Cre recombinase-mediated restoration of nigrostriatal dopamine in dopamine-deficient mice reverses hypophagia and bradykinesia

Midbrain dopaminergic (mDA) neurons are implicated in cognitive functions, neuropsychiatric disorders, and pathological conditions; hence understanding genes regulating their homeostasis has medical relevance. Transcription factors FOXA1 and FOXA2 (FOXA1/2) are key determinants of mDA neuronal identity during development, but their roles in adult mDA neurons are unknown. We used a conditional knockout strategy to specifically ablate FOXA1/2 in mDA neurons of adult mice. We show that deletion of Foxa1/2 results in down-regulation of tyrosine hydroxylase, the rate-limiting enzyme of dopamine (DA) biosynthesis, specifically in dopaminergic neurons of the substantia nigra pars compacta (SNc). In addition, DA synthesis and striatal DA transmission were reduced after Foxa1/2 deletion. Furthermore, the burst-firing activity characteristic of SNc mDA neurons was drastically reduced in the absence of FOXA1/2. These molecular and functional alterations lead to a severe feeding deficit in adult Foxa1/2 mutant mice, independently of motor control, which could be rescued by L-DOPA treatment. FOXA1/2 therefore control the maintenance of molecular and physiological properties of SNc mDA neurons and impact on feeding behavior in adult mice.FOXA1 | FOXA2 | dopamine | burst firing | feeding M ost dopaminergic (DAergic) neurons in the adult midbrain are grouped in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc). VTA and SNc neurons have been classically linked to diverse functions and different projection targets (1). VTA neurons project to the ventral striatum, cortical areas, and limbic structures. Midbrain dopaminergic (mDA) neurons in this group are implicated in emotional behavior, motivational functions, and reward mechanisms (2-4). On the other hand, SNc neurons mainly project to the dorsal striatum and regulate motor function (5). mDA neurons are of major interest in biomedical research because degeneration of SNc mDA neurons is the hallmark of Parkinson's disease (6). In addition, mDA neuron dysfunction is associated with cognitive impairment, motivational deficits, addiction, and drug abuse (7-10). The identification of factors that maintain dopamine (DA) function in developed adult neurons may contribute to the understanding of the mechanisms supporting the homeostasis of mDA neurons and therefore help in identifying therapeutic targets to treat disorders arising from dysfunctional mDA neurons.FOXA1 and FOXA2 (FOXA1/2) are members of the wingedhelix/forkhead transcription factors, which share over 95% homology between mice and humans (11). FOXA1/2 are so-called "pioneer proteins" that, by binding to tightly condensed chromatin in promoters and enhancer regions, facilitate access of other transcription factors (12, 13). FOXA1/2 regulate the development of diverse organs, including the lung, liver, pancreas, prostate, and kidneys (14). We have also found that FOXA1/2 play a crucial role in the generation of mDA neurons during early and late development, regulating both their specification and dif...

Section: Discussionmentioning

confidence: 99%

Transcription factors FOXA1 and FOXA2 maintain dopaminergic neuronal properties and control feeding behavior in adult mice

Pristerà

Lin

Kaufmann

et al. 2015

“…Dopamine-deficient mice (Th fs/fs , Dbh Th/ϩ ) carrying two conditionally inactive Th alleles, were generated as described (18). Dopamine-deficient mice are indistinguishable from littermates at birth and maintain normal growth when given daily L-dihydroxyphenylalanine (L-dopa) treatment (30 mg/kg) that restores locomotion for Ϸ8 h (18). Animal protocols were approved by the Institutional Animal Care and Use Committee.…”

Section: Methodsmentioning

confidence: 99%

“…KOR (Oprk1) gene deletion on C57BL/6 background was generated as previously described (23), and homozygous (KOR KO) and WT (KOR WT) littermate controls were generated by heterozygote crosses. Dopamine-deficient mice (Th fs/fs , Dbh Th/ϩ ) carrying two conditionally inactive Th alleles, were generated as described (18). Dopamine-deficient mice are indistinguishable from littermates at birth and maintain normal growth when given daily L-dihydroxyphenylalanine (L-dopa) treatment (30 mg/kg) that restores locomotion for Ϸ8 h (18).…”

Section: Methodsmentioning

confidence: 99%

“…Dopamine-deficient (Th fs/fs , Dbh Th/ϩ ) mice cannot produce dopamine due to a selective knockout (KO) of the tyrosine hydroxylase gene in dopaminergic cells, yet produce norepinephrine normally through selective restoration of tyrosine hydroxylase under the dopamine-␤-hydroxylase promotor (18). We found that dopamine-deficient mice were still able to show significant conditioned place aversion (CPA) (mean: Ϫ449 Ϯ 165 s; one-sample t-test, P Ͻ 0.05) to the KOR agonist U50,488.…”

Section: Dopamine Is Not Necessary For Kappa Opioid-mediated Place Avmentioning

confidence: 99%

See 1 more Smart Citation

Activation of the kappa opioid receptor in the dorsal raphe nucleus mediates the aversive effects of stress and reinstates drug seeking

