Aberrant acetylation caused by a CDYL splicing mutation contributes to thin mid-piece related asthenoteratozoospermia and male infertility.

Abstract

Objectives: Acetylated tubulin is a hallmark of flagellar stability in spermatozoa, and studies have demonstrated the ability of CDYL to function as a tubulin acetyltransferase in spermatozoa. Of note, germline conditional knockout of Cdyl can lead to asthenoteratozoospermia and infertility in male mice. However, the role of CDYL gene in human fertility remains uncharacterized.

Materials and methods: Data were collected through in silico analysis for an infertile man with asthenoteratozoospermia of Han Chinese descent by performing whole-exome sequencing. Light and electron microscopy were used to characterize the sperm cells of the proband, and the pathogenicity of the genetic factors was determined by functional experiments. To overcome fertility problems, intracytoplasmic sperm injections were performed in the couple.

Main results: Here, we recruited an infertile proband, born to first-cousin parents, displaying idiopathic asthenoteratozoospermia. Whole-exome sequencing identified a splicing mutation (c.103+1G>A) in CDYL, recessively cosegregating in the family. In vitro minigene assays demonstrated that the mutation resulted in aberrant alternative splicing. We found that CDYL co-localizes with Ac-tubulin along the flagella of human spermatozoa. In addition, the expression of Ac-tubulin was severely reduced in spermatozoa from the patient with CDYL mutation. Disruption in CDYL results in thin mid-piece related abnormal flagella morphology and decreased sperm motility. The primary manifestation of sperm ultrastructural abnormalities under the electron microscope is primarily characterized by disorder of axonemal protein complex and anulus.

Discussion and conclusion: We demonstrated that a homozygous CDYL splicing mutation specifically induces a decrease in microtubule acetylation, resulting in thin mid-piece related asthenoteratozoospermia, providing a novel marker for genetic counseling and diagnosis of male infertility.