Novel homozygous mutations in humans and mice cause severe asthenoteratospermia with multiple morphological abnormalities of the sperm flagella.

BACKGROUND

Male infertility is a major issue of human reproduction health. Asthenoteratospermia can impair sperm motility and cause male infertility. Asthenoteratospermia with multiple morphological abnormalities of the flagella (MMAF) presents abnormal spermatozoa with absent, bent, coiled, short and/or irregular-calibre flagella. Previous studies on MMAF reported that genetic defects in cilia-related genes (eg, , , , and ) are the major cause of MMAF. However, the known MMAF-associated genes are only responsible for approximately 30% to 50% of human cases. We further investigated the cases with MMAF in search of additional genes mutated in this condition.

METHODS AND RESULTS

We conducted whole exome sequencing in a male individual with MMAF from a consanguineous Han Chinese family. Sanger sequencing was also conducted in additional individuals with MMAF. Intriguingly, a homozygous frameshift mutation (p.Leu357Hisfs11) was identified in the gene encoding CFAP69 (cilia and flagella-associated protein 69), which is highly expressed in testis. The subsequent Sanger sequencing of the coding regions among 34 additional individuals with MMAF revealed a case with homozygous nonsense mutation (p.Trp216) of . Both of these loss-of-function mutations were not present in the human population genome data archived in the 1000 Genomes Project and ExAC databases, nor in 875 individuals of two Han Chinese control populations. Furthermore, we generated the knockout model in mouse orthologue using the CRISPR-Cas9 technology. Remarkably, male -knockout mice manifested with MMAF phenotypes.

CONCLUSION

Our experimental findings elucidate that homozygous loss-of-function mutations in can lead to asthenoteratospermia with MMAF in humans and mice.