Saturday, December 19, 2009

Netherlands - FSH Research - Epigenetic Causes

Project: Epigenetic causes of facioscapulohumeral muscular dystrophy

* Title (NL) Epigenetische oorzaken van facioscapulohumerale spierdystrofie
* Period 09 / 2004 - 09 / 2008
* Status Current S.M. van der Maarel Project Leader

Facioscapulohumeral muscular dystrophy (FSHD) is caused by an epigenetic disease mechanism involving contraction of the D4Z4 repeat array on chromosome 4qter. This contraction likely induces a local chromatin alteration, possibly resulting in transcriptional deregulation of 4qter genes as (1) some genes on 4qter appear to be transcriptionally upregulated in FSHD, (2) D4Z4 is hypomethylated in FSHD chromosomes, and (3) patients clinically indistinguishable from FSHD but without contraction of D4Z4 are also hypomethylated at D4Z4. Thus, in non-4q-linked FSHD, the pathogenetic pathway also acts through an epigenetic mechanism on chromosome 4. However, the structural and functional consequences of D4Z4 hypomethylation in 4q-linked and non-4q-linked FSHD are unknown. Interestingly, the immunodeficiency, centromere instability and facial anomalies (ICF) syndrome also shows hypomethylation of D4Z4, but does not present with muscular dystrophy. To understand FSHD and ICF etiology, and to better understand the functional and structural role of D4Z4 in FSHD and ICF, we propose to study the chromatin structure of D4Z4 in muscle, myoblast and fibroblast cell lines of 4q-linked FSHD, non-4q-linked FSHD and ICF syndrome patients. This will include precise methylation analysis of D4Z4 by allele-specific bisulfite conversion to identify consistent differences in D4Z4 methylation between FSHD and ICF that may reflect structural domains within D4Z4 through differential methylation-dependent binding of DNA-associated proteins. We will further study the chromatin structure of 4qter by allele-specific DNAseI chromatin-sensitivity, chromatin immunoprecipitation and RNA interference assays. In parallel, we will perform quantitative expression analyses of 4qter genes to study the functional consequences of D4Z4 chromatin changes. Finally, we will establish a cellular model system to study the fundamental involvement of D4Z4 in epigenetic structuring of subtelomeric chromosome domains. We expect that this study will provide a fundamental insight intp the (differential) epigenetic mechanism of FSHD and ICF.


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