ThePIP5K2AandRGS4genes are differentially associated with deficit and non-deficit schizophrenia

Several putative schizophrenia susceptibility genes have recently been reported, but it is not clear whether these genes are associated with schizophrenia in general or with specific disease subtypes. In a previous study, we found an association of the neuregulin 1 (NRG1) gene with non-deficit schizophrenia only. We now report an association study of four schizophrenia candidate genes in patients with and without deficit schizophrenia, which is characterized by severe and enduring negative symptoms. Single-nucleotide polymorphisms (SNPs) were genotyped in the DTNBP1 (dysbindin), G72/G30 and RGS4 genes, and the relatively unknown PIP5K2A gene, which is located in a region of linkage with both schizophrenia and bipolar disorder. The sample consisted of 273 Dutch schizophrenia patients, 146 of whom were diagnosed with deficit schizophrenia and 580 controls. The strongest evidence for association was found for the A-allele of SNP rs10828317 in the PIP5K2A gene, which was associated with both clinical subtypes (P = 0.0004 in the entire group; non-deficit P = 0.016, deficit P = 0.002). Interestingly, this SNP leads to a change in protein composition. In RGS4, the G-allele of the previously reported SNP RGS4-1 (single and as part of haplotypes with SNP RGS4-18) was associated with non-deficit schizophrenia (P = 0.03) but not with deficit schizophrenia (P = 0.79). SNPs in the DTNBP1 and G72/G30 genes were not significantly associated in any group. In conclusion, our data provide further evidence that specific genes may be involved in different schizophrenia subtypes and suggest that the PIP5K2A gene deserves further study as a general susceptibility gene for schizophrenia.

Effects of mutations in the GanB/RgsA G protein mediated signalling on the autolysis of Aspergillus nidulans

Physiological changes taking place in carbon-starved, autolysing cultures of Aspergillus (Emericella) nidulans strains with mutations in the GanB/RgsA heterotrimeric G protein signalling pathway were studied and compared. Deletion of the ganB, rgsA or both genes did not alter markedly either the autolytic loss of biomass or the extracellular chitinase production. However, they caused a significant decrease in the proteinase formation, which was detected by measuring both extracellular enzyme activity and the transcription of the prtA gene. The deletion mutants also showed significantly higher specific gamma -glutamyltranspeptidase activities than the control strain. Deletion of the rgsA gene affected the glutathione peroxidase and catalase formation, as well as the peroxide content of the cells. The concomitant initiations of cell death and developmental genomic programmes may be interconnected via heterotrimeric G-protein signalling and subsequent changes in intracellular ROS levels in ageing A. nidulans.

C. elegans G protein regulator RGS-3 controls sensitivity to sensory stimuli

Signal transduction through heterotrimeric G proteins is critical for sensory response across species. Regulator of G protein signaling (RGS) proteins are negative regulators of signal transduction. Herein we describe a role for C. elegans RGS-3 in the regulation of sensory behaviors. rgs-3 mutant animals fail to respond to intense sensory stimuli but respond normally to low concentrations of specific odorants. We find that loss of RGS-3 leads to aberrantly increased G protein-coupled calcium signaling but decreased synaptic output, ultimately leading to behavioral defects. Thus, rgs-3 responses are restored by decreasing G protein-coupled signal transduction, either genetically or by exogenous dopamine, by expressing a calcium-binding protein to buffer calcium levels in sensory neurons or by enhancing glutamatergic synaptic transmission from sensory neurons. Therefore, while RGS proteins generally act to downregulate signaling, loss of a specific RGS protein in sensory neurons can lead to defective responses to external stimuli.

