Differential structural organization and gene expression regulatory networks of lamin A Ig fold domain mutants of muscular dystrophy

Abstract

AbstractIn metazoan cells, lamins form a proteinaceous meshwork as major structural component of nucleus and also involve in the regulation of essential cellular processes. Lamins along with their interactors act as determinants for chromatin organization throughout the nucleus. Major dominant missense mutations for autosomal dominant forms of muscular dystrophies are resided in the Ig fold domain of lamin A. How lamin A constitutes the distribution of heterochromatin and euchromatin balance, relocates the epigenetic marks in shaping of chromatin states are currently not well defined to make any conclusion about the prognosis of lamin A mediated muscular dystrophies. In the first part of this report, we identified in-vitro organization of full length lamin A proteins due to two well cited Ig LMNA mutations : R453W, W514R by biophysical and electron microscopy observations. We further show both lamin A/C mutant cells were mainly expressed as nucleoplasmic aggregates with reduced amounts at the nuclear envelope.Labelling of specific markers of epigenetics such as H3K9me3,H3K27me3, H3K36me3,Hp1α permitted the correlation of lamin A mutations on epigenetic mechanism. Both immunofluorescence and biochemical analyses are believed to exercise a transcriptional upregulation. Beside the manipulation on epigenetic mechanism, using proteomic studies we trace diverse expressions of transcription regulators, protein components of RNA synthesis and processing, protein translation and posttranslational modification. These data suggests a severe perturbation of targeting of other proteins on nucleus. Our study also portends specific structural configurations of lamin A determined by patterns of it’s interacting partners.