Mutational analysis of ARSB gene in mucopolysaccharidosis type VI: identification of three novel mutations in Iranian patients

Abstract

<em><strong>Objective(s):</strong></em> Mucopolysaccharidosis VI (MPS VI) or Maroteaux-Lamy syndrome is a rare metabolic disorder, resulting from the deficient activity of the lysosomal enzyme arylsulfatase B (ARSB). The enzymatic defect of ARSB leads to progressive lysosomal storage disorder and accumulation of glycosaminoglycan (GAG) dermatan sulfate (DS), which causes harmful effects on various organs and tissues and short stature. To date, more than 160 different mutations have been reported in the ARSB gene.<br /><em><strong>Materials and Methods:</strong></em> Here, we analyzed 4 Iranian and 2 Afghan patients, with dysmorphism indicating MPS VI from North-east Iran. To validate the patients' type of MPS VI, urine mucopolysaccharide and leukocyte ARSB activity were determined. Meanwhile, genomic DNA was amplified for all 8 exons and flanking intron sequences of the ARSB gene to analyze the spectrum of mutations responsible for the disorder in all patients.<br /><em><strong>Results:</strong></em> Abnormal excretion of DS and low leukocyte ARSB activity were observed in the urine samples of all 6 studied patients. In direct DNA sequencing, we detected four different homozygous mutations in different exons, three of which seem not to have been reported previously: p.H178N, p.H242R, and p.*534W. All three novel substitutions were found in patients with Iranian breed. We further detected the IVS5+2T>C mutation in Afghan siblings and four different homozygous polymorphisms, which have all been observed in other populations. <br /><em><strong>Conclusion:</strong></em> results indicated that missense mutations were the most common mutations in the ARSB gene, most of them being distributed throughout the ARSB gene and restricted to individual families, reflecting consanguineous marriages.