The glucocorticoid receptor (Gr, encoded by the gene Grl1) controls transcription of target genes both directly by interaction with DNA regulatory elements and indirectly by cross-talk with other transcription factors. In response to various stimuli, including stress, glucocorticoids coordinate metabolic, endocrine, immune and nervous system responses and ensure an adequate profile of transcription. In the brain, Gr has been proposed to modulate emotional behaviour, cognitive functions and addictive states. Previously, these aspects were not studied in the absence of functional Gr because inactivation of Grl1 in mice causes lethality at birth (F.T., C.K. and G.S., unpublished data). Therefore, we generated tissue-specific mutations of this gene using the Cre/loxP -recombination system. This allowed us to generate viable adult mice with loss of Gr function in selected tissues. Loss of Gr function in the nervous system impairs hypothalamus-pituitary-adrenal (HPA)-axis regulation, resulting in increased glucocorticoid (GC) levels that lead to symptoms reminiscent of those observed in Cushing syndrome. Conditional mutagenesis of Gr in the nervous system provides genetic evidence for the importance of Gr signalling in emotional behaviour because mutant animals show an impaired behavioural response to stress and display reduced anxiety.

In mammals, the transcription factor SRY, encoded by the Y chromosome, is normally responsible for triggering the indifferent gonads to develop as testes rather than ovaries. However, testis differentiation can occur in its absence. Here we demonstrate in the mouse that a single factor, the forkhead transcriptional regulator FOXL2, is required to prevent transdifferentiation of an adult ovary to a testis. Inducible deletion of Foxl2 in adult ovarian follicles leads to immediate upregulation of testis-specific genes including the critical SRY target gene Sox9. Concordantly, reprogramming of granulosa and theca cell lineages into Sertoli-like and Leydig-like cell lineages occurs with testosterone levels comparable to those of normal XY male littermates. Our results show that maintenance of the ovarian phenotype is an active process throughout life. They might also have important medical implications for the understanding and treatment of some disorders of sexual development in children and premature menopause in women.

Human Blepharophimosis/ptosis/epicanthus inversus syndrome (BPES) type I is an autosomal dominant disorder associated with premature ovarian failure (POF)caused by mutations in FOXL2, a winged-helix/forkhead domain transcription factor. Although it has been shown that FOXL2 is expressed in adult ovaries, its function during folliculogenesis is not known. Here, we show that the murine Foxl2 gene is essential for granulosa cell differentiation and ovary maintenance. In Foxl2lacZ homozygous mutant ovaries granulosa cells do not complete the squamous to cuboidal transition leading to the absence of secondary follicles and oocyte atresia. We further demonstrate that activin-βA and anti-Mullerian inhibiting hormone expression is absent or strongly diminished in Foxl2lacZ homozygous mutant ovaries. Unexpectedly, two weeks after birth most if not all oocytes expressed Gdf9 in Foxl2lacZ homozygous mutant ovaries, indicating that nearly all primordial follicles have already initiated folliculogenesis at this stage. This activation, in the absence of functional granulosa cells, leads to oocyte atresia and progressive follicular depletion. In addition to providing a molecular mechanism for premature ovarian failure in BPES, these results suggest that granulosa cell function is not only crucial for oocyte growth but also to maintain follicular quiescence in vivo.

Nephronophthisis (NPHP), an autosomal recessive kidney disease, is the most frequent genetic cause of end-stage renal failure in the first three decades of life. Positional cloning of the six known NPHP genes has linked its pathogenesis to primary cilia function. Here we identify mutation of GLIS2 as causing an NPHP-like phenotype in humans and mice, using positional cloning and mouse transgenics, respectively. Kidneys of Glis2 mutant mice show severe renal atrophy and fibrosis starting at 8 weeks of age. Differential gene expression studies on Glis2 mutant kidneys demonstrate that genes promoting epithelial-to-mesenchymal transition and fibrosis are upregulated in the absence of Glis2. Thus, we identify Glis2 as a transcription factor mutated in NPHP and demonstrate its essential role for the maintenance of renal tissue architecture through prevention of apoptosis and fibrosis.

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