Both RT-PCR and immunostaining ABT-263 data suggest that they might be transit amplifying cells, a hypothesis being tested. The various transcription factors (e.g., SOX17, SOX9, PDX1) were found predominantly intranuclearly both in situ and in cultured cells (Figs. 2-4, S7). Within each peribiliary gland there was heterogeneous expression of transcription factors and of cytoplasmic and membrane-associated stem cell markers, with some cells positive and others negative. Although most of these markers were shared by cell populations from all biliary tree sites examined, there were distinctions in the relative expression

of one versus another marker and in whether key transcription factors (e.g., SOX 17, PDX1) were located within the nucleus (Figs. 2, 4) or perinuclearly (Figs. 3, S7). A perinuclear localization occurred in some cells in situ and in cells at the edges of the type 3 colonies. The transition from intranuclear to perinuclear location is interpreted as sequestration and/or turnover of transcription factors accompanying R428 manufacturer differentiation events. Alternatively, the perinuclear localization could indicate that the factors are in an inactive storage form that can be activated by translocation to the nucleus under appropriate regenerative demands. Interestingly, there were also cells coexpressing multiple transcription factors such as SOX17

and learn more PDX1 (Fig. 4). The percentage of SOX17+ cells is 11.2% ± 3.8% and the PDX1+ cell is the 16.6% ± 3.4% and the percentage of the cells coexpressing SOX17 and PDX1 was variable but ranged

from 10%-15%. This coexpression in some cells and, similarly, expression of multiple transcription factors relevant to liver and pancreas (e.g., HNF6, NGN3) in some peribiliary glands is a unique feature that is distinctive from findings with respect to embryonic stem (ES) cells lineage restricted to liver or pancreas and in which specific genes turn on (and then off) in stages. Marker analyses completed to date of biliary tree stem/progenitors indicate they are stages between definitive endoderm and determined stem cells and mostly at lineage stage 4 in the development of the endocrine pancreas or of the liver from ES cells.18 Cultures of the biliary tree tissue on plastic and in serum-free KM resulted in selection for colonies of cells that divided initially every 36-40 hours, thereafter slowing to a division every ≈2-3 days, with proliferation continuing for months and associated with stable maintenance of the undifferentiated cell phenotype (Table S2). Figure S8 shows a representative colony maintained for more than 8 weeks on culture plastic and in KM. Cells in the colony centers (regions a and b) had an average cell diameter of ≈6-7 μm, whereas those at the colony edges were larger (≈11-12 μm) (regions c-e).