Identification and Functional Characterization of Novel and Recurrent <scp> <i>NTRK1</i> </scp> Variants in Chinese Families With Congenital Insensitivity to Pain With Anhidrosis: A Combined Clinical, Genetic, and Functional Study

BACKGROUND: Congenital insensitivity to pain with anhidrosis (CIPA) is an autosomal recessive disorder caused by variants in the NTRK1 gene (encoding TrkA). The identification and functional analysis of these variants are essential for elucidating the genetic basis of the disease and improving diagnostic efficiency. In this study, we investigated four unrelated Chinese families with CIPA. METHODS: We employed next-generation sequencing to identify the causative genetic variants in 13 individuals (5 affected and 8 unaffected) from four unrelated Chinese families. A comprehensive bioinformatics and in vitro functional analyses were subsequently performed to assess the pathogenicity of the identified variants. RESULTS: We identified seven variants in the NTRK1 gene, including two novel variants (c.2285C > A and c.1990_1993delinsTGCT). Functional characterization of five variants (four missense: c.632 T > A, c.1942C > T, c.2122G > A and c.2285C > A; and one indel: c.1990_1993delinsTGCT) revealed that they disrupted distinct steps within the nerve growth factor (NGF)-TrkA pathway, including TrkA glycosylation and phosphorylation, NGF-TrkA binding, and downstream signaling pathway. CONCLUSIONS: Our findings expand the mutational spectrum of NTRK1 with two novel variants associated with CIPA and delineate the specific step(s) within the NGF-TrkA pathway affected by each variant, thereby establishing a link between genotype and the observed phenotypic severity. This study provides a crucial theoretical and experimental foundation for the future development of personalized therapies for CIPA patients.