Information on gene expression in brain of patients with Down Syndrome (DS,
trisomy 21) is limited and molecular biological research is focussing on m
apping and sequencing chromosome 21. The information on gene expression in
DS available follows the current concept of a gene dosage effect due to a t
hird copy of chromosome 21 claiming overexpression of genes encoded on this
chromosome.
Based upon the availability of fetal brain and recent technology of gene hu
nting, we decided to use subtractive hybridization to evaluate differences
in gene expression between DS and control brains.
Subtractive hybridization was applied on two fetal brains with DS and two a
ge and sex matched controls, 23rd week of gestation, and mRNA steady state
levels were evaluated generating a subtractive library. Subtracted sequence
s were identified by gene bank and assigned by alignments to individual gen
es.
We found a series of up-and downregulated sequences consisting of chromosom
al transcripts, enzymes of intermediary metabolism, hormones, transporters/
channels and transcription factors (TFs).
We show that trisomy 21 or aneuploidy leads to the deterioration of gene ex
pression and the derangement of transcripts described describes the involve
ment of chromosomes other than chromosome 21, explains impairment of transp
ort, carriers, channels, signaling, known metabolic and hormones imbalances
. The dys-coordinated expression of transcription factors including homeobo
x genes, POU-domain TFs, helix-loop-helix-motifs, LIM domain containing TFs
, leucine zippers, forkhead genes, maybe of pathophysiological significance
for abnormal brain development and wiring found in patients with DS. This
is the first description of the concomitant expression of a large series of
sequences indicating disruption of the concerted action of genes in that d
isorder.