Pernilla Nikamo

Genetic Gating of Human Fear Learning and Extinction Possible Implications for Gene-Environment Interaction in Anxiety Disorder

Pavlovian fear conditioning is a widely used model of the acquisition and extinction of fear. Neural findings suggest that the amygdala is the core structure for fear acquisition, whereas prefrontal cortical areas are given pivotal roles in fear extinction. Forty-eight volunteers participated in a fear-conditioning experiment, which used fear potentiation of the startle reflex as the primary measure to investigate the effect of two genetic polymorphisms (5-HTTLPR and COMTval158met) on conditioning and extinction of fear. The 5-HTTLPR polymorphism, located in the serotonin transporter gene, is associated with amygdala reactivity and neuroticism, whereas the COMTval158met polymorphism, which is located in the gene coding for catechol-O-methyltransferase (COMT), a dopamine-degrading enzyme, affects prefrontal executive functions. Our results show that only carriers of the 5-HTTLPR s allele exhibited conditioned startle potentiation, whereas carriers of the COMT met/met genotype failed to extinguish conditioned fear. These results may have interesting implications for understanding gene-environment interactions in the development and treatment of anxiety disorders.

The KMO allele encoding Arg 452 is associated with psychotic features in bipolar disorder type 1, and with increased CSF KYNA level and reduced KMO expression

The kynurenine pathway metabolite kynurenic acid (KYNA), modulating glutamatergic and cholinergic neurotransmission, is increased in cerebrospinal fluid (CSF) of patients with schizophrenia or bipolar disorder type 1 with psychotic features. KYNA production is critically dependent on kynurenine 3-monooxygenase (KMO). KMO mRNA levels and activity in prefrontal cortex (PFC) are reduced in schizophrenia. We hypothesized that KMO expression in PFC would be reduced in bipolar disorder with psychotic features and that a functional genetic variant of KMO would associate with this disease, CSF KYNA level and KMO expression. KMO mRNA levels were reduced in PFC of bipolar disorder patients with lifetime psychotic features (P=0.005, n=19) or schizophrenia (P=0.02, n=36) compared with nonpsychotic patients and controls. KMO genetic association to psychotic features in bipolar disorder type 1 was studied in 493 patients and 1044 controls from Sweden. The KMO Arg(452) allele was associated with psychotic features during manic episodes (P=0.003). KMO Arg(452) was studied for association to CSF KYNA levels in an independent sample of 55 Swedish patients, and to KMO expression in 717 lymphoblastoid cell lines and 138 hippocampal biopsies. KMO Arg(452) associated with increased levels of CSF KYNA (P=0.03) and reduced lymphoblastoid and hippocampal KMO expression (P≤0.05). Thus, findings from five independent cohorts suggest that genetic variation in KMO influences the risk for psychotic features in mania of bipolar disorder patients. This provides a possible mechanism for the previous findings of elevated CSF KYNA levels in those bipolar patients with lifetime psychotic features and positive association between KYNA levels and number of manic episodes.The kynurenine pathway metabolite kynurenic acid (KYNA), modulating glutamatergic and cholinergic neurotransmission, is increased in cerebrospinal fluid (CSF) of patients with schizophrenia or bipolar disorder type 1 with psychotic features. KYNA production is critically dependent on kynurenine 3-monooxygenase (KMO). KMO mRNA levels and activity in prefrontal cortex (PFC) are reduced in schizophrenia. We hypothesized that KMO expression in PFC would be reduced in bipolar disorder with psychotic features and that a functional genetic variant of KMO would associate with this disease, CSF KYNA level and KMO expression. KMO mRNA levels were reduced in PFC of bipolar disorder patients with lifetime psychotic features (P=0.005, n=19) or schizophrenia (P=0.02, n=36) compared with nonpsychotic patients and controls. KMO genetic association to psychotic features in bipolar disorder type 1 was studied in 493 patients and 1044 controls from Sweden. The KMO Arg452 allele was associated with psychotic features during manic episodes (P=0.003). KMO Arg452 was studied for association to CSF KYNA levels in an independent sample of 55 Swedish patients, and to KMO expression in 717 lymphoblastoid cell lines and 138 hippocampal biopsies. KMO Arg452 associated with increased levels of CSF KYNA (P=0.03) and reduced lymphoblastoid and hippocampal KMO expression (P⩽0.05). Thus, findings from five independent cohorts suggest that genetic variation in KMO influences the risk for psychotic features in mania of bipolar disorder patients. This provides a possible mechanism for the previous findings of elevated CSF KYNA levels in those bipolar patients with lifetime psychotic features and positive association between KYNA levels and number of manic episodes.

