Novel mutation in ODF2 causes multiple morphological abnormalities of the sperm flagella in an infertile male

Absence of Rnf126 causes male infertility with multiple morphological abnormalities of the sperm flagella

Male infertility is primarily caused by impaired flagella development, reduced sperm count, and decreased motility. Despite the involvement of many genes in spermatogenesis, the precise processes remain unclear. The critical E3 ubiquitin ligase Rnf126 regulates essential cellular processes through ubiquitination-induced protein degradation. It plays a significant role in DNA repair, immune response, and signaling cascades, underscoring its central importance in maintaining cellular homeostasis. However, the mechanisms by which Rnf126 controls spermatogenesis are not fully understood. This research identifies Rnf126 as a crucial component in sperm flagellar biogenesis and germ cell development. Through genetic lineage tracing, we show that RNF126 is highly expressed in sperm cells and weakly expressed in Sertoli cells. The germ epithelium of RNF126 deficiencies is characterized by a loss of germ cells due to an increase in germ cell apoptosis at various stages of development, which ultimately results in vesiculation of the spermatogenic tubule. Targeting Rnf126 results in different types of germ cells reduction, infertility, and microtubule-associated motor activity failure (MMAF), characterized by spermatozoa with truncated, twisted, and malformed flagella. Detailed ultrastructural studies reveal the extent of flagellar damage in the absence of Rnf126, highlighting its critical role in maintaining flagellar stability. An important finding is the interaction between RNF126 and BAG6, which regulates sperm synthesis and germ cell development. Clinically, reduced RNF126 levels in sperm from individuals with oligoasthenoteratospermia are significantly different from those in fertile individuals. Investigating Rnf126 function in spermatogenesis, together with empirical findings on MMAF presentation, may improve our understanding of the developmental processes involved in sperm flagellum formation and contribute to elucidating the causes of male infertility.

Functional Investigation of a Novel PIWIL4 Mutation in Nonobstructive Azoospermia During the First Wave of Spermatogenesis

PIWI-interacting RNAs (piRNAs) are small noncoding RNAs that are almost exclusively expressed in germ cells to silence harmful transposons to maintain genome stability. PIWIL4 is guided by its associated piRNAs to transposable elements, where it recruits the DNA methylation apparatus and instructs de novo DNA methylation. Herein, we identified a missense variant of PIWIL4 (c.805 C>T p.R269W) in two infertile males. Homozygous male mice carrying the orthologous knock-in variant displayed elevated transposable element expression and aberrant gene expression during the first wave of spermatogenesis, despite exhibiting normal sperm counts and morphology. Mechanistically, the mutated site altered the piRNA-binding ability of PIWIL4 and led to the derepression of endogenous LINE-1 elements. In summary, we identified a piRNA binding mutation in PIWIL4 that may be involved in human nonobstructive azoospermia.

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.

The Molecular Basis of Multiple Morphological Abnormalities of Sperm Flagella and Its Impact on Clinical Practice

Multiple morphological abnormalities of the sperm flagella (MMAF) is a specific form of severe flagellar or ciliary deficiency syndrome. MMAF is characterized by primary infertility with abnormal morphology in the flagella of spermatozoa, presenting with short, absent, bent, coiled, and irregular flagella. As a rare disease first named in 2014, studies in recent years have shed light on the molecular defects of MMAF that comprise the structure and biological function of the sperm flagella. Understanding the molecular genetics of MMAF may provide opportunities for the development of diagnostic and therapeutic strategies for this rare disease. This review aims to summarize current studies regarding the molecular pathogenesis of MMAF and describe strategies of genetic counseling, clinical diagnosis, and therapy for MMAF.

Comparative Study on the Sperm Proteomes of Horses and Donkeys

The reproductive performance of horse sperm and donkey sperm has been reported to differ. Sperm proteins play a crucial role in sperm viability and fertility. Although differences between species are known, no prior study has investigated disparities in the sperm proteome between horses and donkeys. Therefore, this study characterized and compared the sperm proteomes of horses and donkeys using 4D-DIA mass spectrometry technology. We identified 3436 proteins in horse sperm and 3404 proteins in donkey sperm. Of these, 3363 proteins were expressed in both horse and donkey sperm, with 73 proteins being specifically expressed in horse sperm, and 41 in donkey sperm. According to data analysis, donkeys exhibited a greater percentage of motility and progressive movement in straight-line sperm than horses, as well as lower percentages of static and slow sperm than horses. Joint analysis of the results from the horse and donkey sperm proteomes and their CEROS II-read parameters demonstrated a possible association between sperm proteins and their sperm viability patterns. These findings suggest that there are discrepancies in the expression levels and protein compositions of horse and donkey sperm and that certain specific proteins may be responsible for the differences in performance between these two species.

