Dr. Collins and his colleagues discovered in April 2003 that mutations in the lamin A (LMNA) gene cause progeria, spurring renewed interest among researchers to study this rare syndrome. Among those were Capell, a New York University medical student participating in the Howard Hughes Medical Institute/NIH (HHMI/NIH) Research Scholars Program. In July 2004, he joined Dr. Collins' lab and immediately set his sights on understanding the molecular basis of progeria.
"What really interested me in this research in the first place were the potential links to aging and atherosclerotic disease," said Capell. Indeed, understanding progeria at the molecular level may illuminate the general processes involved in normal human aging.
The LMNA gene codes for a protein called lamin A, which constitutes a major component of the scaffold-like network of proteins just inside the cell's nuclear membrane, called the lamina. The gene mutation implicated in progeria causes a section of 50 amino acids within the lamin A protein to be deleted, resulting in a mutated protein that is called progerin. This protein fails to integrate properly into the lamina, thereby disrupting the nuclear scaffolding and causing gross disfigurement of the nucleus. Cells with progerin have a nucleus with a characteristic "blebbed," or lobular, shape.
To find its way to the lamina, lamin A carries two tags, rather like ZIP codes, that help to direct the protein's travels. One tag at the end of lamin A instructs another protein to modify it through a process called farnesylation. Farnesylation tethers lamin A to the inner nuclear membrane. Once there, a second tag within the protein signals an enzyme to cleave off the terminal portion of the protein, including the farnesyl group, freein
Source:NIH/National Human Genome Research Institute