Song competition affects monoamine levels in sensory and motor forebrain regions of male Lincoln's sparrows (Melospiza lincolnii)

Associative gene networks reveal novel candidates important for ADHD and dyslexia comorbidity

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is commonly associated with developmental dyslexia (DD), which are both prevalent and complicated pediatric neurodevelopmental disorders that have a significant influence on children's learning and development. Clinically, the comorbidity incidence of DD and ADHD is between 25 and 48%. Children with DD and ADHD may have more severe cognitive deficiencies, a poorer level of schooling, and a higher risk of social and emotional management disorders. Furthermore, patients with this comorbidity are frequently treated for a single condition in clinical settings, and the therapeutic outcome is poor. The development of effective treatment approaches against these diseases is complicated by their comorbidity features. This is often a major problem in diagnosis and treatment. In this study, we developed bioinformatical methodology for the analysis of the comorbidity of these two diseases. As such, the search for candidate genes related to the comorbid conditions of ADHD and DD can help in elucidating the molecular mechanisms underlying the comorbid condition, and can also be useful for genotyping and identifying new drug targets.

RESULTS

Using the ANDSystem tool, the reconstruction and analysis of gene networks associated with ADHD and dyslexia was carried out. The gene network of ADHD included 599 genes/proteins and 148,978 interactions, while that of dyslexia included 167 genes/proteins and 27,083 interactions. When the ANDSystem and GeneCards data were combined, a total of 213 genes/proteins for ADHD and dyslexia were found. An approach for ranking genes implicated in the comorbid condition of the two diseases was proposed. The approach is based on ten criteria for ranking genes by their importance, including relevance scores of association between disease and genes, standard methods of gene prioritization, as well as original criteria that take into account the characteristics of an associative gene network and the presence of known polymorphisms in the analyzed genes. Among the top 20 genes with the highest priority DRD2, DRD4, CNTNAP2 and GRIN2B are mentioned in the literature as directly linked with the comorbidity of ADHD and dyslexia. According to the proposed approach, the genes OPRM1, CHRNA4 and SNCA had the highest priority in the development of comorbidity of these two diseases. Additionally, it was revealed that the most relevant genes are involved in biological processes related to signal transduction, positive regulation of transcription from RNA polymerase II promoters, chemical synaptic transmission, response to drugs, ion transmembrane transport, nervous system development, cell adhesion, and neuron migration.

CONCLUSIONS

The application of methods of reconstruction and analysis of gene networks is a powerful tool for studying the molecular mechanisms of comorbid conditions. The method put forth to rank genes by their importance for the comorbid condition of ADHD and dyslexia was employed to predict genes that play key roles in the development of the comorbid condition. The results can be utilized to plan experiments for the identification of novel candidate genes and search for novel pharmacological targets.

Bicuculline, a GABAA-receptor antagonist, blocked HPA axis activation induced by ghrelin under an acute stress

Ghrelin is a peptide of 28 amino acids with a homology between species, which acts on the central nervous system to regulate different actions, including the control of growth hormone secretion and metabolic regulation. It has been suggested that central ghrelin is a mediator of behavior linked to stress responses and induces anxiety in rodents and birds. Previously, we observed that the anxiogenic-like behavior induced by ghrelin injected into the intermediate medial mesopallium (IMM) of the forebrain was blocked by bicuculline (a GABA_A receptor competitive antagonist) but not by diazepam (a GABA_A receptor allosteric agonist) in neonatal meat-type chicks (Cobb). Numerous studies have indicated that hypothalamic-pituitary-adrenal (HPA) axis activation mediates the response to stress in mammals and birds. However, it is still unclear whether this effect of ghrelin is associated with HPA activation. Therefore, we investigated whether anxiety behavior induced by intra-IMM ghrelin and mediated through GABA_A receptors could be associated with HPA axis activation in the neonatal chick. In the present study, in an Open Field test, intraperitoneal bicuculline methiodide blocked anxiogenic-like behavior as well as the increase in plasma ACTH and corticosterone levels induced by ghrelin (30pmol) in neonatal chicks. Moreover, we showed for the first time that a competitive antagonist of GABA_A receptor suppressed the HPA axis activation induced by an anxiogenic dose of ghrelin. These results show that the anxiogenic ghrelin action involves the activation of the HPA axis, with a complex functional interaction with the GABA_A receptor.

