Functional identification of two variants in unrelated Chinese patients with DNM1L-related mitochondrial disorders
Zhenkun Zhang1, Zhehui Chen2, Xiaofan Bie1
1Henan Provincial Clinical Research Center for Pediatric Diseases, Henan Provincial Key Laboratory of Children's Genetics and Developmental Diseases, Children's Hospital Affiliated to Zhengzhou University, Zhengzhou, 450018, China.
Background:
The DRP1 protein, a member of the dynamin superfamily of GTPases, is encoded by the dynamin-1-like (DNM1L) gene and plays a critical role in mitochondrial fission. There was significant clinical heterogeneity in DNM1L-related disorders.
Methods:
Whole exome sequencing (WES) was used to identify potential genetic causes of the phenotype in probands. Bioinformatics analysis was performed to analyze the pathogenicity of the identified variants, and 3D protein modeling was constructed to predict their effects on protein structure. Preliminary studies of the functional effects of the variant sites on the encoded proteins were performed by in vitro experiments.
Results:
Two de novo variants, c.1049G>C (p.Gly350Ala) and c.2161C>T (p.Gln721*), were detected in affected individuals. One patient presented with severe epileptic encephalopathy while the other exhibited a distinctive clinical phenotype of hemiparesis. In silico analysis, conservative analysis, and 3D homology modelling indicated that the p.Gly350Ala and the p.Gln721* variants are deleterious. Furthermore, the results of the artificial transfection experiments demonstrated that the p.Gly350Ala variant resulted in a reduction in DNM1L expression at both the transcriptional and protein levels (p < 0.05). In contrast, the p.Gln721* variant exhibited no significant alteration in protein levels (p = 0.08), although it did result in a reduction in mRNA levels.
Conclusions:
The present findings suggest that these variants may contribute to DRP1 deficiency, potentially triggering a range of DNM1L-related disease phenotypes. This study serves to expand the spectrum of variants associated with DNM1L-related disorders.
