Prefrontal cortex MC4R neurons as a target for feeding and cognitive symptoms in PWS

Funding Summary

Dr. Ross will investigate how feeding behavior and cognitive flexibility are jointly regulated in the prefrontal cortex of the brain, in neurons expressing MC4R. This study may define a neuronal circuit to target therapeutically.

Dr. Theresa Strong, Director of Research Programs, shares details on this project in this short video clip. 

Lay Abstract

Prader–Willi Syndrome (PWS) is a genetic disorder characterized by insatiable appetite and development of morbid obesity later in childhood. This leads to a combination of mental and physical problems for these children that persist into adulthood, yet the neural mechanisms underlying these difficulties are not well understood. Using cutting edge neuroscience methods, we recently discovered that a specific population of neurons, in a region called the medial prefrontal cortex, which is responsible for cognitive function regulation, receives satiety signals from other neurons involved in feeding behavior and metabolism. These neurons are molecularly defined by the expression of a protein that is important in regulation of body weight and food intake, called the melanocortin 4 receptor (MC4R). Deleting this protein, which impairs the neurons ability to translate satiety signals, leads to increased food intake and body weight, in addition to cognitive impairment. This suggests that the protein, MC4R, when expressed in the medial prefrontal cortex, is an important integrator of both metabolism and of cognitive behavior as is seen in people with PWS.

In this proposal we will use genetically modified mouse models and a combination of multiple cutting-edge approaches, including chemogenetics (drug-assisted remote stimulation) and direct pharmacologic stimulation of this molecularly and regionally defined population of neurons while animals are awake and behaving normally. We will characterize specific cognitive functions in a mouse model of PWS, and then test the hypothesis that the response of these medial prefrontal cortex neurons to appetite-suppression signals from satiety neurons is relevant to maladaptive behaviors seen in PWS. We will then manipulate this brain circuit in genetically modified mouse model of PWS. Completing the work of this proposal will allow us to identify the impaired brain mechanism for why appetite suppression and maladaptive behavior are seen together in PWS.

The next steps forward for this project will be to determine if the medial prefrontal cortex MC4R neurons could potentially be targeted to control appetite or behavior in PWS. Altogether, this project will help us understand how cognitive function and feeding behavior are jointly regulated in the brain, and suggest novel druggable targets for the development of therapeutic approaches or interventions to treat insatiable appetite and maladaptive behavior in PWS.

Research Outcomes: Public Summary

In this project we aimed to determine the cognitive impairment related to food in the Magel2 null mouse model of Prader Willi Syndrome. Using a battery of behavior tasks, we found Magel2 null mice have a baseline cognitive deficit in associative learning that can be assessed for translational trials. Additionally, we found that the motivation of the Magel2 mice to engage in tasks that require effort is correlated to time spent underfed. This was observed in a number of tasks that required chronic food restriction as part of the training paradigm, and Magel2 null mice engaged less with these tasks than control counterparts. We think this is due to Magel2 mice capacity to maintain their white fat stores even in the setting of chronic restriction; the Magel2 mice have larger fat depots than control mice even when they are the same body weight after chronic food restriction. We are eager to better understand this mechanism of efficient fat storage, and to elucidate how it might influence the animal behavior, thereby providing important insight to how metabolic state influences cognitive function in humans with Prader Willi Syndrome.