BRCA1 function in T lymphocytes: a cellular specificity of a different kind

Recent work by Mak et al demonstrates that mice carrying a T-cell-specific disruption of the brca1 gene display markedly impaired T-lymphocyte develop ment and proliferation in the absence of any increased tendency for the for mation of tumors. Interestingly, the extent of these defects was found to b e highly dependent on cellular context. Contrasting the rather broad tissue expression pattern of brca1 against its exquisitely selective etiologic ro le in cancers of the breast and ovary, many of us are left to ponder - wher e is the specificity?