RESUMO
EXT1/EXT2-CDG (Multiple cartilagineous exostoses, hereditary multiple osteochondroma (MO); OMIM 133700/133701) are common defects of O-xylosylglycan glycosylation. The diagnostic criteria are at least two osteochondromas of the juxta-epiphyseal region of long bones with in the majority of cases a positive family history and/or mutation in one of the EXT genes. The authors report data on clinical symptoms and complications of 23 patients (from 16 families), discussing the family history, age of diagnosis, new clinical and molecular data. Fifteen mutations and large deletions, of which nine are new, were detected in the EXT1 and EXT2 gene by sequence analysis, FISH and MLPA analysis.
Assuntos
Exostose Múltipla Hereditária/genética , N-Acetilglucosaminiltransferases/genética , Adolescente , Adulto , Bulgária , Criança , Pré-Escolar , Defeitos Congênitos da Glicosilação/complicações , Defeitos Congênitos da Glicosilação/genética , Análise Mutacional de DNA/métodos , Exostose Múltipla Hereditária/complicações , Exostose Múltipla Hereditária/diagnóstico , Feminino , Predisposição Genética para Doença/genética , Humanos , Masculino , Pessoa de Meia-Idade , N-Acetilglucosaminiltransferases/fisiologia , Adulto JovemRESUMO
Alterations in GLB1, the gene coding for acid beta-D-galactosidase (beta-Gal), can result in GM1 gangliosidosis (GM1), a neurodegenerative disorder, or in Morquio B disease (MBD), a phenotype with dysostosis multiplex and normal central nervous system (CNS) function. While most MBD patients carry a common allele, c.817TG>CT (p.W273L), only few of the >100 mutations known in GM1 can be related to a certain phenotype. In 25 multiethnic patients with GM1 or MBD, 11 missense mutations were found as well as one novel insertion and a transversion causing aberrant gene products. Except c.602G>A (p.R201H) and two novel alleles, c.592G>T (p.D198Y) and c.1189C>G (p.P397A), all mutants resulted in significantly reduced beta-Gal activities (<10% of normal) upon expression in COS-1 cells. Although c.997T>C (p.Y333H) expressed 3% of normal activity, the mutant protein was localized in the lysosomal-endosomal compartment. A homozygous case presented with late infantile GM1, while a heterozygous, juvenile case carried p.Y333H together with p.R201H. This allele, recently found in homozygous MBD, gives rise to rough endoplasmic reticulum (RER)-located beta-Gal precursors. Thus, unlike classical MBD, the phenotype of heterozygotes carrying p.R201H may rather be determined by poorly active, properly transported products of the counter allele than by the mislocalized p.R201H precursors.