Cover picture: Shown is a motor unit from a transgenic mouse expressing yellow fluorescent protein (YFP) in a single motor neuron (green) that innervates the spinotrapezius muscle at postnatal day 8. This animal received twice-daily subcutaneous injections of glial cell line-derived neurotrophic factor (GDNF) beginning on the day of birth. The GDNF causes an increased number of terminal branches. Acetylcholine receptors were labeled with rhodamine-conjugated -bungarotoxin (red). For details, see the article by Keller-Peck et al. in this issue (pages 6136-6146).