CRY2 is associated with rapid cycling in bipolar disorder patients.

Background Bipolar disorder patients often display abnormalities in circadian rhythm, and they are sensitive to irregular diurnal rhythms. CRY2 participates in the core clock that generates circadian rhythms. CRY2 mRNA expression in blood mononuclear cells was recently shown to display a marked diurnal variation and to respond to total sleep deprivation in healthy human volunteers. It was also shown that bipolar patients in a depressive state had lower CRY2 mRNA levels, nonresponsive to total sleep deprivation, compared to healthy controls, and that CRY2 gene variation was associated with winter depression in both Swedish and Finnish cohorts. Principal Findings Four CRY2 SNPs spanning from intron 2 to downstream 3′UTR were analyzed for association to bipolar disorder type 1 (n = 497), bipolar disorder type 2 (n = 60) and bipolar disorder with the feature rapid cycling (n = 155) versus blood donors (n = 1044) in Sweden. Also, the rapid cycling cases were compared with bipolar disorder cases without rapid cycling (n = 422). The haplotype GGAC was underrepresented among rapid cycling cases versus controls and versus bipolar disorder cases without rapid cycling (OR = 0.7, P = 0.006−0.02), whereas overrepresentation among rapid cycling cases was seen for AAAC (OR = 1.3−1.4, P = 0.03−0.04) and AGGA (OR = 1.5, P = 0.05). The risk and protective CRY2 haplotypes and their effect sizes were similar to those recently suggested to be associated with winter depression in Swedes. Conclusions We propose that the circadian gene CRY2 is associated with rapid cycling in bipolar disorder. This is the first time a clock gene is implicated in rapid cycling, and one of few findings showing a molecular discrimination between rapid cycling and other forms of bipolar disorder.

Cognitive manic symptoms associated with the P2RX7 gene in bipolar disorder

Backlund L, Nikamo P, Sudic Hukic D, Römer EK I, Träskman‐Bendz L, Landén M, Edman G, Schalling M, Frisén L, Ösby U. Cognitive manic symptoms associated with the P2RX7 gene in bipolar disorder. Bipolar Disord 2011: 13: 500–508.

P2RX7: Expression Responds to Sleep Deprivation and Associates with Rapid Cycling in Bipolar Disorder Type 1

Context Rapid cycling is a severe form of bipolar disorder with an increased rate of episodes that is particularly treatment-responsive to chronotherapy and stable sleep-wake cycles. We hypothesized that the P2RX7 gene would be affected by sleep deprivation and be implicated in rapid cycling. Objectives To assess whether P2RX7 expression is affected by total sleep deprivation and if variation in P2RX7 is associated with rapid cycling in bipolar patients. Design Gene expression analysis in peripheral blood mononuclear cells (PBMCs) from healthy volunteers and case-case and case-control SNP/haplotype association analyses in patients. Participants Healthy volunteers at the sleep research center, University of California, Irvine Medical Center (UCIMC), USA (n = 8) and Swedish outpatients recruited from specialized psychiatric clinics for bipolar disorder, diagnosed with bipolar disorder type 1 (n = 569; rapid cycling: n = 121) and anonymous blood donor controls (n = 1,044). Results P2RX7 RNA levels were significantly increased during sleep deprivation in PBMCs from healthy volunteers (p = 2.3*10−9). The P2RX7 rs2230912 _A allele was more common (OR = 2.2, p = 0.002) and the ACGTTT haplotype in P2RX7 (rs1718119 to rs1621388) containing the protective rs2230912_G allele (OR = 0.45–0.49, p = 0.003–0.005) was less common, among rapid cycling cases compared to non-rapid cycling bipolar patients and blood donor controls. Conclusions Sleep deprivation increased P2RX7 expression in healthy persons and the putatively low-activity P2RX7 rs2230912 allele A variant was associated with rapid cycling in bipolar disorder. This supports earlier findings of P2RX7 associations to affective disorder and is in agreement with that particularly rapid cycling patients have a more vulnerable diurnal system.

