Cre activation in adult mice was obtained by administrating tamoxifen twice at 3 weeks of age or twice a week for two weeks starting at 10 weeks of age. these genes results in AGP apoptosis and, as a consequence, agenesis of both gonads and adrenal glands (Kreidberg et al., 1993; Luo et al., 1994; Moore et al., 1999). Whereas both WT1 and SF1 are expressed in the AGP, WT1 is switched off within the adrenal primordium soon after separation (Moore et al., 1998; Vidal and Schedl, 2000). The functional significance of this repression is presently unknown. In the present study we identify WT1 as an essential player in defining AGP cell identity. We show that ectopic expression of the transcriptionally active WT1?KTS isoform is sufficient to prevent differentiation of AGP cells into steroidogenic cells by directly regulating the expression of genes such as and E15.5 embryos. Two cell populations can be distinguished in ?adrenal cortex (insets): WT1high, which have strong GATA4 and low SF1 expression (arrows); and WT1low, which instead have reduced or absent GATA4 and strong SF1 expression (arrowheads). Please note that the cytoplasmic WT1 staining in control adrenals represents background noise. me, mesonephros; ce, coelomic epithelium; ap, adrenal primordium, Co, adrenal cortex; Ca, adrenal capsule. See also Fig. S1. To understand the functional significance of repression during adrenocortical differentiation, we generated mice that permit Cre-mediated activation of WT1 + or ?KTS isoforms in a tissue specific fashion (and lines fig S1A, B). Genetic crosses with the line (Bingham et al., 2006), a transgenic line expressing high levels of CRE within the steroidogenic compartment, resulted in activation of WT1 in the developing adrenal cortex as early as E12.5 (fig. Setiptiline S1C). Heterozygous and embryos developed normal adrenal glands (data not shown). Since is known to be a relatively weak promoter, we crossed the targeted allele to the homozygous state to further increase transgene expression levels. Homozygous embryos (from now on called mice (from now on called mice (fig S1C). Later in development, two subtypes of cells Rabbit Polyclonal to ATP2A1 became apparent that were distinguished by the levels of WT1 expression, perhaps as a result Setiptiline of stochastic/epigenetic factors. WT1high cells (high levels of WT1) showed ectopic activation of GATA4, but exhibited low levels of SF1 (fig. 1E, animals were smaller than controls (table S1) and displayed cortical spindle-shaped cells, effectively dividing the cortex into lobular structures (fig. 2A). In each lobule the zonation of the gland was grossly conserved, as indicated by the expression of the general steroidogenic enzyme 3-HSD2, and the marker AKR1b7 (fig.S2A). The only affected adrenocortical area was the X-zone, which was Setiptiline dramatically reduced in ?mice (fig. S2B). Despite the severe morphological changes, the adrenal glands from ?animals appeared to be functional and transgenic animals showed normal circulating levels of corticosterone (fig. S2C). Expression levels of the main enzymes involved in steroidogenesis were also comparable to those found in control animals (fig. S2E). Maintenance of steroid production was likely achieved through raised ACTH levels in ?mice (fig. S2C). ACTH is known to stimulate the expression of steroidogenic enzymes, and indeed increased cellular staining for AKR1b7 and 3-HSD2 (fig. S2A) and could be observed (fig. S1E) together with Setiptiline a mild increase in steroidogenic cell size (fig. S2D). Open in a separate window Fig. 2 Cells ectopically expressing WT1-KTS are blocked in an AGP-like state throughout life(A) Haematoxylin and eosin staining of adrenals from wild type, + and ?adult mice. Arrows indicate capsular-like cells within the adrenal cortex of ?animals. (B) Immunostaining against WT1 (red) and SF1 (green) on adrenals from wild type, + and ?adult mice shows the persistence of WT1+ expressing cells within the adrenal cortex of ?and mice. (C) Immunostaining for WT1 (green) and SF1 (red) on adult adrenal glands reveals the presence.