Chromatin dynamics and gene positioning.

The mammalian cell nucleus provides a landscape where genes are regulated through their organization and association with freely diffusing proteins and nuclear domains. In many cases, specific genes are highly dynamic, and the principles governing their movements and interchromosomal interactions are currently under intensive study. Recent investigations have implicated actin and myosin in chromatin dynamics and gene expression.

Dynamics and anchoring of heterochromatic loci during development.

Positioning a euchromatic gene near heterochromatin can influence its expression. To better understand expression-relevant changes in locus positioning, we monitored in vivo movement of centromeres and a euchromatic locus (with and without a nearby insertion of heterochromatin) in developing Drosophila tissue. In most undifferentiated nuclei, the rate of diffusion and step size of the locus is unaffected by the heterochromatic insertion.

Changing chromatin dynamics and nuclear organization during differentiation in Drosophila larval tissue.

Global changes in gene expression and exit from the cell cycle underlie differentiation. Therefore, understanding chromatin behavior in differentiating nuclei and late G1 is key to understanding this developmental event. A nuclear event that has been shown to specifically occur in late G1 is the association of two heterochromatic blocks in Drosophila.