Carriers and patients with muscle-eye-brain disease can be rapidly diagnosed by enzymatic analysis of fibroblasts and lymphoblasts.
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.
Vajsar
Jiri
J
The Hospital for Sick Children, Toronto, Ont. Canada. jiri.vajsar@sickkids.ca
Zhang
Wenli
W
Dobyns
William B
WB
Biggar
Doug
D
Holden
Kenton R
KR
Hawkins
Cynthia
C
Ray
Peter
P
Olney
Ann H
AH
Burson
Catherine M
CM
Srivastava
Anand K
AK
Schachter
Harry
H
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
D017351:N-Acetylglucosaminyltransferases; C443106:protein O-mannose beta-1,2-N-acetylglucosaminyltransferase; C024850:alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase I