Identification of a novel mutation of GALNS gene from a Chinese pedigree with mucopolysaccharidosis type IV A / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To study the molecular genetic mechanism of mucopolysaccharidosis type IV A(MPS IV A), and reveal the relationship between the genotype and phenotype, and provide a basis for prenatal gene diagnosis in the future.</p><p><b>METHODS</b>A preliminary diagnosis was made by qualitative detection of urinary glycosaminoglycans of the suspected MPS IV A proband. Then, mutation detection was performed on the proband and her family members with PCR and direct sequencing of the PCR products. After a novel c.1567T to G mutation was detected, Xsp I restriction enzyme digestion and amplification refractory mutation system (ARMS) fast specific identification were established to analyze the sequences of exon 14 in GALNS gene, including 110 randomly selected healthy controls, the proband and other pedigree members. At the same time, bioinformatic approaches for protein secondary, tertiary structure prediction were applied to identify the novel pathologic mutation.</p><p><b>RESULTS</b>The proband's urine GAGs test was a weak positive(± ), and a c.1567T to G heterozygous termination codon mutation in exon 14 and a c.374C to T heterozygous missense mutation in exon 4 were found. The proband was compound heterozygous of the two mutations, so was her younger sister. Her mother was a carrier with only a c.1567T to G heterozygous mutation in exon 14. Her father had a heterozygous mutation of c.374C to T in exon 4. After Xsp I restriction enzyme digestion, healthy controls had three bands including 28 bp, 120 bp and 399 bp, while the proband and her mother had four bands consisting of 28 bp, 120 bp, 148 bp and 399 bp. For amplification by ARMS specific primers, it was negative for the controls, while it was positive for the proband and the carrier. The results of protein secondary and tertiary structure prediction showed that the c.1567T to G mutation located in the stop codon, resulted in stop codon (TAG) changing to glutamic acid (GAG), with the peptide chain extending 92 amino acid residues, and secondary and tertiary protein structure change, which were not found in the controls. The result of enzyme assay showed that the activity of GALNS enzyme in the affected child was 8.3 nmol/17h/mg pr, which was obviously lower than the normal value (the normal range is 41.9-92.1 nmol/17h/mg pr).</p><p><b>CONCLUSION</b>These results illustrate that the c.1567 T to G is a novel pathologic mutation, which is the main cause of the disease in this family.</p>

A new mutation (1062 del 16) of iduronate-2-sulfatase gene from a Chinese patient with Hunter syndrome / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

<p><b>OBJECTIVE</b>To identify the mutations of iduronate-2-sulfatase (IDS) gene, to reveal its mutation features, and to establish a basis for genetic counseling and prenatal gene diagnosis of Hunter syndrome.</p><p><b>METHODS</b>Urine glycosaminoglycans (GAGs) assay, PCR and DNA sequencing were performed to detect mutation of IDS gene of the patient and his parents.</p><p><b>RESULTS</b>The result showed that the patient was: DS(++), HS(++), KS(-), CS(-), and that both of his parents were negative. A frame-shift deletion mutation (1062 del 16) was identified in exon 7 of the patient's IDS gene. His parents' genotypes were normal.</p><p><b>CONCLUSION</b>The patient's mutation was not inherited by his parents but a novel one. The mutation probably altered the primary structure and tertiary structure of IDS enzyme protein remarkably and lowered the activity of IDS enzyme greatly. Therefore it is supposed to be the direct cause of the disorder.</p>