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?