Patients with multiple morphological abnormalities of the sperm flagella harbouring CFAP44 or CFAP43 mutations have a good pregnancy outcome following intracytoplasmic sperm injection

Novel variants of FSIP2 and SPEF2 cause varying degrees of spermatozoa damage in MMAF patients and favorable ART outcomes

PURPOSE

This study identified novel variants of the FSIP2 and SPEF2 genes in multiple morphological abnormalities of the sperm flagella (MMAF) patients and to investigate the potential effect of variations on male infertility and assisted reproductive outcomes.

METHODS

Whole-exome sequencing was performed in 106 Chinese MMAF patients. The discovered variants were evaluated in silico and confirmed by Sanger sequencing. A mini-gene assay and immunofluorescence staining were used to determine the effects on mRNA and protein. Assisted reproductive technology (ART) based on intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF) was used for MMAF patients carrying novel variants.

RESULTS

Biallelic variants in FSIP2 or SPEF2 involving nineteen novel variations were found in eleven MMAF patients. These variations included fourteen missense variants, two nonsense variants, two frameshift variants, and a splicing variant. The FSIP2 protein was markedly reduced or mislocalized to the spermatozoa head. Two novel missense variants of SPEF2 reduced cell diameter. Eleven MMAF couples had 12 ICSI cycles and 2 IVF cycles. The 2PN fertilization rate, good-quality embryos rate, and clinical pregnancy rate were 80.1% (133/166), 74.4% (99/133), and 45.7% (16/35). Four of them have seven babies born.

CONCLUSION

Our work revealed that missense variations of FSIP2 or SPEF2 might cause a milder spermatozoa damage. The infertility caused by FSIP2 and SPEF2 variants can be mitigated through ICSI or even IVF. The results of this study presented signs of the correlation of phenotype/genotype for the FSIP2 and SPEF2, which might provide a reference for clinical genetic and fertility consultation.

Genetic Underpinnings of Oligoasthenoteratozoospermia

Oligoasthenoteratozoospermia (OAT) is a frequent but severe type of male infertility. As one of the most multifaceted male infertility resulting from sperm problems, its genetic etiology remains unknown in most cases. In this review, we systematically sort out the latest literature on clinical reports and animal models leading to OAT, summarise the expression profiles of causative genes for OAT, and highlight the important role of the protein transport system during spermiogenesis, spermatid cell-specific genes, Golgi and acrosome-related genes, manchette-related genes, HTCA-related genes, and axoneme-related genes in OAT development. These causative genes would be instrumental in genetic etiological screening, genetic counseling, and pre-implantation genetic testing of patients with clinical 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.

Single nucleotide polymorphisms of CFAP43 and TEX14 associated with idiopathic male infertility in a Vietnamese population

Male infertility is a multifactorial disease due to spermatogenesis impairment, with etiology remaining unknown for roughly one-third of infertile cases. Several studies have demonstrated that genetic variants are male infertility risk factors. CFAP43 and TEX14 are involved in the spermatogenesis process. The present study aimed to assess the association between single-nucleotide polymorphisms (SNPs) in CFAP43 (rs17116635 and rs10883979) and TEX14 (rs79813370 and rs34818467) and idiopathic male infertility in a Vietnamese population. A cohort of 206 infertile men and 195 controls were recruited for the study. CFAP43 and TEX14 SNPs were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Genotypes of randomly selected samples, accounting for 10% of the total, were confirmed using Sanger sequencing. The obtained data were analyzed using statistical methods. The results showed that 4 SNPs (rs17116635, rs10883979, rs79813370, and rs34818467) were in accordance with Hardy-Weinberg Equilibrium (HWE; P > .05). CFAP43 rs10883979 and TEX14 rs79813370 were associated with male infertility. For CFAP43 rs10883979, in the recessive model, the combination AA + AG was associated with male infertility when compared to the GG genotype (OR = 0.26; 95% CI: 0.06-0.85; P = .02). For TEX14 rs79813370, a protective effect against infertility risk was identified in the presence of the T allele of rs79813370 when compared to the G allele (OR = 0.48; 95% CI: 0.32-0.72; P < .001). Our results suggest that CFAP43 rs10883979 and TEX14 rs79813370 are likely associated with male infertility in the Vietnamese population, in which the G allele of rs79813370 may be a risk factor for male infertility.

Novel biallelic variants in DNAH1 cause multiple morphological abnormalities of sperm flagella with favorable outcomes of fertility after ICSI in Han Chinese males

BACKGROUND

Multiple morphological abnormalities of sperm flagella is an idiopathic asthenoteratozoospermia characterized by absent, short, coiled, angulation, and irregular-caliber flagella. Genetic variants of DNAH1 gene have been identified as a causative factor of multiple morphological abnormalities of sperm flagella and intracytoplasmic sperm injection is an available strategy for infertile males with dynein axonemal heavy chain 1 defects to conceive.

OBJECTIVES

To identify novel variants and candidate mutant hotspots of DNAH1 gene related to multiple morphological abnormalities of sperm flagella and male infertility in humans.

