Differential expression of a proteasomal subunit during chick development.

Removal of cardiac neural crest disrupts normal development of the heart and pharynx. Subtractive hybridization was used to identify differentially expressed messages after neural crest ablation in chick embryos. A 1 kb clone, homologous to PROS-28, a 28 kD alpha subunit of a Drosophila proteasome, was differentially expressed in embryos lacking neural crest. An increase of GPROS-28 expression in the head and pharyngeal arches of stages 12-21 chick embryos without cardiac neural crest accompanied generalized low-level expression throughout experimental and normal embryos. In addition, high levels of GPROS-28 expression were detected in normal embryos at particular sites and times in development in the limb buds, mesonephros, heart, liver, neural tube, dorsal root ganglia, and lung buds, when the cells in these regions were undergoing intense proliferation.