Introduction amp; objective- The murine lower incisor ectodermal organ contains a single epithelial stem cell niche that provides epithelial progenitor cells to the continuously growing rodent incisor. Calvaria sutures also contain stem cells that are regulated by specific factors. We have discovered that the microRNA (miR) -200 family is required for stem cell differentiation through targeting stem cell factors. We asked if the miR-200 family regulated specific stem cell niches during development.
Materials amp; methods- Our group used the plasmid-based miR inhibitor system (PMIS) to knock down specific miR-200 family members in mice and study their role during developmental processes. Our system inhibits one miR within a cluster to understand the role of that miR, which cannot be accomplished using gene targeting methods.
Results- We inhibited the miR-200 family in developing murine embryos using new technology, resulting in an expanded epithelial stem cell niche and lack of cell differentiation. Inhibition of individual miRs within the miR-200 cluster resulted in differential developmental and cell morphology defects. miR-200 inhibition increased the expression of dental epithelial stem cell markers, expanded the stem cell niche and decreased progenitor cell differentiation. RNA-seq. identified miR-200 regulatory pathways involved in cell differentiation and compartmentalization of the stem cell niche. The miR-200 family regulates signaling pathways required for cell differentiation and cell cycle progression. New miR-200 targets demonstrate gene networks and pathways controlling cell differentiation and maintenance of the stem cell niche.
Conclusion- This is the first report demonstrating how the miR-200 family is required for in vivo progenitor cell proliferation and differentiation.
Significance/implication- This new approach has identified several new scientific advancements in stem cell niche biology. 1) miR-200 family members are required for in vivo epithelial stem cell differentiation and stem cell niche maintenance; 2) The miR-200 family regulates genes required for generating the different dental epithelial cell lineages; 3) miR-200 expression may be a common mechanism for defining the boundaries of adult epithelial stem cell niches; 4) By inhibiting the miRs that become active when a progenitor cell becomes fated to differentiate, the in vivo cell differentiation programs are determined assuming their terminal fates; 5) Dental epithelial stem cells and suture stem cells are regulated by members of the miR-200 family to yield the differentiated progeny and determine cell fate.
This research was supported by funding from the University of Iowa.