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.

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.

Lack of CCDC146, a ubiquitous centriole and microtubule-associated protein, leads to non-syndromic male infertility in human and mouse

From a cohort of 167 infertile patients suffering from multiple morphological abnormalities of the flagellum (MMAF), pathogenic bi-allelic mutations were identified in the CCDC146 gene. In somatic cells, CCDC146 is located at the centrosome and at multiple microtubule-related organelles during mitotic division, suggesting that it is a microtubule-associated protein (MAP). To decipher the molecular pathogenesis of infertility associated with CCDC146 mutations, a Ccdc146 knock-out (KO) mouse line was created. KO male mice were infertile, and sperm exhibited a phenotype identical to CCDC146 mutated patients. CCDC146 expression starts during late spermiogenesis. In the spermatozoon, the protein is conserved but is not localized to centrioles, unlike in somatic cells, rather it is present in the axoneme at the level of microtubule doublets. Expansion microscopy associated with the use of the detergent sarkosyl to solubilize microtubule doublets suggests that the protein may be a microtubule inner protein (MIP). At the subcellular level, the absence of CCDC146 impacted all microtubule-based organelles such as the manchette, the head-tail coupling apparatus (HTCA), and the axoneme. Through this study, a new genetic cause of infertility and a new factor in the formation and/or structure of the sperm axoneme were characterized.

CCDC146 is required for sperm flagellum biogenesis and male fertility in mice

Multiple morphological abnormalities of the flagella (MMAF) is a severe disease of male infertility, while the pathogenetic mechanisms of MMAF are still incompletely understood. Previously, we found that the deficiency of Ccdc38 might be associated with MMAF. To understand the underlying mechanism of this disease, we identified the potential partner of this protein and found that the coiled-coil domain containing 146 (CCDC146) can interact with CCDC38. It is predominantly expressed in the testes, and the knockout of this gene resulted in complete infertility in male mice but not in females. The knockout of Ccdc146 impaired spermiogenesis, mainly due to flagellum and manchette organization defects, finally led to MMAF-like phenotype. Furthermore, we demonstrated that CCDC146 could interact with both CCDC38 and CCDC42. It also interacts with intraflagellar transport (IFT) complexes IFT88 and IFT20. The knockout of this gene led to the decrease of ODF2, IFT88, and IFT20 protein levels, but did not affect CCDC38, CCDC42, or ODF1 expression. Additionally, we predicted and validated the detailed interactions between CCDC146 and CCDC38 or CCDC42, and built the interaction models at the atomic level. Our results suggest that the testis predominantly expressed gene Ccdc146 is essential for sperm flagellum biogenesis and male fertility, and its mutations might be associated with MMAF in some patients.

Biallelic mutations in CFAP54 cause male infertility with severe MMAF and NOA

BACKGROUND

Spermatogenic impairments can lead to male infertility by different pathological conditions, such as multiple morphological abnormalities of the sperm flagella (MMAF) and non-obstructive azoospermia (NOA). Genetic factors are involved in impaired spermatogenesis.

METHODS AND RESULTS

Here, we performed genetic analyses through whole-exome sequencing in a cohort of 334 Han Chinese probands with severe MMAF or NOA. Biallelic variants of CFAP54 were identified in three unrelated men, including one homozygous frameshift variant (c.3317del, p.Phe1106Serfs*19) and two compound heterozygous variants (c.878G>A, p.Arg293His; c.955C>T, p.Arg319Cys and c.4885C>T, p.Arg1629Cys; c.937G>A, p.Gly313Arg). All of the identified variants were absent or extremely rare in the public human genome databases and predicted to be damaging by bioinformatic tools. The men harbouring CFAP54 mutations exhibited abnormal sperm morphology, reduced sperm concentration and motility in ejaculated semen. Significant axoneme disorganisation and other ultrastructure abnormities were also detected inside the sperm cells from men harbouring CFAP54 mutations. Furthermore, immunofluorescence assays showed remarkably reduced staining of four flagellar assembly-associated proteins (IFT20, IFT52, IFT122 and SPEF2) in the spermatozoa of CFAP54-deficient men. Notably, favourable clinical pregnancy outcomes were achieved with sperm from men carrying CFAP54 mutations after intracytoplasmic sperm injection treatment.

