AbstractDorsal root ganglia proceed from the coalescence of cell bodies of sensory neurons, which have migrated dorsoventrally from the delaminating neural crest. They are composed of different neuronal subtypes with specific sensory functions, including nociception, thermal sensation, proprioception, and mechanosensation. In contrast to proprioceptors and thermonociceptors, little is known about the molecular mechanisms governing the early commitment and later differentiation into mechanosensitive neurons. This is mainly due to the absence of specific molecular markers for this particular cell type. Using knockout mice, we identified the bZIP transcription factor MafA as the first specific marker of a subpopulation of “early c‐ret” positive neurons characterized by medium‐to‐large diameters. This marker will allow further functional characterization of these neurons. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70:485–497, 2010