Histone H1 degrees expression in the developing cat retina

Histone H1 degrees is a subtype of the non-core H1 histones located in the linker region of DNA between nucleosome cores and postulated to be involved in the regulation of gene expression. Studies in both the mouse retina and rat brain have correlated the terminal differentiation of cell types in th ese tissues to the expression of H1 degrees. The expression of H1 degrees i n mouse retina occurs after light exposure suggesting that light may trigge r the expression of H1 degrees. The aims of the present research were to: ( 1) describe the relationship of the appearance of H1 protein immunoreactivi ty to the formation of cell types and layers in the cat retina; and (2) det ermine whether H1" may be dependent on exposure to light or on other postna tal developmental events. We find the nuclei of ganglion, amacrine, and pro spective bipolar cells contain H1 degrees immunoreactivity before birth, pr ior to the terminal differentiation of these cells. In the cat retina, expr ession of H1 degrees occurs prior to Light exposure. These results show tha t the expression of H1 degrees protein is not required for the terminal dif ferentiation of retinal cell types in the car. Additionally, we find no req uirement for Light exposure prior to H1 degrees expression, These findings are at variance with the findings in the mouse retina and are inconsistent with any cross species requirement for the expression of this histone in th e terminal differentiation of cell types in the retina. (C) 1999 Elsevier S cience B.V. All rights reserved.