MATERIALS AND METHODS

The DNAH1 variants were identified by whole exome sequencing and confirmed with Sanger sequencing. Papanicolaou staining, scanning and transmission electron microscopy, and immunostaining were performed to investigate the morphological and ultrastructural characteristics of spermatozoa. Intracytoplasmic sperm injection was applied for the assisted reproductive therapy of males harboring biallelic DNAH1 variants.

RESULTS

We identified 18 different DNAH1 variants in 11 unrelated families, including nine missense variants (p.A2564T, p.T3657R, p.G1862R, p.L2296P, p.T4041I, p.L611P, p.A913D, p.R1932Q, p.R2356W) and nine loss-of-function variants (c.2301-1G>T, p.Q1518*, p.R1702*, p.D2845Mfs*2, p.P3909Rfs*33, p.Q4040Dfs*33, p.Q4058*, p.E4060Pfs*61, p.V4071Cfs*54). A total of 66.7% (12/18) of the identified variants were novel. Morphological analysis based on Papanicolaou staining and scanning electron microscopy demonstrated the typical multiple morphological abnormalities of sperm flagella characteristics of dynein axonemal heavy chain 1-deficient spermatozoa. Immunostaining further revealed the absence of inner dynein arms but not outer dynein arms, which induced a general ultrastructural disorganization, such as the loss of central pair and mis-localization of the microtubule doublets and outer dense fibers. To date, seven affected couples have accepted the intracytoplasmic sperm injection treatment, and three of them have given birth to five healthy babies.

DISCUSSION AND CONCLUSION

These findings further expand the variant spectrum of DNAH1 gene related to multiple morphological abnormalities of sperm flagella and male infertility in humans, thus providing new information for the molecular diagnosis of asthenoteratozoospermia. The favorable fertility outcomes of intracytoplasmic sperm injection will facilitate the genetic counseling and clinical treatment of infertile males with multiple morphological abnormalities of sperm flagella in the future.

Nuclear sperm integrity and ICSI prognosis in Tunisian patients with MMAF syndrome (multiple morphological abnormalities of the sperm flagella)

Multiple Morphological Abnormalities of the Sperm Flagella (MMAF) is a severe form of teratozoospermia associated with several sperm flagellar abnormalities. The study included 52 patients with MMAF syndrome and a control group of 25 fertile men. The impact of nuclear sperm quality on intracytoplasmic sperm injection (ICSI) results was studied in 20 couples. TUNEL assay was used to assess sperm DNA fragmentation and aniline-blue staining was used to assess chromatin condensation. To investigate chromosomal meiotic segregation, we used fluorescence in situ hybridization (FISH). Semen morphology analysis revealed a mosaic of multiple flagella morphological abnormalities, including 46.73% short flagella, 16.22% bent flagella, 22.07% coiled flagella, and 10.90% absent flagella, all of which were associated with a high percentage of sperm head abnormalities. The mean DNA fragmentation index was substantially higher in patients compared to controls (p = 0.001), whereas the rate of aniline blue-reacted spermatozoa was not significantly different. There was a significant difference in aneuploidy frequencies between the two groups (p < 0.05). Infertile males with MMAF syndrome had lower sperm nuclear quality, which affected ICSI results. As a result, better sperm selection procedures are being employed to increase the success rate of assisted reproductive technologies (ART).

Patients with MMAF induced by novel biallelic CFAP43 mutations have good fertility outcomes after intracytoplasmic sperm injection

As a specific type of asthenoteratozoospermia, multiple morphological abnormalities of the sperm flagella (MMAF) is characterized by composite abnormalities, including absent, short, coiled, angulation, and irregular-caliber flagella. Mutations in cilia- and flagella-associated protein 43 ( CFAP43 ) are one of the main causative factors of MMAF established to date. To identify whether there are other CFAP43 mutations related to MMAF and to determine the clinical outcomes of assisted reproductive technology for patients with MMAF harboring different mutations, we recruited and screened 30 MMAF-affected Chinese men using a 22-gene next-generation sequencing panel. After systematic analysis, seven mutations in CFAP43 , including five novel mutations and two previously reported mutations, were identified from four families and related to MMAF in an autosomal recessive pattern. Papanicolaou staining, immunofluorescence, and electronic microscopy further clarified the semen characteristics and abnormal sperm morphologies, including disorganized axonemal and peri-axonemal structures, of the CFAP43 -deficient men. The female partners of two patients were pregnant after undergoing assisted reproductive technology through intracytoplasmic sperm injection, and one of them successfully gave birth to a healthy boy. This study significantly expands the mutant spectrum of CFAP43 , and together with the available information regarding male infertility and MMAF, provides new information for the genetic diagnosis and counseling of MMAF in the future.