CONCLUSION

Our genetic analyses and experimental observations revealed that biallelic deleterious mutations of CFAP54 can induce severe MMAF and NOA in humans.

Macrophage-Related Testicular Inflammation in Individuals with Idiopathic Non-Obstructive Azoospermia: A Single-Cell Analysis

Male infertility is a global issue that seriously affects reproductive health. This study aimed to understand the underlying causes of idiopathic non-obstructive azoospermia (iNOA), which is a type of male infertility with unknown origins that accounts for 10-15% of cases. By using single-cell analysis techniques, we aimed to uncover the mechanisms of iNOA and gain insight into the cellular and molecular changes in the testicular environment. In this study, we performed bioinformatics analysis using scRNA-seq and microarray data obtained from the GEO database. The analysis included techniques such as pseudotime analysis, cell-cell communication, and hdWGCNA. Our study showed a significant difference between the iNOA and the normal groups, indicating a disorder in the spermatogenic microenvironment in iNOA. We observed a reduction in the proportion of Sertoli cells and blocked germ cell differentiation. Additionally, we found evidence of testicular inflammation related to macrophages and identified ODF2 and CABYR as potential biomarkers for iNOA.

WDR87 interacts with CFAP47 protein in the middle piece of spermatozoa flagella to participate in sperm tail assembly

Spermatogenesis is a complex process that includes spermatogonia self-renewal, spermatocyte meiosis and spermatozoa assembly. Recent studies have revealed that WD40-repeat domain-containing (WDR) proteins play important roles in spermatocyte division, spermatozoa flagella assembly and head shaping. In this study, we investigated the expression pattern of WDR87 and found that it was highly expressed in the testis of both humans and mice. Immunofluorescence staining revealed that mouse WDR87 was distributed in the perinuclear cytoplasm of primary spermatocytes, secondary spermatocytes and round spermatids. In the spermiogenesis stage, with extension of the nucleus, WDR87 migrated to the manchette and finally localized to the middle piece of the spermatozoa tail. Furthermore, we identified a cilia- and flagella-associated protein, CFAP47, which interacted with WDR87 in the flagellar midpiece of the spermatozoa, suggesting that WDR87 may be associated with multiple morphological abnormalities of the flagella (MMAF). Subsequently, we screened gene mutations in seven MMAF individuals and found two novel mutations in CFAP47 (c.706G>A, Val236Met; c.1337C>T, Thr446Met) in one case. Immunoblotting and immunofluorescence revealed that CFAP47 was dramatically reduced in spermatozoa from the CFAP47-mutated man. Meanwhile, the expression of WDR87 was also significantly decreased, and weak signals were detected adjacent to the spermatozoa nuclei, indicating that CFAP47 was necessary for WDR87 transportation during spermatozoa flagella biogenesis. These data indicate that WDR87 is located in the middle piece of the sperm tail and interacts with CFAP47 to form a complex which is involved in spermatozoa tail assembly.

Clinical detection, diagnosis and treatment of morphological abnormalities of sperm flagella: A review of literature

Sperm carries male genetic information, and flagella help move the sperm to reach oocytes. When the ultrastructure of the flagella is abnormal, the sperm is unable to reach the oocyte and achieve insemination. Multiple morphological abnormalities of sperm flagella (MMAF) is a relatively rare idiopathic condition that is mainly characterized by multiple defects in sperm flagella. In the last decade, with the development of high-throughput DNA sequencing approaches, many genes have been revealed to be related to MMAF. However, the differences in sperm phenotypes and reproductive outcomes in many cases are attributed to different pathogenic genes or different pathogenic mutations in the same gene. Here, we will review information about the various phenotypes resulting from different pathogenic genes, including sperm ultrastructure and encoding proteins with their location and functions as well as assisted reproductive technology (ART) outcomes. We will share our clinical detection and diagnosis experience to provide additional clinical views and broaden the understanding of this disease.