Social Complexity as a Driver of Communication and Cognition

Cognition and communication both can be essential for effectively navigating the social environment and thus, social dynamics could select for enhanced abilities for communication and superior cognition. Additionally, social experience can influence both the ability to communicate effectively and performance in cognitive tasks within an individual's lifetime, consistent with phenotypic plasticity in these traits. Historically, research in animal cognition and animal communication has often addressed these traits independently, despite potential commonalities in social function and underlying mechanisms of the brain. Integrating research on animal communication and cognition will provide a more comprehensive understanding of how the social environment may shape behavior and specializations of the brain for sociality through both evolutionary and developmental processes. This selective review of research on the impacts of social dynamics on cognition and communication in animals aims to highlight areas for future research at both the ultimate and proximate levels. In particular, additional work on the effects of the social environment on cognitive performance over an individual's lifetime, and comparative studies of specialized abilities for communication, should be pursued.

Behavioral effects of social challenges and genomic mechanisms of social priming: What's testosterone got to do with it?

Social challenges from rival conspecifics are common in the lives of animals, and changes in an animal's social environment can influence physiology and behavior in ways that appear to be adaptive in the face of continued social instability (i.e. social priming). Recently, it has become clear that testosterone, long thought to be the primary mediator of these effects, may not always change in response to social challenges, an observation that highlights gaps in our understanding of the proximate mechanisms by which animals respond to their social environment. Here, our goal is to address the degree to which testosterone mediates organismal responses to social cues. To this end, we review the behavioral and physiological consequences of social challenges, as well as their underlying hormonal and gene regulatory mechanisms. We also present a new case study from a wild songbird, the dark-eyed junco (Junco hyemalis), in which we find largely divergent genome-wide transcriptional changes induced by social challenges and testosterone, respectively, in muscle and liver tissue. Our review underscores the diversity of mechanisms that link the dynamic social environment with an organisms' genomic, hormonal, and behavioral state. This diversity among species, and even among tissues within an organism, reveals new insights into the pattern and process by which evolution may alter proximate mechanisms of social priming.

Exposure to advertisement calls of reproductive competitors activates vocal-acoustic and catecholaminergic neurons in the plainfin midshipman fish, Porichthys notatus

While the neural circuitry and physiology of the auditory system is well studied among vertebrates, far less is known about how the auditory system interacts with other neural substrates to mediate behavioral responses to social acoustic signals. One species that has been the subject of intensive neuroethological investigation with regard to the production and perception of social acoustic signals is the plainfin midshipman fish, Porichthys notatus, in part because acoustic communication is essential to their reproductive behavior. Nesting male midshipman vocally court females by producing a long duration advertisement call. Females localize males by their advertisement call, spawn and deposit all their eggs in their mate’s nest. As multiple courting males establish nests in close proximity to one another, the perception of another male’s call may modulate individual calling behavior in competition for females. We tested the hypothesis that nesting males exposed to advertisement calls of other males would show elevated neural activity in auditory and vocal-acoustic brain centers as well as differential activation of catecholaminergic neurons compared to males exposed only to ambient noise. Experimental brains were then double labeled by immunofluorescence (-ir) for tyrosine hydroxylase (TH), an enzyme necessary for catecholamine synthesis, and cFos, an immediate-early gene product used as a marker for neural activation. Males exposed to other advertisement calls showed a significantly greater percentage of TH-ir cells colocalized with cFos-ir in the noradrenergic locus coeruleus and the dopaminergic periventricular posterior tuberculum, as well as increased numbers of cFos-ir neurons in several levels of the auditory and vocal-acoustic pathway. Increased activation of catecholaminergic neurons may serve to coordinate appropriate behavioral responses to male competitors. Additionally, these results implicate a role for specific catecholaminergic neuronal groups in auditory-driven social behavior in fishes, consistent with a conserved function in social acoustic behavior across vertebrates.