Novel compound heterozygous mutations in DNAH1 cause primary infertility in Han Chinese males with multiple morphological abnormalities of the sperm flagella

This study aimed to identify genetic causes responsible for multiple morphological abnormalities of the sperm flagella (MMAF) in the Han Chinese population. Three primary infertile males with completely immobile sperm and MMAF were enrolled. Whole-exome sequencing and Sanger sequencing were performed to identify disease-causing genes. Subsequently, morphological and ultrastructural analyses of sperm flagella were investigated. The probable impact of genetic variants on protein function was analyzed by online bioinformatic tools and immunofluorescence assay. Three patients with dynein axonemal heavy chain 1 (DNAH1) gene compound heterozygous variations were identified. DNAH1 c.7435C>T, p.R2479X and c.10757T>C, p.F3586S were identified in the patient from Family 1, c.11726_11727delCT, p.P3909fs and c.12154delC, p.L4052fs were found in the patient from Family 2, and c.10627-3C>G and c.11726_11727delCT, p.P3909fs existed in the patient from Family 3. Four of these variations have not been reported, and all the mutations showed pathogenicity by functional effect predictions. The absence of the center pair and disorganization of the fibrous sheath were present in sperm flagella at the ultrastructural level. Moreover, the expression of DNAH1 was absent in spermatozoa from the participants, validating the pathogenicity of the variants. All three couples have undergone intracytoplasmic sperm injection (ICSI), and two couples of them became pregnant after the treatment. In conclusion, the newly identified DNAH1 mutations can expand the mutational and phenotypic spectrum of MMAF genes and provide a theoretical basis for genetic diagnosis in MMAF patients. It is recommended to conduct genetic screening in male infertility patients with MMAF and provide rational genetic counseling, and ICSI might be an optimal strategy to help with fertilization and conception for patients with DNAH1 mutations.

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.

Successful Results of Intracytoplasmic Sperm Injection of a Chinese Patient With Multiple Morphological Abnormalities of Sperm Flagella Caused by a Novel Splicing Mutation in CFAP251

Asthenospermia is one of the most important causes of male infertility. Among asthenospermia, multiple morphological abnormalities of sperm flagella (MMAF) are relatively rare idiopathic conditions characterized by multiple defects in sperm flagella. Although many studies focusing on the genetic factors of MMAF have been conducted, its pathogenesis and treatment effect remain largely unknown. Here, we report a male patient from a nonconsanguineous Chinese family who exhibited a typical MMAF phenotype revealed by morphological analysis. We identified splicing mutations in CFAP251 (c.1192-3C>G), and the mutation was proven to cause exon skipping. In addition, western blotting and immunofluorescence analysis of the spermatozoa from the proband and a control subject revealed a significantly lower expression of CFAP251 protein due to pathogenic mutation. Interestingly, the patient’s mother was a heterozygous carrier for the mutation, but his father was not, and finally, the inheritance pattern was proven to be maternal uniparental disomy. We applied an intracytoplasmic sperm injection and achieved a successful pregnancy. Above all, our findings expand the spectrum of CFAP251 pathogenic mutations and provide more indications for clinical genetic counseling and assisted reproductive treatment for such patients.

Novel DNAH1 Mutation Loci Lead to Multiple Morphological Abnormalities of the Sperm Flagella and Literature Review

The protein encoded by dynein axonemal heavy chain 1 (DNAH1) is a part of dynein, which regulates the function of cilia and sperm flagella. The mutant of DNAH1 causes the deletion of inner dynein arm 3 in the flagellum, leading to multiple morphological abnormalities of the sperm flagella (MMAF) and severe asthenozoospermia. However, instead of asthenozoospermia and MMAF, the result caused by the mutation of DNAH1 remains unknown. Here we report a male infertility patient with severe asthenozoospermia and teratozoospermia. We found two heterozygous mutations in DNAH1 (c.6912C>A and c.7076G>T) and which were reported to be associated with MMAF for the first time. We next collected and analyzed 65 cases of DNAH1 mutation and found that the proportion of short flagella is the largest, while the bent flagella account for the smallest, and the incidence of head deformity is not high in the sperm of these patients. Finally, we also analyzed 31 DNAH1 mutation patients who were treated with intracytoplasmic sperm injection (ICSI) and achieved beneficial outcomes. We hope our research will be helpful in the diagnosis and treatment of male infertility caused by DNAH1 mutation.

Genetic diagnosis, sperm phenotype and ICSI outcome in case of severe asthenozoospermia with multiple morphological abnormalities of the flagellum

STUDY QUESTION

Are ICSI outcomes impaired in cases of severe asthenozoospermia with multiple morphological abnormalities of the flagellum (MMAF phenotype)?

SUMMARY ANSWER

Despite occasional technical difficulties, ICSI outcomes for couples with MMAF do not differ from those of other couples requiring ICSI, irrespective of the genetic defect.

WHAT IS KNOWN ALREADY

Severe asthenozoospermia, especially when associated with the MMAF phenotype, results in male infertility. Recent findings have confirmed that a genetic aetiology is frequently responsible for this phenotype. In such situations, pregnancies can be achieved using ICSI. However, few studies to date have provided detailed analyses regarding the flagellar ultrastructural defects underlying this phenotype, its genetic aetiologies, and the results of ICSI in such cases of male infertility.

