RESUMO
BACKGROUND AND AIMS: The aim of this study was to investigate the genetic aetiology of intrahepatic cholestasis of pregnancy (ICP) and the impact of known cholestasis genes (BSEP, FIC1, and MDR3) on the development of this disease. PATIENTS AND METHODS: Sixty nine Finnish ICP patients were prospectively interviewed for a family history of ICP, and clinical features were compared in patients with familial ICP (patients with a positive family history, n=11) and sporadic patients (patients with no known family history of ICP, n=58). For molecular genetic analysis, 16 individuals from two independently ascertained Finnish ICP families were genotyped for the flanking markers for BSEP, FIC1, and MDR3. RESULTS: The pedigree structures in 16% (11/69) of patients suggested dominant inheritance. Patients with familial ICP had higher serum aminotransferase levels and a higher recurrence risk (92% v 40%). Both segregation of haplotypes and multipoint linkage analysis excluded BSEP, FIC1, and MDR3 genes in the studied pedigrees. Additionally, the MDR3 gene, previously shown to harbour mutations in ICP patients, was negative for mutations when sequenced in four affected individuals from the two families. CONCLUSIONS: These results support the hypothesis that the aetiology of ICP is heterogeneous and that ICP is due to a genetic predisposition in a proportion of patients. The results of molecular genetic analysis further suggest that the previously identified three cholestasis genes are not likely to be implicated in these Finnish ICP families with dominant inheritance.
Assuntos
Colestase Intra-Hepática/genética , Heterogeneidade Genética , Complicações na Gravidez/etiologia , Subfamília B de Transportador de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/genética , Adulto , Ácidos e Sais Biliares/sangue , Colestase Intra-Hepática/epidemiologia , Saúde da Família , Feminino , Finlândia/epidemiologia , Genes Dominantes/genética , Ligação Genética/genética , Genótipo , Haplótipos/genética , Humanos , Incidência , Linhagem , Gravidez , Complicações na Gravidez/epidemiologia , Estudos Prospectivos , Transaminases/sangueAssuntos
Subfamília B de Transportador de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/genética , Colestase Intra-Hepática/genética , Variação Genética/genética , Complicações na Gravidez , Análise Mutacional de DNA , Éxons/genética , Feminino , Frequência do Gene/genética , Haplótipos/genética , Humanos , Masculino , Linhagem , Gravidez , Reino UnidoRESUMO
Using real time RT-PCR, we have detected expression of seven genes that influence bile acid transport,MDR3, FIC1, BSEP, OATP-A, OATP-C, OATP-D and OATP-E, in normal human placenta. With the exception of OATP-C and OATP-E these genes were found to be differentially expressed in 1st trimester and 3rd trimester placentae. MDR3 gene expression was found to be up regulated four fold in 3rd trimester placentae compared to 1st trimester, OATP-A gene expression was down regulated eight fold, OATP-D was down regulated 17 fold, while FIC1 expression was reduced by 33 fold in the 3rd trimester. OATP-C and BSEP gene expression was not detected in the 3rd trimester placenta, while low levels of transcripts were detected in the 1st trimester placentae. Transcripts of the hepatic sinusoidal bile acid transporter, NTCP, were not detected in placenta.
Assuntos
Proteínas de Transporte/genética , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Membrana Transportadoras , Placenta/metabolismo , Transcrição Gênica , Subfamília B de Transportador de Cassetes de Ligação de ATP/genética , Subfamília B de Transportador de Cassetes de Ligação de ATP/metabolismo , Membro 11 da Subfamília B de Transportadores de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Adulto , Ácidos e Sais Biliares/metabolismo , Proteínas de Transporte/metabolismo , Regulação para Baixo , Feminino , Humanos , Transportadores de Ânions Orgânicos/genética , Transportadores de Ânions Orgânicos/metabolismo , Transportadores de Ânions Orgânicos Dependentes de Sódio , Gravidez , Primeiro Trimestre da Gravidez , Terceiro Trimestre da Gravidez , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Simportadores , Regulação para CimaRESUMO
Intrahepatic cholestasis of pregnancy (ICP) is a liver disease of pregnancy with serious consequences for the mother and fetus. Two pedigrees have been reported with ICP in the mothers of children with a subtype of autosomal recessive progressive familial intrahepatic cholestasis (PFIC) with raised serum gamma-glutamyl transpeptidase (gamma-GT). Affected children have homozygous mutations in the MDR3 gene (also called ABCB4 ), and heterozygous mothers have ICP. More frequently, however, ICP occurs in women with no known family history of PFIC and the genetic basis of this disorder is unknown. We investigated eight women with ICP and raised serum gamma-GT, but with no known family history of PFIC. DNA sequence analysis revealed a C to A transversion in codon 546 in exon 14 of MDR3 in one patient, which results in the missense substitution of the wild-type alanine with an aspartic acid. We performed functional studies of this mutation introduced into MDR1, a closely related homologue of MDR3. Fluorescence activated cell sorting (FACS) and western analysis indicated that this missense mutation causes disruption of protein trafficking with a subsequent lack of functional protein at the cell surface. The demonstration of a heterozygous missense mutation in the MDR3 gene in a patient with ICP with no known family history of PFIC, analysed by functional studies, is a novel finding. This shows that MDR3 mutations are responsible for the additional phenotype of ICP in a subgroup of women with raised gamma-GT.
