss of Spdye4a had no adverse effect on spermatogenesis.

DISCUSSION

Spdye4a is dispensable in the context of mice fertility and spermatogenesis. This study will prevent other laboratories from expending repeated efforts to generate similar knockout mice.

Modeling methods for busulfan-induced oligospermia and asthenozoospermia in mice: a systematic review and meta-analysis

OBJECTIVE

Modeling methods for busulfan-induced oligoasthenozoospermia are controversial. We aimed to systematically review the modeling method of busulfan-induced oligospermia and asthenozoospermia, and analyze changes in various evaluation indicators at different busulfan doses over time.

METHODS

We searched the Cochrane Library, PubMed databases, Web of Science, the Chinese National Knowledge Infrastructure, and the Chinese Biomedical Literature Service System until April 9, 2022. Animal experiments of busulfan-induced spermatogenesis dysfunction were included and screened. The model mortality and parameters of the evaluation indicators were subjected to meta-analysis.

RESULTS

Twenty-nine animal studies were included (control/model: 669/1829). The mortality of mice increased with busulfan dose. Significant spermatogenesis impairment occurred within 5 weeks, regardless of busulfan dose (10-40 mg/kg). Testicular weight (weighted mean difference [WMD]: - 0.04, 95% CI: - 0.05, - 0.03), testicular index (WMD: - 2.10, 95% CI: - 2.43, - 1.76), and Johnsen score (WMD: - 4.67, 95% CI: - 5.99, - 3.35) were significantly decreased. The pooled sperm counts of the model group were reduced by 32.8 × 106/ml (WMD: - 32.8, 95% CI: - 44.34, - 21.28), and sperm motility decreased by 37% (WMD: - 0.37, 95% CI: - 0.47, - 0.27). Sperm counts decreased slightly (WMD: - 3.03, 95% CI: - 3.42, - 2.64) in an intratesticular injection of low-dose busulfan (4 - 6 mg/kg), and the model almost returned to normal after one seminiferous cycle.

CONCLUSION

The model using low-dose busulfan (10 - 20 mg/kg) returned to normal after 10 - 15 weeks. However, in some spermatogenesis cycles, testicular weight reduction and testicular spermatogenic function damage were not proportional to busulfan dose. Sperm counts and motility results in different studies had significant heterogeneity. Standard protocols for sperm assessment in animal models were needed to reduce heterogeneity between studies.

A male germ-cell-specific ribosome controls male fertility

Ribosomes are highly sophisticated translation machines that have been demonstrated to be heterogeneous in the regulation of protein synthesis^1,2. Male germ cell development involves complex translational regulation during sperm formation³. However, it remains unclear whether translation during sperm formation is performed by a specific ribosome. Here we report a ribosome with a specialized nascent polypeptide exit tunnel, Ribosome^ST, that is assembled with the male germ-cell-specific protein RPL39L, the paralogue of core ribosome (Ribosome^Core) protein RPL39. Deletion of Ribosome^ST in mice causes defective sperm formation, resulting in substantially reduced fertility. Our comparison of single-particle cryo-electron microscopy structures of ribosomes from mouse kidneys and testes indicates that Ribosome^ST features a ribosomal polypeptide exit tunnel of distinct size and charge states compared with Ribosome^Core. Ribosome^ST predominantly cotranslationally regulates the folding of a subset of male germ-cell-specific proteins that are essential for the formation of sperm. Moreover, we found that specialized functions of Ribosome^ST were not replaceable by Ribosome^Core. Taken together, identification of this sperm-specific ribosome should greatly expand our understanding of ribosome function and tissue-specific regulation of protein expression pattern in mammals.

Development of the Connecting Piece in ODF1-Deficient Mouse Spermatids

ODF1 is a major protein of the accessory fibres of the mammalian sperm tail. In addition, ODF1 is found in the connecting piece, a complex structure located at the posterior end of the nucleus that connects the sperm head and tail. The tight coupling of the sperm head and tail is critical for the progressive motility of the sperm to reach the oocyte for fertilisation. The depletion of ODF1 by homologous recombination in mice led to male infertility. Although sperm tails were present in the epididymis, no intact spermatozoa were found. Instead, the depletion of ODF1 resulted in sperm decapitation, suggesting that ODF1 is essential for the formation of the coupling apparatus and the tight linkage of the sperm head and tail. However, the development of the linkage complex in the absence of ODF1 has never been investigated. Here, I analysed the fine structure of the developing connecting piece by transmission electron microscopy. I show that the connecting piece develops as in wild-type spermatids. Structural abnormalities were not observed when ODF1 was absent. Thus, ODF1 is dispensable for the development of the connecting piece. However, the decapitation of ODF1-deficient spermatozoa indicates that the heads and tails of the spermatozoa are not linked, so that they separate when force is applied.

