Linking metabolism and cognition: new regulatory pathways involving GABAergic neurons – METACOGNITION

To understand these mechanisms, our entry point will be our recent discovery that expression of the two transcription factors Dlx5 and Dlx6 in GABAergic neurons regulates both metabolism and behaviour. By combining behavioural, metabolic and proteomic approaches after targeted deletion or overexpression of Dlx5/6 in specific regions of the mouse brain, METACOGNITION aims to better understand the links between hypothalamic, cognitive, and rewarding neuronal regulations. Our new conditional mutant mice will permit to modulate the expression of Dlx5 and Dlx6 in all GABAergic neurons or in specific hypothalamic and cortical neuronal populations essential for the control of feeding behaviour. To this end we will use a combination of genetic and viral stereotactic approaches. Metabolic and behavioural phenotyping will be performed in our dedicated platforms.
To understand the molecular mechanisms through which Dlx5 affects physiological processes we will determine the composition of protein complexes involving Dlx5 and its associated protein MAGED1. To this end we will use a combination of immunoprecipitation, mass spectroscopy and targeted mutagenesis to analyse region-specific protein complex formation and propose possible regulatory mechanisms involving Dlx5 in the hypothalamus and in cortical regions. This new knowledge will permit to identify new protein/protein interactions which might become targets for drug design with potential applications to diseases such as schizophrenia, Prader-Willi syndrome and other feeding disorders.

In this first period we have analysed our newly-generated Vgat?Dlx5-6 mice in which Dlx5 and Dlx6 are simultaneously inactivated in all GABAergic interneurons. Vgat?Dlx5-6 mice present a behavioral pattern suggesting reduction of anxiety and obsessive-compulsive activities, and a lower interest in nest building. Twenty-month-old Vgat?Dlx5-6 animals have the same size as their normal littermates, but present a 25% body weight reduction associated with a marked decline in white and brown adipose tissue. A totally unexpected and novel observation is that both Vgat?Dlx5-6/+ and Vgat?Dlx5-6 mice present a 33% longer median survival. Hallmarks of biological aging such as motility, adiposity and coat conditions are improved in mutant animals. Our data imply that GABAergic interneurons can
regulate healthspan and lifespan through Dlx5/6-dependent mechanisms. These findings are the object of the paper “Dlx5 and Dlx6 expression in GABAergic neurons controls behavior, metabolism, healthy aging and lifespan” which has been accepted for publication on the journal “Aging” one of the leading journal in the field. This paper is the product of the combined activity of the groups participating to METACOGNITION. The new findings of the paper provide an entry point to unravel the processes through which the brain affects body homeostasis and, ultimately, longevity and healthy aging.

With a genetic modification made exclusively in a class of neurons the healthy life of mice was prolonged by 30%. This observation could have implications for understanding the control of the lifespan of humans.
In the second part of the grant we will complete the analysis of the new mouse colonies and complete the results of our preliminary analysis.
Viral cre-recombinase administration to the cerebral cortex will permit to understand better the cognitive effects of Dlx5/6 in GABAergic neurons. We already have preliminary data showing a reduction of parvalbumin neurons in the prefrontal cortex following Dlx5/6 inactivation.
Single-cell RNAseq analysis is being performed to define precisely the molecular changes induced by Dlx5/6 inactivation in GABAergic neurons, this analysis will surely be completed before the end of the project, the first data are shown in the published common paper.

Published papers

1: Camille de Lombares, Eglantine Heude , Gladys Alfama, Anastasia Fontaine, 4Rim Hassouna, Cécile Vernochet, Fabrice de Chaumont, Christophe Olivo-Marin, Elodie Ey, Sébastien Parnaudeau, François Tronche, Thomas Bourgeron, Serge Luquet, Giovanni Levi, Nicola Narboux-Nême
Dlx5 and Dlx6 expression in GABAergic neurons controls behavior, metabolism, healthy aging and lifespan
Aging Accepted for publication

2: Narboux-Neme N, Ekker M, Levi G, Heude E. Posterior axis formation requires Dlx5/Dlx6 expression at the neural plate border. PLoS One. 2019 Mar 19;14(3):e0214063. doi: 10.1371/journal.pone.0214063. eCollection 2019. PubMed PMID: 30889190; PubMed Central PMCID: PMC6424422.

3: Shimizu M, Narboux-Nême N, Gitton Y, de Lombares C, Fontaine A, Alfama G, Kitazawa T, Kawamura Y, Heude E, Marshall L, Higashiyama H, Wada Y, Kurihara Y, Kurihara H, Levi G. Probing the origin of matching functional jaws: roles of Dlx5/6 in cranial neural crest cells. Sci Rep. 2018 Oct 8;8(1):14975.

International meetings

1: Postnatal cellular and behavioral effects of Dlx5/6 homozygous deletion from GABAergic interneurons. - Giovanni Levi, Camille de Lombares, Zakaria Maakoul, and Nicolas Narboux-Nême - Cold Spring Harbor Laboratory NY – USA 83rd Symposium: Brains & Behavior: Order & Disorder in the Nervous System


2: Behavioral functions affected by dlx5 and dlx6: possible implications for psychiatric disorders and for the origin of human cognition. - Camille de Lombares, Stephane Peyregne, Nicolas Narboux-Nême and Giovanni Levi - Cold Spring Harbor Laboratory NY – USA 83rd Symposium: Brains & Behavior: Order & Disorder in the Nervous System

National meetings

1. Congres NeuroFrance 2019 22-24 mai Marseille titre : «Behavioural and metabolic consequences of Dlx5 and Dlx6 inactivation in GABAergic neurons.« Nicolas Narboux-Nême, Camille de Lombares, Eglantine Heude et Giovanni Levi

Psychiatric and metabolic disorders present a high co-morbidity suggesting that the aetiology of both disorders depends on common physiological mechanisms. The existence of common genetic and molecular regulatory mechanism is reinforced by the fact that several genetic conditions, such as Prader-Willi syndrome, present both metabolic dysfunctions and cognitive impairment. Emerging findings demonstrate the central role of cortico-hypothalamic crosstalk in the control of body energy homeostasis. However, the underlying pathophysiological, molecular and cellular mechanisms linking metabolism and cognition are still poorly understood.
To understand these mechanisms, our entry point will be our recent discovery that expression of the two transcription factors Dlx5 and Dlx6 in GABAergic neurons regulates both metabolism and behaviour. By combining behavioural, metabolic and proteomic approaches after targeted deletion or overexpression of Dlx5/6 in specific regions of the mouse brain, METACOGNITION aims to better understand the links between hypothalamic, cognitive, and rewarding neuronal regulations. Our new conditional mutant mice will permit to modulate the expression of Dlx5 and Dlx6 in all GABAergic neurons or in specific hypothalamic and cortical neuronal populations essential for the control of feeding behaviour. To this end we will use a combination of genetic and viral stereotactic approaches. Metabolic and behavioural phenotyping will be performed in our dedicated platforms.
To understand the molecular mechanisms through which Dlx5 affects physiological processes we will determine the composition of protein complexes involving Dlx5 and its associated protein MAGED1. To this end we will use a combination of immunoprecipitation, mass spectroscopy and targeted mutagenesis to analyse region-specific protein complex formation and propose possible regulatory mechanisms involving Dlx5 in the hypothalamus and in cortical regions. This new knowledge will permit to identify new protein/protein interactions which might become targets for drug design with potential applications to diseases such as schizophrenia, Prader-Willi syndrome and other feeding disorders.