Adult pituitaries of Tg(Lhb-cre)1Sac; Rosa26LacZ reporter progeny (a) and non-transgenic (b) stained with X-gal. Staining is detectable in the adult anterior lobe of the Tg(Lhb-cre)1Sac;Rosa26LacZ reporter progeny (a, c-g) but not in the non-transgenic (b). Immunohistochemical staining of pituitary hormones shows colocalization of the X-gal staining with LHβ immunoreactivity (c), but very little or no colocalization with GH (d), POMC (e), PRL (f) or TSHβ immunoreactivity (g). Tg(Lhb-cre)1Sac; Rosa26LacZ embryos reveal the onset of transgene activity by X-gal staining in only one or two cells at e16.5 (h), and increased penetrance of X-gal staining comparable to normal LHβ expression at e17.5 (i) and e18.5 (j). Scale bars represent 10μm for panels c-g (100× magnification) and panels h-j (40× magnification).