Genetic Variants Within ND2 Gene of Mitochondria are Associated with the Altered Levels of Ammonia, Vitamin D and Free Thyroxine in Bangladeshi Children with Autism Spectrum Disorder.

Autism spectrum disorder (ASD) is a complex and multifaceted neurodevelopmental disorder that is becoming more common worldwide. While there is growing evidence linking mitochondrial dysfunction to ASD, the exact causes remain unclear. There is little study being done in Bangladesh on the genetic and biochemical causes of ASD. The goal of this study is to identify mitochondrial DNA (mtDNA) variants in the ND2 gene and explore how these variations might be linked to the progression of ASD and biochemical parameters. Eighty children aged 2-10 years were enrolled, comprising 50 ASD children and 30 healthy controls. Biochemical parameters (lactic acid, ammonia, ALT, AST, calcium, magnesium, TSH, vitamin D, and free thyroxine or FT4) were tested, and mtDNA was extracted and amplified for Sanger sequencing. Identified single nucleotide polymorphisms (SNPs) were evaluated for association with disease outcome and biochemical parameters. Bioinformatics tools were used to analyze the impact of SNPs on protein structure and function. The findings demonstrated significant differences in lactic acid, ammonia, ALT, AST, vitamin D, and FT4 levels between the ASD and control groups (p < 0.05). Lactic acid (AUC = 0.993) showed the highest diagnostic accuracy, while ammonia (AUC = 0.899), AST (AUC = 0.884), and vitamin D (AUC = 0.863) showed excellent performance. A total of 37 SNPs were identified in the ND2 gene, three were novel, with 4901 A>G, 5124 C>A, and 5306 C>T. No variant was found to be associated with disease outcome. However, variants located at 5108 T>C, 5262 G>A, 4703 T>C, 4841 G>A, and 5186 A>T were found to be significantly associated with the altered levels of ammonia, vitamin D and FT4, respectively. Among three novel variants, two were synonymous SNPs (4901 A>G and 5306 C>T) and they showed decreased RSCU values, indicating lower efficiency and affect gene expression. Three variants were identified within the tRNA specific for Q and M but they were predicted to be likely benign. Comprehending the association of these genetic variations and biochemical markers with ASD should facilitate early detection and subsequent management strategy in children with these neurodevelopmental disorders.