Senior Scholar Award in Aging
Stanley N. Cohen, M.D.
Stanford University School of Medicine

Genetic Mechanisms Regulating Replicative Aging in Diffierentiated Human Cell Populations

Normal human cells growing outside the body in culture media have a finite ability to reproduce. An internal “clock’ forces them eventually to stop dividing and enter an irreversible state of proliferative arrest termed “replicative senescence” (RS). There is evidence that RS represents aging at the cellular level and that the mechanisms causing it are genetically determined.

The proposed research is aimed at discovering genes involved in replicative senescence and elucidating the cellular pathways that these genes affect. The method to be employed will attempt to abrogate senescence by inactivating genes randomly in normal differentiated human cells and then identifying those individual cells that acquire an extended lifespan. While mutational approaches have long been used to inactivate gene function in viruses and bacteria, the cells of higher organisms contain two copies of each gene, and mutation of both copies ordinarily is required to produce biological consequences. Inactivation of both gene copies (i.e., homozygous inactivation) usually was practical only when the gene previously had been isolated and sequenced. Our laboratory has developed a procedure (random homozygous knockout; RHKO) that accomplishes the functional homozygous inactivation of previously unidentified genes.

Human cells whose replicative lifespan in culture is extended by RHKO will be isolated and the affected genes will be identified and studied. DNA microarrays will be employed in further experiments aimed at elucidating the pathways affected by the functionally inactivated genes. As multiple cycles of RHKO can be carried out serially, additive effects of inactivation of different genes potentially can be detected. The effects of perturbing the expression of certain of the genes may be tested in animal systems during later stages of the project.

Contact Dr. Cohen.