The expression patterns of RGS transcripts in platelets

Regulators of G protein signalling (RGS) are involved in the negative regulation of cell activation processes and are involved in the pathophysiology of cardiovascular diseases. To get some further evidence for a role of RGS proteins in platelets, we determined the expression profile of RGS-specific mRNA in rat platelets using reverse transcription-polymerase chain reaction (RT-PCR) with a poly dT18 primer and transcript-specific primers. We found that RGS2, RGS3, RGS5, RGS6, RGS10, RGS14, RGS16 and RGS18, Leukemia-associated Rho-GEF factor (LARG), and Galpha interacting protein (GAIP) were differentially expressed in platelets. The highest expression rate was found for RGS18 (about 1.3 fold when compared to GAPDH), followed by LARG, RGS6, RGS10 and RGS16 (0.7 to 0.95), whereas expression rates for RGS2, RGS3, RGS5, RGS14, and GAIP were in a range of 0.1 to 0.3. Our results suggest that G-protein-coupled receptor-mediated signalling in platelet may be regulated mainly by RGS 18, 16, 10, 6, and LARG.

Multiple genes for essential-hypertension susceptibility on chromosome 1q

Essential hypertension, defined as elevated levels of blood pressure (BP) without any obvious cause, is a major risk factor for coronary heart disease, stroke, and renal disease. BP levels and susceptibility to development of essential hypertension are partially determined by genetic factors that are poorly understood. Similar to other efforts to understand complex, non-Mendelian phenotypes, genetic dissection of hypertension-related traits employs genomewide linkage analyses of families and association studies of patient cohorts, to uncover rare and common disease alleles, respectively. Family-based mapping studies of elevated BP cover the large intermediate ground for identification of genes with common variants of significant effect. Our genomewide linkage and candidate-gene-based association studies demonstrate that a replicated linkage peak for BP regulation on human chromosome 1q, homologous to mouse and rat quantitative trait loci for BP, contains at least three genes associated with BP levels in multiple samples: ATP1B1, RGS5, and SELE. Individual variants in these three genes account for 2-5-mm Hg differences in mean systolic BP levels, and the cumulative effect reaches 8-10 mm Hg. Because the associated alleles in these genes are relatively common (frequency >5%), these three genes are important contributors to elevated BP in the population at large.

Active Galpha(q) subunits and M3 acetylcholine receptors promote distinct modes of association of RGS2 with the plasma membrane

RGS proteins accelerate the GTPase activity of heterotrimeric G proteins at the plasma membrane. Association of RGS proteins with the plasma membrane can be mediated by interactions with other membrane proteins and by direct interactions with the lipid bilayer. Here we use fluorescence recovery after photobleaching (FRAP) to characterize interactions between RGS2 and M3 acetylcholine receptors (M3Rs), Galpha subunits and the lipid bilayer. Active Galpha(q) and M3Rs both recruited RGS2-EGFP to the plasma membrane. RGS2-EGFP remained bound to the plasma membrane between interactions with active Galpha(q), but rapidly exchanged between membrane-associated and cytosolic pools when recruited by M3Rs.

Rgs1 regulates multiple Galpha subunits in Magnaporthe pathogenesis, asexual growth and thigmotropism

Regulators of G-protein signaling (RGS proteins) negatively regulate heterotrimeric G-protein cascades that enable eukaryotic cells to perceive and respond to external stimuli. The rice-blast fungus Magnaporthe grisea forms specialized infection structures called appressoria in response to inductive surface cues. We isolated Magnaporthe RGS1 in a screen for mutants that form precocious appressoria on non-inductive surfaces. We report that a thigmotropic cue is necessary for initiating appressoria and for accumulating cAMP. Similar to an RGS1-deletion strain, magA(G187S) (RGS-insensitive Galpha(s)) and magA(Q208L) (GTPase-dead) mutants accumulated excessive cAMP and elaborated appressoria on non-inductive surfaces, suggesting that Rgs1 regulates MagA during pathogenesis. Rgs1 was also found to negatively regulate the Galpha(i) subunit MagB during asexual development. Deficiency of MAGB suppressed the hyper-conidiation defect in RGS1-deletion strain, whereas magB(G183S) and magB(Q204L) mutants produced more conidia, similar to the RGS1-deletion strain. Rgs1 physically interacted with GDP.AlF(4)(-)-activated forms of MagA, MagB and MagC (a Galpha(II) subunit). Thus, Rgs1 serves as a negative regulator of all Galpha subunits in Magnaporthe and controls important developmental events during asexual and pathogenic development.

N-terminal residues control proteasomal degradation of RGS2, RGS4, and RGS5 in human embryonic kidney 293 cells

Regulator of G protein signaling (RGS) proteins modulate G protein-coupled receptor (GPCR) signaling. The N termini of some RGS4-family proteins provide receptor specificity and also contain an N-end rule determinant that results in ubiquitylation and decreased protein expression. The relevance of these mechanisms to other RGS proteins is not fully understood. Thus we examined function, receptor specificity, and expression of R4 subfamily RGS proteins (RGS2, -3, -4, -5, and -8). Although the N terminus plays a key role in protein stability in human embryonic kidney (HEK) 293 cells, we were unable to demonstrate specificity of RGS2, -3, -4, -5, or -8 for muscarinic receptors (M(1), M(3), and M(5)). However, cellular RGS activity (8 = 3 > 2) was strongly correlated with expression; RGS4 and -5 had minimal expression and activity. Stabilizing mutations of RGS4 and -5 (C2S) enhanced expression and function with a greater influence on RGS4 than on RGS5. We were surprised to find that a predicted destabilizing mutation in RGS8 (A2C) did not markedly affect expression and had no effect on function. In contrast, a destabilizing mutation in RGS2 (RGS2-Q2L) recently identified as a rare N-terminal genetic variant in a Japanese hypertensive cohort (J Hypertens 23:1497-1505, 2005) showed significantly reduced expression and inhibition of angiotensin II (AT(1)) receptor-stimulated accumulation of inositol phosphates. We were surprised to find that RGS2-Q2R, also predicted to be destabilizing, showed nearly normal expression and function. Thus, proteasomal regulation of RGS expression in HEK293 cells strongly controls RGS function and a novel RGS2 mutation with decreased protein expression could be relevant to the pathophysiology of hypertension in humans.

RGS4 is not a susceptibility gene for schizophrenia in Japanese: association study in a large case-control population

The regulator of the G-protein signaling 4 (RGS4) has been implicated in the susceptibility to schizophrenia. RGS4 interacts with ErbB3 that acts as receptors for neuregulin 1 and these proteins may play a role in the pathogenesis of schizophrenia via glutamatergic dysfunction. Recently, two meta-analysis studies provided different interpretations for the genetic association between RGS4 and schizophrenia. We attempted to confirm this association in a case-control study of 1918 Japanese patients with schizophrenia and 1909 Japanese control subjects. Four widely studied single nucleotide polymorphisms (SNPs) were genotyped, and none showed association with schizophrenia. SNP 1 (rs10917670), p=0.92; SNP 4 (rs951436), p=0.91; SNP 7 (rs951439), p=0.27; and SNP 18 (rs2661319), p=0.43. A haplotype block constructed by these SNPs spans the 5' flanking region to the 5' mid-region of the RGS4 gene. Previous meta-analysis showed that both two major haplotypes of this block were risk haplotypes. The two common haplotypes were observed in the Japanese population. However, neither haplotype was significantly associated with schizophrenia. We conclude that the common haplotypes and SNPs of the RGS4 gene identified thus far are unlikely to contribute to the genetic susceptibility to schizophrenia in the Japanese population.

Altered expression of regulator of G-protein signalling 4 (RGS4) mRNA in the superior temporal gyrus in schizophrenia

To identify altered mRNA expression of regulator of G-protein signalling 4 (RGS4) in the superior temporal gyrus (STG) in schizophrenia mRNA expression of RGS4 was measured from post-mortem STG tissue from 13 individuals with schizophrenia and 13 matched non-psychiatric controls using relative real-time PCR. Significantly decreased expression of RGS4 mRNA in the STG in schizophrenia was identified in 10 of the 13 matched pairs. Altered expression of RGS4 in cortical regions previously implicated in schizophrenia, such as the STG further supports the notion of RGS4 as a potential genetic and functional biological marker of schizophrenia.

Differential effects of RGS proteins on Gαq and Gα11 activity

Heterotrimeric G proteins play a pivotal role in GPCR signalling; they link receptors to intracellular effectors and their inactivation by RGS proteins is a key factor in resetting the pathway following stimulation. The precise GPCR:G protein:RGS combination determines the nature and duration of the response. Investigating the activity of particular combinations is difficult in cells which contain multiples of each component. We have therefore utilised a previously characterised yeast system to express mammalian proteins in isolation. Human G alpha(q) and G alpha(11) spontaneously activated the yeast pheromone-response pathway by a mechanism which required the formation of G alpha-GTP. This provided an assay for the specific activity of human RGS proteins. RGS1, RGS2, RGS3 and RGS4 inhibited the spontaneous activity of both G alpha(q) and G alpha(11) but, in contrast, RGS5 and RGS16 were much less effective against G alpha(11) than G alpha(q). Interestingly, RGS2 and RGS3 were able to inhibit signalling from the constitutively active G alpha(q)QL/G alpha(11)QL mutants, confirming the GAP-independent activity of these RGS proteins. To determine if the RGS-G alpha specificity was maintained under conditions of GPCR stimulation, minor modifications to the C-terminus of G alpha(q)/G alpha(11) enabled coupling to an endogenous receptor. RGS2 and RGS3 were effective inhibitors of both G alpha subunits even at high levels of receptor stimulation, emphasising their GAP-independent activity. At low levels of stimulation RGS5 and RGS16 retained their differential G alpha activity, further highlighting that RGS proteins can discriminate between two very closely related G alpha subunits.

RGS12 is essential for RANKL-evoked signaling for terminal differentiation of osteoclasts in vitro

How RANKL evokes [Ca(2+)](i) oscillations and leads to osteoclast differentiation is unclear. We identified a new signaling protein, RGS12, and found that RGS12 is essential for [Ca(2+)](i) oscillations and osteoclast differentiation induced by RANKL. RGS12 may play a critical role in the RANKL-evoked PLCgamma-calcium channels-[Ca(2+)](i) oscillation-NFAT2 pathway.

INTRODUCTION

RANKL-induced [Ca(2+)](i) oscillations play a switch-on role in NFAT2 expression and osteoclast differentiation. However, RANKL evokes [Ca(2+)](i) oscillations and leads to osteoclast differentiation by an unknown mechanism. In this study, we identified a new RANKL-induced signaling protein, regulator of G signaling protein 12 (RGS12), and investigated its effect on osteoclast differentiation in vitro.

MATERIALS AND METHODS

We used a genome-wide screening approach to identify genes that are specifically or prominently expressed in osteoclasts. To study the role of the RGS12 in osteoclast differentiation, we used vector and lentivirus-based RNAi gene silencing technology to silence the RGS12 gene in the monocyte progenitor cell lines and primary bone marrow-derived monocytes (BMMs). The interaction between RGS12 and N-type calcium channels was elucidated using co-immunoprecipitation and immunoblotting.

RESULTS

We found that RGS12 was prominently expressed in osteoclast-like cells (OLCs) induced by RANKL. This result was further confirmed at both the mRNA and protein level in human osteoclasts and mouse OLCs. Silence of RGS12 expression using vector and lentivirus based RNA interference (RNAi) impaired phosphorylation of phospholipase C (PLC)gamma and blocked [Ca(2+)](i) oscillations, NFAT2 expression, and osteoclast differentiation in RANKL-induced RAW264.7 cells and BMMs. We further found that N-type calcium channels were expressed in OLCs after RANKL stimulation and that RGS12 directly interacted with the N-type calcium channels.

CONCLUSIONS

These results reveal that RGS12 is essential for the terminal differentiation of osteoclasts induced by RANKL. It is possible that RGS12 regulates osteoclast differentiation through a PLC gamma-calcium channel-[Ca(2+)](i) oscillation-NFAT2 pathway.

The membrane anchor R7BP controls the proteolytic stability of the striatal specific RGS protein, RGS9-2

A member of the RGS (regulators of G protein signaling) family, RGS9-2 is a critical regulator of G protein signaling pathways that control locomotion and reward signaling in the brain. RGS9-2 is specifically expressed in striatal neurons where it forms complexes with its newly discovered partner, R7BP (R7 family binding protein). Interaction with R7BP is important for the subcellular targeting of RGS9-2, which in native neurons is found in plasma membrane and its specializations, postsynaptic densities. Here we report that R7BP plays an additional important role in determining proteolytic stability of RGS9-2. We have found that co-expression with R7BP dramatically elevates the levels of RGS9-2 and its constitutive subunit, Gbeta5. Measurement of the RGS9-2 degradation kinetics in cells indicates that R7BP markedly reduces the rate of RGS9-2.Gbeta5 proteolysis. Lentivirus-mediated RNA interference knockdown of the R7BP expression in native striatal neurons results in the corresponding decrease in RGS9-2 protein levels. Analysis of the molecular determinants that mediate R7BP/RGS9-2 binding to result in proteolytic protection have identified that the binding site for R7BP in RGS proteins is formed by pairing of the DEP (Disheveled, EGL-10, Pleckstrin) domain with the R7H (R7 homology), a domain of previously unknown function that interacts with four putative alpha-helices of the R7BP core. These findings provide a mechanism for the regulation of the RGS9 protein stability in the striatal neurons.

Bipolar 1 disorder is not associated with the RGS4, PRODH, COMT and GRK3 genes

Although current psychiatric nosology separates bipolar disorder and schizophrenia into non-overlapping categories, there is growing evidence of a partial aetiological overlap between them from linkage, genetic epidemiology and molecular genetics studies. Thus, it is important to determine whether genes implicated in the aetiology of schizophrenia play a role in bipolar disorder, and vice versa. In this study we investigated a total of 15 single nucleotide polymorphisms (SNPs), and all possible haplotypes, of genes that have been previously implicated in schizophrenia or bipolar disorder - RGS4, PRODH, COMT and GRK3 - in a sample of 213 cases with bipolar affective disorder type 1 and 197 controls from Scotland. We analysed the polymorphisms allele-wise, genotype-wise and, for each gene, haplotype-wise but obtained no result that reached nominal significance (p<0.05) for an association with the disease status. In conclusion, we could not find evidence of association between RGS4, PRODH, COMT and GRK3 genes and bipolar affective disorder 1 in the Scottish population.

Alternative splicing of RGS8 gene changes the binding property to the M1 muscarinic receptor to confer receptor type-specific Gq regulation

RGS proteins constitute a large family that modulates heterotrimeric G-protein signaling. We previously showed that RGS8 suppressed Gq signaling in a receptor type-specific manner. To elucidate molecular mechanisms underlying receptor-specific attenuation by RGS8, we examined whether RGS8 can interact with certain G-protein-coupled receptors. By pull-down assay, we showed that RGS8 directly binds to the third intracellular (i3) loop of M1 and M3 muscarinic acetylcholine receptors (mAChRs). The binding of RGS8S, a splice variant with a different N-terminus, was weaker. RGS8 could bind specifically to the C-terminal part of M1i3 (containing amino acids of 304-353 of i3 of human M1-mAChR), but RGS8S could not. Moreover, deletion of the N-terminal 9 amino acids and substitution of both Arg-8 and Arg-9 of RGS8 with Ala resulted in reduced binding to M1i3. BRET experiments revealed that RGS8 actually interacts with M1-mAChR, but RGS8S does not interact in the living cells. The RGS8 mutant, which had less binding ability to M1i3, showed a reduced inhibitory function of Gq signaling through M1-mAChR. These results demonstrated that RGS8 can directly interact with M1-mAChR via its N-terminus and the i3 loop of the receptor, and this binding must play an essential role in receptor-specific suppression by RGS8.

How regulators of G protein signaling achieve selective regulation

The regulators of G protein signaling (RGS) are a family of cellular proteins that play an essential regulatory role in G protein-mediated signal transduction. There are multiple RGS subfamilies consisting of over 20 different RGS proteins. They are basically the guanosine triphosphatase (GTPase)-accelerating proteins that specifically interact with G protein alpha subunits. RGS proteins display remarkable selectivity and specificity in their regulation of receptors, ion channels, and other G protein-mediated physiological events. The molecular and cellular mechanisms underlying such selectivity are complex and cooperate at many different levels. Recent research data have provided strong evidence that the spatiotemporal-specific expression of RGS proteins and their target components, as well as the specific protein-protein recognition and interaction through their characteristic structural domains and functional motifs, are determinants for RGS selectivity and specificity. Other molecular mechanisms, such as alternative splicing and scaffold proteins, also significantly contribute to RGS selectivity. To pursue a thorough understanding of the mechanisms of RGS selective regulation will be of great significance for the advancement of our knowledge of molecular and cellular signal transduction.

DEP domains: More than just membrane anchors

The DEP domain is present in a number of signaling molecules, including Regulator of G protein Signaling (RGS) proteins, and has been implicated in membrane targeting. New findings in yeast, however, demonstrate a major role for a DEP domain in mediating the interaction of an RGS protein to the C-terminal tail of a GPCR, thus placing RGS in close proximity with its substrate G protein alpha subunit.

RGS3 and RGS4 Differentially Associate with G Protein-coupled Receptor-Kir3 Channel Signaling Complexes Revealing Two Modes of RGS Modulation

RGS3 and RGS4 are GTPase-activating proteins expressed in the brain and heart that accelerate the termination of G(i/o)- and G(q)-mediated signaling. We report here the determinants mediating selective association of RGS4 with several G protein-coupled receptors (GPCRs) that form macromolecular complexes with neuronal G protein-gated inwardly rectifying potassium (Kir3 or GIRK) channels. Kir3 channels are instrumental in regulating neuronal firing in the central and peripheral nervous system and pacemaker activity in the heart. By using an epitope-tagged degradation-resistant RGS4 mutant, RGS4(C2V), immunoprecipitation of several hemagglutinin-tagged G(i/o)-coupled and G(q)-coupled receptors expressed in Chinese hamster ovary (CHO-K1) cells readily co-precipitated both Kir3.1/Kir3.2a channels and RGS4(C2V). In contrast to RGS4(C2V), the closely related and functionally active RGS3 "short" isoform (RGS3s) did not interact with any of the GPCR-Kir3 channel complexes examined. Deletion and chimeric RGS constructs indicate both the N-terminal domain and the RGS domain of RGS4(C2V) are necessary for association with m2 receptor-Kir3.1/Kir3.2a channel complexes, where the GPCR was found to be the major target for RGS4(C2V) interaction. The functional impact of RGS4(C2V) "precoupling" to the GPCR-Kir3 channel complex versus RGS3s "collision coupling" was a 100-fold greater potency in the acceleration of G protein-dependent Kir3 channel-gating kinetics with no attenuation in current amplitude. These findings demonstrate that RGS4, a highly regulated modulator and susceptibility gene for schizophrenia, can directly associate with multiple GPCR-Kir3 channel complexes and may affect a wide range of neurotransmitter-mediated inhibitory and excitatory events in the nervous and cardiovascular systems.

[Construction and verification of bait protein RGS4-fusion expression plasmid in yeast two-hybrid system]

OBJECTIVE

To research the interaction between glucocorticosteroid receptor domains and regulator of G protein signaling 4 (RGS4) protein.

METHODS

The RGS4 gene was used as the bait protein gene to construct the fusion bait expression plasmid of yeast two-hybrid. The whole encoding sequence of RGS4 gene was amplified by RT-PCR method. With confirmed by electrophoresis, the RGS4 gene was cloned into the MCS of the plasmid pGBKT7 to form a recombinant plasmid pGBKT7-RGS4 and the sequence of the recombinant plasmid was sequenced. According to the protocol of yeast two-hybrid system gold III, the competent Y187 yeast was prepared and transformed with recombinant plasmid pGBKT7-RGS4. Following that, the toxicity and autonomous activation of this recombinant plasmid pGBKT7-RGS4 in Y187 yeast were tested. In the end, we verified the normal expression of the RGS4 fusion protein in vitro by TNT system and in vivo by Weston blot.

RESULTS

The sequence of the recombinant plasmid was verified to be correct, as compared with the sequence provided by GenBank. The protein could be correctly synthesized in vivo, and no autonomous activation and toxicity was observed in Y187 yeast.

CONCLUSIONS

The recombinant plasmid may be used as the fusion bait plasmid in yeast two-hybrid system III, and the recombinant RGS4 fusion protein can be used as the bait protein successfully.

Disrupted motor learning and long-term synaptic plasticity in mice lacking NMDAR1 in the striatum

Much research has implicated the striatum in motor learning, but the underlying mechanisms have not been identified. Although NMDA receptor (NMDAR)-dependent long-term potentiation has been observed in the striatum, its involvement in motor learning remains unclear. To examine the role of striatal NMDAR in motor learning, we created striatum-specific NMDAR1 subunit knockout mice, analyzed the striatal anatomy and neuronal morphology of these mice, evaluated their performance on well established motor tasks, and performed electrophysiological recordings to assay striatal NMDAR function and long-term synaptic plasticity. Our results show that deleting the NMDAR1 subunit of the NMDAR specifically in the striatum, which virtually abolished NMDAR-mediated currents, resulted in only small changes in striatal neuronal morphology but severely impaired motor learning and disrupted dorsal striatal long-term potentiation and ventral striatal long-term depression.

Differentially expressed genes in the rat cochlear nucleus

The cochlear nucleus is the first central pathway involved in the processing of peripheral auditory activity. The anterior ventral cochlear nucleus (AVCN), posterior ventral cochlear nucleus (PVCN) and dorsal cochlear nucleus (DCN) each contain predominant populations of neurons that have been well characterized regarding their morphological and electrophysiological properties. Little is known, however, of the underlying genetic factors that contribute to these properties and the initial steps in auditory processing. Serial analysis of gene expression (SAGE), supported by microarray experiments, was performed on each subdivision of the rat cochlear nucleus to identify genes that may sub-serve specialized roles in the central auditory system. Pair-wise comparisons between SAGE libraries from the AVCN, PVCN and DCN were correlated with microarray experiments to identify individual transcripts with significant differential expression. Twelve highly correlated genes were identified representing cytoskeletal, vesicular, metabolic and g-protein regulating proteins. Among these were Rgs4 which showed higher expression in the DCN, Sst and Cyp11b1 with very high expression in the AVCN and Calb2 with preferential expression in the PVCN. The differential expression of these genes was validated with real-time reverse transcriptase-polymerase chain reaction. These experiments provide a basis for understanding normal auditory processing on a molecular level and a template for investigating changes that may occur in the cochlear nucleus with hearing loss, the generation and percept of tinnitus, and central auditory processing disorders.

Evidence for statistical epistasis between catechol-O-methyltransferase (COMT) and polymorphisms in RGS4, G72 (DAOA), GRM3, and DISC1: influence on risk of schizophrenia

