Dual association of a TRKA polymorphism with schizophrenia.

OBJECTIVE: An interaction between predisposing genes and environmental stressors is thought to underlie the neurodevelopmental disorder schizophrenia. In a targeted gene screening, we previously found that the minor allele of the single nucleotide polymorphism (SNP) rs6336 in the neurotrophic tyrosine kinase receptor 1 (NTRK1/TRKA) gene is associated with schizophrenia as a risk factor. METHODS: We genotyped the TRKA SNP in a total of eight independent Caucasian schizophrenia case-control groups. RESULT: Remarkably, although in five of the groups a higher frequency of the risk allele was indeed found in the patients compared with the controls, in the three other groups the SNP acted as a protective factor. CONCLUSION: An intriguing possibility is that this dual character of the TRKA SNP is caused by its interaction with endophenotypic and/or epistatic factors.

Dopamine susceptibility of APO-SUS rats is not per se coupled to HPA-axis activity.

A synergistic relationship is thought to exist between hypothalamic-pituitary-adrenal (HPA) axis activity and dopamine neurotransmission. To test whether a high response to dopamine indeed implies a hyperactive HPA-axis, we here used Wistar rats that were selected twice independently (original and replicate lines) for a high or low susceptibility to the dopamine receptor agonist apomorphine (so-called APO-SUS and APO-UNSUS rats, respectively). The APO-SUS rats from the original line displayed a hyperactive HPA-axis in that higher basal and stress-induced adrenocorticotropic hormone (ACTH) levels, and lower basal free-corticosterone levels were observed than those found in the original APO-UNSUS rats. In contrast, the activity of the HPA-axis in the APO-SUS rats from the replicate line did not differ from that in the replicate APO-UNSUS rats. Thus, in the APO-SUS/APO-UNSUS rat model the level of HPA-axis activity is not necessarily causally linked to dopamine responsiveness, implying that a hyperactive HPA-axis is not a prerequisite for a high dopaminergic response.

Clock genes and body composition in patients with schizophrenia under treatment with antipsychotic drugs.

CONTEXT: In the healthy population, several pathways are known to exert an effect on basal metabolic factors. Previous studies have found associations between single nucleotide polymorphisms in clock genes or downstream hormone receptors such as the leptin receptor (LEPR) or glucocorticoid receptor (NR3C1) and obesity in the healthy population, but this association remains to be examined in patients with schizophrenia treated with antipsychotics. OBJECTIVE: To assess anthropomorphic parameters in patients taking second-generation antipsychotics (SGA) as a function of nine polymorphisms in three core genes of the clock pathway, and two genes of downstream hormone receptors. METHODS: Clinical parameters were evaluated in 261 patients with schizophrenia spectrum disorder. Polymorphisms in LEPR, MC3R, NR3C1, PER2 and SDC3 were genotyped. In order to control for multiple testing, permutation tests were used to generate corrected empirical p-values using the Max(T) procedure in PLINK. RESULTS: A significant effect of the rs6196 polymorphism in the NR3C1 on weight (ß=-4.18; SE=2.02; p=0.018), BMI (ß=-1.88; SE=0.64; p=0.004), waist (ß=-5.77; SE=1.75; p=0.001) and waist/hip ratio (ß=-0.03; SE=0.012; p=0.009) was found. Permutation tests confirmed the findings for BMI (p=0.037) and waist (p=0.024). Carriers of the G allele consistently displayed better parameters than patients with the wild type allele. A weak effect of rs4949184 in SDC3 on BMI was found, but this did not sustain permutation testing (ß=-1.27; SE=0.58; p=0.030, p=0.270 after permutations). CONCLUSION: Variations in genes implicated in circadian regulation or its related downstream pathways may be important in the regulation of antropomorphic parameters in patients with schizophrenia during long-term treatment with SGA.

Gene expression profiling in brain regions of a rat model displaying schizophrenia-related features.

