Novel Compound Heterozygous Mutation in FSIP2 Causes Multiple Morphological Abnormalities of the Sperm Flagella (MMAF) and Male Infertility

Genetic etiological spectrum of sperm morphological abnormalities

PURPOSE

Male infertility manifests in the form of a reduction in sperm count, sperm motility, or the loss of fertilizing ability. While the loss of sperm production can have mixed reasons, sperm structural defects, cumulatively known as teratozoospermia, have predominantly genetic bases. The aim of the present review is to undertake a comprehensive analysis of the genetic mutations leading to sperm morphological deformities/teratozoospermia.

METHODS

We undertook literature review for genes involved in sperm morphological abnormalities. The genes were classified according to the type of sperm defects they cause and on the basis of the level of evidence determined by the number of human studies and the availability of a mouse knockout.

RESULTS

Mutations in the SUN5, CEP112, BRDT, DNAH6, PMFBP1, TSGA10, and SPATA20 genes result in acephalic sperm; mutations in the DPY19L2, SPATA16, PICK1, CCNB3, CHPT1, PIWIL4, and TDRD9 genes cause globozoospermia; mutations in the AURKC gene cause macrozoospermia; mutations in the WDR12 gene cause tapered sperm head; mutations in the RNF220 and ADCY10 genes result in small sperm head; mutations in the AMZ2 gene lead to vacuolated head formation; mutations in the CC2D1B and KIAA1210 genes lead to pyriform head formation; mutations in the SEPT14, ZPBP1, FBXO43, ZCWPW1, KATNAL2, PNLDC1, and CCIN genes cause amorphous head; mutations in the SEPT12, RBMX, and ACTL7A genes cause deformed acrosome formation; mutations in the DNAH1, DNAH2, DNAH6, DNAH17, FSIP2, CFAP43, AK7, CHAP251, CFAP65, ARMC2 and several other genes result in multiple morphological abnormalities of sperm flagella (MMAF).

CONCLUSIONS

Altogether, mutations in 31 genes have been reported to cause head defects and mutations in 62 genes are known to cause sperm tail defects.

Novel bi-allelic DNAH3 variants cause oligoasthenoteratozoospermia

Background

Oligoasthenoteratozoospermia (OAT) is a widespread cause of male infertility. One of the usual clinical manifestations of OAT is multiple morphological abnormalities of the sperm flagella (MMAF), which are frequently associated with mutations and defects in the dynein family. However, the relationship between the newly identified Dynein Axonemal Heavy Chain 3 (DNAH3) mutation and oligonasthenospermia in humans has not yet been established.

Methods

Whole exome sequencing, pathogenicity analysis, and species conservation analysis of mutation sites were conducted on two patients from different unrelated families with DNAH3 mutations. We identified representative mutation sites and predicted the protein structure following these mutations. The sperm characteristics of the two patients with DNAH3 mutations were verified using Papanicolaou staining, scanning electron microscopy, and transmission electron microscopy. Additionally, mRNA and protein levels were assessed through RT-qPCR and Western blotting.

Results

The biallelic mutations in the first progenitor included a heterozygous deletion and insertion, c.6535_6536 delinsAC (to infect mutation (p.Asp2179Thr), and stop codon premutation, c.3249G > A (p.Trp1083Ter). In Family II, the patient (P2) harbored a DNAH3 heterozygous missense mutation, c. 10439G> A(p.Arg3480Gln), along with a stop codon premutation, (c.10260G > A; p.Trp3420Ter). Patients with premature termination of transcription or translation due to DNAH3 mutations exhibit OAT phenotypes, including fibrous sheath dysplasia and multiple tail malformations. We identified the representative sites after mutation, predicted the protein structure, and assessed changes in the protein levels of DNAH3 and related genes following mutations. Notably,a significant reduction in DNAH3 protein expression was validated in these patients. We may explore in the future how DNAH3 affects sperm motility and quality through regulatory mechanisms involving protein structural changes.

Conclusion

Novel biallelic mutations in DNAH3, especially those resulting in a premature stop codon, may alter protein expression, structure, and active site, leading to spermatogenic failure and potentially inducing OAT. The discovery of new mutations in DNAH3 may be the key to the diagnosis and treatment of OAT.

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.

