Conditional deletion of focal adhesion kinase leads to defects in ventricular septation and outflow tract alignment.
To examine a role for focal adhesion kinase (FAK) in cardiac morphogenesis, we generated a line of mice with a conditional deletion of FAK in nkx2-5-expressing cells (herein termed FAKnk mice). FAKnk mice died shortly after birth, likely resulting from a profound subaortic ventricular septal defect and associated malalignment of the outflow tract. Additional less penetrant phenotypes included persistent truncus arteriosus and thickened valve leaflets. Thus, conditional inactivation of FAK in nkx2-5-expressing cells leads to the most common congenital heart defect that is also a subset of abnormalities associated with tetralogy of Fallot and the DiGeorge syndrome. No significant differences in proliferation or apoptosis between control and FAKnk hearts were observed. However, decreased myocardialization was observed for the conal ridges of the proximal outflow tract in FAKnk hearts. Interestingly, chemotaxis was significantly attenuated in isolated FAK-null cardiomyocytes in comparison to genetic controls, and these effects were concomitant with reduced tyrosine phosphorylation of Crk-associated substrate (CAS). Thus, it is possible that ventricular septation and appropriate outflow tract alignment is dependent, at least in part, upon FAK-dependent CAS activation and subsequent induction of polarized myocyte movement into the conal ridges. Future studies will be necessary to determine the precise contributions of the additional nkx2-5-derived lineages to the phenotypes observed.
Hakim
Zeenat S
ZS
Department of Pathology and Carolina Cardiovascular Biology Center, 501 Brinkhous-Bullitt Bldg. CB 7525, University of North Carolina, Chapel Hill, NC 27599, USA.
DiMichele
Laura A
LA
Doherty
Jason T
JT
Homeister
Jonathon W
JW
Beggs
Hilary E
HE
Reichardt
Louis F
LF
Schwartz
Robert J
RJ
Brackhan
Joseph
J
Smithies
Oliver
O
Mack
Christopher P
CP
Taylor
Joan M
JM
D000818:Animals; D002465:Cell Movement; D049109:Cell Proliferation; D002470:Cell Survival; D050719:Crk-Associated Substrate Protein / Q000378:metabolism; D004622:Embryo, Mammalian / Q000002:abnormalities / Q000201:enzymology; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000172:deficiency*; D017353:Gene Deletion; D006330:Heart Defects, Congenital / Q000201:enzymology*; D006352:Heart Ventricles / Q000002:abnormalities* / Q000033:anatomy & histology* / Q000196:embryology / Q000201:enzymology; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D009024:Morphogenesis; D032383:Myocytes, Cardiac / Q000473:pathology; D009210:Myofibrils / Q000473:pathology; D010641:Phenotype; D010766:Phosphorylation; D014157:Transcription Factors / Q000378:metabolism
D050719:Crk-Associated Substrate Protein; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C484469:Nkx2-5 protein, mouse; D014157:Transcription Factors; D051416:Focal Adhesion Protein-Tyrosine Kinases