No evidence of association of the PDCD1 gene with Type 1 diabetes

Aims  To test the association between the immunoreceptor PD‐1 (PDCD1) gene and Type 1 diabetes mellitus (T1DM). This gene has been reported to be associated with other autoimmune diseases such as systemic lupus erythematosus (SLE) as well as T1DM.

Polymorphisms in AKR1C4 and HSD3B2 and differences in serum DHEAS and progesterone are associated with paranoid ideation during mania or hypomania in bipolar disorder

Paranoia is commonly a mood-incongruent psychotic symptom of mania which may be related to dopamine dysregulation. Progesterone and its metabolite allopregnanolone (ALLO) have been found in animals to antagonize the effects of dopamine. We therefore examined serum progesterone, its endogenous antagonist DHEAS and polymorphisms of the genes coding for certain steroidogenetic enzymes (AKR1C4, HSD3B2, and SRD5A1) in 64 males and 96 females with bipolar 1 or 2 disorder with or without paranoid ideation during mood elevation. Euthymic morning serum progesterone, DHEAS and cortisol concentrations were measured in males and in premenopausal women who were in follicular phase and not taking oral contraceptives. In women only, SNPs in AKR1C4 reduced the likelihood of having exhibited paranoid ideation by circa 60%. The haplotype of all 4 SNPs in the AKR1C4 gene reduced the risk of exhibiting paranoia by 80% (OR 0.19, 95% CI 0.06-0.61, p=0.05). A history of paranoid ideation was not, however, related to progesterone or DHEAS concentration. Serum DHEAS and progesterone concentrations were lower in men who had shown paranoid ideation during mania/hypomania compared with those who had not (F=7.30, p=0.006) however this was not coupled to polymorphisms in the selected genes. The ancestral G in rs4659174 in HSD3B2 was in men associated with a lower risk of paranoid ideation (likelihood ratio χ(2) 3.97, p=0.046, OR 0.31 (95% CI 0.10-0.96)) but did not correlate with hormone concentrations. Hence, gene variants in the steroidogenetic pathway and steroids concentration differences may be involved in the susceptibility to paranoia during mood elevation.

AKR1C4 gene variant associated with low euthymic serum progesterone and a history of mood irritability in males with bipolar disorder

BACKGROUND Irritable mood during mood elevation is common in bipolar disorder. The progesterone metabolite allopregnanolone (ALLO) has been implicated in other disorders presenting with irritability. This study aimed to test whether a history of manic/hypomanic irritability is associated with low serum progesterone levels; and whether single nucleotide polymorphisms (SNPs) in gene coding for steroidogenetic enzymes (HSD3B2, SRD5A1 and AKR1C4 were coupled to previous manic irritability and/or with serum progesterone concentrations. METHODS Morning serum progesterone concentrations during euthymic phase of bipolar illness types 1 and 2 were assessed in 71 males and 107 females. Previous manic/hypomanic irritability was assessed using the Affective Disorders Evaluation. Selected SNPs were analyzed: i) aldoketoreductase-type-4 (AKR1C4 - rs17306779, rs3829125, rs10904440, rs12762017, and rs11253048), ii) 3-β-hydroxysteroid-dehydrogenase (HSD3B2 - rs4659174, rs2854964, and rs3765948), iii) steroid-5-α-reductase (SRD5A1 - rs8192139, rs181807, rs3822430, and rs3736316). RESULTS In males, progesterone concentrations were lower in those who had shown manic/hypomanic irritability compared with nonirritable (F=7.05, p=0.0099). SNPs rs17306779, rs3829125, and rs10904440 were associated with manic/hypomanic irritability. A cystine to serine change at position 145 in AKR1C4 (rs3829125) was associated with lower serum progesterone (F=6.34, p=0.014). There were no associations in females. LIMITATIONS Relatively small sample sizes. CONCLUSION Low progesterone levels and a cystine to serine change at position 145 in AKR1C4 gene are associated with manic/hypomanic irritability in males. Given that the enzyme AKR1C4 has both dehydrogenating and reductive activities in the steroidogenetic pathway, a missense variation in the gene may predispose to manic/hypomanic irritability by altering the relationship between progesterone and ALLO concentrations in the brain.

