A novel missense mutation in QRICH2 causes male infertility due to multiple morphological abnormalities of the sperm flagella

Multiple morphological abnormalities of the sperm flagella (MMAF) are characterized by bent, irregular, short, coiled, and absent flagella. MMAF is caused by a variety of genes, some of which have been identified. However, the underlying genetic factors responsible for the majority of MMAF cases are still largely unknown. The glutamine-rich 2 (QRICH2) gene plays an essential role in the development of sperm flagella by regulating the expression of essential sperm flagellar biogenesis-associated proteins, and genetic variants of QRICH2 have been identified as the primary cause of MMAF in humans and mice. Here, we recruited a Pakistani consanguineous family to identify the genetic variant causing infertility in patients with MMAF. Whole-exome sequencing and Sanger sequencing were conducted to identify potentially pathogenic variants causing MMAF in infertile patients. Hematoxylin and eosin (HE) staining was performed to analyze sperm morphology. Quantitative polymerase chain reaction, western blot, and immunofluorescence staining analyses were conducted to observe the expression of QRICH2 in spermatozoa. A novel homozygous missense variant (c.4618C>T) in QRICH2 was identified in the affected patients. Morphological analysis of spermatozoa revealed the MMAF phenotype in infertile patients. qPCR revealed a significant reduction in the level of sperm QRICH2 mRNA, and immunofluorescence staining revealed a lack of sperm QRICH2 expression. Additionally, patients harboring a homozygous QRICH2 mutation presented reduced expression of outer dense fiber 2 (ODF2) in sperm, whereas sperm expression of A-kinase anchor protein 4 (AKAP4) was normal. These findings expand our understanding of the genetic causes of MMAF-associated male infertility and emphasize the importance of genetic counseling.