In HNF6- and HNF1β-deficient biliary cells, the centrioles were randomly
distributed (Fig. 2). The lack of cilia at the apical pole was associated with polarity defects. The apical markers mucin-1 and osteopontin (OPN) were not expressed in the absence of HNF6 or HNF1β (Fig. 2 and Supporting Fig. 4). The Golgi marker GM130 was randomly distributed instead of being located along the apicobasal axis between the nucleus and apical pole (Supporting Fig. 4). The basement membrane component laminin, normally connected to the basal pole, formed a continuous layer encircling the ducts in wild-type livers. In the absence of HNF6 or HNF1β the laminin layer was continuous along the Selleckchem Pifithrin�� basal pole of cells located at the portal side of biliary structures, but was irregular and discontinuous along the cells lining the parenchymal side (arrowheads in Supporting Fig. 4). Phenotypic variability was observed in Hnf6−/−
livers, in which some cystic structures were entirely lined by a near continuous layer of laminin (Fig. 2); this variability was unrelated to the hilar-periphery axis. Tight junctions separate the apical pole from the basolateral pole of cells. In the absence of HNF6, zonula occludens-1 (ZO-1) was localized at the apical/lateral boundary on cells of the parenchymal and portal side (Supporting Fig. 4). When Hnf1b was deleted, ZO-1 was barely detected in cells of the parenchymal side but was clearly detectable at the portal side. On the portal side, ZO-1 staining did not show the expected punctuate pattern MCE公司 of tight junctions but showed
Selleck GW 572016 coverage of the apical surface on serial confocal sections, suggesting lack of apical pole (Supporting Fig. 4). At postnatal day 7, a few Hnf6−/− biliary cells showed normal location of cilia (acetylated tubulin, arrows), mucin-1, and laminin, indicating partial restoration of apicobasal polarity (Supporting Fig. 2A). A fraction of HNF1β-deficient cells expressed mucin-1; no cilia were detected on these cells, the basal bodies remained randomly distributed, and ZO-1 still showed apical coverage (Supporting Fig. 2A). In patients with HNF1B mutation, ZO-1 was irregularly expressed in dysplastic ducts and the DPM did not express ZO-1 (Supporting Fig. 3). We concluded that HNF6 and HNF1β are required for normal development of cilia and for polarization of the cells. The lack of cilia in HNF6- and HNF1β-deficient livers prompted us to investigate whether the expression of genes controlling ciliogenesis or cilium function was affected in these mice. These genes included a set that is regulated by HNF1β in kidneys,15, 16, 26 as well as those associated with hepatorenal fibrocystic diseases27 (Supporting Table 2). In the absence of HNF6 at E17.5, Pkhd1 and Sec63 mRNA levels were up-regulated, but were unaffected in Hnf1b knockout (KO) livers (Fig. 3).