Semen parameters are seriously affected in acephalic spermatozoa syndrome

BACKGROUND

Previous studies have reported that some patients with headless spermatozoa have poor semen quality, but there has been no published systematic analysis of semen quality in patients with different proportions of headless spermatozoa in semen. We aimed to explore the association of acephalic spermatozoa syndrome and semen quality in men with distinct proportions of headless spermatozoa.

MATERIAL AND METHODS

Semen parameter values in patients for whom headless spermatozoa were found in the ejaculates was studied and compared to that of 413 age-matched prenatal examination patients. All semen samples were analyzed following the same methodology in a single laboratory.

RESULTS

All semen parameter values except semen volume were negatively (P < 0.05) correlated with the proportion of headless spermatozoa. The semen samples were divided into four groups on the basis of the proportion of headless spermatozoa (PHS) as follows: 0 < PHS ≤ 5% (n = 172, Group A1); 5 < PHS ≤ 10% (n = 76, Group A2); 10 < PHS ≤ 20% (n = 71, Group B); and PHS > 20% (n = 71, Group C). In Group A1, only one semen parameter value (progressive motility) was lower than those of the control group, but in Group A2, this increased to five (sperm vitality, normal sperm morphology, sperm motility, VCL (curvilinear velocity) and ALH (amplitude of lateral head displacement)). Worse still, all semen parameter values were significantly lower in Group B and Group C than in the control group (P < 0.05).

CONCLUSIONS

Semen samples containing headless spermatozoa tend to have lower quality than samples without headless spermatozoa. Increases in the proportion of headless spermatozoa in semen are associated with decreased semen quality. We suggest that headless spermatozoa should be seriously assessed and accurately counted in semen analysis, especially for ejaculate in which the proportion of headless spermatozoa exceeds 5%.

Genome assembly of the Pendlebury's roundleaf bat, Hipposideros pendleburyi, revealed the expansion of Tc1/Mariner DNA transposons in Rhinolophoidea

Bats (Chiroptera) constitute the second largest order of mammals and have several distinctive features, such as true self-powered flight and strong immunity. The Pendlebury's roundleaf bat, Hipposideros pendleburyi, is endemic to Thailand and listed as a vulnerable species. We employed the 10× Genomics linked-read technology to obtain a genome assembly of H. pendleburyi. The assembly size was 2.17 Gb with a scaffold N50 length of 15,398,518 bases. Our phylogenetic analysis placed H. pendleburyi within the rhinolophoid clade of the suborder Yinpterochiroptera. A synteny analysis showed that H. pendleburyi shared conserved chromosome segments (up to 105 Mb) with Rhinolophus ferrumequinum and Phyllostomus discolor albeit having different chromosome numbers and belonging different families. We found positive selection signals in genes involved in inflammation, spermatogenesis and Wnt signalling. The analyses of transposable elements suggested the contraction of short interspersed nuclear elements (SINEs) and the accumulation of young mariner DNA transposons in the analysed hipposiderids. Distinct mariners were likely horizontally transferred to hipposiderid genomes over the evolution of this family. The lineage-specific profiles of SINEs and mariners might involve in the evolution of hipposiderids and be associated with the phylogenetic separations of these bats from other bat families.

Loss of perinuclear theca ACTRT1 causes acrosome detachment and severe male subfertility in mice

The perinuclear theca (PT) is a cytoskeletal element encapsulating the sperm nucleus; however, the physiological roles of the PT in sperm are largely uncertain. Here, we reveal that ACTRT1, ACTRT2, ACTL7A and ACTL9 proteins interact to form a multimeric complex and localize to the subacrosomal region of spermatids. Furthermore, we engineered Actrt1-knockout (KO) mice to define the functions of ACTRT1. Despite normal sperm count and motility, Actrt1-KO males were severely subfertile owing to a deficiency in fertilization. Loss of ACTRT1 caused a high incidence of malformed heads and detachment of acrosomes from sperm nuclei, caused by loosened acroplaxome structure during spermiogenesis. Furthermore, Actrt1-KO sperm showed reduced ACTL7A and PLCζ protein content as a potential cause of fertilization defects. Moreover, we reveal that ACTRT1 anchors developing acrosomes to the nucleus, likely by interacting with the inner acrosomal membrane protein SPACA1 and the nuclear envelope proteins PARP11 and SPATA46. Loss of ACTRT1 weakened the interaction between ACTL7A and SPACA1. Our study and recent findings of ACTL7A/ACTL9-deficient sperm together reveal that the sperm PT-specific ARP complex mediates the acrosome-nucleus connection.

The blooming of an old story on the bouquet

As an evolutionarily conserved process, the bouquet stage during meiosis was discovered over a century ago, and active research on this important stage continues. Since the discovery of the first bouquet-related protein Taz1p in 1998, several bouquet formation-related proteins have been identified in various eukaryotes. These proteins are involved in the interaction between telomeres and the inner nuclear membrane (INM), and once these interactions are disrupted, meiotic progression is arrested, leading to infertility. Recent studies have provided significant insights into the relationships and interactions among bouquet formation-related proteins. In this review, we summarize the components involved in telomere-INM interactions and focus on their roles in bouquet formation and telomere homeostasis maintenance. In addition, we examined bouquet-related proteins in different species from an evolutionary viewpoint, highlighting the potential interactions among them.

BmPMFBP1 regulates the development of eupyrene sperm in the silkworm, Bombyx mori

Sperm deliver the male complement of DNA to the ovum, and thus play a key role in sexual reproduction. Accordingly, spermatogenesis has outstanding significance in fields as disparate as infertility treatments and pest-control, making it a broadly interesting and important focus for molecular genetics research in a wide range of species. Here we investigate spermatogenesis in the model lepidopteran insect Bombyx mori (silkworm moth), with particular focus on the gene PMFBP1 (polyamine modulated factor 1 binding protein 1). In humans and mouse, PMFBP1 is essential for spermatogenesis, and mutations of this gene are associated with acephalic spermatozoa, which cause infertility. We identified a B. mori gene labeled as “PMFBP1” in GenBank’s RefSeq database and sought to assess its role in spermatogenesis. Like in mammals, the silkworm version of this gene (BmPMFBP1) is specifically expressed in testes. We subsequently generated BmPMFBP1 mutants using a transgenic CRISPR/Cas9 system. Mutant males were sterile while the fertility of mutant females was comparable to wildtype females. In B. mori, spermatogenesis yields two types of sperm, the nucleated fertile eupyrene sperm, and anucleated unfertile apyrene sperm. Mutant males produced abnormal eupyrene sperm bundles but normal apyrene sperm bundles. For eupyrene sperm, nuclei were mislocated and disordered inside the bundles. We also found the BmPMFBP1 deficiency blocked the release of eupyrene sperm bundles from testes to ejaculatory seminalis. We found no obvious abnormalities in the production of apyrene sperm in mutant males, and double-matings with apyrene-deficient sex-lethal mutants rescued the ΔBmPMFBP1 infertility phenotype. These results indicate BmPMFBP1 functions only in eupyrene spermatogenesis, and highlight that distinct genes underlie the development of the two sperm morphs commonly found in Lepidoptera. Bioinformatic analyses suggest PMFBP1 may have evolved independently in lepidoptera and mammals, and that despite the shared name, are likely not homologous genes.

The presence of nucleated and anucleated dimorphic sperm produced by a single male is a notable characteristic of lepidopteran insects. Previously we identified the gene BmSxl and BmPnldc1 are required for apyrene and eupyrene sperm development, respectively. However, there remains very little known about the molecular mechanism of eupyrene and apyrene sperm development and function. In human and mouse, the protein PMFBP1 is related to acephalic spermatozoa syndrome. Here, we generate somatic mutants in the silkworm Bombyx mori for this gene. In the silkworm, BmPMFBP1 is essential for male fertility. Loss of BmPMFBP1 function results in defective eupyrene sperm bundles in the early elongation stage of spermatogenesis. The nuclei of the eupyrene sperm bundles were displaced from sperm heads while the apyrene sperm bundles were normal. This deficiency also results in the failure of the release of eupyrene sperm bundles from testes to the ejaculatory seminalis duct. Our study proves the important function of BmPMFBP1 in the development of the eupyrene sperm in the silkworm and identifies a potential target gene for lepidopteran pest control.

Sperm bauplan and function and underlying processes of sperm formation and selection

The spermatozoon is a highly differentiated and polarized cell, with two main structures: the head, containing a haploid nucleus and the acrosomal exocytotic granule, and the flagellum, which generates energy and propels the cell; both structures are connected by the neck. The sperm's main aim is to participate in fertilization, thus activating development. Despite this common bauplan and function, there is an enormous diversity in structure and performance of sperm cells. For example, mammalian spermatozoa may exhibit several head patterns and overall sperm lengths ranging from ∼30 to 350 µm. Mechanisms of transport in the female tract, preparation for fertilization, and recognition of and interaction with the oocyte also show considerable variation. There has been much interest in understanding the origin of this diversity, both in evolutionary terms and in relation to mechanisms underlying sperm differentiation in the testis. Here, relationships between sperm bauplan and function are examined at two levels: first, by analyzing the selective forces that drive changes in sperm structure and physiology to understand the adaptive values of this variation and impact on male reproductive success and second, by examining cellular and molecular mechanisms of sperm formation in the testis that may explain how differentiation can give rise to such a wide array of sperm forms and functions.

