365 Multivalent chromatin looping orchestrates cellular reprogramming for advanced gene therapy

Abstract

The discovery of cellular plasticity, an epigenetic phenomenon by which differentiated cells alter their identity through reprogramming, dedifferentiation or transdifferentiation has led to a paradigm shift in regenerative medicine for treatment of genetic diseases and injuries. Current surgical methods pose high mortality rates making stem cell-based therapy an attractive option. HOX genes, a set of transcription factor genes, play key roles during stem cell renewal, multilineage differentiation and reprogramming of differentiated cells. Delineating the molecular mechanisms of HOX genes regulation in diverse cellular identities will provide clues to modulate cell fate for development of novel, more effective stem cell-based treatments. Recent studies highlight that a cell identity is determined not only by specific gene expression profile and posttranslational modifications but largely by its characteristic three-dimensional (3D) genomic organization. Chromatin maintains a high-order topology organizing genes into structural domains through long-range chromatin looping that is essential for controlled gene regulation. Existing techniques to study the link between chromatin looping and gene regulation require either large alterations of the linear DNA sequence or prior knowledge of loop-mediating factors. We have pioneered a technology to form multivalent chromosomal contacts and loops in 3D space at will. Previous studies revealed that primary adult fibroblasts retain several HOX gene expression patterns similar to that in embryonic cells. We will affect chromosomal remodeling using our new multiplexed chromatin looping system to examine how 3D architectural reorganization of chromatin at the Hox loci in human dermal fibroblasts can alter cellular identities (via reprogramming and transdifferentiation) with the potential for reproducible and efficient clinical-grade cell production. This study will provide insights for linking chromatin architecture to cutaneous gene expression that affects cellular plasticity in both adult and embryonic cells that may have transformative outcomes for regenerative medicine.