Update: A silencing reporter system to discover factors and pathways implicated in D4Z4 repression in Facioscapulohumeral dystrophy

Posted by Friends of FSH Research on Jan 4, 2025

Report by Ellen M Paatela
See also A silencing reporter system to discover factors and pathways implicated in D4Z4 repression in Facioscapulohumeral dystrophy

Though great strides have been made in the discovery of factors that regulate proper D4Z4 silencing, the precise mechanisms of silencing and how they can be used for FSHD therapeutic intervention are still an area of active research. My work, funded by Friends of FSH Research, the Chris Carrino Foundation for FSHD, and the Wellstone MDSCRC, focuses on dissecting the complex network of epigenetic regulators to identify essential D4Z4 sequences and factors necessary for proper D4Z4 silencing. After designing a functional assay to assess the silencing activity in the absence of genomic context, I have identified one discrete D4Z4 segment and one region of the LRIF1 promoter that are sufficient to recruit silencers in isolation from their respective genomic regions. Using these segments, I have performed an siRNA screen of known epigenetic D4Z4 regulators and identified several factors that initiate silencing activity specifically in these sequences.

For the original aims, technical challenges have limited the efficacy of enChIP-mass spectrometry for identification of high-confidence protein hits, and optimization of the protocol is still ongoing. I have also validated this silencing assay system as a platform for drug discovery, with p38 inhibitor treatment leading to further reporter suppression specifically in the identified D4Z4 and LRIF1 promoter segments. As a modification to previous aims, the focus of the study was shifted towards validation of this system as a simple, cost-effective screening platform for therapeutic discovery. This p38 inhibitor-mediated suppression was replicated in a live cell imaging system, providing an opportunity for more dynamic analysis. I am currently performing a screen of additional therapeutics and kinase inhibitors in collaboration with the lab of Dr. Taran Gujral at FHCC. Other remaining work includes preparation of a manuscript for early 2025 submission.