Tiago Gomes de Andrade

Do suicide attempts occur more frequently in the spring too? A systematic review and rhythmic analysis

BACKGROUND Seasonal variations in suicides have been reported worldwide, however, there may be a different seasonal pattern in suicide attempts. The aim of this study was to perform a systematic review on seasonality of suicide attempts considering potential interfering variables, and a statistical analysis for seasonality with the collected data. METHOD Observational epidemiological studies about seasonality in suicide attempts were searched in PubMed, Web of Science, LILACS and Cochrane Library databases with terms attempted suicide, attempt and season. Monthly or seasonal data available were evaluated by rhythmic analysis softwares. RESULTS Twenty-nine articles from 16 different countries were included in the final review. It was observed different patterns of seasonality, however, suicide attempts in spring and summer were the most frequent seasons reported. Eight studies indicated differences in sex and three in the method used for suicide attempts. Three articles did not find a seasonal pattern in suicide attempts. Cosinor analysis identified an overall pattern of seasonal variation with a suggested peak in spring, considering articles individually or grouped and independent of sex and method used. A restricted analysis with self-poisoning in hospital samples demonstrated the same profile. LIMITATIONS Grouping diverse populations and potential analytical bias due to lack of information are the main limitations. CONCLUSIONS The identification of a seasonal profile suggests the influence of an important environmental modulator that can reverberate to suicide prevention strategies. Further studies controlling interfering variables and investigating the biological substrate for this phenomenon would be helpful to confirm our conclusion.

Validation of suitable reference genes for expression studies in different pilocarpine-induced models of mesial temporal lobe epilepsy.

It is well recognized that the reference gene in a RT-qPCR should be properly validated to ensure that gene expression is unaffected by the experimental condition. We investigated eight potential reference genes in two different pilocarpine PILO-models of mesial temporal lobe epilepsy (MTLE) performing a stability expression analysis using geNorm, NormFinder and BestKepeer softwares. Then, as a validation strategy, we conducted a relative expression analysis of the Gfap gene. Our results indicate that in the systemic PILO-model Actb, Gapdh, Rplp1, Tubb2a and Polr1a mRNAs were highly stable in hippocampus of rats from all experimental and control groups, whereas Gusb revealed to be the most variable one. In fact, we observed that using Gusb for normalization, the relative mRNA levels of the Gfap gene differed from those obtained with stable genes. On the contrary, in the intrahippocampal PILO-model, all softwares included Gusb as a stable gene, whereas B2m was indicated as the worst candidate gene. The results obtained for the other reference genes were comparable to those observed for the systemic Pilo-model. The validation of these data by the analysis of the relative expression of Gfap showed that the upregulation of the Gfap gene in the hippocampus of rats sacrificed 24 hours after status epilepticus (SE) was undetected only when B2m was used as the normalizer. These findings emphasize that a gene that is stable in one pathology model may not be stable in a different experimental condition related to the same pathology and therefore, the choice of reference genes depends on study design.

Daily variations in the expression of miR-16 and miR-181a in human leukocytes

Circadian rhythms are controlled by a molecular mechanism that is organized in transcriptional and translational feedback loops of gene expression. Recent studies have been demonstrating the involvement of microRNAs (miRs) in post-transcriptional/translational control of circadian rhythms. In the present study we aimed to analyze the daily variations of miR-16 and miR-181a expression in human leukocytes. These miRs were independently associated with hematopoiesis and circadian rhythms in previous studies using experimental models. Peripheral blood from 6 subjects was sampled in a 24 hour period for expression analysis using quantitative real-time PCR (RT-qPCR). Initially, we evaluated the expression stability of RNU6-2, RNU1A-1, RNU5A-1, SNORD-25, SCARNA-17 and SNORA-73A as candidate genes for normalization of RT-qPCR data. The combination of the four most stable genes (SNORA-73A/SCARNA-17/SNORD-25/RNU6-2) was indicated to provide a better normalization of miRs expressions. The results show a daily variation of miR-181a and miR-16 expression in human leukocytes, suggesting a potential participation of these genes in the modulation of the circadian rhythms present in blood cells.

