Variant identification of exon 11 of galactosamine (N-acetyl)-6-sulfatase (GALNS) gene in mucopolysaccharidosis type IVA patients in Indonesia

Mucopolysaccharidosis type IVA (MPS IVA) is an autosomal recessive disease, in which lysosomes are unable to catalyze glycosaminoglycans due to deficiency of the enzyme galactosamine (N-acetyl)-6-sulfatase (GALNS), encoded by GALNS gene. The exon 11 of GALNS gene is known as one of the mutation hotspot regions and encode the enzyme scaffolding structure along with exon 8-10 and 12-14. The GALNS enzyme deficiency leads to abnormal accumulation of glycosaminoglycans inside the lysosomes, rendering the cell unable to function properly. Symptoms of MPS IVA are commonly seen as skeletal dysplasia and multi-organ complications. Research on MPS IVA has been done in many countries, but not in Indonesia. This study aims to identify variants that may be present in exon 11 of GALNS gene in MPS IVA patients in Indonesia. The study was conducted using DNA from blood samples of 7 MPS IVA patients and 30 healthy individuals as controls, obtained from Cipto Mangunkusumo Hospital, Jakarta. A set of specific primers of exon 11 was designed and optimized before completing DNA extraction. Then, DNA extraction was performed, further amplified using the polymerase chain reaction technique. PCR products were visualized by electrophoresis and proceeded for Sanger sequencing. The sequencing results indicated that a variant c.1177G>T (p.Ala393Ser) was found in one patient and five healthy individuals. This variant has been reported in Japan before and identified as benign with more than 5% MAF globally. This research may provide additional information to existing databases for research in MPS IVA, especially in Indonesia.