Abnormalities in villin gene expression and canalicular microvillus structure in progressive cholestatic liver disease of childhood.
BACKGROUND
The molecular basis of clinical cholestasis is a subject of intense investigation. Villin is an actin binding, bundling, and severing protein needed for maintenance of structural integrity of canalicular microvilli, in which membrane transporters required for bile secretion are located. We aimed to investigate the role of canalicular cytoskeletal proteins in three genetically unrelated children with a biliary atresia-like clinical disorder, each of whom developed liver failure requiring liver transplantation.


METHODS
Explanted livers from the three patients were examined by standard pathological methods followed by transmission and cryoimmunoelectron microscopy. With archival tissue samples, a panel of cytoskeletal proteins was investigated by immunohistochemistry and western blotting, with purified canalicular membrane preparations. Villin mRNA analyses were undertaken on liver homogenates, with primers from coding regions of the human villin gene. Classic biliary atresia, other types of cholestasis, and normal livers served as controls.


RESULTS
In patients, pronounced ultrastructural deformities of canaliculi and especially of their microvilli were noted, which correlated with absence of villin protein by immunostaining of liver tissue sections and by western blot analysis. Additionally, villin mRNA was strikingly reduced or absent. These results differed greatly from those in controls.


CONCLUSIONS
These results suggest that the disorder described mimics biliary atresia, but structural and molecular pathological findings differ. We propose that a functional abnormality in villin gene expression is key to the mechanism of cholestasis in patients with progressive cholestasis and hepatic failure.
Phillips
M James
MJ
Department of Multi-organ Transplantation Research, Toronto General Hospital, University Health Network, ON, Toronto, Canada. m_james.phillips@sickkids.on.ca
Azuma
Toshifumi
T
Meredith
Sheue-Lim M
SL
Squire
Jeremy A
JA
Ackerley
Cameron A
CA
Pluthero
Fred G
FG
Roberts
Eve A
EA
Superina
Riccardo A
RA
Levy
Gary A
GA
Marsden
Philip A
PA
D001656:Biliary Atresia / Q000235:genetics / Q000503:physiopathology / Q000601:surgery; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D002779:Cholestasis / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D020285:Cryoelectron Microscopy; D005260:Female; D015870:Gene Expression; D006801:Humans; D007223:Infant; D008099:Liver / Q000473:pathology; D016031:Liver Transplantation; D008297:Male; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D008871:Microvilli / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure*
D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D008840:Microfilament Proteins; C026615:villin