Adult-born proopiomelanocortin neurons derived from Rax-expressing precursors mitigate the metabolic effects of congenital hypothalamic proopiomelanocortin deficiency

Abstract

Objective Proopiomelanocortin (POMC) neurons of the hypothalamic arcuate nucleus are essential regulators of energy balance. Selective loss of POMC production in these cells results in extreme obesity and metabolic comorbidities. Neurogenesis occurs in the adult hypothalamus, but it remains uncertain whether functional POMC neurons emerge in physiologically significant numbers during adulthood. Here, we tested whether Rax -expressing precursors generate POMC neurons in adult mice and rescue the metabolic phenotype caused by congenital hypothalamic POMC deficiency. Methods Initially, we identified hypothalamic Rax -expressing cell types using wild-type and Rax-CreERT2:Ai34D mice. Then we generated compound Rax-CreERT2 :Arc Pomc loxTB/loxTB mice in which endogenous hypothalamic Pomc expression is silenced, but can be restored by tamoxifen administration selectively in neurons derived from Rax + progenitors. The number of POMC neurons generated by Rax + progenitors in adult mice and their axonal projections was determined. The metabolic effects of these neurons were assessed by measuring food intake, bodyweight, and body composition, along with glucose and insulin levels. Results We found that Rax is expressed by tanycytes and a previously unrecognized cell type in the hypothalamic parenchyma of adult mice. Rax + progenitors generated ~10% of the normal adult hypothalamic POMC neuron population within two weeks of tamoxifen treatment. The same rate and steady state of POMC neurogenesis persisted from young adult to aged mice. These new POMC neurons established terminal projections to brain regions that were involved in energy homeostasis. Mice with Rax + progenitor-derived POMC neurons had reduced body fat mass, improved glucose tolerance, increased insulin sensitivity, and decreased bodyweight in proportion to the number of new POMC neurons. Conclusions These data demonstrate that Rax + progenitors generate POMC neurons in sufficient numbers during adulthood to mitigate the metabolic abnormalities of hypothalamic POMC-deficient mice. The findings suggest that adult hypothalamic neurogenesis is a robust phenomenon in mice that can significantly impact energy homeostasis.

SHH and Notch regulate SOX9+ progenitors to govern arcuate POMC neurogenesis

“…POMC neurons respond to adipose-derived leptin by signalling to "satiety neurons" expressing the melanocortin receptor, ultimately inhibiting food intake and promoting energy expenditure (Lee and Blackshaw, 2014;Anderson et al, 2016;Quarta et al, 2020). Studies of POMC neurogenesis may therefore lead to the identification of molecular mechanisms that help to prevent metabolic syndrome (Surbhi et al, 2021).…”

Identification of AgRP cells in the murine hindbrain that drive feeding

“…Tanycytes have progenitor cell properties and can give rise to ependymal cells, tanycytes, astrocytes and neurons [ [40] , [41] , [42] ]. Indeed, hypothalamic tanycytes have the capacity to differentiate into neurons [ 40 , 41 , 43 ], and cells resembling tanycytes are present in the AP [ 30 , 44 , 45 ]. CNS neuronal circuits exhibit incredible plasticity, especially during the embryonic and early postnatal period, so that animals can adapt to a new environment.…”