April 9, 2013

Our genome is chock full of so many things that aren’t even genes.  In fact, only about 2% of the human genome actually encodes protein sequences...mind blown, right?!  There are many different kinds of elements and domains within our genome that regulate gene expression through their roles in chromosome architecture and organization.  Today’s image is from a paper that describes the dynamics of one type of domain—the lamina associated domain.

The nuclear lamina is a protein layer that coats the inside nuclear membrane, and serves to anchor chromosomes.  Regions in the genome called lamina associated domains (LADs) specifically associate with the nuclear lamina.  LADs cover about 35-40% of the genome, suggesting that they may affect chromosome position and architecture.  A recent paper tracks LAD-nuclear lamina interactions throughout the cell cycle in single cells.  Kind and colleagues show that about 30% of LADs are positioned at the nuclear periphery.  LADs are stochastically positioned after mitosis, meaning that their position is not directly inherited.  In addition, these contacts are linked with gene expression and histone modifications.  In the images above, the nuclear lamina (blue) and mitotic spindle (red) are shown throughout the different stages of mitosis.  LADs (green) are rounded and at the nuclear periphery during prophase, and then become banded along chromosomes once the nuclear envelope breaks down (prometaphase and metaphase).  During cytokinesis, LADs are seen within the nucleus, but not yet positioned at the periphery.

Kind, J., Pagie, L., Ortabozkoyun, H., Boyle, S., de Vries, S., Janssen, H., Amendola, M., Nolen, L., Bickmore, W., & van Steensel, B. (2013). Single-Cell Dynamics of Genome-Nuclear Lamina Interactions Cell, 153 (1), 178-192 DOI: 10.1016/j.cell.2013.02.028
Copyright ©2013 Elsevier Ltd. All rights reserved.