Runt-related transcription factors (Runx) regulate the development of various cells. It has been reported that Runx1 and Runx3 are expressed in distinct subpopulations of primary sensory neurons in the dorsal root ganglion (DRG), and play important roles in the differentiation of nociceptive and proprioceptive neurons, respectively. In the present study, we examined the developmental changes of the expression of Runx1 and Runx3 in the mouse DRG during embryonic and postnatal stages. We found that the expression of Runx3 preceded that of Runx1, but dramatically decreased before birth, whereas the Runx1 expression was maintained during postnatal periods. These results suggest that roles of Runx1 and Runx3 may change dynamically in the differentiation and maturation of DRG neurons. In addition, several DRG neurons expressed both Runx1 and Runx3 throughout embryonic and postnatal stages and many Runx3-expressing DRG neurons coexpressed Runx1 at postnatal day 28. Double and triple labeling studies suggest that some of the Runx1/Runx3-double expressing neurons coexpressed TrkB, c-ret, and TrkC, which have been shown in the mechanoreceptive DRG neurons. These results suggest that Runx1/Runx3-double expressing neurons may represent mechanoreceptive properties in the DRG.
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