Animal models allow insights into complex neurodevelopmental disorders. Apomorphine-susceptible rats (so-called APO-SUS rats) provide a model that displays a complex phenotype with schizophrenia-related features and together with its phenotypic counterpart (APO-UNSUS rats) has been independently generated twice (original and replicate rat lines). To understand the molecular basis underlying this phenotype, we here performed mRNA expression profiling in various APO-SUS and APO-UNSUS rat brain regions. The expression of only the previously reported Aph-1b and the newly discovered KCnIP1 (a member of the potassium channel-interacting protein family that is known to modulate neuronal channel activity) was significantly different in the APO-SUS and APO-UNSUS rats from both the original and replicate rat lines. Thus, KCnIP1 may constitute a novel candidate gene playing a role in the complex phenotype of the APO-SUS/APO-UNSUS rat model and further studies on this gene are warranted.

Correlation between HIV-1 seropositivity and prevalence of a gamma-secretase polymorphism in two distinct ethnic populations.

Susceptibility for human immunodeficiency virus type 1 (HIV-1) infection may be influenced by host genetics. Recent findings with a Wistar rat model raised the possibility that the gamma-secretase pathway may be associated with an individual's susceptibility to infection. A functional single-nucleotide polymorphism (SNP) in the gamma-secretase component APH1B (Phe217Leu; rs1047552) was therefore analyzed for association with HIV-1 infection. The SNP showed a tendency for association with HIV-1 infection in a Xhosa indigenous South African Bantu study (P = 0.087), and associated significantly in a Caucasian Dutch study (P = 0.049). Together, the results suggest a role for the gamma-secretase pathway in susceptibility to HIV-1 infection.

Three-cohort targeted gene screening reveals a non-synonymous TRKA polymorphism associated with schizophrenia.

Schizophrenia is a complex neurodevelopmental disorder that is thought to be induced by an interaction between predisposing genes and environmental stressors. To identify predisposing genetic factors, we performed a targeted (mostly neurodevelopmental) gene approach involving the screening of 396 selected non-synonymous single-nucleotide polymorphisms (SNPs) in three independent Caucasian schizophrenia case-control cohorts (USA, Denmark and Norway). A meta-analysis revealed ten non-synonymous SNPs that were nominally associated with schizophrenia, nine of which have not been previously linked to the disorder. Risk alleles are in TRKA (rs6336), BARD1 (rs28997576), LAMA5 (rs3810548), DKK2 (rs7037102), NOD2 (rs2066844) and RELN (rs2229860), whereas protective alleles are in NOD2 (rs2066845), NRG1 (rs10503929), ADAM7 (rs13259668) and TNR (rs859427). Following correction for multiple testing, the most attractive candidate for further study concerns SNP rs6336 (q=0.12) that causes the substitution of an evolutionarily highly conserved amino acid residue in the kinase domain of the neurodevelopmentally important receptor TRKA. Thus, TRKA signaling may represent a novel susceptibility pathway for schizophrenia.

Male-specific association between a gamma-secretase polymorphism and premature coronary atherosclerosis.

BACKGROUND: Atherosclerosis is a common multifactorial disease resulting from an interaction between susceptibility genes and environmental factors. The causative genes that contribute to atherosclerosis are elusive. Based on recent findings with a Wistar rat model, we speculated that the gamma-secretase pathway may be associated with atherosclerosis. METHODOLOGY/PRINCIPAL FINDINGS: We have tested for association of premature coronary atherosclerosis with a non-synonymous single-nucleotide polymorphism (SNP) in the gamma-secretase component APH1B (Phe217Leu; rs1047552), a SNP previously linked to Alzheimer's disease. Analysis of a Dutch Caucasian cohort (780 cases; 1414 controls) showed a higher prevalence of the risk allele in the patients (odds ratio (OR) = 1.35), albeit not statistically different from the control population. Intriguingly, after gender stratification, the difference was significant in males (OR = 1.63; p = 0.033), but not in females (OR = 0.50; p = 0.20). Since Phe217Leu-mutated APH1B showed reduced gamma-secretase activity in mouse embryonic fibroblasts, the genetic variation is likely functional. CONCLUSION/SIGNIFICANCE: We conclude that, in a male-specific manner, disturbed gamma-secretase signalling may play a role in the susceptibility for premature coronary atherosclerosis.

The presence of multiple and differentially regulated interleukin-12p40 genes in bony fishes signifies an expansion of the vertebrate heterodimeric cytokine family.

