title: Expression and localization of villin, fimbrin, and myosin I in differentiating mouse F9 teratocarcinoma cells.
abstract: F9 embryonic carcinoma cells are a multipotent cell line which can be induced to differentiate into cells resembling the visceral endoderm, an extraembryonic absorptive epithelium characterized by apical microvilli. We have examined the role of villin, fimbrin, and myosin I, the major actin-binding proteins in the intestinal and visceral yolk sac microvilli, in the development of epithelial polarity and the assembly of the microvillus cytoskeleton in differentiating F9 cells. By immunoblot analysis villin was first detected at 4 days of differentiation. Confocal microscopy localized villin at Day 4 to the apical surface and by Day 6 to the basolateral surfaces as well. In comparison, fimbrin and myosin I were both present in undifferentiated F9 cells and became associated with the apical surface after villin during differentiation to visceral endoderm. The accumulation of villin, fimbrin, and myosin I at the apical surface in differentiating F9 cells correlated with the appearance of microvilli containing organized actin filament bundles. Two mouse villin cDNAs were isolated and characterized to examine villin expression during F9 differentiation. Mouse villin was encoded by two transcripts (3.8 and 3.4 kb) which differ in their 3'-noncoding region. Both villin mRNAs were first detected by Day 4 of differentiation and their appearance coincided with expression of the visceral endoderm marker alpha-fetoprotein. The pattern of expression and order of accumulation of villin, fimbrin, and myosin I in differentiating F9 cells are common to developing gut and yolk sac epithelium. This suggests that microvillus assembly is directed by a sequence of temporally and spatially regulated localizations of these actin-binding proteins.
authors.affiliation: Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge 02142.
authors.forename: R M
authors.initials: RM
authors.lastname: Ezzell
authors.forename: J
authors.initials: J
authors.lastname: Leung
authors.forename: K
authors.initials: K
authors.lastname: Collins
authors.forename: M M
authors.initials: MM
authors.lastname: Chafel
authors.forename: T J
authors.initials: TJ
authors.lastname: Cardozo
authors.forename: P T
authors.initials: PT
authors.lastname: Matsudaira
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics* / Q000302:isolation & purification; D002449:Cell Aggregation; D002454:Cell Differentiation / Q000235:genetics; D003001:Cloning, Molecular; D005314:Embryonic and Fetal Development; D015972:Gene Expression Regulation, Neoplastic; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics* / Q000302:isolation & purification; D008871:Microvilli; D009218:Myosins / Q000235:genetics*; D013724:Teratoma / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; C026742:plastin; C026615:villin; D009218:Myosins