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A common thread links multiple human
cognitive disorders
A new study reveals that a common underlying
mechanism is shared by a group of previously
unrelated disorders which all cause complex
defects in brain development and function.
Rett syndrome (RTT), Cornelia de Lange
syndrome (CdLS) and Alpha-Thalassemia mental
Retardation, X-linked syndrome (ATR-X) have
each been linked with distinct abnormalities
in chromatin, the spools of proteins and DNA
that make up chromosomes and control how
genetic information is read in a cell.
Now, research, published by Cell Press in
the February 16th issue of the journal
Developmental Cell, helps to explain why
these different chromatin abnormalities all
interfere with proper gene expression
patterns necessary for normal development
and mature brain function.
"Although clearly distinct from one another,
human developmental disorders that are
linked with chromatin dysfunction often
share similar cognitive clinical features,"
explains senior study author, Dr. Nathalie
Bérubé from the University of Western
Ontario. "Whether the overlapping cognitive
symptoms are due to underlying interlinked
molecular mechanisms is still poorly
understood."
Her work now demonstrates that chromatin
proteins defective in RTT, CdLS, and ATR-X
syndromes are all associated with each other
– and are required for one another's
function – at certain "imprinted genes" in
the developing mouse brain.
Imprinted genes are a relatively rare type
of gene that carries different information
depending on whether it is inherited from
the mother or the father.
The results support the conclusion that ATRX
(the chromatin protein that is defective in
ATR-X syndrome) and its binding partners
regulate expression of imprinted genes, and
likely other genes required for normal brain
development, by controlling chromatin
structure.
"Our findings provide the first glimpse of
the cooperation between ATRX and multiple
other disease proteins in the regulation of
common gene targets, perhaps explaining
similarities between the associated human
syndromes," says Dr. Bérubé.
"The failure to properly suppress genes that
are essential during embryonic development,
but potentially detrimental in the mature
brain, might contribute to cognitive
deficiencies characteristic of RTT, CdLS and
ATR-X syndromes.
“Further studies are needed to gain a better
understanding of the specific role of these
chromatin proteins and the molecular
pathogenesis of the associated human
disorders."
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