Morphologic changes in the cytoskeleton and adhesion apparatus during the conversion from pseudostratified single columnar to stratified squamous epithelium in the developing mouse esophagus

Abstract

The apico-basal (AB) polarity of epithelial cells is maintained by organized arrays of the cytoskeleton and adhesion apparatus. We previously reported that mouse embryonic esophageal epithelium exhibits interkinetic nuclear migration (INM), an AB-polarity-based regulatory mechanism of stem-cell proliferation, and suggested that the pseudostratified single columnar epithelium, a hallmark of INM, is converted to stratified squamous epithelium via rearrangement of the cytoskeleton and cell-adhesion apparatus. Here, we chronologically examined morphological changes in the cytoskeleton and adhesion apparatus in the mouse esophageal epithelium at embryonic day (E) 11.5, E13.5, E14.5, and E15.5, during which epithelial conversion has been suggested to occur. We used phalloidin to examine the apical terminal web (ATW), immunofluorescent anti-zonula occludens protein (ZO-1) antibody to reveal ZO-1, and anti-gamma tubulin antibody to detect primary cilia (PC). At E11.5, a thick ATW, apically oriented ZO-1 and apical PC were observed, indicating a pseudostratified single columnar structure. At E13.5 and E14.5, the phalloidin-staining, ZO-1, and PC distribution patterns were not apically localized, and the epithelial cells appeared to have lost the AB polarity, suggesting conversion of the epithelial structure and cessation of INM. At E15.5, light and transmission electron microscope observations revealed the ATW, ZO-1, PC, and tight junction which were localized into two-1ayers: the apical and subapical layers of the epithelium. These findings suggest that dynamic remodeling of the cytoskeleton and adhesion apparatus is involved in the conversion from pseudostratified single columnar to stratified squamous morphology and is closely related with temporal perturbation of the AB-polarity and cessation of INM.

Identification and Characterization of Stem Cells in Mammalian Esophageal Stratified Squamous Epithelia

“…Consistent with these results, recent studies showed that the maintenance of Wnt pathway at low level could facilitate the specification of anterior foregut endoderm toward the esophageal progenitor cells lineage[9, 31] while COL17A1 was required for skin keratinocyte stem cell maintenance[35]. High expression of COL17A1 was also identified as a marker of human esophageal quiescent stem/progenitor cells[5]. Hence, these results suggested that high levels of HD components and Wnt pathway negative regulators could sever as prominent markers of QBCs in the basal layer of the esophageal epithelium.…”

“…As these organs are specified via a process of respiratoryesophageal separation (RES), the esophageal epithelium forms a simple columnar epithelium and then transforms into a stratified multi-layered epithelium [1][2][3][4]. The cellular and molecular mechanisms regulating RES and the esophageal epithelial morphogenesis during embryonic development have been extensively studied in recent years [2,[4][5][6][7][8][9]. However, it is less clear how the mature esophageal epithelium executes its self-renewal and maintenance of the proliferation-differentiation homeostasis.…”

Global pattern of interkinetic nuclear migration in tracheoesophageal epithelia of the mouse embryo: Interorgan and intraorgan regional differences

“…The epithelia of the trachea and esophagus are not "simple" columnar but "pseudostratified" columnar, which is a hallmark of the epithelia in which the interkinetic nuclear migration (INM) works as a regulatory mechanism of epithelial proliferation and differentiation. 3 We further reported that transient and dynamic morphologic changes involving the cytoskeleton and cell-adhesion apparatus occur in the esophageal epithelium in close relation with the cessation of INM and transition into the stratified squamous structure. 3 INM is the apicobasal (AB) cell polarity-based oscillatory movement of epithelial cell nuclei that is synchronized with the progression of the cell cycle, that is, the M-phase at the apical surface and S-phase at the basal side, and thus generates the pseudostratified structure of the epithelium.…”

“…3 We further reported that transient and dynamic morphologic changes involving the cytoskeleton and cell-adhesion apparatus occur in the esophageal epithelium in close relation with the cessation of INM and transition into the stratified squamous structure. 3 INM is the apicobasal (AB) cell polarity-based oscillatory movement of epithelial cell nuclei that is synchronized with the progression of the cell cycle, that is, the M-phase at the apical surface and S-phase at the basal side, and thus generates the pseudostratified structure of the epithelium. [4][5][6][7][8][9] It has been suggested that INM maximizes the number of mitoses at the limited apical surface to allow efficient stem/progenitor cell expansion.…”

“…We previously showed the existence of INM in the esophagus and trachea during E11.5-E12.0, and showed that INM ceases at an earlier time point in the esophagus, ranging from E13.0 to E14.0, while it continues until at least E14.0 in the trachea 3,12 as well as in other organs. [13][14][15] In the present study, using statistical analyses of the chronological change in the distribution pattern along the AB axis of the EdU-labeled epithelial nuclei, a method established in our previous series of studies, [12][13][14][15] we proved that there is a significant F I G U R E 8 EdU-positive nuclei distribution to examine a possible planar cell movement (PCM) in the E11.5 (A, B) and E12.5 esophagus (C, D).…”