Novel Variants in the MDR1 Gene with the Potential to Discriminate Steroid Responsiveness in Iraqi Children with Idiopathic Nephrotic Syndrome

Abstract

Steroid-resistant idiopathic nephrotic syndrome (SRNS) is a leading cause of childhood end-stage renal disease, with diverse histological features and a challenging diagnosis. SRNS has been suggested to develop due to variations in the multidrug resistance 1 (MDR1) gene, with variable results from different studies. This study explored the presence of novel variants in the MDR1 gene and evaluated their association with steroid responsiveness in Iraqi children with idiopathic nephrotic syndrome. This case-control study included children with SRNS (n=30) and steroid-sensitive nephrotic syndrome (SSNS; n=30) from the pediatric nephrology clinic in Babylon Hospital for Maternity and Pediatrics. Genomic DNA (gDNA) was extracted for each participant from a venous blood sample using the chemical salting-out method. The soluble gDNA was separated later on using a silica column under high salt conditions. Specifically designed primers were utilized in a polymerase chain reaction to produce the MDR1 gene amplicons. The participants were genotyped by utilizing Sanger sequencing. This study detected three novel variants: g.87531179A>T (NV1), g.87531184T>A (NV2), and g.186784C>T (NV3). A higher risk of SRNS development was significantly associated with the NV1 A/T genotype [odds ratio (OR) and 95% confidence interval (95% CI): 3.29 (1.09–9.95), p=0.035] and the NV2 A/A genotype [OR (95% CI): 14.73 (1.64–132.64), p=0.016] compared to the wild genotype. In contrast, the NV3 C/T genotype was associated with a lower SRNS risk [OR (95% CI): 0.064 (0.016–0.26), p < 0.001] compared to the wild genotype. Moreover, the haplotype analysis showed that the likelihood of developing SRNS was significantly lower among the carriers of the ATT haplotype [OR (95% CI): 0.24 (0.1–0.56), p < 0.001], which represents the wild alleles of the NV1 and NV2 variants and the mutant allele of the NV3 variant. The findings concluded that children with the NV3 wild genotype alone or in combination with the NV1 mutant heterozygous and NV2 mutant homozygous genotypes were more likely to develop SRNS, and an alternative immunosuppressive plan might be necessary. Additional research is needed to decipher the steroid pharmacogenetics, which would reveal further insight that is vital to individualizing medication treatment in nephrotic children.