A new hemizygous missense mutation, c.454T＞C (p.S152P), in AKAP4 gene is associated with asthenozoospermia

Abstract

Asthenozoospermia (ASZ) is a condition characterized by reduced forward motility of spermatozoa affecting approximately 19% of infertile men. A kinase anchor protein 4 (AKAP4) is an X‐linked testis‐specific gene and plays a major role in sperm motility and flagella formation. However, few studies have reported its association with ASZ. Here, we sequenced for exonic mutations of human AKAP4 gene by high‐fidelity PCR/Sanger sequencing in peripheral blood samples from 150 ASZ patients and 150 fertile men. We reported the identification of three novel hemizygous mutations unique to four ASZ patients, including one patient carrying missense mutation c.454T>C (p.S152P), two patient carrying synonymous mutation c.1173T>C (p.H391H), and one patient carrying synonymous mutation c.2007 A>G (p.R669R). The p.S152P mutation was located in a precursor pro‐polypeptide domain of AKAP4 protein, which was predicted to be damaging by SIFT and PolyPhen‐2 and could cause the protein accumulation in the cytoplasm of COS‐7 cells. The mature protein of AKAP4 was absent in spermatozoa of ASZ patient harboring AKAP4 p.S152P mutation. Further in vitro cellular assays showed that reactive oxygen species (ROS), malondialdehyde (MDA), myeloperoxidase (MPO) levels, and apoptotic cells were increased in GC2‐spd cells by AKAP4 p.S152P mutant protein, whereas superoxide dismutase (SOD) level was decreased. AKAP4 p.H391H and p.R669R mutant proteins were coimmunoprecipitated with ribonuclease T2 (RNASET2) protein in GC2‐spd cells, whereas no interaction between the AKAP4 p.S152P mutant protein and RNASET2 protein was observed. In addition, AKAP4 p.S152P mutant protein could decrease the activity of PKA/PI3K signaling. Overall, our study identifies a novel AKAP4 p.S152P mutation is associated with ASZ probably through affecting oxidative stress and cell apoptosis by regulating the interaction with RNASET2 and the activity of the PKA/PI3K signaling pathway.

Decreased AKAP4/PKA signaling pathway in high DFI sperm affects sperm capacitation

“…AKAP4 was also mainly expressed in the caudal fibrous sheath of spermatozoa, recruiting PKA to promote local phosphorylation and participating in the activation of the sperm flagellum. 56 A previously published study reported that a decreased level of AKAP4 expression affected sperm motility. 23 Therefore, this study concluded that it was the reason for the decreased forward motility of spermatozoa in H-DFI population.…”

Homozygous variants inAKAP3induce asthenoteratozoospermia and male infertility

“…AKAP4 is expressed in the principal piece of the sperm flagellum and participates in the assembly of the FS 30 31. A new hemizygous missense mutation in AKAP4 has been reported to be associated with asthenozoospermia,32 but no evidence has yet been found to further confirm the hypothesised role of AKAP3 in human male infertility. Here, our genetic analyses found that homozygous deleterious AKAP3 variants led to severe asthenoteratozoospermia and male infertility.…”

A pathogenic AKAP4 variant, p.R429H, causes male in/subfertility in humans and mice

“…This knowledge suggests that AKAP4 might function beyond flagella development during spermatogenesis. Notably, variants in the AKAP4 gene have been identified in infertile males exhibiting distinct phenotypes, such as asthenozoospermia, 7 MMAF, 2 and azoospermia/NOA, 8 , 9 which shed light on the divergence of male infertility phenotypes of AKAP4 mutations.…”