Interleukin-12 (IL-12) is the founding member of a rapidly growing family of heterodimeric cytokines. It consists of two subunits, designated p35 and p40 that together constitute a disulphide-linked heterodimeric cytokine. IL-12 is well known for its prominent role in both the early innate immune response and the skewing of the ensuing acquired immune response towards Th1. Here, we report the presence of IL-12p35 and three highly distinct IL-12p40 genes in common carp (Cyprinus carpio). The carp is a bony fish species genetically similar to the zebrafish, but its substantially larger body size facilitates immunological studies. A comparison of IL-12p35 genes of mammalian and non-mammalian species reveals the presence of a duplicated exon that is unique to the mammalian lineage. The organisation of the three carp IL-12p40 genes is similar to that of higher vertebrates. Phylogenetic analyses that include the p40-related subunits of other composite cytokines confirm the presence of three genuine IL-12p40 genes in carp and indicate that they are evolutionary ancient and possibly not restricted to bony fishes. The orthology of the different carp p40 subunits to mammalian IL-12p40 is further evident from the conservation of key residues involved in the formation of intra- and interchain disulphide bridges and the tight interlocking topology between p35 and p40. The expression of each of the carp IL-12p40 genes differs profoundly, constitutively as well as in response to in vitro stimulation of carp macrophages. Collectively, the presence of multiple and substantially different IL-12 genes signifies a considerable expansion of the vertebrate heterodimeric cytokine family.

Multiple and highly divergent IL-11 genes in teleost fish.

Interleukin-11 (IL-11) is a key cytokine in the regulation of proliferation and differentiation of hematopoietic progenitors and is also involved in bone formation, adipogenesis, and protection of mucosal epithelia. Despite this prominent role in diverse physiological processes, IL-11 has been described in only four mammalian species, and recently, in rainbow trout (Oncorhynchus mykiss). Here we report the presence of IL-11 in common carp (Cyprinus carpio), a bony fish species related to zebrafish. IL-11 is expressed in most carp organs and tissues. In vitro expression of IL-11 in cultured macrophages is enhanced by stimulation with lipopolysaccharide and is markedly inhibited by cortisol. A detailed and systematic scan of several fish genome databases confirms that IL-11 is present in all fish, but also reveals the presence of a second, substantially different IL-11 gene in the genomes of phylogenetically distant fish species. We designated both fish paralogues IL-11a and IL-11b. Although sequence identity between fish IL-11a and IL-11b peptides is low, the conservation of their gene structures supplemented by phylogenetic analyses clearly illustrate the orthology of both IL-11a and IL-11b genes of fish with mammalian IL-11. The presence of IL-11 genes in fish demonstrates its importance throughout vertebrate evolution, although the presence of duplicate and divergent IL-11 genes differs from the single IL-11 gene that exists in mammals.

Spontaneous excision of BAC vector sequences from bacmid-derived baculovirus expression vectors upon passage in insect cells.

Repeated baculovirus infections in cultured insect cells lead to the generation of defective interfering viruses (DIs), which accumulate at the expense of the intact helper virus and compromise heterologous protein expression. In particular, Autographa californica multicapsid nucleopolyhedovirus (AcMNPV) DIs are enriched in an origin of viral DNA replication (ori) not associated with the homologous regions (hrs). This non-hr ori is located within the coding sequence of the non-essential p94 gene. We investigated the effect of a deletion of the AcMNPV non-hr ori on the heterologous protein expression levels following serial passage in Sf21 insect cells. Using homologous ET recombination in E. coli, deletions within the p94 gene were made in a bacterial artificial chromosome (BAC) containing the entire AcMNPV genome (bacmid). All bacmids were equipped with an expression cassette containing the green fluorescent protein gene and a gene encoding the classical swine fever virus E2 glycoprotein (CSFV-E2). For the parental (intact) bacmid only, a strong accumulation of DIs with reiterated non-hr oris was observed. This was not observed for the mutants, indicating that removal of the non-hr ori enhanced the genetic stability of the viral genome upon passaging. However, for all passaged viruses it was found that the entire BAC vector including the expression cassette was spontaneously deleted from the viral genome, leading to a rapid decrease in GFP and CSFV-E2 production. The rationale for the (intrinsic) genetic instability of the BAC vector in insect cells and the implications with respect to large-scale production of proteins with bacmid-derived baculoviruses are discussed.