VINCULIN KNOCKOUT RESULTS IN HEART AND BRAIN DEFECTS DURING EMBRYONIC-DEVELOPMENT

The vinculin gene codes for a cytoskeletal protein, found in focal adh esion plaques and in cell-cell adherens junctions, Vinculin was inacti vated by homologous recombination using a targeting vector in embryoni c stem (ES) cells, The heterozygous ES cells were introduced into mice by established procedures to produce heterozygous animals that were n ormal and fertile, No homozygous vinculin(-/-) embryos were born and a nalyses during the gestational period showed that the vinculin null em bryos were small and abnormal from day E8 but some survived until E10, The most prominent defect was lack of midline fusion of the rostral n eural tube, producing a cranial bilobular appearance and attenuation o f cranial and spinal nerve development. Heart development was curtaile d at E9.5, with severely reduced and akinetic myocardial and endocardi al structures, Mutant embryos were 30-40% smaller, somites and limbs w ere retarded and ectodermal tissues were sparse and fragile, Fibroblas ts (MEF) isolated from mutant embryos were shown to have reduced adhes ion to fibronectin, vitronectin, laminin and collagen compared to wild -type levels, In addition, migration rates over these substrata were t wo-fold higher and the level of focal adhesion kinase (FAK) activity w as three-fold higher. We conclude that vinculin is necessary for norma l embryonic development, probably because of its role in the regulatio n of cell adhesion and locomotion, cell behaviors essential for normal embryonic morphogenesis, although specific roles in neural and cardia c development cannot be ruled out.