Overall, the results demonstrate marked synaptic disturbances in two actin regulatory proteins in adult DS and AD brains, with greater effects in individuals with AD alone.
In both assays, alterations of actin cytoskeleton were present in DS, sporadic and familial AD cases, and in asymptomatic persons who later progressed to confirmed AD, but not in non-AD donors.
The identification of the actin cytoskeleton as one of cellular targets of DYRK1A action provides new insights into a gene dosage-sensitive mechanism by which DYRK1A could contribute to the pathogenesis of DS.
Fascin dysregulation is of relevance for actin bundling in vesicle trafficking and may represent or lead to impaired neurotransmission that, in turn, may lead to the cognitive defect observed in this mouse model of Down syndrome.
By contrast, expression levels of hypothetical protein KIAA1185, hypothetical protein 55.2 kDa, hypothetical protein 58.8 kDa, actin-related protein 3beta (ARP3beta), and putative GTP-binding protein PTD004 were significantly decreased (P < 0.05) in fetal DS brain, and domain analysis suggests involvement in cytoskeleton, signaling, and chaperone system abnormalities.
This stoichiometrical ratios were aberrant in DS, AD and PD with the main outcome that ratios of members of the neurocytoskeleton (betaIII, NF's) in relation to betaA were remarkably decreased.
BACH1 was even significantly increased in the DS panel when normalised versus the housekeeping protein beta-actin (p < 0.01) or the neuron specific enolase (p < 0.01).
We found significantly increased mRNA levels in DS either related to 10 ng total RNA (P < 0.05 level in cerebellum: DS 2622 +/- 1081 attogr mean +/- SEM and controls 154 +/- 37 attogr. mean +/- SEM) or normalized versus the house keeping gene beta-actin (P < 0.05 level in frontal cortex: DS 1324 +/- 504 attogr. mean +/- SEM and control 131 +/- 32 attogr. mean +/- SEM; P<0.01 in cerebellum: DS 632 +/- 189 attogr. mean +/- SEM and control 21 +/- 2 attogr. mean +/- SEM).
Significantly decreased ETS2 mRNA steady state levels (16.9 +/- 26.7 attogram mRNA ETS2/10 ng total RNA versus 87.7 +/- 92.9 in controls) in frontal lobe of Down Syndrome brain and decreased ETS2 mRNA steady state levels (6.99 +/- 6.4 attogram mRNA ETS2/100 pg beta-actin versus 19.8 +/- 15.7 in controls) in temporal lobe of Down Syndrome brain were found.
Significantly increased levels of mRNA c-fos normalized versus the housekeeping gene beta-actin mRNA were found in frontal, parietal and temporal cortex of DS brain. c-fox mRNA levels comparable to controls were found in occipital cortex and cerebellum.
When normalized versus the housekeeping gene beta-actin to rule out general transcriptional changes in that disorder, the ratio of 0.56 +/- 0.28 (mean, +/- SD) was calculated. ets-2 mRNA in total ventricular tissue of patients with non-DS CHD showed concentrations of 0.45 +/- 0.22 fg/10 ng total RNA (mean, +/-SD) and ratios of 0.48 +/- 0.35 (mean, +/-SD).
As one of the hypotheses for the pathogenesis of brain damage in DS is oxidative stress and cells of patients with DS are more susceptible to ionizing irradiation, we decided to study ERCC2, ERCC3 and XRCC1, representatives of repair genes known to be involved in the repair of oxidative DNA-damage. mRNA steady state levels of ERCC2, ERCC3, XRCC1, a transcription activator (TAF-DBP) and an elongation factor (EF1A) were determined and normalized versus the housekeeping gene beta-actin in five individual brain regions of nine controls and nine DS patients.