title: Metanephrogenic mesenchyme-to-epithelium transition induces profound expression changes of ion channels.
abstract: The expression patterns of plasma membrane transporters that specify the epithelial cell type are acquired with ontogeny. To study this process during metanephrogenic mesenchyme-to-epithelium transition, branching ureteric buds with their adjacent mesenchymal blastema (mouse embryonic day E14) were dissected and explanted on a collagen matrix. In culture, induced mesenchymal cells condensed, aggregated, and converted to the comma- and S-shaped body. During in vitro condensation and aggregation, transcription factor Pax-2 protein was downregulated while the epithelial markers E-cadherin and beta-catenin proteins were upregulated. In addition, Wilms' tumor suppressor protein WT-1 was detectable upon condensation and downregulated in the S stage, where expression persisted in the long arm of the S. Patch-clamp, whole cell conductance (G, in nS/10 pF) of pre-epithelial condensed mesenchymal cells (n = 7) was compared with that of tubular proximal S-shaped-body epithelium (n = 6). Both stages expressed E-cadherin and WT-1 mRNA, as demonstrated by single-cell RT-PCR, testifying further to the epithelial as well as the nephrogenic commitment of the recorded cells. Mesenchymal cells exhibited whole cell currents (G = 6.7 +/- 1.3) with reversal potentials (V(rev), in mV) near equilibrium potential for Cl(-) (E(Cl)) (V(rev) = -40 +/- 7) suggestive of a high fractional Cl(-) conductance. Currents of the S-shaped-body cells (G = 4.0 +/- 1.1), in sharp contrast, had a V(rev) at E(K) (V(rev) = -82 +/- 6) indicating a high fractional K(+) conductance. Further, analysis of K(+)-selective whole cell tail currents and single-channel recording revealed a change in K(+) channel expression. Also, Kir6.1 K(+) channel mRNA and protein were downregulated between both stages, whereas K(v)LQT K(+) channel mRNA was abundant throughout. In conclusion, metanephrogenic mesenchyme-to-epithelium transition is accompanied by a profound reorganization of plasma membrane ion channel conductance.
authors.affiliation: Physiologisches Institut, 80336 Munich, Germany.
authors.forename: S M
authors.initials: SM
authors.lastname: Huber
authors.forename: G S
authors.initials: GS
authors.lastname: Braun
authors.forename: S
authors.initials: S
authors.lastname: Segerer
authors.forename: R W
authors.initials: RW
authors.lastname: Veh
authors.forename: M F
authors.initials: MF
authors.lastname: Horster
mesh_terms: D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002449:Cell Aggregation; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004553:Electric Conductivity; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D007668:Kidney / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D008648:Mesoderm / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D051762:PAX2 Transcription Factor; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025721:WT1 Proteins; D051176:beta Catenin
chemical_list: C495267:CTNNB1 protein, mouse; D015820:Cadherins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D007473:Ion Channels; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496910:Kcnq1 protein, mouse; D051762:PAX2 Transcription Factor; C497319:Pax2 protein, mouse; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D025721:WT1 Proteins; D051176:beta Catenin; D012965:Sodium Chloride; D011188:Potassium