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Recent studies have shown that transcriptomes from different tissues present circadian oscillations. Therefore, the endogenous variation of total RNA should be considered as a potential bias in circadian studies of gene expression. However, normalization strategies generally include the equalization of total RNA concentration between samples prior to cDNA synthesis. Moreover, endogenous housekeeping genes (HKGs) frequently used for data normalization may exhibit circadian variation and distort experimental results if not detected or considered. In this study, we controlled experimental conditions from the amount of initial brain tissue samples through extraction steps, cDNA synthesis, and quantitative real time PCR (qPCR) to demonstrate a circadian oscillation of total RNA concentration. We also identified that the normalization of the RNA's yield affected the rhythmic profiles of different genes, including Per1-2 and Bmal1. Five widely used HKGs (Actb, Eif2a, Gapdh, Hprt1, and B2m) also presented rhythmic variations not detected by geNorm algorithm. In addition, the analysis of exogenous microRNAs (Cel-miR-54 and Cel-miR-39) spiked during RNA extraction suggests that the yield was affected by total RNA concentration, which may impact circadian studies of small RNAs. The results indicate that the approach of tissue normalization without total RNA equalization prior to cDNA synthesis can avoid bias from endogenous broad variations in transcript levels. Also, the circadian analysis of 2-Cycle threshold (Ct) data, without HKGs, may be an alternative for chronobiological studies under controlled experimental conditions. [ABSTRACT FROM AUTHOR]

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Copyright of Arquivos de Neuro-Psiquiatria is the property of Thieme Medical Publishing Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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. [ABSTRACT FROM AUTHOR]

Background: Melatonin modulates the master circadian clock through the activation of G-protein-coupled receptors MT1 and MT2. It is presumed, therefore, that genetic variations in melatonin receptors can affect both sleep and circadian phase. We investigated whether the -1193T > C (rs4753426) polymorphism in the promoter of MT2 receptor gene (MTNR1B) is associated with diurnal preference and sleep habits. This polymorphism was previously associated with sunshine duration, suggesting a role in circadian entrainment.Methods: A total of 814 subjects who completed the Morningness-Eveningness and the Munich Chronotype questionnaires were genotyped for the selected polymorphism. Linear and multinomial regression were performed to test the interaction between gene variants and diurnal preference/sleep habits.Results: The -1193C variant was associated with the extreme morningness phenotype in a codominant model (C/C vs. T/T), recessive model (C/C + C/T vs. T/T) and alleles (C vs. T). A negative correlation was found between -1193C alleles and social jetlag scores. The frequency of -1193T allele was higher in the group that stay in bed more than 8 h/night compared to the group that stay in bed less than 8 h/night on weekends.Conclusion: To the best of our knowledge, these data provide the first insights into the role of MTNR1B gene in the regulation of sleep, biological rhythms, and entrainment in humans. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the behavioral responses and circadian rhythms of mice to both rapid and gradual increases in photoperiod, mimicking the transition from winter to summer, which is associated with a heightened prevalence of hospitalizations for mania and suicidal behavior. Behavioral tests were performed in C57BL/6 male mice exposed to a transitional photoperiod, from short to long durations. To determine if circadian rhythms are affected, we measured spontaneous locomotor activity and body temperature. Mice exhibited heightened exploratory and risk-taking behaviors compared with equatorial and static long (16:8 h of light-dark cycle for several days) groups. These behaviors were prevented by lithium. Spontaneous locomotor activity and body temperature rhythms persisted and were effectively synchronized; however, the relative amplitude of activity and interdaily stability were diminished. Additionally, the animals displayed increased activity during the light phase. Photoperiodic transition modulates behavior and circadian rhythms, mirroring certain features observed in bipolar disorder patients. This study introduces an animal model for investigating mania-like behavior induced by photoperiodic changes, offering potential insights for suicide prevention strategies and the management of mood disorders., (© 2024 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

The aim of the present study was to analyze if the genetic polymorphisms might predict suicide attempts in mental disorder patients. The literature review and meta-analysis were conducted using the PubMed/Medline, Web of science and Scopus database using the terms: "5-HTT or SLC6A4 or 5-SERT and suicide, suicidal ideation or suicidal behavior or suicidal attempt". Thirty articles were analyzed. We found 17 articles that showed association and 13 articles that showed no association between LPR serotonin transporter polymorphism and suicide. A higher study of suicide identified the serotonin transporter polymorphism in patients with schizophrenia, mental disorder, major depression and bipolar disorder. There is an association between the serotonin-transporter-linked polymorphic region and suicidal behavior. The mental disorders with greater relationship with the suicide were the bipolar disorder, major depression and schizophrenia. The L allele had higher risk for suicide.

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.

We developed a semi-automated approach to detect large deletions in the beta-globin gene cluster, based on the quantitative differences in the amplifications of samples by a fluorescent PCR. With this strategy, we were able to detect the presence of HPFH-2 in an African-Brazilian subject, confirmed by sequencing analysis. Differently from other PCR strategies, GAP-PCR for example, it has the potential to identify new deletions., (Copyright 2003 Wiley-Liss, Inc.)