Abstract:
Lamins are structural proteins of the inner nuclear membrane essential for maintaining
nuclear structure and function. In order to study the role of Lamin A in maintaining
nuclear organization and genome stability, we employed gene silencing (siRNA
mediated knockdown) approach to perturb Lamin A levels in a diploid, karyotypically
stable, colorectal cancer cell line – DLD1. Our studies show that perturbation of Lamin A
causes significant changes in nuclear shape in a manner that does not affect B-type
Lamins and only shows small effects on the viability of DLD1 cells. Lamin A knockdown
in DLD1 cells shows a subtle modulation in the number of intranuclear Lamin bodies
that are required for transcription. Lamin A knockdown significantly shifts the stable
diploid phenotype of DLD1 cells and significantly alters copy numbers of two genes -
DNMT1 (Chr.19) and WDR8 (Chr.1) irrespective of the chromosomes that they map to.
These studies for the first time uncover Lamin A as a modulator of gene copy numbers
further reiterating its role in maintaining genome stability. However, knockdown of Lamin
A showed differential effects on the 3-dimensional nuclear organization of DNMT1 and
WDR8 gene loci with respect to its chromosome territory, suggesting a selective
regulatory role of Lamin A in modulating nuclear structure and function.
