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 etiologv of MMAF better.