RT Journal Article
SR Electronic
T1 Unstable expansion of the CAG trinucleotide repeat in MAB21L1: report of a second pedigree and effect on protein expression
JF Journal of Medical Genetics
JO J Med Genet
FD BMJ Publishing Group Ltd
SP 62
OP 64
DO 10.1136/jmg.36.1.62
VO 36
IS 1
A1 Russell L Margolis
A1 O Colin Stine
A1 Christopher M Ward
A1 Mary L Franz
A1 Adam Rosenblatt
A1 Colleen Callahan
A1 Meeia Sherr
A1 Christopher A Ross
A1 Nicholas T Potter
YR 1999
UL http://jmg.bmj.com/content/36/1/62.abstract
AB MAB21L1, originally termed CAGR1, is the human homologue of the C elegans cell fate determining genemab21. MAB21L1, mapped to 13q13, contains a highly polymorphic 5′ untranslated CAG repeat that normally ranges from six to 31 triplets in length. A pedigree has been previously reported in which the repeat length is expanded to 45-50 triplets and is transmitted unstably between generations; the expansion did not correlate to a clinical phenotype but did exhibit somatic mosaicism. We now report a second pedigree with an expanded and unstably transmitted MAB21L1 CAG repeat of similar length. The expansion is not clearly associated with a clinical phenotype, though the complexity of the pedigree renders any conclusion concerning phenotype-genotype relationships speculative. The expansion did not result in decreased expression of MAB21L1 protein. The length, C-G rich composition, somatic mosaicism, and unstable transmission of the expanded CAG repeat in MAB21L1 resemble the premutations observed in other genes, such as FMR1 and MDPK, in which longer expanded repeats are associated with a clinical phenotype. This raises the possibility that longer expansions in the MAB21L1 repeat may also be associated with a clinical phenotype.