Genetic pathogenesis of acephalic spermatozoa syndrome: past, present, and future

Acephalic spermatozoa syndrome (ASS) is one of the most severe spermatogenic failures of all infertility in men. The cognition of ASS has experienced a tortuous process. Over the past years, with the in-depth understanding of spermatogenesis and the emergence of new genetic research technologies, the unraveling of the genetic causes of spermatogenic failure has become highly active. From these advances, we established a genetic background and made significant progress in the discovery of the genetic causes of ASS. It is important to identify pathogenic genes and mutations in ASS to determine the biological reasons for the occurrence of the disease as well as provide genetic diagnosis and treatment strategies for patients with this syndrome. In this review, we enumerate various technological developments, which have made a positive contribution to the discovery of candidate genes for ASS from the past to the present. Simultaneously, we summarize the known genetic etiology of this phenotype and the clinical outcomes of treatments in the present. Furthermore, we propose perspectives for further study and application of genetic diagnosis and assisted reproductive treatment in the future.

The Transformation of the Centrosome into the Basal Body: Similarities and Dissimilarities between Somatic and Male Germ Cells and Their Relevance for Male Fertility

The sperm flagellum is essential for the transport of the genetic material toward the oocyte and thus the transmission of the genetic information to the next generation. During the haploid phase of spermatogenesis, i.e., spermiogenesis, a morphological and molecular restructuring of the male germ cell, the round spermatid, takes place that includes the silencing and compaction of the nucleus, the formation of the acrosomal vesicle from the Golgi apparatus, the formation of the sperm tail, and, finally, the shedding of excessive cytoplasm. Sperm tail formation starts in the round spermatid stage when the pair of centrioles moves toward the posterior pole of the nucleus. The sperm tail, eventually, becomes located opposed to the acrosomal vesicle, which develops at the anterior pole of the nucleus. The centriole pair tightly attaches to the nucleus, forming a nuclear membrane indentation. An articular structure is formed around the centriole pair known as the connecting piece, situated in the neck region and linking the sperm head to the tail, also named the head-to-tail coupling apparatus or, in short, HTCA. Finally, the sperm tail grows out from the distal centriole that is now transformed into the basal body of the flagellum. However, a centriole pair is found in nearly all cells of the body. In somatic cells, it accumulates a large mass of proteins, the pericentriolar material (PCM), that together constitute the centrosome, which is the main microtubule-organizing center of the cell, essential not only for the structuring of the cytoskeleton and the overall cellular organization but also for mitotic spindle formation and chromosome segregation. However, in post-mitotic (G1 or G0) cells, the centrosome is transformed into the basal body. In this case, one of the centrioles, which is always the oldest or mother centriole, grows the axoneme of a cilium. Most cells of the body carry a single cilium known as the primary cilium that serves as an antenna sensing the cell's environment. Besides, specialized cells develop multiple motile cilia differing in substructure from the immotile primary cilia that are essential in moving fluids or cargos over the cellular surface. Impairment of cilia formation causes numerous severe syndromes that are collectively subsumed as ciliopathies. This comparative overview serves to illustrate the molecular mechanisms of basal body formation, their similarities, and dissimilarities, in somatic versus male germ cells, by discussing the involved proteins/genes and their expression, localization, and function. The review, thus, aimed to provide a deeper knowledge of the molecular players that is essential for the expansion of clinical diagnostics and treatment of male fertility disorders.

Pathogenic Variants in ACTRT1 Cause Acephalic Spermatozoa Syndrome

Acephalic spermatozoa syndrome is a rare type of teratozoospermia, but its pathogenesis is largely unknown. Here, we performed whole-exome sequencing for 34 patients with acephalic spermatozoa syndrome and identified pathogenic variants in the X-linked gene, ACTRT1, in two patients. Sanger sequencing confirmed the pathogenic variants of ACTRT1 in the patients. Both pathogenic variants of ACTRT1 were highly conserved, and in silico analysis revealed that they were deleterious and rare. Actrt1-knockout mice exhibited a similar acephalic spermatozoa phenotype. Therefore, we speculated that mutations in ACTRT1 account for acephalic spermatozoa syndrome. Moreover, the patients in this study conceived their children through artificial insemination. This study provides further insights for clinicians and researchers regarding the genetic etiology and therapeutic strategies for acephalic spermatozoa patients with pathogenic variants in ACTRT1.

