Does α-synuclein have a dual and opposing effect in preclinical vs. clinical Parkinson's disease?

α-Synuclein gene (SNCA) multiplications cause familial parkinsonism and allele-length polymorphisms within the SNCA dinucleotide repeat REP1 increase the risk for developing Parkinson's disease (PD). Since SNCA multiplications increase SNCA expression, and REP1 genotypes that increase the risk of developing PD show increased SNCA expression in cell-culture systems, animal models, and human blood and brain, PD therapies seek to reduce SNCA expression. We conducted an observational study of 1098 PD cases to test the hypothesis that REP1 genotypes correlated with reduced SNCA expression are associated with better motor and cognitive outcomes. We evaluated the association of REP1 genotypes with survival free of Hoehn and Yahr stages 4 or 5 (motor outcome) and of Modified Telephone Interview for Cognitive Status score ≤27 or Alzheimer's Disease Dementia Screening Interview score ≥2 (cognitive outcome). Median disease duration at baseline was 3.3 years and median lag time from baseline to follow-up was 7.8 years. Paradoxically, REP1 genotypes associated with increased risk of developing PD and increased SNCA expression were associated with better motor (HR = 0.87, p = 0.046, covariate-adjusted age-scale analysis; HR = 0.85, p = 0.020, covariate-adjusted time-scale analysis) and cognitive outcomes (HR = 0.90, p = 0.12, covariate-adjusted age-scale analysis; HR = 0.85, p = 0.023, covariate-adjusted time-scale analysis). Our findings raise the possibility that SNCA has a dual, opposing, and time-dependent role. This may have implications for the development of therapies that target SNCA expression.     

Functional conservation of suppressors of cytokine signaling proteins between teleosts and mammals: Atlantic salmon SOCS1 binds to JAK/STAT family members and suppresses type I and II IFN signaling

Suppressor of cytokine signaling (SOCS) proteins are crucially involved in the control of inflammatory responses through their impact on various signaling pathways including the JAK/STAT pathway. Although all SOCS protein family members are identified in teleost fish, their functional properties in non-mammalian vertebrates have not been extensively studied. To gain further insight into SOCS functions in bony fish, we have identified and characterized the Atlantic salmon (Salmo salar) SOCS1, SOCS2 and CISH genes. These genes exhibited sequence conservation with their mammalian counterparts and they were ubiquitously expressed. SOCS1 in mammalian species has been recognized as a key negative regulator of interferon (IFN) signaling and recent data for the two model fish Tetraodon (Tetraodon nigroviridis) and zebrafish (Danio rerio) suggest that these functions are conserved from teleost to mammals. In agreement with this we here demonstrate a strong negative regulatory activity of salmon SOCS1 on type I and type II IFN signaling, while SOCS2a and b and CISH only moderately affected IFN responses. SOCS1 also inhibited IFNγ-induced nuclear localization of STAT1 and a direct interaction between SOCS1 and STAT1 and between SOCS1 and the Tyk2 kinase was found. Using SOCS1 mutants lacking either the KIR domain or the ESS, SH2 and SOCS box domains showed that all domains affected the ability of SOCS1 to inhibit IFN-mediated signaling. These results are the first to demonstrate that SOCS1 is a potent inhibitor of IFN-mediated JAK-STAT signaling in teleost fish.     

Serotonin transporter gene polymorphisms and treatment-resistant depression

Major Depression Disorder (MDD) is a serious mental illness that is one of the most disabling diseases worldwide. In addition, approximately 15% of depression patients are defined treatment-resistant (TRD). Preclinical and genetic studies show that serotonin modulation dysfunction exists in patients with TRD. Some polymorphisms in the promoter region of the serotonin transporter gene (SLC6A4) are likely to be involved in the pathogenesis/treatment of MDD; however, no data are available concerning TRD.     

A covalently linked recombinant albumin dimer is more rapidly cleared in vivo than are wild-type and mutant C34A albumin

Mammalian albumins are abundant plasma proteins that exhibit a relatively slow terminal clearance. For this reason they have been fused to potentially therapeutic proteins with rapid terminal clearance to produce fusion proteins with more desirable clearance profiles. A disulfide-linked albumin dimer has been described, but its abundance and stability in plasma are uncertain. To determine whether an obligatory albumin dimer incapable of dissociation would clear less rapidly than monomeric albumin, we expressed 3 recombinant rabbit serum albumin (RSA) polypeptides: H6RSA, RSA modified by the addition of an N-terminal hexahistidinyl tag; H6RSA(C34A), H6RSA with a single cysteine (Cys) 34-to-alanine (Ala) substitution (C34A); and DiRSA, H6RSA(C34A) joined by way of its C-terminus to RSA(C34A) through an intervening hexaglycine spacer. The C34A mutation was introduced to eliminate the possibility of disulfide bond-mediated dimerization. We expressed the proteins with the use of the yeast Pichia pastoris and purified them using nickel-chelate, ion exchange, and gel-filtration chromatography. After radioiodination and injection into rabbits, H6RSA and H6RSA(C34A) exhibited indistinguishable terminal catabolic half-lives (4.9 +/- 0.7 and 4.8 +/- 0.5 days, mean +/- SD), whereas that of DiRSA was reduced to 3.0 +/- 0.3 days (p<.05). The three proteins circulated in intact form, and their distributions in liver, lung, kidney, heart, and spleen did not differ 24 hours after injection. Although more DiRSA than H6RSA(C34A) was present in urine, in both cases it was in acid-soluble form. Ethyl palmitate treatment reduced the relative acceleration of DiRSA clearance compared with that of H6RSA(C34A), suggesting a role for the reticuloendothelial system in the differential clearance of the larger protein. Our results suggest that an albumin fusion protein should include only a single copy of albumin; that if the fusion protein exceeds a certain size, it may not acquire the slow clearance profile of native albumin; and that albumin dimerization through Cys34 probably does not contribute substantially to albumin metabolism in vivo.     

