Homozygous ACTL9 mutations cause irregular mitochondrial sheath arrangement and abnormal flagellum assembly in spermatozoa and male infertility.

PURPOSE: To identify novel variants in ACTL9 and new phenotypes responsible for male infertility. METHODS: Genomic DNA was extracted from peripheral blood samples for whole-exome sequencing (WES). Computer-assisted sperm analysis (CASA) was used to test the motility of spermatozoa. The ultrastructure of flagella and the mitochondrial sheath were assessed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Immunostaining was used to validate the localization and expression of ACTL9 and ACTL7A. An Actl9-mutated mouse model was used to validate the phenotypes by CASA and TEM. RESULTS: We identified novel homozygous variants in ACTL9 in two independent Chinese families. Spermatozoa with ACTL9 mutations showed decreased CASA parameters and a higher proportion of spermatozoa with abnormal morphology, exhibiting coiled flagella and a thickened midpiece. The spermatozoa were characterized by chaotic or irregular '9+2' structures and irregular mitochondrial sheath arrangements in the flagellum. Actl9 knock-in mice also showed abnormal CASA parameters and irregular '9+2' structures in flagella. CONCLUSIONS: Our study expands the mutation spectrum and phenotypic spectrum of ACTL9.

Identification of a new mutation in the ACTL9 gene in men with unexplained infertility.

BACKGROUND: Infertility is defined as the failure to achieve pregnancy after one year of unprotected intercourse within a marital relationship. Approximately 10%-15% of couples worldwide experience infertility issues, with nearly half of these cases attributed to male factors. Among men with unexplained infertility, genetic mutations have been identified as a potential cause. Studies have indicated that mutations affecting the function of the protein encoded by the ACTL9 gene may play a role in male infertility. METHODS: The purpose of this research was to identify mutations in the ACTL9 gene associated with male infertility in a sample of 40 infertile men with unknown causes. Genomic DNA extraction and PCR amplification were carried out on samples from each individual. The genetic material was then analyzed using Sanger sequencing, followed by bioinformatics and segregation analysis to determine the potential effects of the observed variations. RESULT: A novel genetic variant, c.376G>A (p.Glu126Lys), was identified in an infertile male individual, representing a previously unreported finding that was validated through segregation analyses. This specific variant induces a change from glutamate to lysine at the amino acid level by replacing the nucleotide G with A in the genomic DNA sequence, consequently impacting the secondary structure and function of the protein. CONCLUSIONS: The conclusive analysis of the procedure indicated that this alteration has the potential to interfere with the process of fertilization, ultimately resulting in the complete failure of fertilization (TFF) and causing male infertility.

Homozygous pathogenic variants in ACTL9 cause fertilization failure and male infertility in humans and mice.

Total fertilization failure (TFF) can occur during in vitro fertilization (IVF) treatments, even following intracytoplasmic sperm injection (ICSI). Various male or female factors could contribute to TFF. Increasing evidence suggested that genetic variations in PLCZ1, which encodes 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase zeta-1 (PLCζ), is involved in oocyte activation and is a key male factor in TFF. In the present study, we explored the genetic variants in male individuals that led to TFF. A total of 54 couples with TFF or poor fertilization (fertilization rate < 20%) were screened, and 21 couples were determined to have a male infertility factor by the mouse oocyte activation test. Whole-exome sequencing of these 21 male individuals identified three homozygous pathogenic variants in ACTL9 (actin like 9) in three individuals. ACTL9 variations led to abnormal ultrastructure of the perinuclear theca (PT), and PLCζ was absent in the head and present in the neck of the mutant sperm, which contributed to failed normal calcium oscillations in oocytes and subsequent TFF. The key roles of ACTL9 in the PT structure and TFF after ICSI were further confirmed in an Actl9-mutated mouse model. Furthermore, assisted oocyte activation by calcium ionophore exposure successfully overcame TFF and achieved live births in a couple with an ACTL9 variant. These findings identified the role of ACTL9 in the PT structure and the correct localization of PLCζ. The results also provide a genetic marker and a therapeutic option for individuals who have undergone ICSI without successful fertilization.

Correlation of KIF3A and OVOL1, but not ACTL9, with atopic dermatitis in Chinese pediatric patients.

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease in Chinese pediatric patients. To date, the genetic susceptibility to AD in this population has not been fully clarified. Three single nucleotide polymorphisms have previously been associated with AD in Europeans, rs2897442 (KIF3A), rs479844 (OVOL1) and rs2164983 (ACTL9). To verify the correlation between AD and these three SNPs in the Chinese pediatric population, we conducted a case-control study including 235 pediatric patients with AD and 200 health controls. We confirmed the correlation between rs2897442 and rs479844 and AD in this population at both the genotype and allele levels. Statistical analysis showed that the C allele of rs2897442 is associated with an increased risk of developing AD, while the A allele of rs479844 is associated with a reduced risk. No correlation between rs2164983 and AD was identified. Our study indicates that KIF3A and OVOL1 are involved in the development of AD in the Chinese pediatric population.