The coupling apparatus of the sperm head and tail†

A strong sperm head-tail coupling apparatus (HTCA) is needed to ensure the integrity of spermatozoa during their fierce competition to fertilize the egg. A lot of HTCA-specific components have evolved to strengthen the attachment of the tail to the implantation fossa at the sperm head. Defects in HTCA formation lead to acephalic spermatozoa syndrome and pathologies of some male infertility. Recent studies have provided insights into the pathogenic molecular mechanisms of acephalic spermatozoa syndrome. Here, we summarize the proteins involved in sperm neck development and focus on their roles in the formation of HTCA. In addition, we discuss the fine structures of the sperm neck in different species from an evolutionary view, highlighting the potential conservative mechanism of HTCA formation.

The missing linker between SUN5 and PMFBP1 in sperm head-tail coupling apparatus

The sperm head-to-tail coupling apparatus (HTCA) ensures sperm head-tail integrity while defective HTCA causes acephalic spermatozoa, rendering males infertile. Here, we show that CENTLEIN is indispensable for HTCA integrity and function, and that inactivation of CENTLEIN in mice leads to sperm decapitation and male sterility. We demonstrate that CENTLEIN directly interacts with both SUN5 and PMFBP1, two proteins localized in the HTCA and related with acephalic spermatozoa syndrome. We find that the absence of Centlein sets SUN5 and PMFBP1 apart, the former close to the sperm head and the latter in the decapitated tail. We show that lack of Sun5 results in CENTLEIN and PMFBP1 left in the decapitated tail, while disruption of Pmfbp1 results in SUN5 and CENTLEIN left on the detached sperm head. These results demonstrate that CENTLEIN cooperating with SUN5 and PMFBP1 participates in the HTCA assembly and integration of sperm head to the tail, indicating that impairments of CENTLEIN might be associated with acephalic spermatozoa syndrome in humans.

Comparative Proteomics and Phosphoproteomics Analysis Reveal the Possible Breed Difference in Yorkshire and Duroc Boar Spermatozoa

Sperm cells are of unique elongated structure and function, the development of which is tightly regulated by the existing proteins and the posttranslational modifications (PTM) of these proteins. Based on the phylogenetic relationships of various swine breeds, Yorkshire boar is believed to be distinctly different from Duroc boar. The comprehensive differential proteomics and phosphoproteomics profilings were performed on spermatozoa from both Yorkshire and Duroc boars. By both peptide and PTM peptide quantification followed by statistical analyses, 167 differentially expressed proteins were identified from 1,745 proteins, and 283 differentially expressed phosphopeptides corresponding to 102 unique differentially phosphorylated proteins were measured from 1,140 identified phosphopeptides derived from 363 phosphorylated proteins. The representative results were validated by Western blots. Pathway enrichment analyses revealed that majority of differential expression proteins and differential phosphorylation proteins were primarily concerned with spermatogenesis, male gamete generation, sperm motility, energy metabolism, cilium morphogenesis, axonemal dynein complex assembly, sperm–egg recognition, and capacitation. Remarkably, axonemal dynein complex assembly related proteins, such as SMCP, SUN5, ODF1, AKAP3, and AKAP4 that play a key regulatory role in the sperm physiological functions, were significantly higher in Duroc spermatozoa than that of Yorkshire. Furthermore, phosphorylation of sperm-specific proteins, such as CABYR, ROPN1, CALM1, PRKAR2A, and PRKAR1A, participates in regulation of the boar sperm motility mainly through the cAMP/PKA signal pathway in different breeds, demonstrating that protein phosphorylation may be an important mechanism underlying the sperm diversity. Protein–protein interaction analysis revealed that the 14 overlapped proteins between differential expression proteins and differential phosphorylation proteins potentially played a key role in sperm development and motility of the flagellum, including the proteins ODF1, SMCP, AKAP4, FSIP2, and SUN5. Taken together, these physiologically and functionally differentially expressed proteins (DEPs) and differentially expressed phosphorylated proteins (DPPs) may constitute the proteomic backgrounds between the two different boar breeds. The validation will be performed to delineate the roles of these PTM proteins as modulators of Yorkshire and Duroc boar spermatozoa.

SUN5 Interacting With Nesprin3 Plays an Essential Role in Sperm Head-to-Tail Linkage: Research on Sun5 Gene Knockout Mice

