ABERRANT PROTEIN EXPRESSION IN CEREBRAL CORTEX OF FETUS WITH DOWN SYNDROME E. ENGIDAWORK, a T. GULESSERIAN, b M. FOUNTOULAKIS c AND G. LUBEC b * a Department of Neonatology, University of Vienna, Vienna, Austria b Department of Pediatrics, University of Vienna, Wa ¨ hringer Gu ¨ rtel 18-20, A-1090, Vienna, Austria c F. Hoffman-La Roche, Basel, Switzerland Abstract—Down syndrome is the most common birth defect associated with mental retardation. Identifying proteins that are aberrantly expressed therefore helps to understand how chromosomal imbalance leads to subnormal intelligence in Down syndrome. In the present study, we generated a fetal brain map with the use of an analytical method based on two-dimensional electrophoresis coupled with mass spec- trometry and searched the proteome for differential protein expression. Among 49 proteins analyzed in seven control and nine Down syndrome fetuses, we found 11 proteins that have been deregulated in cerebral cortex of fetal Down syn- drome. While double-strand break repair protein rad 21 ho- mologue, eukaryotic translation initiation factor 3 subunit 5, mixed lineage leukemia septin-like fusion protein-B and heat shock protein 75 were increased; -amyloid precursor-like protein 1, tropomyosin 4-anaplastic lymphoma kinase fusion oncoprotein type 2, Nck adaptor protein 2, Src homology domain growth factor receptor bound 2-like endophilin B2,  tubulin, septin 7 and hematopoietic stem/progenitor cells 140 were decreased. The current data suggest that misexpres- sion of proteins that have functions ranging from signaling to cellular structural organization could contribute to or reflect brain dysgenesis in Down syndrome. © 2003 IBRO. Published by Elsevier Ltd. All rights reserved. Key words: septins, -tubulin, fusion oncoproteins, DNA re- pair proteins, Nck adaptor protein 2, -amyloid precursor-like protein. Down syndrome (DS) is the most common birth defect associated with mental retardation and occurs with an incidence of one in 700 – 800 live births. It results from trisomy of chromosome 21, 95% of which are free tri- somies and the remainder are mosaics or have transloca- tion trisomy 21 (Antonarakis, 1998; Epstein, 2001). DS is associated with developmental failure followed by pro- cesses of neurodegeneration that are known to supervene at later ages. These neurodegenerative changes are char- acterized by progressive accumulation of senile plaques and neurofibrillary tangles, and occur with similar regional distribution as in Alzheimer’s disease (Wisniewski et al., 1985; Mann, 1988; Cork, 1990). The molecular mechanisms underlying the pathologi- cal alterations in DS are not known nor whether they are reflection of developmental failure or degenerative pro- cesses. Moreover, while certain aspects of morphological development of the DS cerebral cortex appear to be nor- mal during gestation, anomalies have been detected in the postnatal period (Takashima et al., 1981; Becker et al., 1991). This indicates that abnormalities most likely occur in the last trimester or abnormalities do exist in the second trimester as well; however, they are at subthreshold level to exert any significant morphological changes. It is of interest therefore to examine biochemically the brain spec- imen of 19 weeks of gestation, as it is near to the age of peak nerve cell formation in the human forebrain (Dobbing and Sands, 1973) and not compounded by neurodegen- eration. The field of proteomics in brain research is becoming increasingly important as genome sequences are being completed and annotated (Dutt and Lee, 2000). Moreover, studying protein expression and differential screening of the protein library give specific information that cannot be predicted or obtained from genomic analysis. Thus, we have generated a brain map for fetal proteins and searched the proteome for differential protein expression. This search (reviewed in Engidawork and Lubec, 2001), demonstrated aberrant expression of proteins involved in signal transduction and brain morphogenesis as well as synaptic markers. As part of our ongoing efforts to hunt proteins that have relevance to neuropathology of DS, we updated the first fetal brain protein map, which eventually enabled us to identify previously unidentified proteins and analyzed the newly identified proteins. In this paper, we attempt to describe expression profiles of an array of pro- teins, including cytoskeleton-associated proteins, signaling proteins, apoptosis-related proteins, proteins involved in a variety of metabolic pathways and oncoproteins. EXPERIMENTAL PROCEDURES Fetal brain tissue Brain tissue (cerebral cortex) of aborted control fetuses with no obvious abnormalities (n=7; one female and six males with mean gestational age of 18.82.2 weeks) and DS (n=9; two females *Corresponding author. Tel: +43-40-400-3215; fax: +43-40-400- 3194. E-mail address: gert.lubec@akh-wien.ac.at (G. Lubec). Abbreviations: ALK, anaplastic lymphoma kinase; APLP, -amyloid precursor protein; DS, Down syndrome; EDTA, ethylenediaminetet- raacetic acid; eIF, eukaryotic translation initiation factor; HSP, heat shock protein; HSPC, hematopoietic stem/progenitor cells; MALDI-MS, matrix-assisted laser desorption ionization mass spectroscopy; MLL, mixed lineage leukemia; MSF, mixed lineage leu- kemia septin-like fusion protein; NPM, nucleophosmin; SH, Src homology; SH3GLB2, SH3 domain growth factor receptor bound 2-like endophilin B2; TCP, t-complex polypeptide; TNF, tumor necrosis factor; TPM, tropomyosin; 2-DE, two-dimensional electrophoresis. Neuroscience 122 (2003) 145–154 0306-4522/03$30.00+0.00 © 2003 IBRO. Published by Elsevier Ltd. All rights reserved. doi:10.1016/S0306-4522(03)00605-5 145