Hutchinson Gilford Progeria Syndrome and the role of lamin A in the onset of the progeroid cellular phenotype

The goal of my research is to gain mechanistic insights on the molecular basis of progeria and its role to normal aging. To dissect the role of lamin A in Hutchinson Gilford Progeria Syndrome (HGPS) and the possible contribution to normal cellular aging, I created a cell model by transducing HGPS mutant lamin A (progerin) or prelamin A into normal fibroblasts. Fibroblasts expressing progerin displayed growth defects, senescence, death, nuclear membrane blebs, and irregular lamin A redistribution and aggregates recapitulating the HGPS cellular phenotype. Interestingly, fibroblats with elevated levels of prelamin A also displayed the progeria phenotype with slightly delayed kinetics. Furthermore, we observed aberrant lamin A redistribution and aggregates in cells form old aged donors suggesting a possible link between lamin A and normal aging. Growth defects and nuclear membrane blebs were rescued by farnesyl transferase inhibitor treatment or ZMPSTE24 overexpression, for cells with elevated prelamin A, suggesting the existence of one or more toxic prelamin A intermediates. Construction of prelamin A intermediates and their characterization demonstrated a cellular toxicity associated with all the variants, with the farnesylated intermediates showing the greatest toxicity. Mechanistical studies of the progeroid cellular phenotype uncovered that transcription and TBP levels are significantly reduced in cells ectopically expressing all prelamin A variants except for the mature form. To determine if alteration in gene transcription contributes to the development of the progeroid cellular phenotype we performed transcriptome analysis. Analysis of the progeroid gene expression changes allowed us to identify signaling pathways and transcription factor binding motifs that may contribute to the progeroid cellular phenotype. Furthermore, I attempted to define the first set of genes altered upon expression of progerin. Finally, I built on these transcriptome analyses to identify genes that are successfully reverted by the treatment of FTI or ZMPSTE24. The transcription factor FOXQ1 was identified through this analysis and we showed this gene individually altered growth and nuclear morphology in normal cells. Collectively, my data provide functional insights of lamin A and its role in the progeroid cellular phenotype that suggest nuclear lamin A processing, levels, and structure are important for proper cell homeostasis.