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Updated: Jun 19, 2025
Rapid, Directed Differentiation of Retinal Pigment Epithelial Cells from Human Embryonic or Induced Pluripotent Stem Cells
Published on: October 30, 2017
Initial Characterization of WDR5B Reveals a Role in the Proliferation of Retinal Pigment Epithelial Cells
Jeffrey K Bailey1,2, Dzwokai Ma1, Dennis O Clegg1,2
1Department of Molecular, Cellular and Developmental Biology, Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, USA.
Abstract:
The chromatin-associated protein WDR5 has been widely studied due to its role in histone modification and its potential as a pharmacological target for the treatment of cancer. In humans, the protein with highest sequence homology to WDR5 is encoded by the retrogene WDR5B, which remains unexplored. Here, we used CRISPR-Cas9 genome editing to generate WDR5B knockout and WDR5B-FLAG knock-in cell lines for further characterization. In contrast to WDR5, WDR5B exhibits low expression in pluripotent cells and is upregulated upon neural differentiation. Loss or shRNA depletion of WDR5B impairs cell growth and increases the fraction of non-viable cells in proliferating retinal pigment epithelial (RPE) cultures. CUT&RUN chromatin profiling in RPE and neural progenitors indicates minimal WDR5B enrichment at established WDR5 binding sites. These results suggest that WDR5 and WDR5B exhibit several divergent biological properties despite sharing a high degree of sequence homology.
Insights
The unexplored WDR5B protein, homologous to cancer target WDR5, shows distinct functions. WDR5B loss impairs cell growth and viability, suggesting unique biological roles despite sequence similarity.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- WDR5 is a key chromatin protein in histone modification and a cancer drug target.
- WDR5B is the most homologous human protein to WDR5 but is largely uncharacterized.
- Understanding WDR5B is crucial for a complete picture of WDR5 family functions.
Purpose of the Study:
- To characterize the biological properties of the WDR5B retrogene.
- To investigate the expression patterns and cellular functions of WDR5B.
- To compare the chromatin association of WDR5B with WDR5.
Main Methods:
- CRISPR-Cas9 genome editing to create WDR5B knockout and knock-in cell lines.
- Analysis of WDR5B expression during neural differentiation.
- Assessment of cell growth and viability upon WDR5B depletion.
- CUT&RUN chromatin profiling to determine WDR5B binding sites.
Main Results:
- WDR5B expression is low in pluripotent cells and increases during neural differentiation.
- WDR5B depletion negatively impacts cell proliferation and viability in retinal pigment epithelial cells.
- WDR5B shows minimal enrichment at known WDR5 binding sites.
- WDR5 and WDR5B exhibit distinct biological functions and chromatin association patterns.
Conclusions:
- WDR5B possesses unique biological properties that diverge from WDR5.
- WDR5B plays a role in cell growth and viability, particularly in differentiated cells.
- The distinct functions of WDR5 and WDR5B highlight their independent biological significance.
