Hamada, H., Watanabe, M., Lau, H.E., Nishida, T., Hasegawa, T., Parichy, D.M., and Kondo, S. (2014) Involvement of Delta/Notch signaling in zebrafish adult pigment stripe patterning. Development (Cambridge, England). 141(2):318-324.
The skin pigment pattern of zebrafish is a good model system in which to study the mechanism of biological pattern formation.
Although it is known that interactions between melanophores and xanthophores play a key role in the formation of adult pigment
stripes, molecular mechanisms for these interactions remain largely unknown. Here, we show that Delta/Notch signaling contributes
to these interactions. Ablation of xanthophores in yellow stripes induced the death of melanophores in black stripes, suggesting
that melanophores require a survival signal from distant xanthophores. We found that deltaC and notch1a were expressed by xanthophores and melanophores, respectively. Moreover, inhibition of Delta/Notch signaling killed melanophores,
whereas activation of Delta/Notch signaling ectopically in melanophores rescued the survival of these cells, both in the context
of pharmacological inhibition of Delta/Notch signaling and after ablation of xanthophores. Finally, we showed by in vivo imaging of cell membranes that melanophores extend long projections towards xanthophores in the yellow stripes. These data
suggest that Delta/Notch signaling is responsible for a survival signal provided by xanthophores to melanophores. As cellular
projections can enable long-range interaction between membrane-bound ligands and their receptors, we propose that such projections,
combined with direct cell-cell contacts, can substitute for the effect of a diffusible factor that would be expected by the
conventional reaction-diffusion (Turing) model.