On Apr. 18, 2012, The Journal of Neuroscience published online a research article entitled "c-Maf Is Required for the Development of Dorsal Horn Laminae III/IV Neurons and Mechanoreceptive DRG Axon Projections". This work was mainly carried out by graduate students Jia Hu and Tianwen Huang, under the supervision of Dr. Leping Cheng.

Dorsal root ganglion (DRG) neurons convey sensory signals of different modalities via their axon projections to distinct laminae in the dorsal horn of the spinal cord. In this study, we found that c-Maf was expressed predominantly in the interneurons of laminae III/IV, which primarily receive inputs from mechanoreceptive DRG neurons. In the DRG, c-Maf⁺ neurons also co-expressed neurofilament-200 (NF200), a marker for the medium- and large-diameter myelinated afferents that transmit non-noxious information. Furthermore, mouse embryos deficient in c-Maf displayed abnormal development of dorsal horn laminae III/IV neurons, as revealed by the marked reduction in the expression of several marker genes for these neurons. In addition, among the four major subpopulations of DRG neurons marked by expression of TrkA, TrkB, TrkC, and MafA/GFRα2/Ret, c-Maf was required selectively for the proper differentiation of MafA⁺/Ret⁺/GFRα2⁺ low-threshold mechanoreceptors (LTMs). Lastly, we found that the central and peripheral projections of mechanoreceptive DRG neurons were compromised in c-Maf deletion mice. Our results therefore indicate that c-Maf is required for the proper development of MafA⁺/Ret⁺/GFRα2⁺ LTMs in the DRG, their afferent projections in the dorsal horn and Pacinian corpuscles, as well as neurons in laminae III/IV of the spinal cord.

This work was supported by the 973 Program of The Ministry of Science and Technology of China and the “Strategic Priority Research Program” of the Chinese Academy of Sciences.

Aberrant projections of mechanoreceptive neurons in the deep dorsal horn of c-Maf deletion mice