Novel CCDC188 variants cause acephalic spermatozoa syndrome with poor intracytoplasmic sperm injection outcome

To identify novel CCDC188 variants in acephalic spermatozoa syndrome (ASS) patients and investigated the potential effect on the outcome of intracytoplasmic sperm injection (ICSI).

Sixteen patients diagnosed as ASS by morphological analysis were recruited in the first half of 2023. Whole exome sequencing (WES) and Sanger sequencing were performed to identify the genetic cause and define the hereditary mode, using genomic DNA extracted from peripheral blood. Morphological characteristics of sperm were revealed by hematoxylin and eosin (H&E) staining and transmission electron microscopy (TEM). Pathogenicity of variants was evaluated in silico, and further confirmed in vitro and vivo by western blotting (WB), reverse transcript-polymerase chain reaction (RT-PCR), quantitative real-time PCR (qPCR), and immunofluorescence (IF). ICSI was performed with a standard operation procedure as the treatment strategy.

Two novel variants in CCDC188 (NM_001365892.2: c.481C > T[p.Gln161*] and c.1022 + 1G > A[p. K325Afs*110]) were identified in two unrelated infertile men. Morphological analysis displayed the typical ASS phenotype of patients' sperm. The depletion of CCDC188 protein was observed accompanied with SUN5 and PMFBP1 in patients' sperm. Notably, a poor ICSI outcome occurred after a sperm head and a detached tail from one patient were simultaneously microinjected, caused by fertilization failure and abnormal embryo development.

Our results broadened the variant spectrum of CCDC188. We firstly reported a poor outcome of one proband after ICSI treatment, which suggested the role played by CCDC188 in male infertility might involve not only spermatogenesis but also fertilization and early embryonic development.