Novel biallelic mutations in TTC29 cause asthenoteratospermia and male infertility

BACKGROUND

Multiple morphological abnormalities of the sperm flagella (MMAF), which is characterized as asthenoteratospermia involving absent, short, bent, coiled, and/or irregular-caliber flagella, is a rare recessive inherited disorder associated with male infertility. To date, genetic causes of MMAF cases are not fully explored.

METHODS

Whole-exome sequencing was conducted to identify pathogenic variants in a patient with MMAF. The functional effect of the identified mutations was investigated by immunofluorescence staining and western blotting. Intracytoplasmic sperm injection was used to assist fertilization for the patient with MMAF.

RESULTS

We identified novel biallelic mutations, a splicing variant NC_000004.12:g.146937593C>T (c.254+1G>A), and a nonsense mutation NM_001300761.4:c.1185C>G (NP_001287690.1:p.Tyr395*), in TTC29 from an infertile patient. In addition to the typical MMAF phenotype, the patient also presented aberrant morphology of sperm heads. Further functional experiments confirmed the absence of TTC29 expression in the spermatozoa. We also explored the specific expression pattern of TTC29 in human and mouse spermatogenesis. The outcome of intracytoplasmic sperm injection in the patient was unsuccessful, while additional female risk factors should not be excluded.

CONCLUSIONS

Our study revealed the novel biallelic mutations in TTC29 in a MMAF patient, which findings expand the mutational spectrum of TTC29 and further contribute to the diagnosis, genetic counseling, and prognosis of male infertility.

LRRC46 Accumulates at the Midpiece of Sperm Flagella and Is Essential for Spermiogenesis and Male Fertility in Mouse

The sperm flagellum is essential for male fertility. Multiple morphological abnormalities of the sperm flagella (MMAF) is a severe form of asthenoteratozoospermia. MMAF phenotypes are understood to result from pathogenic variants of genes from multiple families including AKAP, DANI, DNAH, RSPH, CCDC, CFAP, TTC, and LRRC, among others. The Leucine-rich repeat protein (LRRC) family includes two members reported to cause MMAF phenotypes: Lrrc6 and Lrrc50. Despite vigorous research towards understanding the pathogenesis of MMAF-related diseases, many genes remain unknown underlying the flagellum biogenesis. Here, we found that Leucine-rich repeat containing 46 (LRRC46) is specifically expressed in the testes of adult mice, and show that LRRC46 is essential for sperm flagellum biogenesis. Both scanning electron microscopy (SEM) and Papanicolaou staining (PS) presents that the knockout of Lrrc46 in mice resulted in typical MMAF phenotypes, including sperm with short, coiled, and irregular flagella. The male KO mice had reduced total sperm counts, impaired sperm motility, and were completely infertile. No reproductive phenotypes were detected in Lrrc46-/- female mice. Immunofluorescence (IF) assays showed that LRRC46 was present throughout the entire flagella of control sperm, albeit with evident concentration at the mid-piece. Transmission electron microscopy (TEM) demonstrated striking flagellar defects with axonemal and mitochondrial sheath malformations. About the important part of the Materials and Methods, SEM and PS were used to observe the typical MMAF-related irregular flagella morphological phenotypes, TEM was used to further inspect the sperm flagellum defects in ultrastructure, and IF was chosen to confirm the location of protein. Our study suggests that LRRC46 is an essential protein for sperm flagellum biogenesis, and its mutations might be associated with MMAF that causes male infertility. Thus, our study provides insights for understanding developmental processes underlying sperm flagellum formation and contribute to further observe the pathogenic genes that cause male infertility.

CCDC38 is required for sperm flagellum biogenesis and male fertility in mice

The sperm flagellum is essential for male fertility, and defects in flagellum biogenesis are associated with male infertility. Deficiency of coiled-coil domain-containing (CCDC) 42 (CCDC42) is specifically associated with malformation of mouse sperm flagella. Here, we find that the testis-specific protein CCDC38 interacts with CCDC42, localizing on the manchette and sperm tail during spermiogenesis. Inactivation of CCDC38 in male mice results in a distorted manchette, multiple morphological abnormalities of the flagella of spermatozoa and eventually male sterility. Furthermore, we find that CCDC38 interacts with intraflagellar transport protein 88 (IFT88), as well as outer dense fibrous 2 (ODF2), and the knockout of Ccdc38 reduces transport of ODF2 to the flagellum. Altogether, our results uncover the essential role of CCDC38 in sperm flagellum biogenesis, and suggest that some mutations of these genes might be associated with male infertility in humans.