Probes for INS

Cholinergic interneurons (CINs) are critical regulators of striatal network activity and output. Changes in CIN activity are thought to encode salient changes in the environment and stimulus-response-outcome associations. Here we report that the stress-associated neuropeptide corticotropin releasing factor (CRF) produces a profound and reliable increase in the spontaneous firing of CINs in both dorsal striatum and nucleus accumbens (NAc) through activation of CRF type 1 receptors, production of cAMP and reduction in spike accommodation in male mice. The increase of CIN firing by CRF results in the activation muscarinic acetylcholine receptors type 5, which mediate potentiation of dopamine transmission in the striatum. This study provides critical mechanistic insight into how CRF modulates striatal activity and dopamine transmission in the NAc to likely account for CRF facilitation of appetitive behaviors.SIGNIFICANCE STATEMENT Although the presence of CRF receptors in the dorsal and ventral striatum has been acknowledged, the cellular identity and the functional consequences of receptor activation is unknown. Here we report that striatal cholinergic interneurons express CRF-R1 receptors and are acutely activated by the neuropeptide CRF that is released in response to salient environmental stimuli. Cholinergic interneurons make <1% of the cells in the striatum but are critical regulators of the striatal circuitry and its output. CRF's fast and potent activation of cholinergic interneurons could have far reaching behavioral implications across motivated behaviors controlled by the striatum.

Dopaminergic signaling in the striatum, particularly at dopamine 2 receptors (D2R), has been a topic of active investigation in obesity research in the past decades. However, it still remains unclear whether variations in striatal D2Rs modulate the risk for obesity and if so in which direction. Human studies have yielded contradictory findings that likely reflect a complex nonlinear relationship, possibly involving a combination of causal effects and compensatory changes. Animal work indicates that although chronic obesogenic diets reduce striatal D2R function, striatal D2R down-regulation does not lead to obesity. In this study, we evaluated the consequences of striatal D2R up-regulation on body-weight gain susceptibility and energy balance in mice. We used a mouse model of D2R overexpression (D2R-OE) in which D2Rs were selectively up-regulated in striatal medium spiny neurons. We uncover a pathological mechanism by which striatal D2R-OE leads to reduced brown adipose tissue thermogenesis, reduced energy expenditure, and accelerated obesity despite reduced eating. We also show that D2R-OE restricted to development is sufficient to promote obesity and to induce energy-balance deficits. Together, our findings indicate that striatal D2R-OE during development persistently increases the propensity for obesity by reducing energy output in mice. This suggests that early alterations in the striatal dopamine system could represent a key predisposition factor toward obesity.

Forkhead box A2 (FOXA2) is a pioneer transcription factor involved in organ development, function, and cancer. In the uterus, FOXA2 is essential for pregnancy and expressed specifically in the glands of the endometrium. Loss of FOXA2 function occurs during development of endometrial cancer in humans. The current study describes the development of a mouse model for conditional expression of mouse FOXA2. Using a system consisting of a minigene located at the Rosa26 locus, we generated a CAG-S-mFOXA2 allele in embryonic stem cells and subsequently in mice; before activation, the minigene is silent because of a floxed stop cassette inserted between the promoter and the transgene. To validate functionality, mice with the CAG-S-mFOXA2 allele were crossed with progesterone receptor (Pgr)-Cre mice and lactotransferrin (Ltf)-iCre mice that express Cre in the immature and adult uterus, respectively. In immature Pgr-Cre-CAG-S-mFoxa2 mice, FOXA2 protein was expressed in the luminal epithelium (LE), glandular epithelium (GE), stroma, and inner layer of the myometrium. Interestingly, FOXA2 protein was not observed in most of the LE of uteri from adult Pgr-Cre-CAG-S-mFoxa2 mice, although FOXA2 was maintained in the stroma, GE, and myometrium. The adult Pgr-Cre-CAG-S-mFoxa2 females were completely infertile. In contrast, Ltf-iCre-CAG-S-mFoxa2 mice were fertile with no detectable histological differences in the uterus. The adult uterus of Pgr-Cre-CAG-S-mFoxa2 mice was smaller, contained few endometrial glands, and displayed areas of partially stratified LE and GE. This transgenic mouse line is a valuable resource to elucidating and exploring FOXA2 function.

Dysfunction of cholinergic signaling in the brain has long been believed to be associated with depressive disorders. However, the functional impact of habenular cholinergic signaling on the specified depressive behaviors is not well understood. Here, we demonstrated that the expression levels of cholinergic signaling genes (CHAT, VACHT, CHT, CHRNA3, CHRNB3 and CHRNB4) were down-regulated in a chronic restraint stress (CRS) rat model of depression, in which rats display depression-like behaviors such as anhedonia and mood despair. Moreover, knockdown of CHAT in the rat habenula was sufficient to evoke anhedonia-like behavior. The anhedonia-like behavior induced by CHAT knockdown was not reversed by chronic administration of the selective serotonin reuptake inhibitor fluoxetine. To determine whether habenular cholinergic signaling is associated with regulation of dopamine neurons in the ventral tegmental area (VTA) and serotonin neurons in the dorsal raphe nucleus (DRN), we used CHAT::cre transgenic mice expressing the Designer Receptors Exclusively Activated by Designer Drugs (DREADD). Pharmacogenetic activation of habenular cholinergic neurons induces the excitation of dopamine neurons in the VTA and reduces the immunoreactivity of 5-hydroxytryptamine (5-HT) in the DRN. Habenular cholinergic gene down-regulation was recapitulated in the postmortem habenula of suicide victims diagnosed with major depressive disorder (MDD).

Neuronal circuit asymmetries are important components of brain circuits, but the molecular pathways leading to their establishment remain unknown. Here we found that the mutation of FRMD7, a gene that is defective in human congenital nystagmus, leads to the selective loss of the horizontal optokinetic reflex in mice, as it does in humans. This is accompanied by the selective loss of horizontal direction selectivity in retinal ganglion cells and the transition from asymmetric to symmetric inhibitory input to horizontal direction-selective ganglion cells. In wild-type retinas, we found FRMD7 specifically expressed in starburst amacrine cells, the interneuron type that provides asymmetric inhibition to direction-selective retinal ganglion cells. This work identifies FRMD7 as a key regulator in establishing a neuronal circuit asymmetry, and it suggests the involvement of a specific inhibitory neuron type in the pathophysiology of a neurological disease.