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Transcobalamin deficiency due to activation of an intra exonic cryptic splice site
Author(s) -
Namour Fares,
Helfer AnneCatherine,
Quadros Edward V.,
Alberto JeanMarc,
Bibi Ha M.,
Orning Lars,
Rosenblatt David S.,
JeanLouis Guéant
Publication year - 2003
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.2003.04685.x
Subject(s) - exon , splice site mutation , intron , rna splicing , biology , point mutation , genetics , splice , mutation , vitamin b12 , gene , genetic disorder , frameshift mutation , alternative splicing , endocrinology , rna
Summary. Transcobalamin (TC), a vitamin B12 (cobalamin, Cbl) binding protein in plasma, promotes the cellular uptake of the vitamin by receptor‐mediated endocytosis. Inherited TC deficiency is an autosomal recessive disorder characterized by megaloblastic anaemia caused by cellular vitamin B12 depletion. It may be accompanied by neurological complications, including a delay in psychomotor and mental development. This report describes three sisters with inherited TC deficiency resulting from a splicing defect in the TC gene. A point mutation was identified in intron 3 splice site of the TC gene that activates a cryptic splice site in exon 3. The transcript generated has an in‐frame deletion of 81 nucleotides and the resulting truncated protein is unstable and not secreted by the cells. Until now, genetic studies have been reported in only five patients with TC deficiency and the molecular defect was different in each of them, which gives evidence for a genetic heterogeneity of the disease.