IDENTIFICATION OF NUCLEAR PROTEINS THAT ARE DEVELOPMENTALLY-REGULATEDIN EMBRYONIC RAT-BRAIN

To identify nuclear proteins that might play a role in the acquisition of neuronal phenotype, two-dimensional polyacrylamide gel electrophor esis (2D-PAGE) was used to analyze nuclear proteins expressed over the course of embryonic rat brain development. Metabolically labeled rat brain nuclear proteins from embryonic day 14 (E14) were compared with proteins from embryonic day 20 (E20). Over this period, the rat brain develops from a collection of relatively homogeneous precursor cells i nto a complex structure containing many different classes of neurons. Computer-assisted analysis of 2D-PAGE fluorograms identified 11 protei ns that show increases in their rate of synthesis between E14 and E20. Twenty proteins that consistently appear at E20 are not detectable on fluorograms of E14 nuclear proteins, even after long exposures, and t hus may be considered to appear de novo. Fifty-eight proteins show con sistent down-regulation between E14 and E20, and of these, 19 are not detectable on fluorograms of E20 nuclear proteins. The electrophoretic properties of many of these proteins suggest that they are previously unreported, developmentally regulated nuclear proteins. Some of the d evelopmentally regulated, brain-enriched nuclear proteins identified h ere may play a role in regulating the expression of neural genes impor tant for cellular differentiation in the mammalian CNS.