Implication of SSAT by gene expression and genetic variation in suicide and major depression.

CONTEXT: A large body of evidence suggests that predisposition to suicide, an important public health problem, is mediated to a certain extent by neurobiological factors. OBJECTIVE: To investigate patterns of expression in suicide with and without major depression and to identify new molecular targets that may play a role in the neurobiology of these conditions. DESIGN: Brain gene expression analysis was performed using the Affymetrix HG-U133 chipset in the orbital cortex (Brodmann area [BA] 11), the dorsolateral prefrontal cortex (BA8/9), and motor cortex (BA4). Subsequent studies were carried out in independent samples from adjacent areas to validate positive findings, confirm their relevance at the protein level, and investigate possible effects of genetic variation. SUBJECTS: We investigated 12 psychiatrically normal control subjects and 24 suicide victims, including 16 with and 8 without major depression, in the brain gene expression analysis, validation, and protein studies. The genetic studies included 181 suicide completers and 80 psychiatrically normal controls. All subjects investigated were male and of French Canadian origin. MAIN OUTCOME MEASURES: Gene expression measures from microarray, semiquantitative reverse transcription-polymerase chain reaction, immunohistochemistry, and Western blot analyses. RESULTS: Twenty-six genes were selected because of the consistency of their expression pattern (fold change, >1.3 in either direction [P

Orexin neurons express a functional pancreatic polypeptide Y4 receptor.

The receptor subtypes that mediate the effects of neuropeptide Y (NPY) on food intake have not been clearly defined. The NPY Y4 receptor has been identified recently as a potential mediator of the regulation of food intake. The purpose of the present study was to characterize the central site of action of the Y4 receptor using a combination of neuroanatomical and physiological approaches. Using immunocytochemistry, Y4-like immunoreactivity was found to be colocalized with orexin cell bodies in the lateral hypothalamic area (LHA) and orexin fibers throughout the brain. In situ hybridization confirmed the expression of Y4 mRNA in orexin neurons. To determine the functional interaction between Y4 receptors and orexin neurons, we examined the effects of rat pancreatic polypeptide (rPP), a Y4-selective ligand, or NPY, a nonselective ligand, administered directly into the LHA on the stimulation of food and water intake and c-Fos expression. Both rPP and NPY significantly increased food and water intake when they were administered into the LHA, although NPY was a more potent stimulator of food intake. Furthermore, both NPY and rPP significantly stimulated c-Fos expression in the LHA. However, whereas rPP stimulated c-Fos expression in orexin neurons, NPY did not. Neither rPP nor NPY stimulated c-Fos in melanin-concentrating hormone neurons, but both activated neurons of an unknown phenotype in the LHA. These results suggest that a functional Y4 receptor is expressed on orexin neurons and that these neurons are activated in response to a ligand with high affinity for the Y4 receptor (rPP). Although these data suggest a role for central Y4 receptors, the endogenous ligand for this receptor has yet to be clearly established.

Molecular characterization of suicide by microarray analysis.

Several lines of evidence support the idea that individuals who commit suicide have a certain biological predisposition, part of which is given by genes. Studies investigating genetic factors increasing suicide predisposition have been limited by current knowledge of the suicide neurobiology and have typically investigated one or a few genes at a time, whereas it is anticipated that several genes account for the total genetic variance mediating suicide. This review focuses on the advantages and the interest of using the microarray technology to investigate the neurobiology of suicide and discusses, by means of a data analysis example, the possible methodological problems and bioinformatic strategies that should be employed in order to separate the signal from the large amount of background noise, which is usually generated in such studies. Microarray expression studies and related platforms are promising tools to gain better insight into the neurobiology of suicide.