title: Carriers and patients with muscle-eye-brain disease can be rapidly diagnosed by enzymatic analysis of fibroblasts and lymphoblasts.
abstract: We report a new fibroblast and lymphoblast based protein O-mannosyl beta-1,2-N-acetylglucosaminyltransferase 1 enzymatic assay, which allows rapid and accurate diagnosis of carriers and patients with muscle-eye-brain type of congenital muscular dystrophy. Seven patients with genetically confirmed muscle-eye-brain disease were assayed for protein O-mannosyl beta-1,2-N-acetylglucosaminyltransferase 1 enzyme activity. In three patients and their heterozygous parents, the assays were done on EBV-transformed lymphoblasts, in another three patients they were done on cultured fibroblasts and in the last patient on both fibroblasts and lymphoblasts. Cultured fibroblasts and lymphoblasts from the muscle-eye-brain patients showed a highly significant decrease in protein O-mannosyl beta-1,2-N-acetylglucosaminyltransferase 1 activity relative to controls. The residual protein O-mannosyl beta-1,2-N-acetylglucosaminyltransferase 1 level in fibroblasts (average 0.11 nmoles/h per mg) was about 13% of normal controls. The ratio of protein O-mannosyl beta-1,2-N-acetylglucosaminyltransferase 1 activity to the activity of a glycosyltransferase control (N-acetylglucosaminyltransferase 1; GnT1) in fibroblasts was on average 0.006 in muscle-eye-brain patients and 0.045 in controls. The average residual protein O-mannosyl beta-1,2-N-acetylglucosaminyltransferase 1 level in lymphoblasts was 15% of normal controls. The average ratio of protein O-mannosyl beta-1,2-N-acetylglucosaminyltransferase 1/GnT1 activity was 0.007 in muscle-eye-brain patients, 0.026 in heterozygous carriers and 0.046 in normal controls. Assay of protein O-mannosyl beta-1,2-N-acetylglucosaminyltransferase 1 activity in fibroblasts and lymphoblasts from muscle-eye-brain carriers and patients provides a rapid and relatively simple diagnostic test for this disease and could be used as a screening test in carriers and patients with complex congenital muscular dystrophy.
authors.affiliation: The Hospital for Sick Children, Toronto, Ont. Canada. jiri.vajsar@sickkids.ca
authors.forename: Jiri
authors.initials: J
authors.lastname: Vajsar
authors.forename: Wenli
authors.initials: W
authors.lastname: Zhang
authors.forename: William B
authors.initials: WB
authors.lastname: Dobyns
authors.forename: Doug
authors.initials: D
authors.lastname: Biggar
authors.forename: Kenton R
authors.initials: KR
authors.lastname: Holden
authors.forename: Cynthia
authors.initials: C
authors.lastname: Hawkins
authors.forename: Peter
authors.initials: P
authors.lastname: Ray
authors.forename: Ann H
authors.initials: AH
authors.lastname: Olney
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Burson
authors.forename: Anand K
authors.initials: AK
authors.lastname: Srivastava
authors.forename: Harry
authors.initials: H
authors.lastname: Schachter
mesh_terms: D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D004796:Clinical Enzyme Tests; D005260:Female; D005347:Fibroblasts / Q000201:enzymology*; D006580:Genetic Carrier Screening / Q000379:methods*; D005820:Genetic Testing; D006801:Humans; D007223:Infant; D008214:Lymphocytes / Q000201:enzymology*; D008297:Male; D009136:Muscular Dystrophies / Q000151:congenital* / Q000175:diagnosis* / Q000201:enzymology; D009154:Mutation; D017351:N-Acetylglucosaminyltransferases / Q000032:analysis / Q000235:genetics
chemical_list: D017351:N-Acetylglucosaminyltransferases; C443106:protein O-mannose beta-1,2-N-acetylglucosaminyltransferase; C024850:alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase I