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Based on recent developments in glioblastoma subtyping, we examined DARPP32 (PPP1R1B), a neuronal marker against STAT5 and STAT3 that are pro-oncogenic in glioblastoma. mRNA ratios of DARPP32, STAT1, STAT3, STAT5A and STAT5B were assessed in routinely diagnosed gliomas s including a series of glioblastomas from patients (n = 67) treated with chemoradiotherapy (temozolomide), out of which 88 % had sequencing validated IDH-negative disease. DARPP32/STAT1 (p = 0.0007), DARPP32/STAT3 (p = 0.0004) and DARPP32/STAT5B (p = 0.0039) ratios were significantly higher in grade II and III as compared to grade IV tumours. The same high ratios were also associated with absence of immunohistochemically assessed AKT/PKB phosphorylation and survivin protein expression. High DARPP32/STAT3, DARPP32/STAT5B, and STAT5B/STAT3 ratios were associated with longer patient progression free (PFS) and overall survival (OS). Upon multivariate analysis, total/subtotal removal of the tumour (HR:0.431; 95%CI:0.241–0.771, Wald p = 0.005), high DARPP32/STAT5B (HR:0.341; 95%CI:0.169–0.690; Wald p = 0.003) and STAT5B/STAT3 mRNA ratios (HR:0.480; 95%CI:0.280–0.824; Wald p = 0.008) were independent favorable parameters for prolonged PFS. Extent of surgery (HR:0.198; 95%CI:0.101–0.390; p

The objective of this study was to identify new candidate genes involved in experience-dependent plasticity. To this aim, we combined previously obtained data from recombinant inbred BXD strains on ocular dominance (OD) plasticity and gene expression levels in the neocortex. We validated our approach using a list of genes which alter OD plasticity when inactivated. The expression levels of one fifth of these genes correlated with the amount of OD plasticity. Moreover, the two genes with the highest relative inter-strain differences were among the correlated genes. This suggests that correlation between gene expression levels and OD plasticity is indeed likely to point to genes with a causal role in modulating or generating plasticity in the visual cortex. After this validation on known plasticity genes, we identified new candidate genes by a multi-step approach. First, a list was compiled of all genes of which the expression level in BXD strains correlate with the amount of OD plasticity. To narrow this list to the more promising candidates, we took its cross-section with a list of genes co-regulated with the sensitive period for OD plasticity and a list of genes associated with pathways implicated in OD plasticity. This analysis resulted in a list of 32 candidate genes. The list contained unproven, but not surprising, candidates, such as the genes for IGF-1, NCAM1, NOGO-A, the gamma2 subunit of the GABA(A) receptor, acetylcholine esterase and the catalytic subunit of cAMP-dependent protein kinase A. This was indicative of the viability of our approach, but more interesting were the novel candidate genes: Akap7, Akt1, Camk2d, Cckbr, Cd44, Crim1, Ctdsp2, Dnajc5, Gnai1, Itpka, Mapk8, Nbea, Nfatc3, Nlk, Npy5r, Phf21a, Phip, Ppm1l, Ppp1r1b, Rbbp4, Slc1a3, Slit2, Socs2, Spock3, St8sia1, Zfp207. The possible role of some of these candidates is discussed in the article.

Associative emotional learning, which is important for the social emotional functioning of individuals and is often impaired in psychiatric illnesses, is in part mediated by dopamine and glutamate pathways in the brain. The protein DARPP-32 is involved in the regulation of dopaminergic and glutaminergic signaling. Consequently, it has been suggested that the haplotypic variants of the gene PPP1R1B that encodes DARPP-32 are associated with working memory and emotion processing. We hypothesized that PPP1R1B should have a significant influence on the network of brain regions involved in associative emotional learning that are rich in DARPP-32, namely the striatum, prefrontal cortex (comprising the medial frontal gyrus and inferior frontal gyrus (IFG)), amygdala and parahippocampal gyrus (PHG). Dynamic causal models were applied to functional MRI data to investigate how brain connectivity during an associative emotional learning task is affected by different single-nucleotide polymorphisms (SNPs) of PPP1R1B: rs879606, rs907094 and rs3764352. Compared to heterozygotes, homozygotes with GTA alleles displayed increased intrinsic connectivity between the IFG and PHG, as well as increased excitability of the PHG for negative emotional stimuli. We have also elucidated the directionality of these genetic influences. Our data suggest that homozygotes with GTA alleles involve stronger functional connections between brain areas in order to maintain activation of these regions. Homozygotes might engage a greater degree of motivational learning and integration of information to perform the emotional learning task correctly. We conclude that PPP1R1B is associated with the neural network involved in associative emotional learning.

Review on PPP1R1B (protein phosphatase 1, regulatory (inhibitor) subunit 1B (dopamine and cAMP regulated phosphoprotein, DARPP-32)), with data on DNA, on the protein encoded, and where the gene is implicated.

Recent findings have highlighted the importance of DARPP-32 (dopamine- and cAMP-regulated phosphoprotein, 32 kDa), a key regulatory molecule in the dopaminergic signalling pathway for dopamine related phenotypes like antisocial-behavior, drug addiction and schizophrenia. This is the first study investigating the role of the DARPP-32 gene for personality. In a sample of n=838 healthy German Caucasian subjects we found a significant association between rs907094 and ANGER. Carriers of the T-allele showed significantly higher ANGER scores than participants without a T-allele (F((1,837))=9.52, p=0.002). In a second step we validated self-report data of ANGER by investigating their relation to structural brain differences in anger-related brain regions using voxel-based morphometry. A negative association between ANGER scores and the volume of the left amygdala could be detected. The present findings yield genetic evidence for the importance of dopaminergic signal transduction for the personality trait of ANGER. In addition volumetric MRI data support the role of the amygdala for the processing of anger.

Dopamine-and-cAMP-regulated neuronal phosphoprotein (32 kDa) (DARPP-32), encoded by PPP1R1B, is expressed in brain regions receiving dopaminergic projections, including the prefrontal cortex (PFC), and is implicated in the pathophysiology of schizophrenia. The broad functional capacity of DARPP-32 has potential relevance to both psychotic and negative symptoms of schizophrenia. We wished to determine if DARPP-32 gene expression and variation at selected SNPs correlated significantly with patient phenotypes. We performed RT-PCR to quantify DARPP-32 mRNA from brain samples (Brodmann Area 46) donated by the Stanley Medical Research Institute (SMRI, Array Collection): 35 from unaffected controls (UC), 35 from patients with schizophrenia (SCZ), and 35 with bipolar disorder (BP). Relative mRNA expression was calculated in relation to the housekeeping gene Cyclophilin. SNP genotyping was conducted by PCR on DNA obtained from Brodmann Area 46. We found a significant difference in gene expression levels between SCZ patients who died by suicide (SCZ-S) (n=6) vs. other causes of death (SCZ-NS) (P

Attention deficit hyperactivity disorder (ADHD) has a strong genetic basis, and evidence from human and animal studies suggests that a dopamine system dysfunction plays a role in the disorder pathophysiology. Several genes involved in dopamine neurotransmission have shown replicated genetic association with ADHD. These include the dopamine receptors D4 (DRD4), D5 (DRD5), and the dopamine transporter (DAT1) genes. Recently, evidence has also accumulated in favor of the dopamine receptor D1 gene (DRD1). The dopamine- and cAMP-regulated phosphoprotein of relative molecular mass of 32 kDa (DARPP-32) is a key component of dopamine signaling, acting as a converging point for several neurotransmitter systems influencing dopaminergic neurons and regulating a wide variety of downstream effectors. Here, we tested the DARPP-32 gene, PPP1R1B, for association with ADHD using four polymorphic markers selected across the gene in a sample of 255 ADHD families. We did not detect evidence of association of individual marker alleles and haplotype analysis did not reveal significant association in this sample of families. Moreover, we found no relationship between the same alleles or haplotypes and symptom scores of inattention or hyperactivity/impulsivity in these families using a quantitative approach. In conclusion, albeit a key regulatory role in dopamine signaling, our data do not support a major contribution of the DARPP-32 gene in ADHD.

