ABSTRACT
BACKGROUND: Ankyrin 3 (ANK3) has been strongly implicated as a risk gene for bipolar disorder (BD) by recent genome-wide association studies of patient populations. However, the genetic variants of ANK3 contributing to BD risk and their pathological function are unknown. METHODS: To gain insight into the potential disease relevance of ANK3, we examined the function of mouse Ank3 in the regulation of psychiatric-related behaviors using genetic, neurobiological, pharmacological, and gene-environment interaction (G×E) approaches. Ank3 expression was reduced in mouse brain either by viral-mediated RNA interference or through disruption of brain-specific Ank3 in a heterozygous knockout mouse. RESULTS: RNA interference of Ank3 in hippocampus dentate gyrus induced a highly specific and consistent phenotype marked by decreased anxiety-related behaviors and increased activity during the light phase, which were attenuated by chronic treatment with the mood stabilizer lithium. Similar behavioral alterations of reduced anxiety and increased motivation for reward were also exhibited by Ank3+/- heterozygous mice compared with wild-type Ank3+/+ mice. Remarkably, the behavioral traits of Ank3+/- mice transitioned to depression-related features after chronic stress, a trigger of mood episodes in BD. Ank3+/- mice also exhibited elevated serum corticosterone, suggesting that reduced Ank3 expression is associated with elevated stress reactivity. CONCLUSIONS: This study defines a new role for Ank3 in the regulation of psychiatric-related behaviors and stress reactivity that lends support for its involvement in BD and establishes a general framework for determining the disease relevance of genes implicated by patient genome-wide association studies.
Subject(s)
Ankyrins/genetics , Anxiety Disorders/genetics , Anxiety Disorders/physiopathology , Bipolar Disorder/genetics , Lithium Chloride/pharmacology , Stress, Psychological/genetics , Stress, Psychological/physiopathology , Animals , Ankyrins/physiology , Anxiety Disorders/blood , Anxiety Disorders/drug therapy , Corticosterone/blood , Dentate Gyrus/physiology , Male , Mice , Mice, Knockout , Mice, Transgenic , Stress, Psychological/blood , Stress, Psychological/drug therapyABSTRACT
Target identification remains challenging for the field of chemical biology. We describe an integrative chemical genomic and proteomic approach combining the use of differentially active analogs of small molecule probes with stable isotope labeling by amino acids in cell culture-mediated affinity enrichment, followed by subsequent testing of candidate targets using RNA interference-mediated gene silencing. We applied this approach to characterizing the natural product K252a and its ability to potentiate neuregulin-1 (Nrg1)/ErbB4 (v-erb-a erythroblastic leukemia viral oncogene homolog 4)-dependent neurotrophic factor signaling and neuritogenesis. We show that AAK1 (adaptor-associated kinase 1) is a relevant target of K252a, and that the loss of AAK1 alters ErbB4 trafficking and expression levels, providing evidence for a previously unrecognized role for AAK1 in Nrg1-mediated neurotrophic factor signaling. Similar strategies should lead to the discovery of novel targets for therapeutic development.
Subject(s)
ErbB Receptors/metabolism , Nerve Growth Factors/metabolism , Neuregulin-1/metabolism , Protein Serine-Threonine Kinases/metabolism , Animals , Carbazoles/metabolism , ErbB Receptors/genetics , Gene Knockdown Techniques , Genomics/methods , Humans , Indole Alkaloids/metabolism , Models, Molecular , Nerve Growth Factors/genetics , Neuregulin-1/genetics , Neurites/metabolism , PC12 Cells , Protein Serine-Threonine Kinases/genetics , Proteomics/methods , Rats , Receptor, ErbB-4 , Signal TransductionABSTRACT
Because the piglet is frequently used as a model for developmental disorders of the medullary serotonergic (5-HT) system in the human infant, this review compares the topography and developmental profile of selected 5-HT markers between humans in the first year of life and piglets in the first 60 days of life. The distribution of tryptophan hydroxylase-immunoreactive 5-HT neurons in the human infant medulla is very similar, but not identical, to that in the piglet. One notable difference is the presence of compact clusters of 5-HT neurons at the ventral surface of the piglet medulla. While it lacks these distinctive clusters, the human infant medulla contains potentially homologous 5-HT neurons scattered along the ventral surface embedded in the arcuate nucleus. Each species shows evidence of age-related changes in the 5-HT system, but the changes are different in nature; in the human infant, statistically significant age-related changes are observed in the proportional distribution of medullary 5-HT cells, while in the piglet, statistically significant age-related changes are observed in the levels of 5-HT receptor binding in certain medullary nuclei. Analyses of 5-HT receptor binding profiles in selected nuclei in the two species suggest that the equivalent postnatal ages for 5-HT development in piglets and human infants are, respectively, 4 days and 1 month, 12 days and 4 months, 30 days and 6 months, and 60 days and 12 months. Collectively, when certain species differences are considered, these data support the use of the piglet as a model for the human infant medullary 5-HT system.
Subject(s)
Developmental Disabilities/pathology , Medulla Oblongata , Neurons/metabolism , Serotonin/metabolism , Animals , Animals, Newborn , Child , Child, Preschool , Developmental Disabilities/metabolism , Disease Models, Animal , Humans , Medulla Oblongata/growth & development , Medulla Oblongata/metabolism , Medulla Oblongata/pathology , Neurons/pathology , SwineABSTRACT
The anatomy of the 5-HT system in the medulla oblongata is well defined in several vertebrate species, but not in the piglet. A detailed map and developmental profile of this system is particularly important in the piglet because this species increasingly is used as a model for physiological studies of medullary homeostatic control and its disorders in human infancy, especially the sudden infant death syndrome. Tryptophan hydroxylase immunohistochemistry was used to identify 5-HT cells and map their distribution in the medullae of piglets between postnatal days 4 and 30, the putative comparable period to early human infancy. Tritiated (3H)-lysergic acid diethylamide (LSD) binding to 5-HT1A-D and 5-HT2 receptors and 3H-8-hydroxy-2-[di-N-propylamine]tetralin (8-OH-DPAT) binding to 5-HT1A receptors were used to quantify and map the distribution of these serotonin receptors between 4 and 60 postnatal days. The distribution of 5-HT cells was similar to that observed in other vertebrate species, with cell bodies in and lateral to the caudal raphé. Tritiated-LSD and 3H-8-OH-DPAT binding both showed significant age-related changes in select raphé and extra-raphé subnuclei. Taken together, these findings suggest that while the medullary 5-HT cells are topographically in place at birth in the piglet, changes in 5-HT neurotransmission take place during the first 30 days of life, as reflected by changes in patterns of receptor binding. Therefore, the first 30 days of life represent a critical period in the development of the 5-HT system and the homeostatic functions it mediates.