Expression of New Red Cell-Related Genes in Erythroid Differentiation

Using a suppression subtractive hybridization method, we have previously identified genes differentially expressed in erythroid cells heterozygous for large deletions in β-like globin cluster. Herein, we investigated the expression of four newly detected red cell–related genes in erythroid differentiation. ARID1B and TSPYL1, genes with chromatin remodeling properties, presented similar patterns of expression with an upregulation after erythropoietin (EPO) addition, similar to previous data found in reticulocytes. ZHX2, a transcriptional repressor, was downregulated, and a redoxin-related gene, SH3BGRL2, had higher levels of expression on differentiation. These are the first investigations of these newly described genes in erythroid differentiation and demonstrate that the expression of these genes is affected by EPO stimulation. These genes may participate in globin regulation and may be important in the normal physiology of erythrocytes.

Predicted microRNAs for mammalian circadian rhythms.

There is little evidence for the involvement of microRNAs (miRs) in the regulation of circadian rhythms, despite the potential relevance of these elements in the posttranscriptional regulation of the clock machinery. The present work aimed to identify miRs targeting circadian genes through a predictive analysis of conserved miRs in mammals. Besides 23 miRs previously associated with circadian rhythms, we found a number of interesting candidate genes, equally predicted by the 3 software programs used, including miR-9, miR-24, miR25, miR-26, miR-27, miR-29, miR-93, miR-211, miR-302, and miR-346. Moreover, several miRs are predicted to be regulated by circadian transcription factors, such as CLOCK/BMAL, DEC2, and REV-ERBalpha. Using real-time PCR we demonstrated that the selected candidate miR-27b showed a daily variation in human leukocytes. This study presents predicted feedback loops for mammalian molecular clock and the first description of an miR with in vivo daily variation in humans.

Identification of Endogenous Reference Genes for the Analysis of microRNA Expression in the Hippocampus of the Pilocarpine-Induced Model of Mesial Temporal Lobe Epilepsy

Real-time quantitative RT-PCR (qPCR) is one of the most powerful techniques for analyzing miRNA expression because of its sensitivity and specificity. However, in this type of analysis, a suitable normalizer is required to ensure that gene expression is unaffected by the experimental condition. To the best of our knowledge, there are no reported studies that performed a detailed identification and validation of suitable reference genes for miRNA qPCR during the epileptogenic process. Here, using a pilocarpine (PILO) model of mesial temporal lobe epilepsy (MTLE), we investigated five potential reference genes, performing a stability expression analysis using geNorm and NormFinder softwares. As a validation strategy, we used each one of the candidate reference genes to measure PILO-induced changes in microRNA-146a levels, a gene whose expression pattern variation in the PILO injected model is known. Our results indicated U6SnRNA and SnoRNA as the most stable candidate reference genes. By geNorm analysis, the normalization factor should preferably contain at least two of the best candidate reference genes (snoRNA and U6SnRNA). In fact, when normalized using the best combination of reference genes, microRNA-146a transcripts were found to be significantly increased in chronic stage, which is consistent with the pattern reported in different models. Conversely, when reference genes were individually employed for normalization, we failed to detect up-regulation of the microRNA-146a gene in the hippocampus of epileptic rats. The data presented here support that the combination of snoRNA and U6SnRNA was the minimum necessary for an accurate normalization of gene expression at the different stages of epileptogenesis that we tested.

Lack of association between rs211037 of the GABRG2 gene and juvenile myoclonic epilepsy in Brazilian population

BACKGROUND Juvenile myoclonic epilepsy (JME) is an idiopathic generalized epilepsy syndrome with genetic basis and accounts for 10% of all forms of epilepsy. Despite the existence of rare mutations responsible for some familial forms inherited in a Mendelian pattern, the genetics of JME is complex and probably involves multiple genes. Because of widespread distribution in the central nervous system (CNS) and their ability to produce postsynaptic inhibition, GABA (A) receptor subunits (GABRs) encoding genes represent high ranking candidates for epilepsy susceptibility. AIM This case/control study was designed to investigate whether the rs211037 of the GABRG2 gene is a risk factor for JME in the Brazilian population. MATERIALS AND METHODS The polymorphism was genotyped in 98 patients and 130 controls using polymerase chain reaction-restriction fragment length polymorphism method. Descriptive and statistical analyses were performed using SNP stat software. RESULTS Genotype proportions and allele frequencies for the rs211037 polymorphism of the GABARG2 gene did not differ significantly between the groups, even when the odds ratio was adjusted for clinical variables. CONCLUSION These results present no evidence for an association of rs211037 with JME. Further studies are required to investigate the involvement of the GABRG2 gene in the genetic susceptibility to this epileptic syndrome.

