Reduced hepatic expression of farnesoid X receptor in hereditary cholestasis associated to mutation in ATP8B1.
Farnesoid X receptor (FXR) is a transcription factor that controls bile acid homeostasis. The phenotype of Fxr null mice is characterized by hypercholanaemia, impaired secretion of bile acids and failure to thrive. Human disorders with these characteristics include FIC1 disease (caused by mutations in ATP8B1, which encodes a putative aminophospholipid translocase, FIC1, whose function in bile handling is unknown) and bile salt export pump (BSEP) disease (caused by mutation in ABCB11, which encodes BSEP, the primary canalicular bile salt export pump). We investigated the possibility of hepatic down-regulation of FXR in FIC1 disease and BSEP disease. Three siblings with this phenotype, born to consanguine parents, were initially studied. The children were demonstrated to be compound heterozygotes for missense and nonsense mutations in ATP8B1. Expression of specific genes in liver was analysed, comparing one of these siblings with a child homozygous for missense mutation in ABCB11, as well as with a child having idiopathic cholestatic liver disease, a child with extrahepatic biliary atresia and a normal organ donor. The expression of two main FXR isoforms was specifically decreased in the liver of the FIC1 disease patient. A consistent and concomitant reduction in messenger RNA levels of FXR targets, such as BSEP and small heterodimer partner, was also found. Gene-profiling experiments identified 163 transcripts whose expression changed significantly in FIC1-disease liver. Of note was that several genes involved in synthesis, conjugation and transport of bile acids were down-regulated. A cluster of genes involved in lipid metabolism was also differentially expressed. Our findings suggest that hepatic down-regulation of FXR contributes to the severe cholestasis of FIC1 disease.
Research Unit, La Paz University Hospital, Madrid, Spain. luisalvarez.hulp@salud.madrid.org
Luis
L
Alvarez
Paloma
P
Jara
Elena
E
Sánchez-Sabaté
Loreto
L
Hierro
Javier
J
Larrauri
María C
MC
Díaz
Carmen
C
Camarena
Angela
A
De la Vega
Esteban
E
Frauca
Eduardo
E
López-Collazo
Pablo
P
Lapunzina
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000032:analysis / Q000235:genetics; D000251:Adenosine Triphosphatases / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D002780:Cholestasis, Intrahepatic / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D005091:Exons / Q000235:genetics; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008297:Male; D026901:Membrane Transport Proteins / Q000032:analysis; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000032:analysis; D009154:Mutation / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D000099150:Receptor, Farnesoid X-Activated
D018435:ATP Binding Cassette Transporter, Subfamily B; D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; D000251:Adenosine Triphosphatases; D004268:DNA-Binding Proteins; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D020033:Protein Isoforms; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D000099150:Receptor, Farnesoid X-Activated; C093491:ABCB11 protein, human; C095122:multidrug resistance protein 3; C111067:ATP8B1 protein, human