Decoding molecular sexual dimorphism of neuromuscular function

Motor functions implement evolutionary relevant and necessary actions, such as running and breathing. They rely on electric impulses which produce muscle contractions through the neuromuscular junction (NMJ). Sex-dependent features including hormone production and genetics influence neuromuscular pathophysiology, but the molecular players involved are unknown.Here, I will unravel how sex hormones shape and maintain NMJs by dissecting the unconventional signalling exerted by peripheral hormone receptors. Indeed, unexpectedly, androgen receptor (AR) localizes at the neuron periphery and is regulated by neuronal activity. Trinucleotide repeat expansions (TRE) in AR gene cause spinal and bulbar muscular atrophy (SBMA), a neuromuscular disease caused by motor neuron degeneration and muscle wasting. As AR interacts with components of the translation machinery and RNA-binding proteins, I hypothesize that extra-nuclear AR is a regulator of NMJ stability mediated by hormone binding, regulating sex-specific local translation of key mRNA targets in a phosphorylation/dephosphorylation-dependent manner, mechanisms which fail to support neuron/muscle crosstalk in SBMA.Applying sophisticated in vitro models such as cocultures in microfluidic devices and cutting-edge spatial technologies, I propose to test this by: 1. Dissecting the in vivo NMJ transcriptome in healthy males/females and SBMA mice using unbiased Nova-ST technology and snRNA-seq.2. Elucidating the sex-specific synaptic translation events in motor axons and NMJs using ribosome sequencing from microdissected subcellular compartments.3. Identifying the molecular players involved in the AR-dependent local translation at the NMJ and their dysregulation in disease using proximity labelling. AR-NMJ will be the first of its kind to identify the unprecedented spatial AR function and its dysregulation in SBMA at the NMJ, uncovering a novel sex-specific pathway for NMJ function, and original therapeutic strategies for SBM