The protein phosphatase 1 regulatory subunit 1B gene (PPP1R1B; also known as dopamine and cAMP-regulated phosphoprotein; DARPP32) is a target for the actions of dopamine. Because the mesolimbic dopaminergic system is implicated in the reinforcing effects of many drugs, including nicotine, PPP1R1B is considered a plausible candidate for involvement in the development of vulnerability to nicotine dependence (ND). Further, this gene is located within a region on chromosome 17 that demonstrated "suggestive linkage" to ND in our previous genome-wide scan. In the present study, we analyzed six single nucleotide polymorphisms (SNPs) within PPP1R1B for association with three ND measures: smoking quantity (SQ), the heaviness of smoking index (HSI), and the Fagerstrom Test for ND (FTND) score. Our sample consisted of 602 nuclear families of African-American (AA) or European-American (EA) origin. No significant associations were found for single SNPs after correction for multiple testing. However, haplotype analysis indicated that in the EA sample, the C-T-G-C haplotype formed by rs2271309-rs907094-rs3764352-rs3817160 with a frequency of 32.0% was significantly associated with SQ (Z = 2.50; P = 0.01), even after Bonferroni correction. No significant associations with haplotypes were found in the AA sample. In summary, our findings provide the first evidence for the potential involvement of PPP1R1B in the etiology of ND and further investigation is thus warranted.

Dopamine- and cAMP-regulated phosphoprotein of molecular weight 32 kDa (DARPP-32), encoded by PPP1R1B, is a pivotal integrator of information in dopaminoceptive neurons, regulating the response to neuroleptics, psychotomimetics, and drugs of abuse, and affecting striatal function and plasticity. Despite extensive preclinical work, there are almost no data on DARPP-32 function in humans. Here, we identify, through resequencing in 298 chromosomes, a frequent PPP1R1B haplotype predicting mRNA expression of PPP1R1B isoforms in postmortem human brain. This haplotype was associated with enhanced performance on several cognitive tests that depend on frontostriatal function. Multimodal imaging of healthy subjects revealed an impact of the haplotype on neostriatal volume, activation, and the functional connectivity of the prefrontal cortex. The haplotype was associated with the risk for schizophrenia in 1 family-based association analysis. Our convergent results identify a prefrontal-neostriatal system affected by variation in PPP1R1B and suggest that DARPP-32 plays a pivotal role in cognitive function and possibly in the pathogenesis of schizophrenia.

The dopamine receptor subtype in brain is DRD1. This receptor modulates several cellular functions and its expression has been studied in detail concerning extracellular signaling. A publication [1] indicates that there is also miRNA regulation (suppression) of DRD1 transcription and translation due to miR-142-3p interaction with the DRD1 3'-untranslated region (1,277 bp) of the DRD1 mRNA. This affects dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) expression as well, consequently [1]. DARPP-32 is also known as Protein phosphatase 1, regulatory (inhibitor) subunit 1B (PPP1R1B). This protein as well as DRD1 is expressed in medium spiny neurons and DARPP-32 is crucial in a number of pathways relating to drug abuse and neuropsychiatric disease. Discovery of DARPP-32 lead to the award of the Nobel Prize to Dr. P. Greengard (Rockefeller University, NY, NY) [3]. Dopamine participates in reward and function in the brain and dopamine pathway dysfunction is involved in drug abuse (e.g. cocaine, amphetamine, nicotine, caffeine, LSD, PCP, ethanol morphine, alcoholism, and smoking), gambling, novelty seeking, and additional neuropsychiatric diseases including schizophrenia, attention-deficit/hyperactivity disorder, Huntington's disease, and Parkinson's disease. Dopamine transporter (SLC6A3) is a participant as well. Signaling pathways interconnect DARPP-32 and dopamine pathways. The kinase, CK2 is also implicated among these pathways [3–5]. It is left as a puzzle for the interested reader to identify the various genes and their functions in the (Figure 1 & Figure 2) [2, 6, 7]. Figure 1 Network of input proteins (DARPP-32, Dopamine receptor DRD1, Dopamine transporter SLC6A3, and casein kinase 2 CK2) with input neighbors of these proteins. In this figure, line-colors and various interactions with other genes are red Down-regulation, green ... Figure 2 Network of input proteins (DARPP-32, Dopamine receptor DRD1, Dopamine transporter SLC6A3, and casein kinase 2 CK2) and additional neighbors of these proteins. miRNA affects DRD1 expression and probably miRNAs affect several additional proteins in the ... Thus, the continued study of DARPP-32 and related pathways may lead to cures for the many pathologies stemming from diseases as mentioned above.

