This image shows cultured cells three weeks after sympathetic neuroblasts were transfected with expression vectors for GFP and a constitutively active form of the kinase ALK. Activated ALK promotes neuronal differentiation and long-term survival. Cells were stained for GFP (green) and tyrosine hydroxylase (red). Note the large neuron cell bodies and extensive neurite network of ALK-induced neurons (yellow) compared to untransfected small sympathetic neuroblasts (red). For more information, see the article by Kramer et al. (pages 10425-10439).