PER2 rs2304672, CLOCK rs1801260, and PER3 rs57875989 polymorphisms are not associated with juvenile myoclonic epilepsy

Sleep disturbance is common in several epilepsy types, such as juvenile myoclonic epilepsy (JME). Genetic background could increase susceptibility to seizure and sleep abnormalities. From this perspective, a susceptibility gene for sleep disturbance or chronotype could contribute to the genetic susceptibility threshold for epilepsy and vice versa. Accordingly, we investigated whether functional clock gene polymorphisms (PER2 111C>G, CLOCK 3111T>C, and PER3 VNTR) might influence the risk for JME. All these polymorphisms have recently been reported to be associated with sleep disturbance, diurnal variation, and neurological diseases. The polymorphisms were genotyped in 97 patients and 212 controls using polymerase chain reaction or restriction fragment length polymorphism methods. No significant differences were observed in the genotypic and allelic frequencies of these polymorphisms between cases and controls even when analyses were restricted to patients that presented a diurnal preferential seizure occurrence. We also tested for interactions between polymorphisms by multifactor dimensionality reduction analysis. None of the combined genotypes differed significantly between the groups. These results present no evidence for an association of these polymorphisms with JME. Further studies including other types of epilepsy and/or other functional polymorphisms are required to investigate the possible relationship between clock genes and the genetic susceptibility to chronic seizure.

Association of BDNF Val66MET Polymorphism With Parkinson’s Disease and Depression and Anxiety Symptoms

An association between Parkinsons disease (PD) and brain-derived neurotrophic factor (BDNF) was suggested by several studies, with contradictory results. BDNF is necessary for the survival of dopaminergic neurons in substantia nigra. Val66Met is a common polymorphism of the BDNF gene that affects cognitive and motor processes. The authors studied 104 Brazilian patients with PD and 96 control participants. The G/G genotype was significantly associated with depression and anxiety symptoms and development of PD. This is the first study that associates this genotype with PD.

Variants in SNCA Gene Are Associated with Parkinson’s Disease Risk and Cognitive Symptoms in a Brazilian Sample

Genetic susceptibility contributes to the etiology of sporadic Parkinson’s Disease (PD) and worldwide studies have found positive associations of polymorphisms in the alpha-synuclein gene (SNCA) with the risk for PD. However, little is known about the influence of variants of SNCA in individual traits or phenotypical aspects of PD. Further, there is a lack of studies with Latin-American samples. We evaluated the association between SNCA single nucleotide polymorphisms (single nucleotide polymorphisms, SNPs – rs2583988, rs356219, rs2736990, and rs11931074) and PD risk in a Brazilians sample. In addition, we investigated their potential interactions with environmental factors and specific clinical outcomes (motor and cognitive impairments, depression, and anxiety). A total of 105 PD patients and 101 controls participated in the study. Single locus analysis showed that the risk allele of all SNPs were more frequent in PD patients (p < 0.05), and the associations of SNPs rs2583988, rs356219, and rs2736990 with increased PD risk were confirmed. Further, the G-rs356219 and C-rs2736990 alleles were associated with early onset PD. T-rs2583988, G-rs356219 and C-2736990 alleles were significantly more frequent in PD patients with cognitive impairments than controls in this condition. In addition, in a logistic regression model, we found an association of cognitive impairment with PD, and the practice of cognitive activity and smoking habits had a protective effect. This study shows for the first time an association of SNCA polymorphism and PD in a South-American sample. In addition, we found an interaction between SNP rs356219 and a specific clinical outcome, i.e., the increased risk for cognitive impairment in PD patients.