MicroRNA-146a suppresses IL-17–mediated skin inflammation and is genetically associated with psoriasis

Background: Psoriasis is an immune‐mediated inflammatory skin disease with a strong genetic background in which activation of IL‐17 signaling is central in the pathogenesis. Little has been known about the role of noncoding RNAs, including microRNAs (miRNAs), in predisposition to the disease. Objective: We sought to investigate the genetic association of single nucleotide polymorphisms in microRNA‐146a (miR‐146a) to psoriasis and to explore its function in the initiation and resolution of the disease. Methods: Analysis of the genetic association of miR‐146a rs2910164 and psoriasis was carried out on 1546 patients with psoriasis and 1526 control subjects. The role of miR‐146a in patients with psoriasis was assessed by using miR‐146a−/− mice in conjunction with the imiquimod‐induced mouse model of psoriasis. The severity of psoriasis‐like skin inflammation was evaluated at morphologic, histologic, and molecular levels. miR‐146a was ectopically overexpressed and inhibited in keratinocytes treated with IL‐17. Synthetic miR‐146a was injected intradermally into mice. Results: Here we report protective association of a functional polymorphism in the miR‐146a precursor (rs2910164). Genetic deficiency in miR‐146a leads to earlier onset and exacerbated pathology of skin inflammation, with increased expression of IL‐17–induced keratinocyte‐derived inflammatory mediators, epidermal hyperproliferation, and increased neutrophil infiltration. Moreover, miR‐146a–deficient mice do not resolve inflammation after discontinuation of imiquimod challenge. The overexpression of miR‐146a suppressed, whereas its inhibition enhanced, IL‐17–driven inflammation in keratinocytes. Functionally, miR‐146a impairs the neutrophil chemoattractant capacity of keratinocytes. Finally, delivery of miR‐146a mimics into the skin leads to amelioration of psoriasiform skin inflammation, decreased epidermal proliferation, and neutrophil infiltration. Conclusions: Our results define a crucial role for miR‐146a in modulating IL‐17–driven inflammation in the skin.

HTR1A a Novel Type 1 Diabetes Susceptibility Gene on Chromosome 5p13-q13

Background We have previously performed a genome-wide linkage study in Scandinavian Type 1 diabetes (T1D) families. In the Swedish families, we detected suggestive linkage (LOD≤2.2) to the chromosome 5p13-q13 region. The aim of our study was to investigate the linked region in search for possible T1D susceptibility genes. Methodology/Principal Findings Microsatellites were genotyped in the Scandinavian families to fine-map the previously linked region. Further, SNPs were genotyped in Swedish and Danish families as well as Swedish sporadic cases. In the Swedish families we detected genome-wide significant linkage to the 5-hydroxytryptamine receptor 1A (HTR1A) gene (LOD 3.98, p<9.8×10−6). Markers tagging two separate genes; the ring finger protein 180 (RNF180) and HTR1A showed association to T1D in the Swedish and Danish families (p<0.002, p<0.001 respectively). The association was not confirmed in sporadic cases. Conditional analysis indicates that the primary association was to HTR1A. Quantitative PCR show that transcripts of both HTR1A and RNF180 are present in human islets of Langerhans. Moreover, immunohistochemical analysis confirmed the presence of the 5-HTR1A protein in isolated human islets of Langerhans as well as in sections of human pancreas. Conclusions We have identified and confirmed the association of both HTR1A and RFN180, two genes in high linkage disequilibrium (LD) to T1D in two separate family materials. As both HTR1A and RFN180 were expressed at the mRNA level and HTR1A as protein in human islets of Langerhans, we suggest that HTR1A may affect T1D susceptibility by modulating the initial autoimmune attack or either islet regeneration, insulin release, or both.