Search

Anterior–posterior (A–P) specification of the neural tube involves initial acquisition of anterior fate followed by the induction of posterior characteristics in the primitive anterior neuroectoderm. Several morphogens have been implicated in the regulation of A–P neural patterning; however, our understanding of the upstream regulators of these morphogens remains incomplete. Here, we show that the Krüppel‐like zinc finger transcription factor GLI‐Similar 3 (GLIS3) can direct differentiation of human embryonic stem cells (hESCs) into posterior neural progenitor cells in lieu of the default anterior pathway. Transcriptomic analyses reveal that this switch in cell fate is due to rapid activation of Wingless/Integrated (WNT) signaling pathway. Mechanistically, through genome‐wide RNA‐Seq, ChIP‐Seq, and functional analyses, we show that GLIS3 binds to and directly regulates the transcription of several WNT genes, including the strong posteriorizing factor WNT3A, and that inhibition of WNT signaling is sufficient to abrogate GLIS3‐induced posterior specification. Our findings suggest a potential role for GLIS3 in the regulation of A–P specification through direct transcriptional activation of WNT genes. Stem Cells2018StemCells2019;37:202–215 Expression of the Krüppel‐like zinc finger transcription factor GLI Similar 3 in human embryonic stem cells induces differentiation along the posterior neural progenitor lineage instead of the default anterior lineage through the transcriptional activation of the strong posteriorizing factor WNT3A.

The expression and function of several multidrug transporters (including ABCB1 and ABCG2) have been studied in human cancer cells and in mouse and human adult stem cells. However, the expression of ABCG2 in human embryonic stem cells (hESCs) remains unclear. Limited and contradictory results in the literature from two research groups have raised questions regarding its expression and function. In this study, we used quantitative real‐time PCR, Northern blots, whole genome RNA sequencing, Western blots, and immunofluorescence microscopy to study ABCG2expression in hESCs. We found that full‐length ABCG2mRNA transcripts are expressed in undifferentiated hESC lines. However, ABCG2 protein was undetectable even under embryoid body differentiation or cytotoxic drug induction. Moreover, surface ABCG2 protein was coexpressed with the differentiation marker stage‐specific embryonic antigen‐1 of hESCs, following constant BMP‐4 signaling at days 4 and 6. This expression was tightly correlated with the downregulation of two microRNAs (miRNAs) (i.e., hsa‐miR‐519c and hsa‐miR‐520h). Transfection of miRNA mimics and inhibitors of these two miRNAs confirmed their direct involvement in the regulation ABCG2 translation. Our findings clarify the controversy regarding the expression of the ABCG2gene and also provide new insights into translational control of the expression of membrane transporter mRNAs by miRNAs in hESCs. STEMCells2012;30:2175–2187