DNA methyltransferases

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been conserved remarkably during evolution and is widely expressed in the mammalian brain. In Drosophila, mutation of the PACAP homologue results in behavioral defects, including impaired olfaction-associated learning and changes in ethanol sensitivity. Here, we report the generation of mice lacking the PACAP gene (PACAP ؊/؊ ). PACAP ؊/؊ mice were born in the expected Mendelian ratios but had a high early-mortality rate. The surviving adult PACAP ؊/؊ mice displayed remarkable behavioral changes; they exhibited hyperactive and explosive jumping behaviors in an open field, increased exploratory behavior, and less anxiety in the elevated plus maze, emergence, and novel-object tests. Analysis of PACAP ؊/؊ mice brains revealed that the serotonin metabolite 5-hydroxyindoleacetic acid was slightly decreased in the cortex and striatum compared with wild-type mice. The present study provides evidence that PACAP plays a previously uncharacterized role in the regulation of psychomotor behaviors. P ituitary adenylate cyclase-activating polypeptide (PACAP) is a member of the vasoactive intestinal peptide (VIP)͞ secretin͞glucagon family of peptides and exists in two amidated forms, PACAP38 and PACAP27, that share an identical 27-aa N terminus and are alternatively processed from a 176-aa precursor called preproPACAP (1, 2). The primary structure of PACAP38 has been conserved significantly during evolution from protochordates to mammals, suggesting that the peptide exerts important activities throughout the vertebrate phylum (1, 2). In Drosophila, recent molecular cloning and transgenic rescue experiments in the memory-mutant amnesiac, which has behavioral defects that include impaired olfaction-associated learning and changes in ethanol sensitivity, demonstrated that the amnesiac gene encodes a neuropeptide homologous to vertebrate PACAP (3, 4). In addition, mammalian PACAP activated both the cAMP and Ras͞Raf signal-transduction pathways in Drosophila neurons, suggesting a neuromodulatory role of amnesiac (Drosophila PACAP) in specific neuronal populations (5). In mammals, PACAP occurs in neuronal elements, where it acts as a pleiotropic neuropeptide via three heptahelical G protein-linked receptors-one PACAP-specific (PAC 1 ) receptor and two receptors that it shares with VIP (VPAC 1 and VPAC 2 ). PACAP stimulates several different signaling cascades in neurons, leading to the activation of adenylate cyclase, phospholipase C, and mitogen-activated protein kinase and the mobilization of calcium (1, 2, 6). Histochemical studies have shown that PACAP immunoreactivity is observed in several brain regions, including the dopamine (DA) and serotonin (5-HT) systems, with high concentrations found in the nucleus accumbens, hypothalamus, amygdala, substantia nigra, and dorsal raphe (7-9). PAC 1 receptor also is expressed throughout the target areas of both the mesocorticolimbic and nigrostriatal DA systems as well as 5-HT system (10). In addition, VPAC 1 and VPAC 2 recepto...

To identify the physiological functions of the retinoid-related orphan receptor ␥ (ROR␥), a member of the nuclear receptor superfamily, mice deficient in ROR␥ function were generated by targeted disruption. ROR␥ ؊/؊ mice lack peripheral and mesenteric lymph nodes and Peyer's patches, indicating that ROR␥ expression is indispensable for lymph node organogenesis. Although the spleen is enlarged, its architecture is normal. The number of peripheral blood CD3 ؉ and CD4 ؉ lymphocytes is reduced 6-and 10-fold, respectively, whereas the number of circulating B cells is normal. The thymus of ROR␥ ؊/؊ mice contains 74.4% ؎ 8.9% fewer thymocytes than that of wild-type mice. Flow cytometric analysis showed a decrease in the CD4 ؉ CD8 ؉ subpopulation. T he nuclear hormone receptor superfamily consists of structurally related, ligand-dependent transcription factors and a large number of orphan receptors for which the ligand has not yet been identified (1, 2). Nuclear receptors share a common modular structure composed of several domains that have functions in DNA binding, ligand binding, nuclear localization, dimerization, repression, and transactivation (3). Typically, the transactivation activity of nuclear receptors is controlled by small lipophilic molecules that bind to the receptor, thereby causing a conformational change in the receptor. This change in conformation causes dissociation of corepressor complexes and promotes interaction of the receptor with coactivators (4). The latter leads then to increased gene expression and consequently modulation of many physiological processes.The retinoid-related orphan receptors ROR␣, -␤, and -␥ constitute a subfamily of nuclear orphan receptors (5-11). Each of these receptors binds as a monomer to response elements (ROREs) consisting of the consensus core motif AGGTCA preceded by an A͞T-rich region (7, 12). RORs have been reported to play critical roles in a wide variety of biological processes (13,14). ROR␥ is highly expressed in thymus, kidney, liver, muscle, and brown fat but not in white fat tissue (6,7,10,15). In the thymus, two isoforms, ␥1 and ␥2 (also named ROR␥T), have been identified (15). The ␥2 differs from the ␥1 isoform in that it lacks the amino terminus of ␥1. The expression of the ␥2 isoform is highly restricted to the double-positive thymocytes, suggesting a regulatory role for ROR␥2 in these cells (15, 16). Recently, overexpression of ROR␥ in T-cell hybridomas has been shown to inhibit T cell antigen receptor (TCR)-activation-induced apoptosis by repressing the induction of Fas ligand (FasL) (15) (M.S., S.K., and A.M.J., unpublished observations).To investigate the biological role(s) of ROR␥ in vivo, we used homologous recombination in embryonic stem cells to generate mice in which the ROR␥ gene was disrupted. In this study, we show that ROR␥ Ϫ/Ϫ mice lack lymph nodes and Peyer's patches, suggesting that ROR␥ is essential for their development. In addition, we demonstrate that ROR␥ plays a critical role in thymopoiesis and T cell homeostasis. The rapid induct...