Telomeric Theory-Back Ground

Excelife excelife at
Tue Aug 25 23:46:37 EST 1998


A) Origin Of The Theory

In 1961 L. Hayflick and P.S. Moorhead published a paper showing that 
replicating cells have a finite life span and that cells in culture and 
presumably the body would only reproduce up to a specified limit and then 
stop reproducing altogether.

In 1972 J.D. Watson showed that the telomeres at the of the chromosomes 
shortened with each cellular reproduction.

Putting these two findings together a Russian scientist A,M. Olovnikov 
proposed in 1973 that "each DNA replication depletes telomere material to a 
point that signals the cell to stop dividing."  This was the origin of the 
telomeric theory of aging.

B) Early Research & Finding Telomerase

Research in 1985 by E.H. Blackburn and C.W. Greider found an enzyme that 
maintained telomeric length in yeast that allowed the yeast to continue 
replicating without depleting the telomeres.  In 1987 this same team named 
this enzyme telomerase.

G.B. Morin in 1989 showed that telomerase was active in the immortal cell 
line HeLa and suggested that this was the cause of the cell lines 

Subsequent research by C. Harley and others showed that the enzyme telomerase 
was active in almost all cancerous tissue.  In 1992 Dr. Harley formed the 
Geron Corporation primarily to find a means of inactivating telomerase in 
these cancers with the expectation that the uncontrolled growth of the tumors 
would be halted in the absence of telomerase.  Geron Corp would also be 
looking into both senescent gene expression and telomere length modulation.

The implications of attempts to effect a change in telomeric length would 
soon become apparent.

C) Relating Telomeres To Aging

On March 15th, 1996, in the European Molecular Biology Organization Journal 
Dr. J. Shay and Dr. W. Wright published research showing that the enzyme 
telomerase could maintain telomeric length in normal human tissues and extend 
their life span beyond their expected Hayflick limit.  This confirmed the 
research in cancerous and HeLa cells that maintaining telomeric length could 
extend the life span of cells but for the first time it was with human cells 
that continued to function and reproduce in a normal manner.

These finding were confirmed by research published in Science, in January 
1998.  Geron Corps. Dr. Harley in collaboration with Dr. Shay and Dr. Wright, 
among others, showed that normal human cells could be maintained in a 
"phenotypically youthful state".

(Next: State of the research into the telomeric theory of aging.)     

Thomas Mahoney, Pres.
Lifeline Laboratories, Inc.

More information about the Cellbiol mailing list