Targeted deletion of beta 1 integrins in F9 embryonal carcinoma cells affects morphological differentiation but not tissue-specific gene expression.
The integrin superfamily of heterodimeric transmembrane adhesion receptors mediates many cell-cell and cell-matrix interactions whose functions are believed to be critical for normal morphogenesis and differentiation. By eliminating the beta 1 integrin gene through homologous recombination, we have assessed the role of the beta 1 integrin family in the F9 embryonal carcinoma model for endodermal differentiation. F9 cells were unexpectedly found to maintain three copies of the beta 1 gene and complete elimination required three sequential rounds of targeting to generate triple knockout lines (beta 1 TKO). Elimination of the beta 1 integrin family of adhesion receptors from F9 cells resulted in reduced adhesion to fibronectin, laminin and collagen, but strongly enhanced adhesion to vitronectin. The absence of beta 1 integrins did not promote significant compensatory upregulation of either beta 3 or beta 5 subunits, both of which are known to act as vitronectin receptors when associated with alpha v. The loss of beta 1 integrins severely affected morphological differentiation when the beta 1-deficient cells were induced to differentiate to either parietal or visceral endoderm. Parietal endoderm derived from beta 1-deficient cells retained a rounded morphology and migrated poorly on both fibronectin and vitronectin. Visceral endoderm derived from beta 1-deficient cells were also unable to form a normal, confluent epithelial monolayer; instead, a non-contiguous layer containing clumps of disorganized cells was observed. However, loss of beta 1 integrins did not interfere with induction by differentiating agents of tissue-specific gene products for either visceral or parietal endoderm. These results suggest that beta 1 integrins mediate morphological differentiation (migration and epithelial formation) but not tissue-specific gene expression in induced F9 cells, and that these two processes are not necessarily linked in this system.
Stephens
L E
LE
Department of Stomatology, University of California San Francisco 94143-0512.
Sonne
J E
JE
Fitzgerald
M L
ML
Damsky
C H
CH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018236:Carcinoma, Embryonal / Q000473:pathology*; D002448:Cell Adhesion; D002454:Cell Differentiation; D002465:Cell Movement; D003094:Collagen / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D005353:Fibronectins / Q000378:metabolism; D015870:Gene Expression; D006023:Glycoproteins / Q000378:metabolism; D066298:In Vitro Techniques; D016023:Integrins / Q000502:physiology*; D007797:Laminin / Q000378:metabolism; D016256:Lewis X Antigen / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009024:Morphogenesis; D016254:Mutagenesis, Insertional; D009842:Oligopeptides; D012333:RNA, Messenger / Q000235:genetics; D014407:Tumor Cells, Cultured; D019096:Vitronectin; D000509:alpha-Fetoproteins / Q000235:genetics
D017931:DNA Primers; D005353:Fibronectins; D006023:Glycoproteins; D016023:Integrins; D007797:Laminin; D016256:Lewis X Antigen; D009842:Oligopeptides; D012333:RNA, Messenger; D019096:Vitronectin; D000509:alpha-Fetoproteins; C047981:arginyl-glycyl-aspartic acid; D003094:Collagen