Expression of at least one ERK isoform is necessary for DRG neuron survival. A, Representative images of L5 DRG demonstrate total DRG neurons identified using the pan-neuronal marker, βIII tubulin, in WT (A) and ERK dKO (B) mice. Scale bar, 100 μm. B, Total neuron counts for WT (n = 6) and ERK dKO (n = 6) mice were performed assessing neuronal number in the L5 DRGs using the pan-neuronal marker, βIII tubulin, to identify neurons. C, D, Size distribution data of βIII tubulin+ neurons were acquired for WT (n = 3) and ERK dKO (n = 3) mice using MetaMorph software to manually measure cross-sectional area of neurons in 18-μm-thick sections. Data are graphed both as a total number of neurons per bins (C) and cumulative frequency of neuron sizes (D). Data are mean ± SEM. *p < 0.05 and ***p < 0.001.