TY - JOUR
T1 - Splice-site mutations
T2 - A novel genetic mechanism of Crigler-Najjar syndrome type 1
AU - Gantla, Shailaja
AU - Bakker, Conny T.M.
AU - Deocharan, Bishram
AU - Thummala, Narsing R.
AU - Zweiner, Jeffry
AU - Sinaasappel, Maarten
AU - Chowdhury, Jayanta Roy
AU - Bosma, Piter J.
AU - Chowdhury, Namita Roy
N1 - Funding Information:
This work was supported, in part, by National Institute of Health grants RO1 DK39137 (to N.R.C.), RO1 DK 46057 (to J.R.C.), and P30 DK 41296 (Liver Research Core Center, Director: D.A. Shafritz) and by the Seaver Institute of Human Genetics of the Albert Einstein College of Medicine.
PY - 1998/3
Y1 - 1998/3
N2 - Crigler-Najjar syndrome type 1 (CN-1) is a recessively inherited, potentially lethal disorder characterized by severe unconjugated hyperbilirubinemia resulting from deficiency of the hepatic enzyme bilirubin- UDP-glucuronosyltransferase. In all CN-1 patients studied, structural mutations in one of the five exons of the gene (UGT1A1) encoding the uridinediphosphoglucuronate glucuronosyltransferase (UGT) isoform bilirubin- UGT1 were implicated in the absence or inactivation of the enzyme. We report two patients in whom CN-1 is caused, instead, by mutations in the noncoding intronic region of the UGT1A1 gene. One patient (A) was homozygous for a G→C mutation at the splice-donor site in the intron, between exon 1 and exon 2. The other patient (B) was heterozygous for an A→G shift at the splice- acceptor site in intron 3, and in the second allele a premature translation- termination codon in exon 1 was identified. Bilirubin-UGT1 mRNA is difficult to obtain, since it is expressed in the liver only. To determine the effects of these splice-junction mutations, we amplified genomic DNA of the relevant splice junctions. The amplicons were expressed in COS-7 cells, and the expressed mRNAs were analyzed. In both cases, splice-site mutations led to the use of cryptic splice sites, with consequent deletions in the processed mRNA. This is the first report of intronic mutations causing CN-1 and of the determination of the consequences of these mutations on mRNA structure, by ex vivo expression.
AB - Crigler-Najjar syndrome type 1 (CN-1) is a recessively inherited, potentially lethal disorder characterized by severe unconjugated hyperbilirubinemia resulting from deficiency of the hepatic enzyme bilirubin- UDP-glucuronosyltransferase. In all CN-1 patients studied, structural mutations in one of the five exons of the gene (UGT1A1) encoding the uridinediphosphoglucuronate glucuronosyltransferase (UGT) isoform bilirubin- UGT1 were implicated in the absence or inactivation of the enzyme. We report two patients in whom CN-1 is caused, instead, by mutations in the noncoding intronic region of the UGT1A1 gene. One patient (A) was homozygous for a G→C mutation at the splice-donor site in the intron, between exon 1 and exon 2. The other patient (B) was heterozygous for an A→G shift at the splice- acceptor site in intron 3, and in the second allele a premature translation- termination codon in exon 1 was identified. Bilirubin-UGT1 mRNA is difficult to obtain, since it is expressed in the liver only. To determine the effects of these splice-junction mutations, we amplified genomic DNA of the relevant splice junctions. The amplicons were expressed in COS-7 cells, and the expressed mRNAs were analyzed. In both cases, splice-site mutations led to the use of cryptic splice sites, with consequent deletions in the processed mRNA. This is the first report of intronic mutations causing CN-1 and of the determination of the consequences of these mutations on mRNA structure, by ex vivo expression.
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U2 - 10.1086/301756
DO - 10.1086/301756
M3 - Article
C2 - 9497253
AN - SCOPUS:0031971043
SN - 0002-9297
VL - 62
SP - 585
EP - 592
JO - American Journal of Human Genetics
JF - American Journal of Human Genetics
IS - 3
ER -