The role of muscle LIM protein in the nervous system

The first hints as to MLP’s expression in the CNS and its regenerative role there came from a microarray study, which had characterized the gene expression patterns of axotomized retinal ganglion cells (RGCs) (Fischer et al., 2004). Surprisingly, of the MLP-positive neurons observed at 2 days after the nerve crush, almost half of them could be co-stained for IB4; however, by day 7, this number had fallen to just 1%. [...]the nerve injury was causing the non-peptidergic nociceptive sensory neurons to lose their canonical marker (IB4), hiding their identity. Treatment with glial-derived neurotrophic factor delayed axotomy-induced downregulation of IB4 sensitivity without altering the total number of neurons, which then brought the number of co-labeled neurons up to 51% (from 11%). [...]as the glial-derived neurotrophic factor receptor is another marker for non-peptidergic nociceptive sensory neurons, it confirms that the majority of MLP-positive neurons belong to this group in the PNS (Levin et al., 2017). (2019) also showed most recently MLP expression (also on the protein level) in injured and growth-stimulated RGCs of adult rats, allowing us to scrutinize its functional role in this context.