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Deciphering the MicroRNA-mediated Control of Pluripotent Stem Cell Differentiation

Review ofmiR-183/96/182 cluster is an important morphogenetic factor targeting PAX6 expression in differentiating human retinal organoidsfrom STEM CELLS by Stuart P. Atkinson

The polycistronic miR‐183/96/182 cluster, an evolutionarily conserved micro (mi)RNA cluster containing three highly similar members, may represent a crucial regulatory nexus during the differentiation of pluripotent stem cells into neural tissues and sensory organs [1]. With this in mind, researchers led by Tomáš Bárta (Masaryk University, Brno, Czech Republic) recently set out to understand the role of the miR‐183/96/182 cluster in the generation of retinal organoids, which can be generated from both human embryonic stem cells [2] and induced pluripotent stem cells (iPSCs) [3] (See the related STEM CELLS article here!). In a new STEM CELLS article, Peskova et al. now report that the miR‐183/96/182 cluster controls retinal tissue morphogenesis and represents an important regulator of PAX6 expression [4].

The authors first confirmed an expression profile for the miR‐183/96/182 cluster that agreed with the involvement of these miRNAs in the generation of neural tissue - the downregulated expression of miR‐183/96/182 during the early stages of retinal organoid differentiation followed by their later upregulated expression, reaching a level similar to that observed in undifferentiated iPSCs.

The inhibition of miR‐183/96/182 cluster expression used a “clustered tough decoy” approach, which involves DNA-encoded miRNA inhibitors expressed from plasmids or virus-based vectors that provide for the persistent suppression of function for multiple miRNA species [5]. Interestingly, miR‐183/96/182 cluster suppression significantly altered retinal organoid morphology, which manifested as the expansion of the neuroepithelium and the appearance of an abnormal “bulged” neural retina phenotype that correlates with the upregulated expression of neuro‐ (e.g., SOX1, SOX2, and PAX6) and retina‐ (e.g., RAX, VSX2) specific genes. Therefore, the authors propose that miR‐183/96/182 cluster inhibition may allow for the enhanced neural retina differentiation of iPSCs.

Of added interest, the transcriptomic data combined with subsequent in vitro confirmation established the master regulator of neuroectoderm specification and eye development PAX6 as a target of the miR‐183/96/182 cluster in differentiating retinal organoids; however, whether PAX6 upregulation directly causes the bulged phenotype of retinal organoids remains unconfirmed.

Overall, these findings support a role for the miR‐183/96/182 cluster in retinal tissue differentiation and morphogenesis and contribute to the ongoing description of the miRNA-mediated regulation of pluripotent stem cell differentiation and normal human development.

For more on miRNAs, organoids, and retinal differentiation and development, stay tuned to the Stem Cells Portal!


References

  1. Dambal S, Shah M, Mihelich B, et al., The microRNA-183 cluster: the family that plays together stays together. Nucleic Acids Research 2015;43:7173-7188.
  2. Kuwahara A, Ozone C, Nakano T, et al., Generation of a ciliary margin-like stem cell niche from self-organizing human retinal tissue. Nature Communications 2015;6:6286.
  3. Hallam D, Hilgen G, Dorgau B, et al., Human-Induced Pluripotent Stem Cells Generate Light Responsive Retinal Organoids with Variable and Nutrient-Dependent Efficiency. STEM CELLS 2018;36:1535-1551.
  4. Peskova L, Jurcikova D, Vanova T, et al., miR-183/96/182 cluster is an important morphogenetic factor targeting PAX6 expression in differentiating human retinal organoids. STEM CELLS 2020;38:1557-1567.
  5. Hollensen AK, Bak RO, Haslund D, et al., Suppression of microRNAs by dual-targeting and clustered Tough Decoy inhibitors. RNA Biology 2013;10:406-414.