STUDY DESIGN, SIZE, DURATION

We performed a retrospective study of 25 infertile men exhibiting severe asthenozoospermia associated with the MMAF phenotype identified through standard semen analysis. They were recruited at an academic centre for assisted reproduction in Paris (France) between 2009 and 2017. Transmission electron microscopy (TEM) and whole exome sequencing (WES) were performed in order to determine the sperm ultrastructural phenotype and the causal mutations, respectively. Finally 20 couples with MMAF were treated by assisted reproductive technologies based on ICSI.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients with MMAF were recruited based on reduced sperm progressive motility and increased frequencies of absent, short, coiled or irregular flagella compared with those in sperm from fertile control men. A quantitative analysis of the several ultrastructural defects was performed for the MMAF patients and for fertile men. The ICSI results obtained for 20 couples with MMAF were compared to those of 378 men with oligoasthenoteratozoospermia but no MMAF as an ICSI control group.

MAIN RESULTS AND THE ROLE OF CHANCE

TEM analysis and categorisation of the flagellar anomalies found in these patients provided important information regarding the structural defects underlying asthenozoospermia and sperm tail abnormalities. In particular, the absence of the central pair of axonemal microtubules was the predominant anomaly observed more frequently than in control sperm (P < 0.01). Exome sequencing, performed for 24 of the 25 patients, identified homozygous or compound heterozygous pathogenic mutations in CFAP43, CFAP44, CFAP69, DNAH1, DNAH8, AK7, TTC29 and MAATS1 in 13 patients (54.2%) (11 affecting MMAF genes and 2 affecting primary ciliary dyskinesia (PCD)-associated genes). A total of 40 ICSI cycles were undertaken for 20 MMAF couples, including 13 cycles (for 5 couples) where a hypo-osmotic swelling (HOS) test was required due to absolute asthenozoospermia. The fertilisation rate was not statistically different between the MMAF (65.7%) and the non-MMAF (66.0%) couples and it did not differ according to the genotype or the flagellar phenotype of the subjects or use of the HOS test. The clinical pregnancy rate per embryo transfer did not differ significantly between the MMAF (23.3%) and the non-MMAF (37.1%) groups. To date, 7 of the 20 MMAF couples have achieved a live birth from the ICSI attempts, with 11 babies born without any birth defects.

LIMITATIONS, REASONS FOR CAUTION

The ICSI procedure outcomes were assessed retrospectively on a small number of affected subjects and should be confirmed on a larger cohort. Moreover, TEM analysis could not be performed for all patients due to low sperm concentrations, and WES results are not yet available for all of the included men.

WIDER IMPLICATIONS OF THE FINDINGS

An early and extensive phenotypic and genetic investigation should be considered for all men requiring ICSI for severe asthenozoospermia. Although our study did not reveal any adverse ICSI outcomes associated with MMAF, we cannot rule out that some rare genetic causes could result in low fertilisation or pregnancy rates.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used for this study and there are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

The mutation c.346-1G > a in SOHLH1 impairs sperm production in the homozygous but not in the heterozygous condition

Non-obstructive azoospermia (NOA) is an important cause of male infertility, and the genetic pathogenesis is still incompletely understood. The previous study reported that heterozygous mutation of c.346-1G > A in spermatogenesis and oogenesis specific basic helix–loop–helix 1 (SOHLH1) was identified in two NOA patients and suggested it is the pathogenic factor for NOA. However, in our research, this heterozygous mutation was confirmed in three Chinese infertile patients who suffered from teratozoospermia, but they had normal sperm number. Intriguingly, a homozygous mutation of c.346-1G > A in SOHLH1 was detected in a severe oligozoospermia (SOZ) patient, characterized with severely decreased sperm count. Notably, we unprecedently revealed that this homozygous mutation of c.346-1G > A in SOHLH1 leads to the sharp decrease in various germ cells and spermatogenesis dysfunction, which is similar to the phenotype of SOHLH1 knockout male mice. Moreover, western blotting confirmed that the homozygous mutation declined SOHLH1 protein expression. Additionally, we correlated the good prognosis of intracytoplasmic sperm injection (ICSI) in the patients carrying the mutation of c.346-1G > A in SOHLH1. Thus, we suggested that the heterozygous mutation of c.346-1G > A in SOHLH1 is responsible for teratozoospermia, and this homozygous mutation in SOHLH1 impairs spermatogenesis and further leads to the reduced sperm count, eventually causing male infertility, which unveils a new recessive-inheritance pattern of SOHLH1-associated male infertility initially.

Exome sequencing reveals variants in known and novel candidate genes for severe sperm motility disorders

STUDY QUESTION

What are the causative genetic variants in patients with male infertility due to severe sperm motility disorders?

SUMMARY ANSWER

We identified high confidence disease-causing variants in multiple genes previously associated with severe sperm motility disorders in 10 out of 21 patients (48%) and variants in novel candidate genes in seven additional patients (33%).

WHAT IS KNOWN ALREADY

Severe sperm motility disorders are a form of male infertility characterised by immotile sperm often in combination with a spectrum of structural abnormalities of the sperm flagellum that do not affect viability. Currently, depending on the clinical sub-categorisation, up to 50% of causality in patients with severe sperm motility disorders can be explained by pathogenic variants in at least 22 genes.

STUDY DESIGN, SIZE, DURATION

We performed exome sequencing in 21 patients with severe sperm motility disorders from two different clinics.

PARTICIPANTS/MATERIALS, SETTING, METHOD

Two groups of infertile men, one from Argentina (n = 9) and one from Australia (n = 12), with clinically defined severe sperm motility disorders (motility <5%) and normal morphology values of 0-4%, were included. All patients in the Argentine cohort were diagnosed with DFS-MMAF, based on light and transmission electron microscopy. Sperm ultrastructural information was not available for the Australian cohort. Exome sequencing was performed in all 21 patients and variants with an allele frequency of <1% in the gnomAD population were prioritised and interpreted.

MAIN RESULTS AND ROLE OF CHANCE

In 10 of 21 patients (48%), we identified pathogenic variants in known sperm assembly genes: CFAP43 (3 patients); CFAP44 (2 patients), CFAP58 (1 patient), QRICH2 (2 patients), DNAH1 (1 patient) and DNAH6 (1 patient). The diagnostic rate did not differ markedly between the Argentinian and the Australian cohort (55% and 42%, respectively). Furthermore, we identified patients with variants in the novel human candidate sperm motility genes: DNAH12, DRC1, MDC1, PACRG, SSPL2C and TPTE2. One patient presented with variants in four candidate genes and it remains unclear which variants were responsible for the severe sperm motility defect in this patient.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

In this study, we described patients with either a homozygous or two heterozygous candidate pathogenic variants in genes linked to sperm motility disorders. Due to unavailability of parental DNA, we have not assessed the frequency of de novo or maternally inherited dominant variants and could not determine the parental origin of the mutations to establish in all cases that the mutations are present on both alleles.

WIDER IMPLICATIONS OF THE FINDINGS

Our results confirm the likely causal role of variants in six known genes for sperm motility and we demonstrate that exome sequencing is an effective method to diagnose patients with severe sperm motility disorders (10/21 diagnosed; 48%). Furthermore, our analysis revealed six novel candidate genes for severe sperm motility disorders. Genome-wide sequencing of additional patient cohorts and re-analysis of exome data of currently unsolved cases may reveal additional variants in these novel candidate genes.

STUDY FUNDING/COMPETING INTEREST(S)

This project was supported in part by funding from the Australian National Health and Medical Research Council (APP1120356) to M.K.O.B., J.A.V. and R.I.M.L., The Netherlands Organisation for Scientific Research (918-15-667) to J.A.V., the Royal Society and Wolfson Foundation (WM160091) to J.A.V., as well as an Investigator Award in Science from the Wellcome Trust (209451) to J.A.V. and Grants from the National Research Council of Argentina (PIP 0900 and 4584) and ANPCyT (PICT 9591) to H.E.C. and a UUKi Rutherford Fund Fellowship awarded to B.J.H.

Novel biallelic loss-of-function mutations in CFAP43 cause multiple morphological abnormalities of the sperm flagellum in Pakistani families

Multiple morphological abnormalities of the sperm flagella (MMAF) is a specific type of asthenoteratozoospermia, presenting with multiple morphological anomalies in spermatozoa, such as absent, bent, coiled, short, or irregular caliber flagella. Previous genetic studies revealed pathogenic mutations in genes encoding cilia and flagella-associated proteins (CFAPs; e.g., CFAP43, CFAP44, CFAP65, CFAP69, CFAP70, and CFAP251) responsible for the MMAF phenotype in infertile men from different ethnic groups. However, none of them have been identified in infertile Pakistani males with MMAF. In the current study, two Pakistani families with MMAF patients were recruited. Whole-exome sequencing (WES) of patients and their parents was performed. WES analysis reflected novel biallelic loss-of-function mutations in CFAP43 in both families (Family 1: ENST00000357060.3, p.Arg300Lysfs*22 and p.Thr526Serfs*43 in a compound heterozygous state; Family 2: ENST00000357060.3, p.Thr526Serfs*43 in a homozygous state). Sanger sequencing further confirmed that these mutations were segregated recessively in the families with the MMAF phenotype. Semiquantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) was carried out to detect the effect of the mutation on mRNA of the affected gene. Previous research demonstrated that biallelic loss-of-function mutations in CFAP43 accounted for the majority of all CFAP43-mutant MMAF patients. To the best of our knowledge, this is the first study to report CFAP43 biallelic loss-of-function mutations in a Pakistani population with the MMAF phenotype. This study will help researchers and clinicians to understand the genetic etiology of MMAF better.

A novel mutation in DNAH17 is present in a patient with multiple morphological abnormalities of the flagella

RESEARCH QUESTION

Asthenoteratospermia is characterized by malformed spermatozoa with motility defects, which results in male infertility. Multiple morphological abnormalities of the sperm flagella (MMAF) is a hallmark of asthenoteratospermia. The genetic causes of MMAF, however, are unknown in about one-third of cases. Which other MMAF-associated genes are waiting to be discovered?

DESIGN

Whole-exome sequencing was conducted to identify causative genes in a man with MMAF. Immunofluorescence staining and western blot were applied to assess the pathogenicity of the identified variant. Intracytoplasmic sperm injection (ICSI) was used to assist fertilization for the patient with MMAF.