Background: The neurotransmitters dopamine and glutamate have been implicated in the prefrontal dysfunction associated with schizophrenic illness. Studies suggest that the D1 subclass of dopamine receptor and the N-methylD-aspartate subclass of glutamate receptor are involved in this prefrontal dysfunction. These 2 receptors regulate, in opposing directions, the amount of phosphorylated activated DARPP-32, a potent inhibitor of protein phosphatase 1 that modulates the activity of several classes of receptors and ion channels. Thus, DARPP-32 occupies a key regulatory position, and may play an important role in the pathophysiological changes in dopamine and glutamate function reported in patients with schizophrenia. Methods: The amounts of DARPP-32, synapsin I, and the subunit of calcium/calmodulin-dependent protein kinase II were measured by immunoblotting in postmortem samples from 14 schizophrenic subjects and their age-, gender-, and autolysis time–matched control subjects. Possible confounding influences of neuroleptic treatment were analyzed by comparing subjects with Alzheimer disease who were and were not treated with neuroleptic agents. Results: DARPP-32 was significantly reduced in the dorsolateral prefrontal cortex in more schizophrenic subjects relative to matched controls. The ratios of 2 other synaptic phosphoproteins, synapsin I and the subunit of calcium/calmodulin-dependent protein kinase II, did not differ between schizophrenic and control subjects, nor between subjects with Alzheimer disease who were and were not treated with neuroleptic agents. Conclusions: Our findings are consistent with a selective reduction in DARPP-32 levels in schizophrenic subjects. This may be involved in the prefrontal dysfunction associated with schizophrenia. Arch Gen Psychiatry. 2002;59:705-712

Darpp-32 (dopamine and cAMP regulated phosphoprotein of 32 kD) and t-Darpp are expressed in various types of cancer, including several forms of breast cancer. Both are transcribed from the gene PPP1R1B (Protein phosphatase 1, regulatory (inhibitor) subunit 1B) via alternative promoters, t-Darpp being an N-terminally truncated version of the full length protein, Darpp-32. Although Darpp-32 is a well-known regulator of neurotransmission, its role in cancer is less well understood. t-Darpp is believed to be a putative oncogene: increasing cellular growth, inhibiting apoptosis and contributing to acquired drug resistance. In humans, Darpp-32 is found in both normal and malignant breast tissue, whereas t-Darpp has only been found in malignant breast tissue. Overall, however, the exact biological functions of these proteins in normal and malignant breast tissues are not well understood, and to date they have only been examined in patient samples, cell lines and xenograft mouse models. The use of transgenic mouse mammary tumor models, such as MMTV-PyVT and MMTV-Neu, to study the roles of Darpp-32 and t-Darpp in breast cancer in vivo have been limited by the lack of knowledge regarding t-Darpp expression in mice. In this study, we investigated Darpp-32 and t-Darpp mRNA and protein expression in normal and malignant mouse mammary tissue. We found that Darpp-32 was expressed in normal mouse mammary tissue and in some breast tumors, whereas t-Darpp was found only in the malignant mammary tissue. t-Darpp was expressed in the majority of breast tumors often at equal or higher levels than Darpp-32. t-Darpp expression did not seem to be correlated with either tumor location or tumor size. This shift in expression from Darpp-32 to t-Darpp during mouse mammary malignant transformation is reminiscent of the expression patterns observed in human breast tissue, suggesting that transgenic mouse mammary tumor models might be an ideal tool for future investigation of Darpp-32 and t-Darpp in breast cancer. Citation Format: Jessica L. Christenson, Kane E. Susan. Darpp-32 and t-Darpp are differentially expressed in normal and malignant mouse mammary tissue. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr A003.

