Role of DLX5/6 in GABAergic neurons: deciphering metabolism/behavior interplay – METABRAIN

Metabolic status is one of the major determinants of healthy aging and life expectancy. The brain controls metabolism through the activity of neuronal networks that integrate hormonal signals from peripheral organs and induce behavioural and metabolic responses. We have shown that reduction of Dlx5/6 expression in mouse GABAergic neurons affects simultaneously behavioural patterns and metabolism, with a significant extension of healthspan and lifespan.
METABRAIN wants to provide new understanding on the physiological and pathophysiological mechanisms which link cognition and behaviour to metabolism and energy homeostasis.

Dlx5 and Dlx6 are two transcription factors expressed by cortical, striatal and hypothalamic GABAergic neurons.
In the ANR project “METACOGNITION” we have shown that inactivation of Dlx5/6 in mouse GABAergic neurons (Dlx5/6VgatCre mice) results in:
1) a decline in adult adipose tissues resulting in 25% body weight reduction,
2) a reduction of anxiety-like and obsessive-compulsive behaviours and,
3) in a 33% extension of lifespan and healthspan.
These findings imply that GABAergic interneurons contribute to regulate metabolism, behaviour, health span and lifespan through Dlx5/6-dependent mechanisms that still remain to be understood.
Our preliminary results, that constitute the basis for the present proposal, shown that:
- Despite the strong reduction in body fat, Dlx5/6VgatCre mice present increased calorie consumption per body weight which is partly counterbalanced by enhanced energy expenditure, enhanced glucose metabolism and higher insulin sensitivity. In addition, Dlx5/6VgatCre mice do not respond to the orexigenic factor ghrelin. These results suggest a Dlx5/6 role in central control of feeding behaviour and energy expenditure.
- Dlx5/6VgatCre mice present a decrease in brain gamma-waves recorded by EEG, shorter periods of sleep, an altered vocalisation profile, a reduced working memory and an increased motor response to cocaine.
- During normal brain ageing the relative expression of two, functionally different, Dlx5 isoforms is reverted suggesting their implication in the Dlx5/6-mediated longevity phenotype.
In METABRAIN we will elucidate the regional, cellular and molecular mechanisms through which Dlx5/6-expression in GABAergic neurons affects metabolism, behaviour and longevity.
Our work plan is structured around the following tasks:
- To disentangle the function of Dlx5/6 in different brain areas, we will perform behavioural and metabolic phenotyping of mice in which Dlx5/6 will be deleted or over-expressed in specific brain areas by Cre-recombinase viral delivery. We will target the prefrontal cortex, the striatum and specific hypothalamic nuclei.
- We will analyse the physiological and electrophysiological processes supporting the behavioural and metabolic phenotypes of our mice by assessing their neuronal activity and hormonal profiles.
- We will assess the mechanisms supporting the metabolic resilience of Dlx5/6VgatCre mice to high-fat induced obesity and diabetes by studying their role in hypothalamic neurons and in their capacity to associate reward circuit to metabolic control and sensory processing to metabolic response.
- We will analyse the ageing trajectories of our mice and we will determine the methylation status of their DNA to understand the effect of different Dlx5 splice variants during aging.
- We will apply single-nuclei RNA-Seq (snRNA-seq) and ATAQ-seq analysis to dissected adult brain regions to determine the transcriptional consequences of Dlx5/6 invalidation in GABAergic neurons.
- We will use mass-spectroscopy and molecular modeling to understand the structure and predict the function of protein complexes containing Dlx5, MAGED1 and/or NECDIN (a Prader-Willi Syndrome associated gene present in Dlx5 protein complexes).

METABRAIN has potential impact for child and adult nutrition, for rare diseases such as Prader-Willi syndrome and for age-related comorbidity.