Abstract 16948: Numb and Numb-Like Are Required for Renewing Cardiac Progenitor Cell Fate
Aim Nascent cardiac progenitor cells (CPCs) must make proper decisions to form the heart, but the intrinsic determinants of this process are unknown. The aim of this study was to determine the role of two mammalian Numb (Nb) homologues, Nb and numb-like (Nbl), in CPC fate decisions.
Methods Nb and Nbl were conditionally ablated in early cardiovascular progenitors to assess their purpose in the developing embryo. CPC-specific somatic clones lacking Nb and Nbl were generated by blastocyst injection of Nb and Nbl mutant embryonic stem cells.
Results: Nb/Nbl double knockout embryos exhibited early embryonic lethality with a severely atrophic and dysmorphic heart. To more precisely analyze the fate of Nb- and Nbl-deficient CPCs, we fully rescued the lethality by developing a novel method to generate somatic clones lacking Nb and Nbl in early cardiovascular progenitors in-vivo. By tracing the mutant clones at single cell resolution we discovered a niche for CPCs in the developing embryo, where a few self-renewing CPCs proliferate to expand the pool of CPCs that change their fates to myo-, endo-, and pericardial cells as they exit the niche. Our clonal analysis revealed that Nb- and Nbl-deficient CPCs migrate normally and retain the ability to differentiate into cardiovascular cells, but failed to become self-renewing CPCs in the niche (see figure).
Conclusions: 1. CPCs are expanded in their niche, which until now had eluded the field. 2. Nb and Nbl are required for specifying renewing CPCs in the niche that likely represent “embryonic cardiac stem cells”. 3. Our method to generate cell lineage-specific somatic clones provides a powerful way to determine cell autonomous gene function and to trace mutant clones at single-cell resolution.
- © 2012 by American Heart Association, Inc.