Erf Affects Commitment and Differentiation of Osteoprogenitor Cells in Cranial Sutures via the Retinoic Acid Pathway

ABSTRACT

ETS2 repressor factor (ERF) haploinsufficiency causes late-onset craniosynostosis (CRS) (OMIM entry 600775; CRS4) in humans, while in mice Erf insufficiency also leads to a similar multisuture synostosis phenotype preceded by mildly reduced calvarium ossification. However, neither the cell types affected nor the effects per se have been identified so far. Here, we establish an ex vivo system for the expansion of suture-derived mesenchymal stem and progenitor cells (sdMSCs) and analyze the role of Erf levels in their differentiation. Cellular data suggest that Erf insufficiency specifically decreases osteogenic differentiation of sdMSCs, resulting in the initially delayed mineralization of the calvarium. Transcriptome analysis indicates that Erf is required for efficient osteogenic lineage commitment of sdMSCs. Elevated retinoic acid catabolism due to increased levels of the cytochrome P450 superfamily member Cyp26b1 as a result of decreased Erf levels appears to be the underlying mechanism leading to defective differentiation. Exogenous addition of retinoic acid can rescue the osteogenic differentiation defect, suggesting that Erf affects cranial bone mineralization during skull development through retinoic acid gradient regulation.

KEYWORDS:

• craniosynostosis
• mesenchymal stem cells
• Ets transcription factors
• retinoic acid

SUPPLEMENTAL MATERIAL

Supplemental material is available online only.

ACKNOWLEDGMENTS

We are grateful to the IMBB Animal House and Gene Targeting Facility personnel for mouse breeding and maintenance and to the Genomics Facility personnel for high-throughput RNA sequencing.

This work was supported by IKY-SIEMENS grant AP2788 and by Onassis Foundation Fellowship GZM 008-1 to A.V. We acknowledge support of this work by the project “BIOIMAGING-GR: a Greek Research Infrastructure for Visualizing and Monitoring Fundamental Processes in Biology and Medicine” (MIS 5002755), which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure,” funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014-2020) and cofinanced by Greece and the European Union (European Regional Development Fund). Work in Oxford was supported by Action Medical Research (GN2483; S.R.F.T.), the MRC through the WIMM Strategic Alliance (G0902418 and MC_UU_12025), the National Institute for Health Research, and Wellcome (investigator award 102731 to A.O.M.W. and project grant 093329 to A.O.M.W. and S.R.F.T.).

We declare no conflicts of interest.