[Genetic analysis of a family with Dentinogenesis imperfecta type Ⅰ caused by a novel mutation in the COL1A2 gene].

Objective: To investigate the clinical phenotype and genetic characteristics of a family with Dentinogenesis imperfecta type Ⅰ(DGI-Ⅰ).

Methods: Clinical data were collected from a patient with DGI-Ⅰ admitted to the Reproductive Medicine Department of the Affiliated Hospital of Jining Medical University in March 2024. Clinical and familial data were retrospectively collected. Peripheral blood samples (5 mL each) were obtained from the proband and her family members for genomic DNA extraction, followed by whole-exome sequencing (WES) and Sanger sequencing validation. The pathogenicity of the detected variants was assessed according to the Classification Standards and Guidelines for Genetic Variants formulated by the American Society of Medical Genetics and Genomics (ACMG) (hereinafter referred to as the "ACMG Guidelines"). The study was approved by the Ethics Committee of the Affiliated Hospital of Jining Medical University (Ethics No. 2024-08-C012), and written informed consent for clinical research were obtained from all participants.

Results: The proband, a 35-year-old female, presented with translucent yellow primary teeth and progressive browning, darkening, and loss of permanent teeth, without skeletal abnormalities. Affected family members exhibited similar phenotypes. Genetic testing revealed a heterozygous COL1A2 variant (c.1503+1G>A) in the patient and other affected members, while unaffected family members all lacked this variant. Based on the ACMG Guidelines, this variant was classified as likely pathogenic (PM4 + PP1_Strong + PM2_Supporting).

Conclusion: The COL1A2 c.1503+1G>A heterozygous variant is the disease-causing mutation in this family. Above finding has expanded the mutational spectrum of the COL1A2 gene and provided a basis for genetic counseling and diagnosis in similar cases.