Cover photograph (Copyright © 2000, American Society for Microbiology. All rights reserved.): Zac1, a regulator of cell cycle progression and apoptosis, is a maternally imprinted gene in the mouse. Here, Zac1 transcripts are detected by in situ hybridization in day 11 embryos. Zac1 expression is observed in the neural tube, somites, sympathetic ganglia, distal second branchial arch, and telencephalic vesicles. (See related article by Piras et al. in the next issue.)