Manifold decreased protein levels of matrin 3, reduced motor protein HMP and hlark in fetal Down's syndrome brain.

Down's syndrome (DS) is the most frequent genetic cause of mental retardation and although known for more than a hundred years, the underlying pathomechanisms for the phenotype and abnormal brain functions remain elusive. Performing protein hunting in fetal Down's syndrome (trisomy 21) brain we detected aberrant expression of several proteins. Fetal brain cortex from controls and Down's syndrome at the early second trimester of gestation was used for expressional analysis. Two-dimensional electrophoresis with subsequent in-gel digestion of spots and matrix-assisted laser desorption/ionization spectroscopical identification followed by quantification of spots with specific software was applied. The nuclear matrix protein matrin 3, cytoskeletal motor protein HMP, and the circadian clock protein hlark were significantly decreased in fetal DS brain. C8ORF2 protein was reduced but did not reach statistical significance. Prox1 and predicted protein Dj149A16.6 were comparable between groups. Reduction of brain proteins may represent or cause deficient cytoskeletal structure, transcription machinery and exocytosis, functions already known to be deteriorated in DS brain. Some of the described proteins were only predicted and we here show the existence of the corresponding proteins in fetal human brain.