RESULT

Sanger sequencing of the family demonstrated that the infertile man carried a homozygous DNAH17 variant (c. 4810C>T [p.R1604C]). The obviously decreased DNAH17 expression was observed in HEK293T cells transfected with MUT-DNAH17 plasmid compared with cells with WT-DNAH17 plasmid. Immunofluorescence analysis showed that this mutation induced significant decrease in DNAH17 expression, which negatively affected the DNAH8 expression in the patient's spermatozoa. Moreover, the outcome of ICSI in the patient was unsuccessful.

CONCLUSION

Our study revealed a novel homozygous missense mutation in DNAH17 involved in MMAF phenotype. The finding of the novel mutation in DNAH17 enriches the gene variant spectrum of MMAF, further contributing to diagnosis, genetic counselling and prognosis for male infertility.

Mutational landscape of DNAH1 in Chinese patients with multiple morphological abnormalities of the sperm flagella: cohort study and literature review

PURPOSE

Multiple morphological abnormalities of the sperm flagella (MMAF) are important causes of male infertility. Mutations in DNAH1 are the main causative factors proven so far. We aim to determine the mutational landscape of DNAH1 in Chinese patients with MMAF.

METHODS

Forty-one Chinese patients with MMAF were enrolled and underwent a 10-gene next-generation sequencing panel screening.

RESULTS

Only the DNAH1 gene was found to have mutations in 12 of these unrelated individuals (29%). Combining published data from two other cohorts of Chinese men with MMAF, we suggest that p.P3909fs*33, p.R868X, p.Q1518X, p.E3284K, and p.R4096L are hotspot mutations. A polymorphism-rs12163565 (G>A)- showed linkage to p.P3909fs*33, suggesting that this involved a founder effect. Four of the 12 patients with DNAH1 mutations were able to use intracytoplasmic sperm injection with their partners and all were successful in obtaining embryos.

CONCLUSIONS

Hotspot mutations were identified for Chinese patients with MMAF. MMAF sub-phenotypes might be associated with different combinations of DNAH1 mutations.

Novel bi-allelic mutations in DNAH1 cause multiple morphological abnormalities of the sperm flagella resulting in male infertility

Background

Male infertility is a major health concern and approximately 10–15% of cases are caused by genetic abnormalities. Defects in the sperm flagella are closely related to male infertility, since flagellar beating allows sperm to swim. The sperm of males afflicted with multiple morphological abnormalities of the flagella (MMAF) possess severe defects of the sperm flagella, may impair sperm motility and lead to male infertility. Currently, known genetic defects only account for MMAF in about 60% of patients and need more intensive efforts to explore the relationship between genes and MMAF.

Methods

The whole-exome sequencing (WES) was performed to analyze the genetic cause of the MMAF patient. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the morphology of sperm cells and to identify the ultrastructural characteristics of the flagella in the patient. The expression of DNAH1 was analyzed by sperm immunofluorescence staining.

Results

We identified the negative effects produced by the DNAH1 mutations c. 8170.C>T (p. R2724*) and c. 4670C>T (p. T1557M) on DNAH1 expression and the development of sperm flagella.

Conclusions

Our findings suggest that DNAH1 is associated with the formation of sperm flagella and homozygous loss-of-function mutations in DNAH1 can impair sperm motility and cause male infertility.

Mutations in DNAH8 contribute to multiple morphological abnormalities of sperm flagella and male infertility

Asthenoteratospermia is an important cause of male infertility. Here, we report two infertile patients with severe asthenoteratospermia accompanied by new genetic abnormality. Whole-exome sequencing and bioinformatics analysis suggested that compound heterozygous mutations in DNAH8 (MIM:603337) may be responsible for multiple morphological abnormalities of the sperm flagella (MMAF). Immunofluorescence assay showed that DNAH8 protein expression was significantly decreased in the sperm tail of the patients, and electron microscopy exhibited an abnormal flagellum ultrastructure, while clinical pregnancy could be achieved by intracytoplasmic sperm injection. Therefore, the compound heterozygous mutations in the DNAH8 gene may be responsible for MMAF.

Evaluation of a Custom Design Gene Panel as a Diagnostic Tool for Human Non-Syndromic Infertility

Infertility is a global healthcare problem, which affects men and women equally. With the advance of genome-wide analysis, an increasing list of human genes involved in infertility is now available. In order to evaluate the diagnostic interest to analyze these genes, we have designed a gene panel allowing the analysis of 51 genes involved in non-syndromic human infertility. In this initial evaluation study, a cohort of 94 non-syndromic infertility cases with a well-defined infertility phenotype was examined. Five patients with previously known mutations were used as positive controls. With a mean coverage of 457×, and 99.8% of target bases successfully sequenced with a depth coverage over 30×, we prove the robustness and the quality of our panel. In total, we identified pathogenic or likely pathogenic variations in eight patients (five male and three female). With a diagnostic yield of 8.5% and the identification of a variety of variants including substitution, insertion, deletion, and copy number variations, our results demonstrate the usefulness of such a strategy, as well as the efficiency and the quality of this diagnostic gene panel.

