BACKGROUND & AIMS:
Methyl-CpG binding protein 2 (MECP2), which binds to methylated regions of DNA to regulate transcription, is expressed by hepatic stellate cells (HSCs) and is required for development of liver fibrosis in mice. We investigated the effects of MECP2 deletion from HSCs on their transcriptome and of phosphorylation of MECP2 on HSC phenotype and liver fibrosis.
We isolated HSCs from Mecp2-/y mice and wild-type (control) mice. HSCs were activated in culture and used in array analyses of mRNAs and long non-coding RNAs. KEGG pathway analyses identified pathways regulated by MECP2. We studied mice that expressed a mutated form of Mecp2 that encodes the S80A substitution (MECP2S80), causing loss of MECP2 phosphorylation at serine 80. Liver fibrosis was induced in these mice by administration of CCl4, and liver tissues and HSCs were collected and analyzed.
MECP2 deletion altered expression of 284 mRNAs and 244 long non-coding RNAs, including those that regulate DNA replication, are members of the minichromosome maintenance protein complex family, or encode CDC7, HAS2, DNA2 (a DNA helicase), or RPA2 (a protein that binds single-strand DNA). We found MECP2 to regulate the DNA repair Fanconi anemia pathway in HSCs. Phosphorylation of MECP2S80 and its putative kinase, HAS2, were induced during transdifferentiation of HSCs. HSCs from MECP2S80 mice had reduced proliferation and livers from these mice had reduced fibrosis following CCl4 administration.
In studies of mice with disruption of Mecp2 or that expressed a form of MECP2 that is not phosphorylated at S80, we found phosphorylation of MECP2 to be required for HSC proliferation and induction of fibrosis. In HSCs, MECP2 regulates expression of genes required for DNA replication and repair. Strategies to inhibit MECP2 phosphorylation at S80 might be developed for treatment of liver fibrosis.