During mammalian gonadal development, nuclear import/export of the transcription factor SOX9 is a critical step of the Sry-initiated testis-determining cascade. In this study, we identify a molecular mechanism contributing to the SOX9 nuclear translocation in NT2/D1 cells, which is mediated by the prostaglandin D2 (PGD2) signalling pathway via stimulation of its adenylcyclase-coupled DP1 receptor. We find that activation of cAMP-dependent protein kinase A (PKA) induces phosphorylation of SOX9 on its two S64 and S181 PKA sites, and its nuclear localization by enhancing SOX9 binding to the nucleocytoplasmic transport protein importin b. Moreover, in embryonic gonads, we detect a male-specific prostaglandin D synthase expression and an active PGD2 signal at the time and place of SOX9 expression. We thus propose a new step in the sex-determining cascade where PGD2 acts as an autocrine factor inducing SOX9 nuclear translocation and subsequent Sertoli cell differentiation.

In mammals, male sex determination starts when the Y chromosome Sry gene is expressed within the undetermined male gonad. One of the earliest effect of Sry expression is to induce upregulation of Sox9 gene expression in the developing gonad. SOX9, like SRY, contains a high mobility group domain and is sufficient to induce testis differentiation in transgenic XX mice. Before sexual differentiation, SOX9 protein is initially found in the cytoplasm of undifferentiated gonads from both sexes. At the time of testis differentiation and anti-Mü llerian hormone expression, it becomes localized to the nuclear compartment in males whereas it is down-regulated in females. In this report, we used NIH 3T3 cells as a model to examine the regulation of SOX9 nucleo-cytoplasmic shuttling. SOX9-transfected cells expressed nuclear and cytoplasmic SOX9 whereas transfected cells treated with the nuclear export inhibitor leptomycin B, displayed an exclusive nuclear localization of SOX9. By using SOX9 deletion constructs in green fluorescent protein fusion proteins, we identified a functional nuclear export signal sequence between amino acids 134 and 147 of SOX9 high mobility group box. More strikingly, we show that inhibiting nuclear export with leptomycin B in mouse XX gonads cultured in vitro induced a sex reversal phenotype characterized by nuclear SOX9 and anti-Mü llerian hormone expression. These results indicate that SOX9 nuclear export signal is essential for SOX9 sexspecific subcellular localization and could be part of a regulatory switch repressing (in females) or triggering (in males) male-specific sexual differentiation. E xpression of Sry (1, 2) in the undetermined male gonad induces a variety of morphogenetic events including cell proliferation, cell migration, Sertoli cell fate determination, and subsequent sex cord formation (3-6). The earliest downstream effect of Sry may be up-regulation of Sox9 expression in the developing gonad (7), although it has yet to be shown at the molecular level. SOX9 is related to SRY by its high mobility group (HMG) domain. Interestingly, SOX9 is better conserved during evolution and, like SRY, is sufficient to induce testis differentiation in female transgenic mice (8). Furthermore, heterozygous mutations in SOX9 lead to campomelic dysplasia, a skeletal malformation syndrome associated with sex reversal in 75% of XY patients (9, 10).Immunofluorescence studies on mouse and human XX and XY embryo gonad sections revealed that cytoplasmic SOX9 protein is present in undifferentiated gonads of both sexes, but that in the male gonad it becomes nuclear at the onset of testis differentiation (7, 11). These results, together with the previous identification of two nuclear localization signal (NLS) sequences in the HMG box (12), let us to hypothesize that SOX9 is able to shuttle between the nucleus and the cytoplasm and thus may contain a nuclear export signal (NES). Prototypic NESs are short hydrophobic sequences rich in leucine residues (13-16) regulating the subcellular localization of several ...

X-linked congenital nephrogenic diabetes insipidus (cNDI) results from inactivating mutations of the human arginine vasopressin (AVP) V2 receptor (hV 2 R). Most of these mutations lead to intracellular retention of the hV 2 R, preventing its interaction with AVP and thereby limiting water reabsorption and concentration of urine. Because the majority of cNDI-hV 2 Rs exhibit protein misfolding, molecular chaperones hold promise as therapeutic agents; therefore, we sought to identify pharmacochaperones for hV 2 R that also acted as agonists. Here, we describe high-affinity nonpeptide compounds that promoted maturation and membrane rescue of L44P, A294P, and R337X cNDI mutants and restored a functional AVP-dependent cAMP signal. Contrary to pharmacochaperone antagonists, these compounds directly activated a cAMP signal upon binding to several cNDI mutants. In addition, these molecules displayed original functionally selective properties (biased agonism) toward the hV 2 R, being unable to recruit arrestin, trigger receptor internalization, or stimulate mitogen-activated protein kinases. These characteristics make these hV 2 R agonist pharmacochaperones promising therapeutic candidates for cNDI. The antidiuretic hormone arginine-vasopressin (AVP) is crucial for osmoregulation, cardiovascular control, and water homeostasis. The human AVP V 2 receptor (hV 2 R), localized in the principal cells of the kidney collecting duct, mediates AVP antidiuretic effect and therefore helps in maintaining physiologic plasma osmolality, blood volume, and arterial pressure. Binding of AVP to hV 2 R first triggers a cAMP signal through activation of the G protein ␣ s (Gs) subunit and adenylyl cyclase (AC). Then, the cAMP-activated protein kinase A phosphorylates aquaporin 2 water channels, resulting in their insertion into the luminal membrane of principal cells and finally to water reabsorption. 1 AVP binding to hV 2 R also induces arrestin recruitment, receptor internalization, 2 and mitogen-activated protein kinase (MAPK) activation. 3 Mutations in the hV 2 R gene lead to the X-linked congenital nephrogenic diabetes insipidus (cNDI), a rare disease characterized by the kidney's inability to concentrate urine despite normal or elevated plasma concentrations of AVP. 4 More than 200 different mutations have been described and are responsible for polyuria, a main consequence of the disease. Most of the mutant receptors (cNDIhV 2 Rs), trapped in the endoplasmic reticulum

SRY, a Y chromosome-encoded DNA-binding protein, is required for testis organogenesis in mammals. Expression of the SRY gene in the genital ridge is followed by diverse early cell events leading to Sertoli cell determination/differentiation and subsequent sex cord formation. Little is known about SRY regulation and its mode of action during testis development, and direct gene targets for SRY are still lacking. In this study, we demonstrate that interaction of the human SRY with histone acetyltransferase p300 induces the acetylation of SRY both in vitro and in vivo at a single conserved lysine residue. We show that acetylation participates in the nuclear localisation of SRY by increasing SRY interaction with importin b, while specific deacetylation by HDAC3 induces a cytoplasmic delocalisation of SRY. Finally, by analysing p300 and HDAC3 expression profiles during both human or mouse gonadal development, we suggest that acetylation and deacetylation of SRY may be important mechanisms for regulating SRY activity during mammalian sex determination.