X-linked spinal and bulbar muscular atrophy (SBMA) is an inherited neuromuscular disorder characterized by lower motor neuron degeneration. SBMA is caused by polyglutamine repeat expansions in the androgen receptor (AR). To determine the basis of AR polyglutamine neurotoxicity, we introduced human AR yeast artificial chromosomes carrying either 20 or 100 CAGs into mouse embryonic stem cells. The AR100 transgenic mice developed a late-onset, gradually progressive neuromuscular phenotype accompanied by motor neuron degeneration, indicating striking recapitulation of the human disease. We then tested the hypothesis that polyglutamine-expanded AR interferes with CREB binding protein (CBP)-mediated transcription of vascular endothelial growth factor (VEGF) and observed altered CBP-AR binding and VEGF reduction in AR100 mice. We found that mutant AR-induced death of motor neuron-like cells could be rescued by VEGF. Our results suggest that SBMA motor neuronopathy involves altered expression of VEGF, consistent with a role for VEGF as a neurotrophic/survival factor in motor neuron disease.
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