Novel mutations in FSIP2 lead to multiple morphological abnormalities of the sperm flagella and poor ICSI prognosis

Multiple morphological abnormalities of the sperm flagella (MMAF) is defined as deformities that cause sperm motility disorders, further resulting in male infertility. However, the reported genes related to sperm flagellar defects can only explain approximately 60% of human MMAF cases. Here, we report two novel compound heterozygous mutations, c.16246_16247insCCCAAATATCACC (p. T5416fs*7) and c.17323C > T (p.Q5774*), in the fibrous sheath-interacting protein 2 gene (FSIP2; OMIM: 615796) in an infertile patient by whole-exome sequencing (WES). Western blotting and immunofluorescence staining confirmed that the compound heterozygous mutations abrogated FSIP2 protein expression. Notably, our staining revealed that FSIP2 is expressed in the cytoplasm of primary germ cell and flagella of spermatids during the spermiogenesis. Moreover, intracytoplasmic sperm injection (ICSI) was carried out using sperm from this patient; however, pregnancy failed after embryo transfer through one cycle. Our findings may be helpful in establishing a genetic diagnosis for MMAF, as well as provide additional beneficial knowledge for genetic counseling and infertility treatment.

Genetic underpinnings of asthenozoospermia

Asthenozoospermia (AZS), defined by reduced motility or absent sperm motility, is one of the main causes of male infertility. This condition may be divided into isolated AZS in the absence of other symptoms and syndromic AZS, which is characterized by several concurrent clinical symptoms. Sperm motility depends on fully functional flagellum, energy availability, and the crosstalk of several signaling pathways; therefore, mutations in genes involved in flagellar assembly and motile regulation can cause AZS. Thus, it is crucial to understand the genetic causes and mechanisms contributing to AZS. In this review, we summarize the current knowledge about the particular genes and mechanisms involved in intact flagellum, energy availability, and signaling transduction that could cause human AZS and discuss the respective gene defects known to be responsible for these abnormalities. Additionally, we discuss intracytoplasmic sperm injection outcomes and offspring health where available in these cases.

Canary in the Coal Mine? Male Infertility as a Marker of Overall Health

Male factor infertility is a common problem. Evidence is emerging regarding the spectrum of systemic disease and illness harbored by infertile men who otherwise appear healthy. In this review, we present evidence that infertile men have poor overall health and increased morbidity and mortality, increased rates of both genitourinary and non-genitourinary malignancy, and greater risks of systemic disease. The review also highlights numerous genetic conditions associated with male infertility as well as emerging translational evidence of genitourinary birth defects and their impact on male infertility. Finally, parallels to the overall health of infertile women are presented. This review highlights the importance of a comprehensive health evaluation of men who present for an infertility assessment.

Sperm defects in primary ciliary dyskinesia and related causes of male infertility

The core axoneme structure of both the motile cilium and sperm tail has the same ultrastructural 9 + 2 microtubular arrangement. Thus, it can be expected that genetic defects in motile cilia also have an effect on sperm tail formation. However, recent studies in human patients, animal models and model organisms have indicated that there are differences in components of specific structures within the cilia and sperm tail axonemes. Primary ciliary dyskinesia (PCD) is a genetic disease with symptoms caused by malfunction of motile cilia such as chronic nasal discharge, ear, nose and chest infections and pulmonary disease (bronchiectasis). Half of the patients also have situs inversus and in many cases male infertility has been reported. PCD genes have a role in motile cilia biogenesis, structure and function. To date mutations in over 40 genes have been identified cause PCD, but the exact effect of these mutations on spermatogenesis is poorly understood. Furthermore, mutations in several additional axonemal genes have recently been identified to cause a sperm-specific phenotype, termed multiple morphological abnormalities of the sperm flagella (MMAF). In this review, we discuss the association of PCD genes and other axonemal genes with male infertility, drawing particular attention to possible differences between their functions in motile cilia and sperm tails.

Mutational effect of human CFAP43 splice-site variant causing multiple morphological abnormalities of the sperm flagella

Multiple morphological abnormalities of the sperm flagella (MMAF) is a rare disease associated with male infertility. In our previous study, we identified a homozygous CFAP43 splice-site variant, c.3661-2delA, in a patient with MMAF. However, the mutational effect of this variant was unknown. Here, using a minigene assay, we demonstrated that the c.3661-2delA variant may cause exon-30 to be skipped, thus generating the p.E1221_K1256del protein. By secondary and three-dimensional structural biology prediction analysis, we found that the mutant protein became 'tighter' in comparison with the wild-type protein, resulting in amino acid rearrangements in CFAP43 protein structure. We elucidated the molecular mechanism of the c.3661-2delA splice-site variant causing MMAF in the current study.

Homozygous mutations in DZIP1 can induce asthenoteratospermia with severe MMAF

BACKGROUND

Asthenoteratospermia, one of the most common causes for male infertility, often presents with defective sperm heads and/or flagella. Multiple morphological abnormalities of the sperm flagella (MMAF) is one of the common clinical manifestations of asthenoteratospermia. Variants in several genes including DNAH1, CEP135, CATSPER2 and SUN5 are involved in the genetic pathogenesis of asthenoteratospermia. However, more than half of the asthenoteratospermia cases cannot be explained by the known pathogenic genes.

