Compositions and methods for enhancing the pluripotency of stem cells

Abstract

Described herein is the finding that increasing the frequency of Zscan4 activation in mouse ES cells not only enhances, but also maintains their developmental potency in long-term cell culture. As the potency increases, even a whole animal can be produced from a single ES cell injected into a 4N blastocyst at an unexpectedly high success rate. The studies disclosed herein indicate that ES cells acquire higher potency by going through the transient Zscan4 activation state more frequently than the regular state. Particularly disclosed herein is the finding that the constitutive presence of Zscan4-ERT2, even in the absence of its usual activator tamoxifen, can increase the frequency of endogenous Zscan4 activation in ES cells, resulting in the increase of developmental potency of the ES cells. Accordingly, provided herein are Zscan4-ERT2 fusion proteins and nucleic acid molecules and vectors encoding Zscan4-ERT2 fusion proteins. Further provided are methods of prolonging and/or enhancing stem cell pluripotency using the disclosed Zscan4-ERT2 nucleic acid molecules and fusion proteins.

We claim: 
     
         1 . A recombinant polypeptide selected from a Zscan4-ERT2 fusion protein and a Zscan4-ΔC protein. 
     
     
         2 . The recombinant polypeptide of  claim 1 , wherein the Zscan4 or the Zscan4-ΔC protein comprises mouse Zscan4c, mouse Zscan4d, mouse Zscan4f or human ZSCAN4, or a functional fragment or variant thereof. 
     
     
         3 . The recombinant polypeptide of  claim 1 , comprising an amino acid sequence at least 95% identical to the amino acid sequence of SEQ ID NO: 22 or SEQ ID NO: 23. 
     
     
         4 . The recombinant polypeptide of  claim 1 , wherein the Zscan4-ΔC protein comprises mouse Zscan4c, mouse Zscan4d, mouse Zscan4f or human ZSCAN4 comprising a deletion of at least one zinc finger domain. 
     
     
         5 . An isolated cell comprising the recombinant polypeptide of  claim 1 . 
     
     
         6 . The isolated cell of  claim 5 , which is a stem cell. 
     
     
         7 . The isolated cell of  claim 6 , which is an ES cell or an iPS cell. 
     
     
         8 . The isolated cell of  claim 6 , wherein the stem cell is a mouse, rat, human or non-human primate stem cell. 
     
     
         9 . A composition comprising the recombinant polypeptide of  claim 1  and a pharmaceutically acceptable carrier.