sunflowery's Diaryland Diary

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FSH MD Tidbits

Just some tidbits I found at the MDA website re: FSH MD i.e. what Supe has.

By the way, did anyone notice that today it's warmer here in the Northland than it is in sunny FL? Yippee! Not that I get to enjoy it, other than sitting in the sunshine filtering in to my office window. On to the tidbits:

Basis of FSHD Discovered: In August 2002, MDA grantee Rossella Tupler at Massachusetts General Hospital in Boston discovered that the mutations underlying FSHD mapped to chromosome 4 in 1992 are not in a single gene, but in a DNA region that controls genes. Deletions (missing pieces of DNA) in that region cause genes that are normally "off" to turn "on." Finding ways to block these overactive genes could lead to effective treatments.

GENES IN FSHD FOUND TO BE 'MISREGULATED' People with Facioscapulohumeral muscular dystrophy (FSHD) are making the wrong amounts of many different muscle proteins, reports a group led by Michael Green of the University of Massachusetts Medical School and Howard Hughes Medical Institute in Worcester. The surprise finding may shed light on the mechanism by which FSHD causes muscle weakness.

A common form of muscular dystrophy, FSHD affects the muscles of the face and shoulders, although generalized weakness can occur with time. Unlike most other neuromuscular disorders for which the genetic defects have been found, the problem in the DNA that leads to FSHD doesn't seem to cause mutations in a specific gene.

Instead, researchers have found that people with FSHD lack regions of their DNA on chromosome 4 that normally contain multiple copies of a particular sequence of nucleotides (the building blocks of DNA). Oddly, these repeated sequences don't seem to code for proteins, and it isn't known how lacking them causes problems in the muscles of those affected by FSHD.

One theory held by many researchers is that the lack of these repetitive sequences (known as 3.3kb repeats) somehow changes the shape of chromosome 4 in such a way that genes in neighboring regions of DNA are affected negatively. Researchers are studying several nearby genes to see whether their activity is affected by the loss of the 3.3kb repeats.

Now Green reports that many muscle-specific genes are over- or under-active in people with FSHD. This conclusion was reached after comparing the activity of the genes in muscle samples from people with FSHD, Becker muscular dystrophy, amyotrophic lateral sclerosis and healthy people. Only the samples from people with FSHD demonstrated what the authors describe as a "profound" misregulation of gene expression.

Green speculates that global misregulation of muscle genes in FSHD may be caused when the loss of 3.3kb repeats interferes with the normal function of a muscle-specific "transcription factor." Transcription factors are specialized proteins that bind to DNA and activate the expression of other proteins. If the activity of a transcription factor isn't normal, then the activity of all of the other genes it regulates may also be abnormal.

For nearly a decade, researchers were stymied by the search for the culprit gene behind Facioscapulohumeral muscular dystrophy (FSHD), and thus, they had few clues to treatment.

4:51 p.m. - Wednesday, Apr. 28, 2004
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