Land

Bruchas²,

Schattauer³

et al. 2009

Self Cite

268

292

Although stress has profound effects on motivated behavior, the underlying mechanisms responsible are incompletely understood. In this study we elucidate a functional pathway in mouse brain that encodes the aversive effects of stress and mediates stress-induced reinstatement of cocaine place preference (CPP). Activation of the dynorphin/kappa opioid receptor (KOR) system by either repeated stress or agonist produces conditioned place aversion (CPA). Because KOR inhibition of dopamine release in the mesolimbic pathway has been proposed to mediate the dysphoria underlying this response, we tested dopamine-deficient mice in this study and found that KOR agonist in these mice still produced CPA. However, inactivation of serotonergic KORs by injection of the KOR antagonist norBNI into the dorsal raphe nucleus (DRN), blocked aversive responses to the KOR agonist U50,488 and blocked stress-induced reinstatement of CPP. KOR knockout (KO) mice did not develop CPA to U50,488; however, lentiviral re-expression of KOR in the DRN of KOR KO mice restored place aversion. In contrast, lentiviral expression in DRN of a mutated form of KOR that fails to activate p38 MAPK required for KORdependent aversion, did not restore place aversion. DRN serotonergic neurons project broadly throughout the brain, but the inactivation of KOR in the nucleus accumbens (NAc) coupled with viral re-expression in the DRN of KOR KO mice demonstrated that aversion was encoded by a DRN to NAc projection. These results suggest that the adverse effects of stress may converge on the serotonergic system and offers an approach to controlling stress-induced dysphoria and relapse.depression ͉ drug addiction ͉ dynorphin ͉ serotonin S tress has profound effects on human health and can lead to mood disorders including clinical depression, anxiety, and can increase comorbid drug addiction risk (1-3). Corticotropin releasing factor (CRF) orchestrates the complex endocrine and neuronal responses to behavioral stress exposure (4), and recent studies have suggested that the dysphoric properties of stress are encoded by CRF-induced activation of the endogenous dynorphin opioid system (5). Systemic administration of kappa opioid receptor (KOR) antagonists block the aversive (5) and pro-addictive effects of stress (6-9), and dynorphin activation of KOR is thought to mediate opponent processes evoked by addictive drugs (10), yet the key sites of dynorphin/KOR action mediating these behavioral responses are not resolved.Mice subjected to behavioral stress show dynorphin release and robust KOR activation in both dopaminergic and serotonergic nuclei (5), implying that these neurotransmitters could be important for KOR-dependent stress-induced behavioral responses. Ventral tegmental area (VTA) dopaminergic projections to the nucleus accumbens (NAc) have been linked to addiction (11), making this an obvious target for the regulation of appetitive and aversive behaviors. However, prior studies have shown that mice lacking dopamine can still develop place preference for drugs of...

“…Licking data were processed and grouped into 2-h bins by using the MatLab software (Mathworks). Meal number and meal size were analyzed as described (50), and the average lick volume was 1.07 l per lick.…”

Section: Methodsmentioning

confidence: 99%

Starvation after AgRP neuron ablation is independent of melanocortin signaling

Howell

Cowley

et al. 2008

Self Cite

105

Ablation of inhibitory agouti-related protein (AgRP)-expressing neurons in the arcuate nucleus that also synthesize ␥-aminobutyric acid (GABA) and neuropeptide Y in adult mice leads to starvation within 1 week. The removal of inhibition from the AgRP neurons onto neighboring proopiomelanocortin neurons and their common postsynaptic neurons is predicted to stimulate melanocortin signaling, which is known to inhibit appetite. To examine the importance of uncontrolled melanocortin signaling in mediating starvation in this model, we ablated AgRP neurons in A y /a mice that have chronic blockade of the melanocortin signaling. The blockade of melanocortin signaling did not ameliorate the rate of starvation. On both WT and A y /a genetic backgrounds, there was a progressive decrease in meal frequency after AgRP neuron ablation. Surprisingly, intraoral feeding also was dramatically reduced after the ablation of AgRP neurons. These results indicate that both the appetitive and consummatory aspects of feeding become impaired in a melanocortin-independent manner after AgRP neuron ablation.T he melanocortin signaling pathway in the medial hypothalamus has emerged as a critical mediator of hormonal and neuronal signals that regulate energy balance (1-3). Genetic, pharmacological, anatomical, and electrophysiological techniques have established a pivotal role for proopiomelanocortin (POMC) neurons in the arcuate (ARC) and their signaling via melanocortin (␣-MSH) to cells bearing melanocortin-4 receptors (MC4R) in the paraventricular nucleus (PVN) and other brain regions in the control of appetite and metabolism (1,4,5). Neighboring cells that coexpress neuropeptide Y (NPY) and agouti-related protein (AgRP) also have been implicated in appetite and energy balance because these peptides stimulate robust feeding when injected into the brain, and their mRNA levels increase in the ARC under starvation conditions, as well as in obese animals deficient in leptin signaling (2,(6)(7)(8). Various experiments suggest that NPY acts by inhibiting the activity of POMC neurons and postsynaptic MC4R-bearing cells by activating G␣i-coupled NPY Y1 and/or Y5 receptors (7, 9-12). The activation of these receptors is predicted to counteract melanocortin activation of G␣s-coupled MC4R. AgRP acts in concert with NPY by blocking the binding of ␣-MSH to MC4R (8,13,14). The neurons that make NPY and AgRP also produce GABA, which inhibits POMC neurons and probably MC4R-bearing cells (15,16). Thus, these AgRP neurons are poised to inhibit melanocortin signaling by the neighboring POMC cells.The activation of melanocortin signaling by leptin inhibits appetite while stimulating metabolism (1, 2, 6). Consequently, the inactivation of mouse genes encoding leptin, leptin receptor, POMC, or MC4R leads to obesity (17)(18)(19)(20). However, the inactivation of genes encoding NPY, AgRP, or both has little effect on energy balance (21-23). These genetic results suggest that compensatory mechanisms in the KO mice mask the normal role of these peptides. Nevertheles...