Catechol-O-methyltransferase (COMT) regulates dopamine degradation and is located in a genomic region that is deleted in a syndrome associated with psychosis, making it a promising candidate gene for schizophrenia. COMT also has been shown to influence prefrontal cortex processing efficiency. Prefrontal processing dysfunction is a common finding in schizophrenia, and a background of inefficient processing may modulate the effect of other candidate genes. Using the NIMH sibling study (SS), a non-independent case-control set, and an independent German (G) case-control set, we performed conditional/unconditional logistic regression to test for epistasis between SNPs in COMT (rs2097603, Val158Met (rs4680), rs165599) and polymorphisms in other schizophrenia susceptibility genes. Evidence for interaction was evaluated using a likelihood ratio test (LRT) between nested models. SNPs in RGS4, G72, GRM3, and DISC1 showed evidence for significant statistical epistasis with COMT. A striking result was found in RGS4: three of five SNPs showed a significant increase in risk [LRT P-values: 90387 = 0.05 (SS); SNP4 = 0.02 (SS), 0.02 (G); SNP18 = 0.04 (SS), 0.008 (G)] in interaction with COMT; main effects for RGS4 SNPs were null. Significant results for SNP4 and SNP18 were also found in the German study. We were able to detect statistical interaction between COMT and polymorphisms in candidate genes for schizophrenia, many of which had no significant main effect. In addition, we were able to replicate other studies, including allelic directionality. The use of epistatic models may improve replication of psychiatric candidate gene studies.

RGS expression rate-limits recovery of rod photoresponses

Signaling through G protein-coupled receptors (GPCRs) underlies many cellular processes, yet it is not known which molecules determine the duration of signaling in intact cells. Two candidates are G protein-coupled receptor kinases (GRKs) and Regulators of G protein signaling (RGSs), deactivation enzymes for GPCRs and G proteins, respectively. Here we investigate whether GRK or RGS governs the overall rate of recovery of the light response in mammalian rod photoreceptors, a model system for studying GPCR signaling. We show that overexpression of rhodopsin kinase (GRK1) increases phosphorylation of the GPCR rhodopsin but has no effect on photoresponse recovery. In contrast, overexpression of the photoreceptor RGS complex (RGS9-1.Gbeta5L.R9AP) dramatically accelerates response recovery. Our results show that G protein deactivation is normally at least 2.5 times slower than rhodopsin deactivation, resolving a long-standing controversy concerning the mechanism underlying the recovery of rod visual transduction.

Bacterial artificial chromosome transgenic analysis of dynamic expression patterns of regulator of G-protein signaling 4 during development. I. Cerebral cortex

Signaling through G-protein-coupled receptors is modulated by a family of regulator of G protein signaling (RGS) proteins that have been implicated in several neurological and psychiatric disorders. Defining the detailed expression patterns and developmental regulation of RGS proteins has been hampered by an absence of antibodies useful for mapping. We have utilized bacterial artificial chromosome (BAC) methods to create transgenic mice that express GFP under the control of endogenous regulator of G-protein signaling 4 (RGS4) enhancer elements. This report focuses on expression patterns in the developing and mature cerebral cortex. Based on reporter distribution, RGS4 is expressed by birth in neurons across all cortical domains, but in different patterns that suggest region- and layer-specific regulation. Peak expression typically occurs before puberty, with complex down-regulation by adulthood. Deep and superficial neurons, in particular, vary in their patterns across developmental age and region and, in primary sensory cortices, layer IV neurons exhibit low or no expression of the GFP reporter. These data suggest that altering RGS4 function will produce a complex neuronal phenotype with cell- and subdomain-specificity in the cerebral cortex.

Bacterial artificial chromosome transgenic analysis of dynamic expression patterns of regulator of G-protein signaling 4 during development. II. Subcortical regions

A large family of regulator of G protein signaling (RGS) proteins modulates signaling through G-protein-coupled receptors. Previous studies have implicated RGS4 as a vulnerability gene in schizophrenia. To begin to understand structure-function relationships, we have utilized bacterial artificial chromosome (BAC) methods to create transgenic mice that express green fluorescent protein (GFP) under the control of endogenous RGS4 enhancer elements, circumventing the lack of suitable antibodies for analysis of dynamic patterns of expression. This report follows from the accompanying mapping paper in cerebral cortex, with a focus on developmental and mature expression patterns in subcortical telencephalic, diencephalic and brainstem areas. Based on reporter distribution, the data suggest that alterations in RGS4 function will engender a complex phenotype of increased and decreased neuronal output, with developmental, regional, and cellular specificity.