Safe, rapid telomere extension in diverse progenitor cell types


Abstract:

We recently showed for the first time that delivery of nucleoside-modified mRNA encoding the telomerase protein hTERT to cells extends their telomeres in six days by an amount by which telomeres shorten over approximately 15 years of normal human aging on average. This important discovery opens the door to safe, rapid telomere extension, for several reasons that are unique to our approach. First, nucleoside-modified mRNA comprises the same modified nucleosides recently discovered to make up mature human mRNA, and is thus treated as such by cells: it does not integrate in the genome, is turned over within days, and if sufficiently pure, it is non-immunogenic. Second, and critically, our nucleoside-modified mRNA encoding telomerase extends telomeres so rapidly that the extension treatment can be very brief (a few days), and thus after the extension is completed, the normal anti-cancer mechanism of telomere shortening remains intact. Finally, we can deliver nucleoside-modified mRNA encoding hTERT which is modified at known sites that mediate its posttranslational cell cycle-dependent inhibition, enabling rapid telomere extension even in slowly- or non-dividing cells which include many progenitors. We are motivated in this work by our (Blau lab) recent discovery that short telomere length in muscle stem cells (MuSCs) underlies the debilitating and fatal myopathy of muscular dystrophy (Cell, 2010)1, and more generally by the fact that we, like many others, find that in vitro, human primary progenitor cell populations are limited in their replicative capacity, an effect at least partially mediated by short telomeres.2,3 Here we propose to realize the full potential of our discovery by generating, testing, and optimizing the modified and fully purified forms of telomerase mRNA that will enable safe, rapid telomere extension in a diverse range of progenitor cell types, even those in G0. To this end we will adapt a novel method for RNA purification recently invented by us (Santiago lab), work that will dramatically reduce the cost of nucleoside-modified mRNA purification, currently a prohibitive barrier to the rapid and widespread adoption of nucleoside-modified mRNA for telomere extension and other applications. We plan to make these tools for telomere extension and mRNA purification available to all PCBC members in a timely manner.