Identification and functional analysis of NPR2 truncating mutations in two Chinese families with Short Stature

Background: The signaling pathway of C-type natriuretic peptide (CNP) and its receptor (natriuretic peptide receptor 2, NPR2) is implicated in the process of endochondral ossification, which is crucial for the linear growth of long bones. Loss-of-function mutations in the NPR2 gene cause short stature. This study aimed to identify and characterize truncating mutations in NPR2 among Chinese families with short stature. Methods: Whole-exome sequencing and Sanger sequencing were conducted to identify potential mutations. Bioinformatic analysis was utilized to assess the pathogenicity of two mutations. The effects of candidate mutation on gene expression, subcellular localization, protein stability, and protein function were further assessed through in vitro assays. Results: In this study, A novel mutation, c.2629_2630delAG, p.S877Hfs*10 and a previously reported mutation, c.1162C>T, p.R388* (ClinVar database) in NPR2, were identified in the individuals, and these variants were inherited from the mother and father, respectively. Both mutations were predicted to be deleterious and have a significant impact on protein structure based on bioinformatics analysis. In vitro experiments demonstrated that mutant mRNAs evaded nonsense-mediated mRNA decay (NMD) to produce truncated NPR2 proteins with reduced stability and increased degradation. Furthermore, two truncated NPR2 proteins exhibited impaired localization at the cell membrane and almost completely lost their ability to stimulate cyclic guanosine monophosphate (cGMP) production in HEK293T cells compared to wild-type (WT) NPR2 (p <0.05). Conclusion: Our study identified two loss-of-function mutations of the NPR2 gene in two Chinese families and offered new insights on the pathogenesis of short stature caused by NPR2 truncating mutations.