ABSTRACT
Patients with Morquio disease characteristically have increased concentrations of keratan sulfate in the urine. An effective preventive strategy for Morquio disease and other lysosomal storage disorders is preimplantation genetic diagnosis which has been carried out on 3-day embryos in Saudi Arabia with an almost 90 percent success rate. In Morquio type A, the defective enzyme catalyzes the removal of 6-sulfate moieties from galactose, and from the N-acetylgalactosamine residues of chondroitin sulfate. Morquio syndrome is transmitted by autosomal recessive genes. Gene transfer therapy has been studied by transduction of human mucopolysaccharidosis IVA fibroblasts using adenoassociated virus-based vectors, which carry human GALNS cDNA. The full length of cDNA has been cloned and sequenced for human N-acetylgalactosamine-6-sulfatase, and transfection into deficient fibroblasts led to activity. The type A gene has 14 exons, and the sequence of 522 amino acids of the enzyme has considerable homology with other sulfatases, such as iduronate-2-sulfatase.
