P-047 A novel mutation of DRC1 gene causes multiple morphological abnormalities of the sperm flagella and male infertility in humans
Authors: Fu T , Liao H , Long S , Tang X , Huang G , Han W , Liu W , Lin T 
Published: June 2023

Abstract

Study question
Can novel mutations of DRC1 gene affect the sperm morphology in humans and how about the outcomes of assisted reproductive therapy of the affected patients?

Summary answer
An infertile man with multiple morphological abnormalities of the sperm flagella caused by DRC1 biallelic mutations has good outcomes of fertility after intracytoplasmic sperm injection.

What is known already
The nexin-dynein regulatory complex (N-DRC) functions by linking neighboring doublet microtubules within motile cilia and flagella, stabilizing the axonemal structure and thereby regulating ciliary motility. As a core of N-DRC protein, the disruptions of DRC1 gene have been identified to cause multiple morphological abnormalities of the sperm flagella (MMAF) and male infertility in humans and mice. DRC1 mutations usually resulted in decreased flagellum axoneme stability, thereby causing flagellar structural disorder.

Study design, size, duration
The 35 patients with MMAF were recruited from the center for reproductive medicine from August 2019 to June 2022. They were diagnosed with primary male infertility caused by abnormal morphologies of sperm flagella and decreased sperm motility. Genetic testing, pedigree analysis, sperm morphological analysis, functional assays, and assisted reproductive therapy were performed in 2022.

Participants/materials, setting, methods
We identified and confirmed the DRC1 mutation through a 22-gene next-generation sequencing panel and sanger sequencing. Papanicolaou-staining, scanning electronic microscope, and transmission electronic microscope were performed to reveal the changes of sperm morphology and ultrastructure. Immunostaining was conducted to show the effect of DRC1 mutation on the expression and localization on sperm structural proteins. After the ovarian stimulation, a time-lapse monitoring system was applied for the assisted reproductive therapy of DRC1 mutant patient.

Main results and the role of chance
Biallelic mutations in DRC1 were identified in a 39-years-old proband who suffered from primary infertility for 9 years due to severe asthenoteratozoospermia. Pedigree analysis of the non-consanguineous family manifested an autosomal recessive inheritance pattern. Papanicolaou-staining, scanning and transmission electronic microscopy showed the abnormalities of sperm flagella and severe disorganization of the axoneme in DRC1-deficient male compared to control subject. Immunostaining with sperm-specific markers, TOM20, DNAI1, and DNALI1, showed the composite changes of flagella morphology and molecular components. After intracytoplasmic sperm injection (ICSI), the rate of fertilization was 71.4% (5/7), the rate of embryo cleavage was 100% (5/5), the rate of transferable embryo was 60% (3/5), respectively. Following frozen-thawed embryo transfer, the wife of the proband became pregnant.

Limitations, reasons for caution
Additional cases are needed to investigate the gene-disease relationship between DRC1 mutations and male infertility owing to abnormal sperm morphology and motility.

Wider implications of the findings
This study expands the mutant spectrum of DRC1 and describes a good fertility outcome of assisted reproduction therapy with ICSI for the DRC1 mutant patient. Together with the available information regarding male infertility, it provides new information for the genetic diagnosis and counseling of MMAF in the future.

Trial registration number
Not applicable