Quantitative FISH analysis with a dual color probe detecting both chromosome 21 (SpectrumOrange) and 12 (SpectrumGreen) revealed induction of trisomy 21 and 12 (AC), but no significant increase of either tetrasomy 21 or 12 (data not shown). tau phosphorylation and cell toxicity. These results indicate that A-induced microtubule dysfunction leads to aneuploid neurons and may thereby contribute to the pathogenesis of AD. == INTRODUCTION == Developing early diagnoses and successful treatments for Alzheimer’s disease (AD) will be greatly aided by a clear understanding of all steps in the pathogenic pathway that leads to amyloid deposition, neurofibrillary tangle formation, inflammation, and neurodegeneration in the brain. Although most AD is sporadic, a large proportion is at least partly familial in AN-3485 that patients develop the disease by inheriting a mutant gene or a risk-enhancing genetic polymorphism. Autosomal dominant mutations, accounting for 5% of AD, have been described in three genes, and their analysis has provided especially important insights into the AD pathogenic pathway (Glenner and Wong, 1984;Hardy and Selkoe, 2002). One of these genes encodes the amyloid precursor protein (APP) from which the key amyloid component, the A peptide, is derived by proteolysis. Although mutations in theAPPgene itself account for <1% of AD, they provided the AN-3485 proof that APP and A are central to the disease process. Most autosomal dominantly inherited familial Alzheimer's disease (FAD) is caused by mutations in two presenilin genes, most commonly PS-1. The PS proteins must therefore also occupy a key place in the AD pathogenic pathway together with APP and the A peptide. The role of the presenilins in AD pathology was clarified when they were found to form the enzymatic core of the -secretase AN-3485 complex that cleaves APP in its transmembrane region and generates the C-terminus of the A peptide (Wolfe, 2003). Several lines of evidence indicate that both sporadic and familiar AD patients, including those carryingAPPandPSmutations, are abnormal in one or more aspects of the cell cycle (for reviews, seeObrenovichet al., 2003;Potter, 2004,2008). For example, Down syndrome (DS) patients, who carry three copies of chromosome 21 in all of their cells due to meiotic chromosome mis-segregation in one of (usually) their mother’s germ cells, invariably develop AD-like pathology by the age 3040 (Olson and Shaw, 1969;Glenner and Wong 1984;Epstein, 1990). This and other findings led us to propose that over a lifetime, defective mitoses lead to the accumulation of aneuploid cells throughout the body, including the brain. When such chromosome mis-segregation generates trisomy 21 cells, the extra copy of theAPPgene on chromosome 21 contributes to the development of Alzheimer neuropathology and dementia (Potter, 1991). The microtubule (MT) disfunction likely responsible for the aneuploidy in AD patients could also affect other aspects of cell physiology, especially in neurons. The chromosome mis-segregation/MT disfunction hypothesis of AD makes several easily-testable predictions (Potter, 1991). For example, AD patients should be mosaic for trisomy 21, Rabbit polyclonal to GAPDH.Glyceraldehyde 3 phosphate dehydrogenase (GAPDH) is well known as one of the key enzymes involved in glycolysis. GAPDH is constitutively abundant expressed in almost cell types at high levels, therefore antibodies against GAPDH are useful as loading controls for Western Blotting. Some pathology factors, such as hypoxia and diabetes, increased or decreased GAPDH expression in certain cell types and, indeed, we found trisomy 21 and other aneuploid cells in primary skin fibroblast cultures from patients with both the familial (early age of onset) and sporadic (late age of onset) forms of the disease (Potteret al., 1995;Geller and Potter, 1999). Trisomy 21 cells AN-3485 have also been observed among peripheral blood lymphocytes, buccal cells, and brain neurons from sporadic AD patients and among lymphocytes of mothers who, at a young age, gave birth to a DS child and are prone themselves to develop AD later in life (Schupfet al., 1994;Miglioreet al., 1999,2006;Yanget al., 2001;Moschet al., 2007;Thomas and Fenech, 2008;Iourovet al., 2009). Conversely, between 1 and 10% trisomy 21 mosaicism has also been found in individuals with otherwise unexplained AD-like dementia in middle age, indicating that even small numbers of trisomy 21 cells can lead to cognitive deficits (Roweet al., 1989;Shapiroet al., 1989;Puriet al., 1994;Ringmanet al., 2008). Advanced AD patients also develop tetraploid neurons (Yanget al., 2001;Moschet al., 2007), which may indicate entry into an incomplete cell cycle (Vincentet al., 1996;Obrenovichet al., 2003;Varvelet al., 2008). Through the AN-3485 elegant use of several techniques, Arendt and colleagues found increases in both aneuploid and tetraploid neurons in AD brain, with the 30% aneuploid cells (between 2n and 4n) being >10 times more common than tetraploid neurons (Moschet al., 2007). Another prediction of the chromosome mis-segregation/MT disfunction hypothesis for AD is that the very genes that, when mutant, cause familial AD should encode proteins that are involved in the cell.