Association between the MnSOD Ala-9Val polymorphism and development of schizophrenia and abnormal involuntary movements in the Xhosa population

Reactive oxygen species (ROS)-mediated damage has been hypothesized to play a role in the development and poor outcome of schizophrenia, as well as the development of neuroleptic-induced abnormal involuntary movements. Recently, the functional polymorphism (Ala-9Val) in the manganese superoxide dismutase (MnSOD) gene (part of the antioxidant defense mechanism) was found to be associated with schizophrenia in a Turkish population. This study was aimed at replicating this finding in a Xhosa population. In addition, the role of Ala-9Val in abnormal involuntary movement and tardive dyskinesia development in the Xhosa population was also investigated. The schizophrenic patient group (n=286) and a healthy control group (n=243) were genotyped for the Ala-9Val polymorphism using heteroduplex-single stranded conformational polymorphism (HEX-SSCP) analysis. No significant difference in genotype or allele frequency could be observed between the schizophrenia and control group (P=0.294 and P=0.528 respectively). In addition no association could be found between the polymorphism and symptom severity (SANS and SAPS). The Xhosa schizophrenia patient group with abnormal involuntary movements (n=54) and a subgroup with tardive dyskinesia (n=30) was found to significantly differ in Ala-9Val genotype frequency (P=0.008 and P=0.011 respectively) compared to the Xhosa schizophrenia patient group without abnormal involuntary movements (n=204). However, no significant difference was found for the allele frequencies (P=0.955 and P=0.161). Further, using ANCOVA no association was found between AIMS score and genotype in the group with abnormal involuntary movements (P=0.1234). However, in the patient group with tardive dyskinesia an association was observed between genotype and AIMS score (P=0.0365). These results do not support a major role of the MnSOD Ala-9Val polymorphism in the development of schizophrenia or symptom severity in the Xhosa population. Yet it seems to be involved in the development of abnormal involuntary movements and tardive dyskinesia and may even modulate the severity of tardive dyskinesia.     

Do we know all there is to know about Familial Adenomatous Polyposis?

Familial Adenomatous Polyposis (FAP) and Attenuated FAP (AFAP) are caused by a germline mutation in the Adenomatous polyposis coli (APC) gene. Recently, a new pathway characterized by a biallelic mutation in the MYH gene, with a recessive model of inheritance was discovered for this inherited syndrome. This report describes a Tunisian patient with an attenuated FAP phenotype, presenting seven colon polyps and an adenocarcinoma but no detectable germline mutations in the FAP target genes. A well known somatic mutation was found in the APC mutation cluster region (MCR). This case shows that further studies are needed to fully understand all the pathways of the FAP syndrome.     

Correlation between cystathionine beta synthase gene polymorphisms,plasma homocysteine and idiopathic mental retardation in Indian individuals from Kolkata

Deficiency in cystathionine beta synthase (CBS) enzyme sometimes leads to hyperhomocysteinemia/homocystinuria, conditions often associated with mental retardation (MR). In this investigation, association of idiopathic MR (IMR) with six CBS gene polymorphisms and fasting total plasma homocysteine (plHcy) was explored. Nuclear families with IMR probands (N = 180) and control subjects (N = 106) were recruited. Genomic DNA was subjected to PCR amplification and RFLP analysis. plHcy was measured by enzyme immunoassay. Data obtained was subjected to statistical analyses. Linkage disequilibrium between polymorphic sites was computed. T833C/844ins68 polymorphism revealed significant maternal transmission in IMR cases. The 31 bpVNTR 21 repeat allele was significantly higher in male IMR cases as compared to sex-matched controls (P = 0.004). A significant difference was also noticed in genotype frequencies of male IMR cases (P = 0.005). Four other sites, G919A, C1105T, G1316A and G1330A, were not polymorphic in the studied population. While no significant contribution of any particular genotype was observed, plHcy level was significantly higher in male IMR cases as compared to sex-matched controls (P = 0.0001). The data presented here is probably indicative of a higher risk of IMR in male subjects in association with two CBS polymorphisms and mild elevation in plHcy concentration.