Abstract
Introduction. Runx1, a Runt domain transcription factor, controls the differentiation of nociceptors that express the neurotrophin receptor Ret, regulates the expression of many ion channels and receptors, and controls the lamina-specific innervation pattern of nociceptive afferents in the spinal cord. Moreover, mice lacking Runx1 exhibit specific defects in thermal and neuropathic pain. We investigated whether conditional activation of Runx1 short isoform (Runx1a), which lacks a transcription activation domain, influences differentiation of neural crest stem cells (NCSCs) in vitro and in vivo during development and whether postnatal Runx1a activation affects the sensitivity to neuropathic pain.Methods. We activated ectopic expression of Runx1a in cultured NCSCs using the Tet-ON gene regulatory system during the formation of neurospheres and analyzed the proportion of neurons and glial cells originating from NCSCs. In in vivo experiments we applied doxycycline (DOX) to pregnant mice (days 8–11), i.e. when NCSCs actively migrate, and examined the phenotype of offsprings. We also examined whether DOX-induced activation of Runx1a in adult mice affects their sensitivity to mechanical stimulation following a constriction injury of the sciatic nerve.Results. Ectopic Runx1a expression in cultured NCSCs resulted in predominantly glial differentiation. Offsprings in which Runx1a had been activated showed retarded growth and displayed megacolon, pigment defects, and dystrophic dorsal root ganglia. In the neuropathic pain model, the threshold for mechanical sensitivity was markedly increased following activation of Runx1a.Conclusion. These data suggest that Runx1a has a specific role in NCSC development and that modulation of Runx1a activity may reduce mechanical hypersensitivity associated with neuropathic pain.
Highlights
Runx1, a Runt domain transcription factor, controls the differentiation of nociceptors that express the neurotrophin receptor Ret, regulates the expression of many ion channels and receptors, and controls the lamina-specific innervation pattern of nociceptive afferents in the spinal cord
We investigated whether conditional activation of Runx1 short isoform (Runx1a), which lacks a transcription activation domain, influences differentiation of neural crest stem cells (NCSCs) in vitro and in vivo during development and whether postnatal Runx1a activation affects the sensitivity to neuropathic pain
These data suggest that Runx1a has a specific role in NCSC development and that modulation of Runx1a activity may reduce mechanical hypersensitivity associated with neuropathic pain
Summary
Dorsal root ganglia (DRGs) are composed of subsets of anatomically and functionally specialized sensory neurons and glial cells, which like all other neurons and glial cells of the peripheral nervous system are derived from the neural crest The development of these cell populations is regulated by sequential expression of a limited number of transcription factors in concert with environmental components. We have examined the role of Runx1a in differentiation of neural crest stem cells (NCSCs) in vitro and in vivo and in the development of neuropathic pain behavior in adult mice. For this purpose we have employed the Tet system [7] to conditionally activate Runx1a in Rosa or Sox10-expressing cells. The activation of Runx1a was accompanied by the expression of enhanced green fluorescent protein (EGFP), which was activated through the internal ribosome entry site (IRES)-EGFP
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