Intranuclear relocation of the Plc beta3 sequence in cerebellar purkinje neurons: temporal association with de novo expression during development.

Abstract

Interphase nuclei exhibit a cell type-specific topology of chromatin domains. This topology has been proposed to be established at a specific developmental stage and to be associated, in turn, with cell type-specific gene expression. Using murine, cerebellar Purkinje neurons, we have shown previously that the number and the extent of clustering as well as the spatial, intranuclear distribution of centromeric domains change as a function of postnatal development. Specifically, the redistribution of centromeric domains was determined to be associated temporally with major changes in gene expression. Given that centromeric sequences are not transcribed, we tested the hypothesis that the de novo expression of a specific sequence is similarly associated with a change in its spatial, intranuclear position. In Purkinje neurons, Plc beta3 is expressed de novo between postnatal day 2 and 7. In contrast, the level of expression of Rora remains constant throughout development, following its initial expression at embryonic day 15. Plc beta3 and Rora were labeled by fluorescence in situ hybridization within intact nuclei and their intranuclear, spatial positions quantified by confocal microscopy. When analyzed as the distance from the nuclear centroid, the mean fraction of radial distance of Plc beta3 signals changed from 57.3%+/-2.35 (+/-SEM) (n=50) at P3 to 37.9%+/-2.35 (n=50) at P5. In contrast, the mean fraction of the radial distance of Rora signals did not change during postnatal development, remaining at a mean of 60.1%+/-2.01 (n=208) from the nuclear centroid. While the results do not support a causal relationship between the spatial relocation of Plc beta3 and its de novo expression, their temporal association, as described herein, may be taken to support the hypothesis that its intranuclear, spatial positioning may represent one level of transcriptional control.