Enhancing Cell Fate Conversions By The Directed Evolution Of The Oct4 Transcription Factor

Cellular fate change drived by transcription factor(TF) over-expression is one of the cardinal approach to obtain induced pluripotent stem cell(iPSC) and other differentiated functional cells, which could model human disease for drug identification, produce functional cells for cell therapy and even regenerate new tissue to replace the aged and injured tissue. Directed evolution based on protein engineering can produce synthetic TFs (sTFs) to generate high quality functional cells more efficiently to promote the development of regeneration medicine. Oct3/4 is the critical TF of maintaining pluripotent and can achieve somatic cells reprogramming. The goal to obtain more functional Oct4 to enhance the efficiency of reprogramming, there were two types of libraries have been constructed. The one is saturation mutagenesis library of six key amino acids(K7, Q18,121, T22, E78, S151) in the POU domain of mOct4. Library screening was via different libraries transfecting OG2 MEF with Sox2, Klf, c-Myc to induce iPSC respectively. Higher efficient mutants were screening out from each site, and the mutant T22R was the highest about 2.5 as wild-type(WT). And with the combining different high efficient mutations, the efficiency of mutant T22R/E78P/S151N possess about 9 times as WT. The other is chimera-genesis library of POU domain from Oct4, Oct6, Brn2 and Octl by User enzyme recombination.The strongest mutant POUhBrn2 were screened out with the efficiency of 6.5 times as WT, and based on the POUhBrn2, T22R and E78P were introduced respectively, both of POUhBrn2R/T22R and POUhBrn2/E78P had about 12 times as WT.