Fusion genes result from genomic aberrations such as translocation, amplification and rearrangement. They have the potential to be new targets for the diagnosis and therapeutics in several different types of cancers. To identify fusion genes in gastric cancer, we conducted RNA sequencing with 18 gastric cancer cell lines and 11 pairs of primary human gastric cancer tissues and their adjacent normal tissues. We identified PPP1R1B-STARD3 fusion gene and validated the expression of this fusion gene by Real-Time PCR in the expanded panel of the human gastric tissue samples. Interestingly, PPP1R1B-STRAD3 fusion gene was detected in approximately 30% of primary human gastric cancers, but not in adjacent matched normal gastric tissues. Overexpression of PPP1R1B-STARD3 in MKN-28 significantly increased cell proliferation and colony formation. This increased proliferation was mediated by activation of PI3K/Akt signaling. To confirm if the expression of PPP1R1B-STARD3 fusion gene affects the tumorigenic capacity of gastric cancer cells in vivo, we performed the xenograft assay with MKN-28 cells that stably express PPP1R1B-STARD3 fusion gene. Overexpression of the fusion gene enhanced the MKN-28 tumor growth in nude mice. Hence, PPP1R1B-STARD3 fusion gene overexpression gives growth advantage in vitro and in vivo. Taken together, these findings indicate that PPP1R1B-STRAD3 fusion gene increased cell proliferation through the activation of PI3K/Akt signaling in gastric cancer cells. Citation Format: Sun Mi Yun. PPP1R1B-STARD3 fusion gene promotes gastric tumorigenesis through activation of PI3K/Akt signaling. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4304. doi:10.1158/1538-7445.AM2013-4304

Human Dopamine- and cAMP-regulated phosphoprotein of molecular weight 32kDa (DARPP-32, also known as PPP1R1B) gene codes for different transcripts that are mainly translated into two DARPP-32 protein isoforms, full length (fl)-DARPP-32 and truncated (t)-DARPP. The t-DARPP lacks the first 36 residues at the N-terminal, which alters its function. In the central nervous system, fl-DARPP-32 is highly expressed in GABAergic striatal medium spiny neurons (MSNs), where it integrates dopaminergic and glutamatergic input signaling. However, no information about human DARPP-32 isoform expression during MSNs maturation is available. In this study, our aim is to determine the expression of the two DARPP-32 isoforms in human fetal and adult striatal samples. We show that DARPP-32 isoform expression is differentially regulated during human striatal development, with the t-DARPP isoform being virtually absent from whole ganglionic eminence (WGE) and highly induced in the adult striatum (in both caudate and putamen). We next compared the four most common anti-DARPP-32 antibodies used in human specimens, to study their recognition of the two isoforms in fetal and adult human striatal samples by western blot and immunohistochemistry. The four antibodies specifically identify the fl-DARPP-32 in both fetal and adult samples, while t-DARPP form was only detected in adult striatal samples. In addition, the lack of t-DARPP recognition in human adult striatum by the antibody generated against the full-length domain produces in turn different efficacy by immunohistochemical analysis. In conclusion, our results show that expression of human DARPP-32 protein isoforms depends on the striatal neurodevelopmental stage with t-DARPP being specific for the human adult striatum.

The neurotransmitter dopamine has been demonstrated by biochemical, histochemical and immunocytochemical techniques to be unevenly distributed in the mammalian central nervous system. DARPP-32 (dopamine- and cyclic-AMP-regulated phosphoprotein of molecular weight 32,000) is a neuronal phosphoprotein that displays a regional distribution in the mammalian brain very similar to that of dopamine-containing nerve terminals, being highly concentrated in the basal ganglia. The state of phosphorylation of DARPP-32 can be regulated by dopamine and by cyclic AMP in intact nerve cells, suggesting a role for this phosphoprotein in mediating certain of the effects of dopamine on dopaminoceptive cells. The observation that many of the physical and chemical properties of purified DARPP-32 resemble those of phosphatase inhibitor-1 (inhibitor-1), a widely distributed inhibitor of protein phosphatase-1, suggests that DARPP-32 might also function as a phosphatase inhibitor. We report here that DARPP-32 inhibits protein phosphatase-1 at nanomolar concentrations. Moreover, like inhibitor-1, DARPP-32 is effective as an inhibitor in its phosphorylated but not its dephosphorylated form. Thus, the basal ganglia of mammalian brain contain a region-specific neuronal phosphoprotein that is a protein phosphatase inhibitor.

