p59^fyn-p125^FAK cooperation in Development of CD4⁺CD8⁺ Thymocytes

p59^fyn is an Src family nonreceptor tyrosine kinase that has been suggested to play an important role in T-cell development and function. p125^FAK is a unique nonreceptor tyrosine kinase and has been known to respond to integrin-extracellular matrix interactions. To examine their roles in thymocytes, heterozygous fak mutation was introduced into homozygous Fyn deficiency. The double mutation, but neither Fyn deficiency nor FAK heterozygosity alone, displayed impaired development of CD4⁺CD8⁺ thymocytes with atrophy of the thymic cortex, suggesting a unique cooperation between P59^fyn and p125^FAK in CD4⁺CD8⁺ T-cell development.