Acephalic spermatozoa syndrome is a rare genetic and reproductive disease. Recent studies have shown that approximately 33–47% of patients with acephalic spermatozoa syndrome have SUN5 mutations, but the molecular mechanism underlying this phenomenon has not been elucidated. In this study, we generated Sun5 knockout mice and found that the head-to-tail linkage was broken in Sun5^–/– mice, which was similar to human acephalic spermatozoa syndrome. Furthermore, ultrastructural imaging revealed that the head-tail coupling apparatus (HTCA) and the centrosome were distant from the nucleus at steps 9–10 during spermatid elongation. With the manchette disappearing at steps 13–14, the head and the tail segregated. To explore the molecular mechanism underlying this process, bioinformatic analysis was performed and showed that Sun5 may interact with Nesprin3. Further coimmunoprecipitation (Co-IP) and immunofluorescence assays confirmed that Sun5 and Nesprin3 were indeed bona fide interaction partners that formed the linker of the nucleoskeleton and cytoskeleton (LINC) complex participating in the connection of the head and tail of spermatozoa. Nesprin3 was located posterior and anterior to the nucleus during spermiogenesis in wild-type mice, whereas it lost its localization at the implantation fossa of the posterior region in Sun5^–/– mice. Without correct localization of Nesprin3 at the nuclear membrane, the centrosome, which is the originator of the flagellum, was distant from the nucleus, which led to the separation of the head and tail. In addition, isobaric tag for relative and absolute quantitation results showed that 47 proteins were upregulated, and 56 proteins were downregulated, in the testis in Sun5^–/– mice, and the downregulation of spermatogenesis-related proteins (Odf1 and Odf2) may also contribute to the damage to the spermatozoa head-to-tail linkage. Our findings suggested that Sun5 is essential for the localization of Nesprin3 at the posterior nuclear membrane, which plays an essential role in the sperm head-tail connection.

Biallelic mutations in spermatogenesis and centriole-associated 1 like (SPATC1L) cause acephalic spermatozoa syndrome and male infertility

Acephalic spermatozoa syndrome is a rare type of teratozoospermia that severely impairs the reproductive ability of male patients, and genetic defects have been recognized as the main cause of acephalic spermatozoa syndrome. Spermatogenesis and centriole-associated 1 like (SPATC1L) is indispensable for maintaining the integrity of sperm head-to-tail connections in mice, but its roles in human sperm and early embryonic development remain largely unknown. Herein, we conducted whole-exome sequencing (WES) of 22 infertile men with acephalic spermatozoa syndrome. An in silico analysis of the candidate variants was conducted, and WES data analysis was performed using another cohort consisting of 34 patients with acephalic spermatozoa syndrome and 25 control subjects with proven fertility. We identified biallelic mutations in SPATC1L (c.910C>T:p.Arg304Cys and c.994G>T:p.Glu332X) from a patient whose sperm displayed complete acephalia. Both SPATC1L variants are rare and deleterious. SPATC1L is mainly expressed at the head–tail junction of elongating spermatids. Plasmids containing pathogenic variants decreased the level of SPATC1L in vitro. Moreover, none of the patient's four attempts at intracytoplasmic sperm injection (ICSI) resulted in a transplantable embryo, which suggests that SPATC1L defects might affect early embryonic development. In conclusion, this study provides the first identification of SPATC1L as a novel gene for human acephalic spermatozoa syndrome. Furthermore, WES might be applied for patients with acephalic spermatozoa syndrome who exhibit reiterative ICSI failures.

Towards Post-Meiotic Sperm Production: Genetic Insight into Human Infertility from Mouse Models

Declined quality and quantity of sperm is currently the major cause of patients suffering from infertility. Male germ cell development is spatiotemporally regulated throughout the whole developmental process. While it has been known that exogenous factors, such as environmental exposure, diet and lifestyle, et al, play causative roles in male infertility, recent progress has revealed abundant genetic mutations tightly associated with defective male germline development. In mammals, male germ cells undergo dramatic morphological change (i.e., nuclear condensation) and chromatin remodeling during post-meiotic haploid germline development, a process termed spermiogenesis; However, the molecular machinery players and functional mechanisms have yet to be identified. To date, accumulated evidence suggests that disruption in any step of haploid germline development is likely manifested as fertility issues with low sperm count, poor sperm motility, aberrant sperm morphology or combined. With the continually declined cost of next-generation sequencing and recent progress of CRISPR/Cas9 technology, growing studies have revealed a vast number of disease-causing genetic variants associated with spermiogenic defects in both mice and humans, along with mechanistic insights partially attained and validated through genetically engineered mouse models (GEMMs). In this review, we mainly summarize genes that are functional at post-meiotic stage. Identification and characterization of deleterious genetic variants should aid in our understanding of germline development, and thereby further improve the diagnosis and treatment of male infertility.