Several mammalian neurotransmitter candidates, for example, serotonin1, dopamine2,3 and noradrenaline4,5, may exert some of their synaptic effects by regulating protein phosphorylation systems6,7. Comparison of the regional distribution of brain phosphoproteins with neurotransmitter systems may help to identify the specific phosphoproteins involved in the functions of particular neurotransmitters. Here we report the association of one such phosphoprotein with the dopamine pathways in brain. This protein, of apparent molecular weight (MW) 32,000 (32K), seems to be present only in nervous tissue. Its regional distribution within the brain is very similar to the pattern of dopamine-containing nerve terminals; more specifically, the protein appears to be enriched in those dopaminoceptive neurones which possess D-1 receptors (dopamine receptors coupled to adenylate cyclase8). The state of phosphorylation of the protein in these dopaminoceptive neurones can be regulated by both dopamine and cyclic AMP. These results suggest that the phosphoprotein may mediate certain of the transsynaptic effects of dopamine acting on dopaminoceptive neurones.

Immunocytochemical studies have been carried out to determine the regional and cellular distribution of DARPP-32, a protein the phosphorylation of which can be regulated by dopamine and cAMP in intact cells. These immunocytochemical studies indicate tha DARPP-32 is localized primarily in those brain regions enriched in dopaminergic nerve terminals. Moreover, the staining pattern supports the conclusion that the DARPP-32 is present in dopaminoceptive neurons, i.e., neurons that receive a dopamine input, and that it is absent from the dopaminergic neurons themselves. Within the caudatoputamen, nucleus accumbens, olfactory tubercle, bed nucleus of the stria terminalis, and portions of the amygdaloid complex, all of which receive a strong dopamine input, DARPP-32 immunoreactivity is present in neuronal cell bodies and dendrites. In brain regions that are known to receive projections from these nuclei, puncta (presumed nerve terminals) are strongly immunoreactive for DARPP-32 but indigenous cell bodies and dendrites are not immunoreactive. These target areas include the globus pallidus, ventral pallidum, entopeduncular nucleus, and the pars reticulata of the substantia nigra. No immunoreactivity is detected in neuronal cell bodies or dendrites in any of the dopaminergic nuclei. Furthermore, nerve terminals immunoreactive for DARPP-32 do not resemble dopaminergic varicosities in either their morphology or their pattern of distribution. Many neurons are weakly immunoreactive for DARPP-32 and some of these are found in areas that apparently lack a dopaminergic input: weakly labeled neuronal cell bodies and dendrites were found throughout the neocortex, primarily in layer VI, and in the Purkinje neurons of the cerebellum. DARPP-32 immunoreactivity is also present in certain glial cells, especially in the median eminence, arcuate nucleus, and medial habenula. The present immunocytochemical studies, taken together with biochemical studies (Hemmings, H.C., Jr., A.C. Nairn, D.W. Aswad, and P. Greengard (1984) J. Neurosci. 4: 99–110; Walaas, S.I., and P. Greengard (1984) J. Neurosci. 4: 84–98) on DARPP- 32, indicate that DARPP-32, is present in the subclass of dopaminoceptive neurons containing D-1 receptors (dopamine receptors coupled to adenylate cyclase). DARPP-32 may be an effective marker for certain of the actions of dopamine that are mediated through cAMP and its associated protein kinase.

Dopaminergic pathways play a crucial role in reward processing, and advanced age can modulate its efficiency. DARPP-32 controls dopaminergic function and is a chemical nexus of reward processing. In 61 younger (20-30 years) and older adults (54% ♀) (65-74 years), we examined how blood-oxygen-level dependent (BOLD) activation to emotional faces, vary over genotypes at three single nucleotide polymorphism (SNPs), coding for DARPP-32 (rs879606; rs907094; 3764352). We also assessed age-magnification of DARPP-32 effects on BOLD activation. We found that major homozygote G, T or A genotypes, with higher cortical expression of DARPP-32, higher dopamine receptor efficacy, and greater bias toward positive cues, had increased functional connectivity in cortical-subcortical circuits in response to happy faces, engaging the dorsal prefrontal cortex (DLPFC), fusiform gyrus (FG) and the midbrain (MB). Local BOLD response to happy faces in FG, and MB was age-dependent, so that older carriers of the major G, T or A alleles showed lesser activation than minor genotypes. These genetic variants of DARPP-32 did not modulate BOLD response to angry faces, or engagement of the inferior occipital gyrus, to happy or angry faces. Taken together our results lend support for a potential role of DARPP-32 genetic variants in neural response to potential reward triggering cues.

