[Pathogenicity analysis and genetic counseling for a hemizygous c.1042-10G>C variant of SLC9A7 gene].

OBJECTIVE

To evaluate the clinical significance of a hemizygous c.1042-10G>C variant of the SLC9A7 gene NM_001257291.2) previously identified in individuals with neurodevelopmental disorders, and to provide an evidence-based guidance for prenatal genetic counseling.

METHODS

Four families presented at the Medical Genetics Center of Henan Provincial People's Hospital between December 2022 and July 2024 were included in this study. Phenotypic information and biological samples were collected from family members. Genomic DNA was extracted and subjected to whole-exome sequencing and copy number variation analysis to identify candidate pathogenic variants. Sanger sequencing was performed for familial co-segregation analysis. Reverse-transcription PCR was used to assess the RNA splicing pattern of the variant in peripheral blood samples. Quantitative PCR was employed to analyze the expression profiles of various SLC9A7 transcripts in fetal brain tissue and peripheral blood samples. Pathogenicity of the variant was classified based on guidelines from the American College of Medical Genetics and Genomics (ACMG). This study was approved by the Medical Ethics Committee of Henan Provincial People's Hospital (Ethics No.: 2021-171).

RESULTS

Six hemizygous males carrying the SLC9A7 c.1042-10G>C variant were identified among the four families, which included three adult males and two male infants with normal phenotypes. Only one affected male from family 3 exhibited global developmental delay, short neck, webbed neck, ocular dysplasia, and congenital corneal leukoma. He also had a history of perinatal asphyxia and carried an additional hemizygous variant HUWE1 c.12283C>G. Reverse-transcription PCR showed no aberrant splicing in heterozygous or hemizygous carriers compared to healthy controls, suggesting that the variant does not affect RNA splicing. Quantitative PCR revealed that NM_001257291.2 is the predominant transcript expressed in fetal brain tissue and peripheral blood.

CONCLUSION

The SLC9A7 c.1042-10G>C variant does not alter RNA splicing and is present in multiple phenotypically normal males, which supported its classification as a benign variant.