LINCking the Nuclear Envelope to Sperm Architecture

Nuclear architecture undergoes an extensive remodeling during spermatogenesis, especially at levels of spermatocytes (SPC) and spermatids (SPT). Interestingly, typical events of spermiogenesis, such as nuclear elongation, acrosome biogenesis, and flagellum formation, need a functional cooperation between proteins of the nuclear envelope and acroplaxome/manchette structures. In addition, nuclear envelope plays a key role in chromosome distribution. In this scenario, special attention has been focused on the LINC (linker of nucleoskeleton and cytoskeleton) complex, a nuclear envelope-bridge structure involved in the connection of the nucleoskeleton to the cytoskeleton, governing mechanotransduction. It includes two integral proteins: KASH- and SUN-domain proteins, on the outer (ONM) and inner (INM) nuclear membrane, respectively. The LINC complex is involved in several functions fundamental to the correct development of sperm cells such as head formation and head to tail connection, and, therefore, it seems to be important in determining male fertility. This review provides a global overview of the main LINC complex components, with a special attention to their subcellular localization in sperm cells, their roles in the regulation of sperm morphological maturation, and, lastly, LINC complex alterations associated to male infertility.

Unraveling the Balance between Genes, Microbes, Lifestyle and the Environment to Improve Healthy Reproduction

Humans’ health is the result of a complex and balanced interplay between genetic factors, environmental stimuli, lifestyle habits, and the microbiota composition. The knowledge about their single contributions, as well as the complex network linking each to the others, is pivotal to understand the mechanisms underlying the onset of many diseases and can provide key information for their prevention, diagnosis and therapy. This applies also to reproduction. Reproduction, involving almost 10% of our genetic code, is one of the most critical human’s functions and is a key element to assess the well-being of a population. The last decades revealed a progressive decline of reproductive outcomes worldwide. As a consequence, there is a growing interest in unveiling the role of the different factors involved in human reproduction and great efforts have been carried out to improve its outcomes. As for many other diseases, it is now clear that the interplay between the underlying genetics, our commensal microbiome, the lifestyle habits and the environment we live in can either exacerbate the outcome or mitigate the adverse effects. Here, we aim to analyze how each of these factors contribute to reproduction highlighting their individual contribution and providing supporting evidence of how to modify their impact and overall contribution to a healthy reproductive status.

Pathogenesis of acephalic spermatozoa syndrome caused by SUN5 variant

Acephalic spermatozoa syndrome (ASS) is a rare teratozoospermia that leads to male infertility. Previous work suggested a genetic origin. Variants of Sad1 and UNC84 domain containing 5 (SUN5) are the main genetic cause of ASS; however, its pathogenesis remains unclear. Here, we performed whole-exome sequencing in 10 unrelated ASS and identified 2 homozygous variants, c.381delA[p.V128Sfs7*] and c.675C>A[p.Y225X], and 1 compound variant, c.88 C > T[p.R30X] and c.381 delA [p.V128Sfs7*], in SUN5 in 4 patients. The c.381delA variant had been identified as pathogenic in previous reports, while c.675C>A and c.88 C > T were two novel variants which could lead to a premature termination codon (PTC) and resulted in loss of SUN5, and may also be pathogenic. SUN5 mRNA and protein were present at very low levels in ASS patients with SUN5 nonsense mutation. Furthermore, the distribution of outer dense fiber protein 1 (ODF1) and Nesprin3 was altered in sperm of ASS patients with SUN5 variants. The co-immunoprecipitation analysis indicated that SUN5 and ODF1, SUN5 and Nesprin3, and ODF1 and Nesprin3 interacted with each other in transfected HEK293T cells. Thus, we propose that SUN5, Nesprin3, and ODF1 may form a 'triplet' structure through interactions at neck of sperm. When gene variants resulted in a loss of SUN5, the 'triplet' structure disappears and then the head-tail junction becomes fragile, leading to the occurrence of ASS.

SLC22A14 is a mitochondrial riboflavin transporter required for sperm oxidative phosphorylation and male fertility

Ablation of Slc22a14 causes male infertility in mice, but the underlying mechanisms remain unknown. Here, we show that SLC22A14 is a riboflavin transporter localized at the inner mitochondrial membrane of the spermatozoa mid-piece and show by genetic, biochemical, multi-omic, and nutritional evidence that riboflavin transport deficiency suppresses the oxidative phosphorylation and reprograms spermatozoa energy metabolism by disrupting flavoenzyme functions. Specifically, we find that fatty acid β-oxidation (FAO) is defective with significantly reduced levels of acyl-carnitines and metabolites from the TCA cycle (the citric acid cycle) but accumulated triglycerides and free fatty acids in Slc22a14 knockout spermatozoa. We demonstrate that Slc22a14-mediated FAO is essential for spermatozoa energy generation and motility. Furthermore, sperm from wild-type mice treated with a riboflavin-deficient diet mimics those in Slc22a14 knockout mice, confirming that an altered riboflavin level causes spermatozoa morphological and bioenergetic defects. Beyond substantially advancing our understanding of spermatozoa energy metabolism, our study provides an attractive target for the development of male contraceptives.

