P-052 A novel variant in CFAP69 gene causes morphological abnormalities of human sperm flagella with good ART outcomes
Authors: Tang X , Lin T , Huang G , Long S , Ma J , Yu H , Wang X , Wan L , Yang J 
Published: June 2023

Abstract

Study question
Is there any novel variant in CFAP69 gene related to multiple morphological abnormalities of sperm flagella (MMAF) in humans?

Summary answer
We identified a loss-of-function variant of CFAP69 in a Chinese man with MMAF and intracytoplasmic sperm injection (ICSI) is favorable for the affected couple.

What is known already
MMAF is a specific type of asthenoteratozoospermia characterized by immotile and malformed spermatozoa. Genetic defects are the major cause of MMAF, and more than 20 genes have been related to approximately 70% MMAF-affected cases. CFAP69, a cilia- and flagella-associated gene, is abundantly expressed in the testis and associated with infraglabellar transport. To date, four variants in CFAP69 were related to four MMAF patients in the literatures, and the male Cfap69-knockout mice mimicked the infertility and profound flagellum morphology defects phenotype.

Study design, size, duration
A cohort of 35 infertile Chinese men with MMAF were recruited in the center for reproductive medicine from August 2019 to October 2022. Genetic testing was based on a targeted-sequencing panel of 22 MMAF-related genes. Morphological, ultrastructural, and immunostaining analyses were conducted in 2022. We also performed assisted reproductive technology (ART) with ICSI to explore the treatment strategies.

Participants/materials, setting, methods
Peripheral blood and semen samples were collected from every participant. The CFAP69 variant was identified by genetic testing with targeted-panel sequencing of 22 MMAF-associated genes and validated through Sanger sequencing, pedigree analysis and in silico analysis. Papanicolaou staining, SEM, immunofluorescence, and TEM were performed to explore the effect of the variant. ICSI was carried out for the affected couples to get their own progenies.

Main results and the role of chance
We identified a novel frameshift variant in CFAP69 (c.2061dup, p. Pro688Thrfs*5) from a MMAF-affected infertile male with low sperm motility and malformed morphology of sperm. Furthermore, immunofluorescence staining, and transmission electronic microscopy revealed that the variant induced reduction of CFAP69 expression and the aberrant ultrastructure including the absence of the central pair and disorder of the microtubule doublets in the patient’s spermatozoa. Moreover, the partner of the proband was able to conceive through ICSI and birthed a healthy girl.

Limitations, reasons for caution
A limitation of this study is the low number of variants identified in CFAP69 and the small number of CFAP69-mutant patients available. Additional CFAP69 variants and cases are needed to better characterize the genetic etiology of the MMAF phenotype and to improve the management of MMAF patients with CFAP69 variants.

Wider implications of the findings
This study extended the mutant spectrum of the CFAP69 gene and could facilitate researchers and clinicians to understand the genetic etiology of MMAF better, thus improving counseling of infertile men with MMAF in the future.

Trial registration number
not applicable