METHODS AND RESULTS

Two asthenoteratospermia-affected men with severe MMAF (absent flagella in >90% spermatozoa) from consanguineous families were subjected to whole-exome sequencing. The first proband had a homozygous missense mutation c.188G>A (p.Arg63Gln) of DZIP1 and the second proband had a homozygous stop-gain mutation c.690T>G (p.Tyr230*). Both of the mutations were neither detected in the human population genome data (1000 Genomes Project, Exome Aggregation Consortium) nor in our own data of a cohort of 875 Han Chinese control populations. DZIP1 encodes a DAZ (a protein deleted in azoospermia) interacting protein, which was associated with centrosomes in mammalian cells. Immunofluorescence staining of the centriolar protein Centrin1 indicated that the spermatozoa of the proband presented with abnormal centrosomes, including no concentrated centriolar dot or more than two centriolar dots. HEK293T cells transfected with two DZIP1-mutated constructs showed reduced DZIP1 level or truncated DZIP1. The Dzip1-knockout mice, generated by the CRSIPR-Cas9, revealed consistent phenotypes of severe MMAF.

CONCLUSION

Our study strongly suggests that homozygous DZIP1 mutations can induce asthenoteratospermia with severe MMAF. The deficiency of DZIP1 induces sperm centrioles dysfunction and causes the absence of flagella.

The genetic architecture of morphological abnormalities of the sperm tail

Spermatozoa contain highly specialized structural features reflecting unique functions required for fertilization. Among them, the flagellum is a sperm-specific organelle required to generate the motility, which is essential to reach the egg. The flagellum integrity is, therefore, critical for normal sperm function and flagellum defects consistently lead to male infertility due to reduced or absent sperm motility defined as asthenozoospermia. Multiple morphological abnormalities of the flagella (MMAF), also called short tails, is among the most severe forms of sperm flagellum defects responsible for male infertility and is characterized by the presence in the ejaculate of spermatozoa being short, coiled, absent and of irregular caliber. Recent studies have demonstrated that MMAF is genetically heterogeneous which is consistent with the large number of proteins (over one thousand) localized in the human sperm flagella. In the past 5 years, genomic investigation of the MMAF phenotype allowed the identification of 18 genes whose mutations induce MMAF and infertility. Here we will review information about those genes including their expression pattern, the features of the encoded proteins together with their localization within the different flagellar protein complexes (axonemal or peri-axonemal) and their potential functions. We will categorize the identified MMAF genes following the protein complexes, functions or biological processes they may be associated with, based on the current knowledge in the field.

A novel homozygous CFAP65 mutation in humans causes male infertility with multiple morphological abnormalities of the sperm flagella

Multiple morphological abnormalities of the sperm flagella (MMAF) is a rare autosomal recessive inherited disorder associated with male infertility. To date, 14 genetic causative genes have been identified in MMAF, which can only explain the genetic causes of ~60% of MMAF cases. Here, we report a man with primary infertility, who had a typical MMAF phenotype. Whole-exome sequencing (WES) was performed on the patient and a homozygous mutation (c. 2675 G>A [p. Trp892*]) was identified in cilia and flagella-associated protein 65 (CFAP65) gene, which is primarily expressed in the testis. Another loss-of-function mutation of CFAP65 has been detected in a MMAF patient, and the orthologue of CFAP65 also plays a vital role in sperm motility in chickens. Our experimental observations on human subjects suggested that CFAP65 is involved in sperm flagellum structure and assembly and that loss-of-function mutations could lead to male infertility in humans by causing the MMAF phenotype.

Bi-allelic Mutations in TTC21A Induce Asthenoteratospermia in Humans and Mice

Male infertility is a major concern affecting human reproductive health. Asthenoteratospermia can cause male infertility through reduced motility and abnormal morphology of spermatozoa. Several genes, including DNAH1 and some CFAP family members, are involved in multiple morphological abnormalities of the sperm flagella (MMAF). However, these known genes only account for approximately 60% of human MMAF cases. Here, we conducted further genetic analyses by using whole-exome sequencing in a cohort of 65 Han Chinese men with MMAF. Intriguingly, bi-allelic mutations of TTC21A (tetratricopeptide repeat domain 21A) were identified in three (5%) unrelated, MMAF-affected men, including two with homozygous stop-gain mutations and one with compound heterozygous mutations of TTC21A. Notably, these men consistently presented with MMAF and additional abnormalities of sperm head-tail conjunction. Furthermore, a homozygous TTC21A splicing mutation was identified in two Tunisian cases from an independent MMAF cohort. TTC21A is preferentially expressed in the testis and encodes an intraflagellar transport (IFT)-associated protein that possesses several tetratricopeptide repeat domains that perform functions crucial for ciliary function. To further investigate the potential roles of TTC21A in spermatogenesis, we generated Ttc21a mutant mice by using CRISPR-Cas9 technology and revealed sperm structural defects of the flagella and the connecting piece. Our consistent observations across human populations and in the mouse model strongly support the notion that bi-allelic mutations in TTC21A can induce asthenoteratospermia with defects of the sperm flagella and head-tail conjunction.