Immunochemical analysis of uridine diphosphate-glucuronosyltransferase in four patients with the Crigler-Najjar syndrome type I.

Abstract

The functional heterogeneity of uridine diphosphateglucuronosyltransferase (UDPGT) and its deficiency in human liver were investigated. The monoclonal antibody (MAb) WP1, which inhibits bilirubin and phenol-glucuronidating activity, was used to immunopurify UDPGTs from human liver. Purified UDPGTs were injected into mice to obtain new MAbs. Immunoblotting of microsomes with MAb HEB7 revealed at least three polypeptides in liver (56, 54, and 53 kD) and one in kidney (54 kD). In liver microsomes from four patients (A, B, C, and D) with Crigler-Najjar syndrome type I (CN type I), UDPGT activity towards bilirubin was undetectable (A, B, C, and D) and activity towards phenolic compounds and 5-hydroxytryptamine either reduced (A and B) or normal (C and D). UDPGT activity toward steroids was normal. Immunoblot studies revealed that the monoclonal antibody WP1 recognized two polypeptides (56 and 54 kD) in liver microsomes from patient A and none in patient B. With HEB7 no immunoreactive polypeptides were seen in these two patients. Patient C showed a normal banding pattern and in patient D only the 53-kD band showed decreased intensity. These findings suggest considerable heterogeneity with regard to the expression of UDPGT isoenzymes among CN type I patients. (J. Clin.

Sequence of exons and the flanking regions of human bilirubin-UDP-glucuronosyltransferase gene complex and identification of a genetic mutation in a patient with Crigler-Najjar syndrome, type I

“…CN-I is a heterogeneous disorder. In some patients only bilirubin glucuronidation is absent, whereas in other patients, UGT activities toward other substrates are also decreased (5,6). In human beings, two species of complementary DNA (cDNA), bilirubin-UGT, (B-UGT,) and bilirubin-UGT, (B-UGT,), have been shown to express UGT activity toward bilirubin (B-UGT) on transfection into COS cells (7).…”

Assignment of the human UDP glucuronosyltransferase gene (UGT1A1) to chromosome region 2q37

“…As in the Gunn rat (Roy Chowdhury et al, 1991), mutation(s) in one of the exons encoding the shared C-terminal half of the UGT1 Al isoform enzymes produce inactive or unstable UGT1A1 en zymes, resulting in the phenotype of unconjugated hyperbilirubimenia (van Es. 1990;van Es et al. 1990;Bosnia et al.…”

Prenatal diagnosis of bilirubin-UDP-glucuronosyltransferase deficiency in rats by genomic DNA analysis

“…These subjects are expected to have mutations in the common region of the mRNAs (191, as seen in Gunn rats (28). Other CN-I patients have deficiency of B-UGT activity only (47) and may be predicted to have mutations in the unique region of B-UGT mRNAs. The diagnosis of CN-I based on genomic DNA analysis has been facilitated by the recent description of nucleotide sequences of introns fhking each exon encoding the B-UGT isoforms (19) and the development of a panel of oligonucleotide primers for amplification of each exon by polymerase chain reaction (19).…”