A novel homozygous frameshift variant in DNAH8 causes multiple morphological abnormalities of the sperm flagella in a consanguineous Pakistani family

Multiple morphological abnormalities of the sperm flagella(MMAF)is a severe form of asthenozoospermia categorized by immotile spermatozoa with abnormal flagella in ejaculate.Whole-exome sequencing(WES)is used to detect pathogenic variants in patients with MMAF.In this study,a novel homozygous frameshift variant(c.6158_6159insT)in dynein axonemal heavy chain 8(DNAH8)from two infertile brothers with MMAF in a consanguineous Pakistani family was identified by WES.Reverse transcription-polymerase chain reaction(RT-PCR)confirmed DNAH8 mRNA decay in these patients with the DNAH8 mutation.Hematoxylin–eosin staining and transmission electron microscopy revealed highly divergent morphology and ultrastructure of sperm flagella in these patients.Furthermore,an immunofluorescence assay showed the absence of DNAH8 and a reduction in its associated protein DNAH17 in the patients'spermatozoa.Collectively,our study expands the phenotypic spectrum of patients with DNAH8-related MMAF worldwide.

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 recurrent homozygous missense mutation in CCDC103 causes asthenoteratozoospermia due to disorganized dynein arms

Asthenoteratozoospermia is one of the most severe types of qualitative sperm defects.Most cases are due to mutations in genes encoding the components of sperm flagella,which have an ultrastructure similar to that of motile cilia.Coiled-coil domain containing 103(CCDC103)is an outer dynein arm assembly factor,and pathogenic variants of CCDC103 cause primary ciliary dyskinesia(PCD).However,whether CCDC103 pathogenic variants cause severe asthenoteratozoospermia has yet to be determined.Whole-exome sequencing(WES)was performed for two individuals with nonsyndromic asthenoteratozoospermia in a consanguineous family.A homozygous CCDC103 variant segregating recessively with an infertility phenotype was identified(ENST00000035776.2,c.461A>C,p.His154Pro).CCDC103 p.His154Pro was previously reported as a high prevalence mutation causing PCD,though the reproductive phenotype of these PCD individuals is unknown.Transmission electron microscopy(TEM)of affected individuals’spermatozoa showed that the mid-piece was severely damaged with disorganized dynein arms,similar to the abnormal ultrastructure of respiratory ciliary of PCD individuals with the same mutation.Thus,our findings expand the phenotype spectrum of CCDC103 p.His154Pro as a novel pathogenic gene for nonsyndromic asthenospermia.