Florence Appaix

How the energy status of enteric progenitors controls neurogliogenesis and the subsequent formation of the complex enteric nervous system (ENS) remains poorly understood. We previously showed that the tumor suppressor kinase LKB1 is essential for postnatal ENS maintenance through amino acid homeostasis. Here, we investigated LKB1's functions during embryonic ENS formation using a genetically engineered mouse model with conditional Lkb1 inactivation in neural crest progenitors during gut colonization. Using advanced 3D imaging techniques on cleared tissue including light sheet microscopy and adaptive optics confocal microscopy, we found that Lkb1 loss impairs early neuronal differentiation followed by progressive glial degeneration, leading to hypoganglionosis and compromised digestive tissue integrity. Notably, Lkb1 inactivation induced a transient upregulation of the glial stress marker S100β during gestation, suggestive of a reactive glial state preceding glial loss. Consistent with this response, Lkb1 loss elevated oxidative stress in the digestive tract and in neural crest progenitors and their glial derivatives, triggering DNA damage and p53 activation. Although p53 ablation rescued glial specification in vitro and glial maintenance in vivo, it only partially restored ENS architecture in vivo without rescuing enteric neuron numbers. Together, these findings establish LKB1 as a critical metabolic checkpoint governing neuronal–glial balance during ENS development and suggest that dysregulated LKB1 signaling may contribute to human enteric neurogliopathies.

Neurodevelopmental axonal pathfinding plays a central role in correct brain wiring and subsequent cognitive abilities. Within the growth cone, various intracellular effectors transduce axonal guidance signals by remodeling the cytoskeleton. Semaphorin-3E (Sema3E) is a guidance cue implicated in development of the fornix, a neuronal tract connecting the hippocampus to the hypothalamus. Microtubule-associated protein 6 (MAP6) has been shown to be involved in the Sema3E growth-promoting signaling pathway. In this study, we identified the collapsin response mediator protein 4 (CRMP4) as a MAP6 partner and a crucial effector in Sema3E growth-promoting activity. CRMP4-KO mice displayed abnormal fornix development reminiscent of that observed in Sema3E-KO mice. CRMP4 was shown to interact with the Sema3E tripartite receptor complex within detergent-resistant membrane (DRM) domains, and DRM domain integrity was required to transduce Sema3E signaling through the Akt/GSK3 pathway. Finally, we showed that the cytoskeleton-binding domain of CRMP4 is required for Sema3E’s growth-promoting activity, suggesting that CRMP4 plays a role at the interface between Sema3E receptors, located in DRM domains, and the cytoskeleton network. As the fornix is affected in many psychiatric diseases, such as schizophrenia, our results provide new insights to better understand the neurodevelopmental components of these diseases.