title: A functional classification of ABCB4 variations causing progressive familial intrahepatic cholestasis type 3.
abstract: Progressive familial intrahepatic cholestasis type 3 is caused by biallelic variations of ABCB4, most often (≥70%) missense. In this study, we examined the effects of 12 missense variations identified in progressive familial intrahepatic cholestasis type 3 patients. We classified these variations on the basis of the defects thus identified and explored potential rescue of trafficking-defective mutants by pharmacological means. Variations were reproduced in the ABCB4 complementary DNA and the mutants, thus obtained, expressed in HepG2 and HEK293 cells. Three mutants were either fully (I541F and L556R) or largely (Q855L) retained in the endoplasmic reticulum, in an immature form. Rescue of the defect, i.e., increase in the mature form at the bile canaliculi, was obtained by cell treatments with cyclosporin A or C and, to a lesser extent, B, D, or H. Five mutations with little or no effect on ABCB4 expression at the bile canaliculi caused a decrease (F357L, T775M, and G954S) or almost absence (S346I and P726L) of phosphatidylcholine secretion. Two mutants (T424A and N510S) were normally processed and expressed at the bile canaliculi, but their stability was reduced. We found no defect of the T175A mutant or of R652G, previously described as a polymorphism. In patients, the most severe phenotypes appreciated by the duration of transplant-free survival were caused by ABCB4 variants that were markedly retained in the endoplasmic reticulum and expressed in a homozygous status.
  
  
  CONCLUSIONS
  ABCB4 variations can be classified as follows: nonsense variations (I) and, on the basis of current findings, missense variations that primarily affect the maturation (II), activity (III), or stability (IV) of the protein or have no detectable effect (V); this classification provides a strong basis for the development of genotype-based therapies.
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Delaunay
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Durand-Schneider
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Dossier
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Falguières
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Gautherot
authors.affiliation: Assistance Publique-Hôpitaux de Paris, Hôpital de Bicêtre, Laboratoire de biochimie, Le Kremlin Bicêtre, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Davit-Spraul
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France.
authors.forename: Tounsia
authors.initials: T
authors.lastname: Aït-Slimane
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France.|Assistance Publique-Hôpitaux de Paris, Hôpital Saint-Antoine, Centre de Référence Maladies Rares Maladies Inflammatoires des Voies Biliaires & Service d'Hépatologie, Paris, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Housset
authors.affiliation: Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Hépatologie Pédiatrique & Unité de Transplantation Hépatique, Centre de Référence Maladies Rares Atrésies des Voies Biliaires de l'Enfant, Le Kremlin Bicêtre, France.|Université Paris-Sud 11, INSERM, UMR_S 1174, Hepatinov, Orsay, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Jacquemin
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France.
authors.forename: Michèle
authors.initials: M
authors.lastname: Maurice
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000172:deficiency* / Q000235:genetics; D002780:Cholestasis, Intrahepatic / Q000235:genetics*; D016572:Cyclosporine / Q000494:pharmacology; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006801:Humans; D009154:Mutation; D010713:Phosphatidylcholines / Q000378:metabolism
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D010713:Phosphatidylcholines; D016572:Cyclosporine; C095122:multidrug resistance protein 3