Despite evidence of a fundamental role of DARPP-32 in integrating dopamine and glutamate signaling, studies examining gene coding for DARPP-32 in relation to neural and behavioral correlates in humans are scarce. Post mortem findings suggest genotype specific expressions of DARPP-32 in the dorsal frontal lobes. Therefore, we investigated the effects of genomic variation in DARPP-32 coding on frontal lobe volumes and episodic memory. Volumetric data from the dorsolateral (DLPFC), and visual cortices (VC) were obtained from 61 younger and older adults (♀54%). The major homozygote G, T, or A genotypes in single nucleotide polymorphisms (SNPs: rs879606; rs907094; rs3764352, the two latter in complete linkage disequilibrium), at the DARPP-32 regulating PPP1R1B gene, influenced frontal gray matter volume and episodic memory (EM). Homozygous carriers of allelic variants with lower DARPP-32 expression had an overall larger prefrontal volume in addition to greater EM recall accuracy after accounting for the influence of age. The SNPs did not influence VC volume. The genetic effects on DLPFC were greater in young adults and selective to this group for EM. Our findings suggest that genomic variation maps onto individual differences in frontal brain volumes and cognitive functions. Larger DLPFC volumes were also related to better EM performance, suggesting that gene-related differences in frontal gray matter may contribute to individual differences in EM. These results need further replication from experimental and longitudinal reports to determine directions of causality.

Gene expression changes are a hallmark of the neuropathology of Huntington's disease (HD), but the exact molecular mechanisms of this effect remain uncertain. Here, we report thatin vitromodels of disease comprised of primary striatal neurons expressing N-terminal fragments of mutant huntingtin (via lentiviral gene delivery) faithfully reproduce the gene expression changes seen in human HD. Neither viral infection nor unrelated (enhanced green fluorescent protein) transgene expression had a major effect on resultant RNA profiles. Expression of a wild-type fragment of huntingtin [htt171-18Q] also caused only a small number of RNA changes. The disease-related signal in htt171-82Q versus htt171-18Q comparisons was far greater, resulting in the differential detection of 20% of all mRNA probe sets. Transcriptomic effects of mutated htt171 are time- and polyglutamine-length dependent and occur in parallel with other manifestations of polyglutamine toxicity over 4–8 weeks. Specific RNA changes in htt171-82Q-expressing striatal cells accurately recapitulated those observed in human HD caudate and included decreases in PENK (proenkephalin), RGS4 (regulator of G-protein signaling 4), dopamine D1receptor (DRD1), DRD2, CNR1 (cannabinoid CB1receptor), and DARPP-32 (dopamine- and cAMP-regulated phosphoprotein-32; also known as PPP1R1B) mRNAs. HD-related transcriptomic changes were also observed in primary neurons expressing a longer fragment of mutant huntingtin (htt853-82Q). The gene expression changes observed in cultured striatal neurons are not secondary to abnormalities of neuronal firing or glutamatergic, dopaminergic, or brain-derived neurotrophic factor signaling, thereby demonstrating that HD-induced dysregulation of the striatal transcriptome might be attributed to intrinsic effects of mutant huntingtin.

Maximizing gains during probabilistic reinforcement learning requires the updating of choice–outcome expectations at the time when the feedback about a specific choice or action is given. Extant theories and evidence suggest that dopaminergic modulation plays a crucial role in reinforcement learning and the updating of choice–outcome expectations. Furthermore, recently a positive component of the event-related potential (ERP) about 200 msec (P2) after feedback has been suggested to reflect such updating. The efficacy of dopaminergic modulation changes across the life span. However, to date investigations of age-related differences in feedback-related P2 during reinforcement learning are still scarce. The present study thus aims to investigate whether individual differences in the feedback-related P2 would be associated with polymorphic variations in a dopamine relevant gene PPP1R1B (also known as DARPP-32) and whether the genetic effect may differ between age groups. We observed larger P2 amplitudes in individuals carrying the genotype associated with higher dopamine receptor efficacy, i.e., A allele homozygotes of a single nucleotide polymorphism (rs907094) of the PPP1R1B gene. Moreover, this effect was more pronounced in children and older adults in comparison to adolescents and younger adults. Together, our findings indicate that polymorphic variations in a dopamine relevant gene are associated with individual differences in brain-evoked potentials of outcome updating and hint at the possibility that genotype effects on neurocognitive phenotypes may vary as a function of brain maturation and aging.