Loss of N-acetylglucosamine-1-phosphotransferase gamma subunit due to intronic mutation in GNPTG causes mucolipidosis type III gamma: Implications for molecular and cellular diagnostics.

TY - JOUR

T1 - Loss of N-acetylglucosamine-1-phosphotransferase gamma subunit due to intronic mutation in GNPTG causes mucolipidosis type III gamma: Implications for molecular and cellular diagnostics.

AU - Pohl, Sandra

AU - Encarnação, Marisa

AU - Castrichini, Monica

AU - Müller-Loennies, Sven

AU - Muschol, Nicole

AU - Braulke, Thomas

PY - 2010/1

Y1 - 2010/1

N2 - Mucolipidosis type III gamma (MLIII, pseudo-Hurler polydystrophy) is a rare autosomal recessive disorder where the activity of the multimeric GlcNAc-1-phosphotransferase is reduced and formation of the mannose 6-phosphate (M6P) recognition marker on lysosomal enzymes is impaired. In this disease, the targeting of lysosomal enzymes is affected resulting in their hypersecretion, and an intracellular deficiency of multiple hydrolases. We report the biochemical and molecular diagnosis of MLIII in three siblings, aged 17, 15, and 14 years, who presented with joint pain and progressive joint stiffness. In addition to missorting of newly synthesized lysosomal protease cathepsin D, there were low levels of M6P-containing proteins in cell extracts and media of cultured fibroblasts of the Patients. Direct sequencing identified a novel homozygous mutation in intron 7, IVS7-10G>A, of the GNPTG gene, which encodes the gamma-subunit of the GlcNAc-1-phosphotransferase. This mutation created a cryptic 3'-splice site resulting in a frameshift and premature translational termination (p.V176GfsX18). The GNPTG mRNA levels were markedly reduced in Patients' fibroblasts indicating that the intronic mutation mediates mRNA decay, which was confirmed by absence of the gamma-subunit protein. These data contribute to an efficient diagnostic strategy to identify Patients with MLIII gamma and characterize their biochemical defect in fibroblasts.

AB - Mucolipidosis type III gamma (MLIII, pseudo-Hurler polydystrophy) is a rare autosomal recessive disorder where the activity of the multimeric GlcNAc-1-phosphotransferase is reduced and formation of the mannose 6-phosphate (M6P) recognition marker on lysosomal enzymes is impaired. In this disease, the targeting of lysosomal enzymes is affected resulting in their hypersecretion, and an intracellular deficiency of multiple hydrolases. We report the biochemical and molecular diagnosis of MLIII in three siblings, aged 17, 15, and 14 years, who presented with joint pain and progressive joint stiffness. In addition to missorting of newly synthesized lysosomal protease cathepsin D, there were low levels of M6P-containing proteins in cell extracts and media of cultured fibroblasts of the Patients. Direct sequencing identified a novel homozygous mutation in intron 7, IVS7-10G>A, of the GNPTG gene, which encodes the gamma-subunit of the GlcNAc-1-phosphotransferase. This mutation created a cryptic 3'-splice site resulting in a frameshift and premature translational termination (p.V176GfsX18). The GNPTG mRNA levels were markedly reduced in Patients' fibroblasts indicating that the intronic mutation mediates mRNA decay, which was confirmed by absence of the gamma-subunit protein. These data contribute to an efficient diagnostic strategy to identify Patients with MLIII gamma and characterize their biochemical defect in fibroblasts.

KW - Adolescent

KW - Female

KW - Humans

KW - Introns

KW - Male

KW - Mucolipidoses/enzymology

KW - Mutation

KW - Pathology, Molecular

KW - RNA, Messenger/genetics

KW - Transferases (Other Substituted Phosphate Groups)/genetics

U2 - 10.1002/ajmg.a.33170

DO - 10.1002/ajmg.a.33170

M3 - SCORING: Journal article

C2 - 20034096

VL - 152

SP - 124

EP - 132

JO - AM J MED GENET A

JF - AM J MED GENET A

SN - 1552-4825

IS - 1

M1 - 1

ER -