Information provided by the skeletal muscle and associated neurons is necessary for proper brain development

Previously, motor cortex of term Myf5(-/-):MyoD(-/-) fetuses (e.g. have ablated skeletal myogenesis and consequent early loss of lower motor and proprioceptive neurons) was found to lack giant pyramidal cells. We further investigated how the absence of the extrinsic stimuli from the lacking structures influences brain development. Apparently normal motor cortex of mutant fetuses was found to have dramatically reduced presence of nestin-expressing processes of neural precursors, calretinin-expressing pyramidal neurons and calbindin-expressing neurons. Consistently, some areas of the extrapyramidal tract had significantly decreased number of differentiated neurons in mutant brains. Surprisingly, we were unable to detect any change in proliferation or cell death in the mutant neuroepithelium. Together, it appears that the information provided by the lacking structures influences the ratios of the differentiated neuronal types and their progenitor cells.