Evolution and Functional Divergence of SUN Genes in Plants

SUN-domain containing proteins are crucial nuclear membrane proteins involved in a plethora of biological functions, including meiosis, nuclear morphology, and embryonic development, but their evolutionary history and functional divergence are obscure. In all, 216 SUN proteins from protists, fungi, and plants were divided into two monophyletic clades (Cter-SUN and Mid-SUN). We performed comprehensive evolutionary analyses, investigating the characteristics of different subfamilies in plants. Mid-SUNs further evolved into two subgroups, SUN3 and SUN5, before the emergence of the ancestor of angiosperms, while Cter-SUNs retained one subfamily of SUN1. The two clades were distinct from each other in the conserved residues of the SUN domain, the TM motif, and exon/intron structures. The gene losses occurred with equal frequency between these two clades, but duplication events of Mid-SUNs were more frequent. In cotton, SUN3 proteins are primarily expressed in petals and stamens and are moderately expressed in other tissues, whereas SUN5 proteins are specifically expressed in mature pollen. Virus-induced knock-down and the CRISPR/Cas9-mediated knockout of GbSUN5 both showed higher ratios of aborted seeds, although pollen viability remained normal. Our results indicated divergence of biological function between SUN3 and SUN5, and that SUN5 plays an important role in reproductive development.

Genetic basis of acephalic spermatozoa syndrome, and intracytoplasmic sperm injection outcomes in infertile men: a systematic scoping review

PURPOSE

Acephalic spermatozoa syndrome (ASS) is known as a severe type of teratozoospermia, defined as semen composed of mostly headless spermatozoa that affect male fertility. In this regard, this systematic review aimed to discuss gene variants associated with acephalic spermatozoa phenotype as well as the clinical outcomes of intracytoplasmic sperm injection (ICSI) treatment for the acephalic spermatozoa-associated male infertility.

METHODS

A systematic search was performed on PubMed, Embase, Scopus, and Ovid databases until May 17, 2020. This systematic scoping review was reported in terms of the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) statement.

RESULTS

Twenty articles were included in this systematic review. Whole-exome and Sanger sequencing have helped in the identification of variants in SUN5, PMFBP1, BRDT, TSGA10, DNAH6, HOOK1, and CEP112 genes as possible causes of this phenotype in humans. The results of the ICSI are conflicting due to both positive and negative reports of ICSI outcomes.

CONCLUSION

ASS has a genetic origin, and several genetic alterations related to the pathogenesis of this anomaly have been recently identified. Notably, only SUN5 and PMFBP1 mutations are well-known to be implicated in ASS. Accordingly, more functional studies are needed to confirm the pathogenicity of other variants. ICSI could provide a promising treatment for acephalic spermatozoa-associated male infertility. Besides the importance of sperm head-tail junction integrity, some other factors, whether within the sperm cell or female factors, may be involved in the ICSI outcome.

Identification and Characterization of the Most Common Genetic Variant Responsible for Acephalic Spermatozoa Syndrome in Men Originating from North Africa

Acephalic spermatozoa syndrome (ASS) is a rare but extremely severe type of teratozoospermia, defined by the presence of a majority of headless flagella and a minority of tail-less sperm heads in the ejaculate. Like the other severe monomorphic teratozoospermias, ASS has a strong genetic basis and is most often caused by bi-allelic variants in SUN5 (Sad1 and UNC84 domain-containing 5). Using whole exome sequencing (WES), we investigated a cohort of nine infertile subjects displaying ASS. These subjects were recruited in three centers located in France and Tunisia, but all originated from North Africa. Sperm from subjects carrying candidate genetic variants were subjected to immunofluorescence analysis and transmission electron microscopy. Moreover, fluorescent in situ hybridization (FISH) was performed on sperm nuclei to assess their chromosomal content. Variant filtering permitted us to identify the same SUN5 homozygous frameshift variant (c.211+1_211+2dup) in 7/9 individuals (78%). SUN5 encodes a protein localized on the posterior part of the nuclear envelope that is necessary for the attachment of the tail to the sperm head. Immunofluorescence assays performed on sperm cells from three mutated subjects revealed a total absence of SUN5, thus demonstrating the deleterious impact of the identified variant on protein expression. Transmission electron microscopy showed a conserved flagellar structure and a slightly decondensed chromatin. FISH did not highlight a higher rate of chromosome aneuploidy in spermatozoa from SUN5 patients compared to controls, indicating that intra-cytoplasmic sperm injection (ICSI) can be proposed for patients carrying the c.211+1_211+2dup variant. These results suggest that the identified SUN5 variant is the main cause of ASS in the North African population. Consequently, a simple and inexpensive genotyping of the 211+1_211+2dup variant could be beneficial for affected men of North African origin before resorting to more exhaustive genetic analyses.