[Clinical and genetic analysis of two children with TANC2 gene variants and a literature review].

Abstract

Objetive: To explore the clinical and genetic characteristics of two children with Neurodevelopmental disorders (NDDs) due to variants of TANC2 gene.

Methods: Clinical data of two children who were admitted to the Third Affiliated Hospital of Zhengzhou University respectively in April 2020 and April 2021 were retrospectively analyzed. Peripheral blood samples of the children and their parents were collected and subjected to whole exome sequencing. Candidate variants were verified by Sanger sequencing. By using "TANC2 gene", "Neurodevelopmental disorders", "Nervous system development disorders", "TANC2" as the key words, similar cases were searched from the CNKI, Wanfang database platform and PubMed database, with the search time set as from the establishment of the database to December 2023. This study was approved by the Third Affiliated Hospital of Zhengzhou University (Ethics No. 2020-57).

Results: Case 1 was a 1-year-and-3-month-old girl who had developed convulsions at 1 year old and had three episodes of seizures. Her epilepsy had resolved with the treatment of oxcarbazepine, which was stopped at the age of 2-year-and-7-month. Her language, movement and intelligence development were all normal. Case 2 was a 1-year-and-10-month-old boy, who had developed convulsions at 1 year old. His seizure type was myoclonus, and the frequency was dozens of times a day. His epilepsy had resolved with the treatment of sodium valproate. His language, movement and intelligence development was delayed for about half a year. Genetic analysis showed that both children had harbored novel variants of the TANC2 gene (NM_025185.4), including c.3398G>A (p.Gly1133Glu) and c.2829+1G>A, respectively. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the former was rated as likely pathogenic (PS2+PM2_Supporting+PP3) and the latter was rated as pathogenic (PVS1+PS2+PM2_Supporting). Two previous reports were retrieved, which had involved 17 cases and 16 variants. Common features had included autism spectrum disorder (70.6%, 12/17) , intellectual disability (94.1%,16/17) , language and motor retardation (88.2%, 15/17；58.8%, 10/17), facial dysmorphism, epilepsy, ataxia, and thoracic and spinal deformities.

Conclusion: Variants of the TANC2 gene probably underlay the epilepsy and development delay in these children with NDDs.