SPEM1 Gene Mutation in a Case with Sperm Morphological Defects Leading to Male Infertility

The present study aimed at identifying the genetic mutation responsible for teratozoospermic infertility in a case with coiled sperm tails. A 33-year-old infertile male was diagnosed with teratozoospermic infertility, with sperm head in coiled (HIC) tail as the most common deformity. We employed whole exome sequencing to identify the genetic cause in this case. Exome sequencing data was filtered using the following criteria: MAF (< 0.003), ALFA project (< 0.001), 1000 Genomes (< 0.003), Granthem (> 50), Polyphen-2 (> 0.70), SIFT (< 0.03), and PhyloP (> = 0) scores. Shortlisted variants were looked in the in-house 29 exomes data available with us, and the variants that affected conserved amino acid residues or led to insertion/deletion or to protein-truncation with a Combined Annotation Dependent Depletion (CADD) score ≥ 10 were shortlisted. The variants thus populated were prioritized according to their roles in spermiogenesis. The study identified a heterozygous mutation c.826C > T (Arg276Trp) in the SPEM1 gene as a potential pathogenic variant that led to teratozoospermic infertility in the case under investigation. The mutation had a minor allele frequency of 0.00008176 in the gnomAd database and was absent in the Indian Genome Variations database. This is the first human study reporting a mutation in the SPEM1 gene as a cause of coiled sperm tails.

Ovine fertility by artificial insemination in the breeding season could be affected by intraseasonal variations in ram sperm proteomic profile

It is important to note that seasonality could affect ram reproductive parameters, and therefore, fertility results after artificial insemination. In this work, 1) we assessed fertility rates after cervical artificial insemination of 11,805 ewes at the beginning (June 21st to July 20th) and at the end (November 20th to December 21st) of the reproductive season in the Assaf breed for the last four years, and 2) we aimed to identify male factors influencing the different reproductive success obtained depending on the time at the mating season in which ovine artificial insemination was performed. For this purpose, we evaluated certain ram reproductive and ultrasonographical parameters as well as we performed a multiparametric and proteomic sperm analysis of 6-19 rams at two very distant points in the mating season (July as Early Breeding Season -EBS- and November as Late Breeding Season -LBS-). Rutinary assessments carried out in the ovine reproduction centers (testicular volume, libido, sperm production and mass motility) showed non-significant differences (P ≥ 0.05) between both studied times, as well as the ram ultrasonographic evaluation (Resistive and Pulsatility Index as Doppler parameters; and pixels mean gray level, and hypoechoic areas percentage and density as echotexture parameters). However, at level of sperm functionality, although sperm quality appeared non-significantly lower (P ≥ 0.05) in the EBS, we identified a significantly different (P < 0.05) sperm proteomic profile between the seasonality points. The following proteins were identified with the lowest abundance in the EBS with a fold change > 4, a P = 2.40e-07, and a q = 2.23e-06: Fibrous Sheath-Interacting Protein 2, Disintegrin and Metalloproteinase Domain-Containing Protein 20-like, Phosphoinositide-Specific Phospholipase C, Tektin 5, Armadillo Repeat-Containing Protein 12 Isoform X3, Solute Carrier Family 9B1, Radial Spoke Head Protein 3 Homolog, Pro-Interleukin-16, NADH Dehydrogenase [Ubiquinone] 1 Alpha Subcomplex Subunit 8, Testis, Prostate and Placenta-Expressed Protein, and Acyl Carrier Protein Mitochondrial. In conclusion, while our basic analyses on male and sperm quality showed similar results between the beginning and the end of the breeding season, on a proteomic level we detected a lower expression of sperm proteins linked to the energy metabolism, sperm-oocyte interactions, and flagellum structure in the EBS. Probably, this different protein expression could be related to the lower fertility rate of Assaf ewes after cervical artificial insemination at this time. More importantly, sperm proteins can be used as highly effective molecular markers in predicting sperm fertilization ability related to intraseasonal variations.

Mapping the human sperm proteome - novel insights into reproductive research

INTRODUCTION

Spermatozoa are highly specialized cells with unique morphology. In addition, spermatozoa lose a considerable amount of cytoplasm during spermiogenesis, when they also compact their DNA, resulting in a transcriptionally quiescent cell. Throughout the male reproductive tract, sperm will acquire proteins that enable them to interact with the female reproductive tract. After ejaculation, proteins undergo post-translational modifications for sperm to capacitate, hyperactivate and fertilize the oocyte. Many proteins have been identified as predictors of male infertility, and also investigated in diseases that compromise reproductive potential.

AREAS COVERED

In this review we proposed to summarize the recent findings about the sperm proteome and how they affect sperm structure, function, and fertility. A literature search was performed using PubMed and Google Scholar databases within the past 5 years until August 2022.

EXPERT OPINION

Sperm function depends on protein abundance, conformation, and PTMs; understanding the sperm proteome may help to identify pathways essential to fertility, even making it possible to unravel the mechanisms involved in idiopathic infertility. In addition, proteomics evaluation offers knowledge regarding alterations that compromise the male reproductive potential.

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.

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.