ABSTRACT
The gene that codes for beta-amyloid precursor protein (beta-APP), a protein centrally involved in senile plaque formation in Down syndrome (DS) and Alzheimer's disease (AD), is located on chromosome 21. In DS beta-APP expression is three- to fourfold higher than what is expected from the 1.5-fold increased gene load, suggesting that other genes on chromosome 21 directly or indirectly can further up-regulate beta-APP. Here we show that the chromosome 21 transcription factor ETS2 transactivates the beta-APP gene via specific Ets binding sites in the beta-APP promoter and, in this respect, cooperates with the transcription factor complex AP1. We further show that brains and primary neuronal cultures from Ets2 transgenic mice, as well as 3T3 fibroblasts that overexpress ETS2, display molecular abnormalities also seen in DS, such as elevated expression of beta-APP protein, an increase in presenilin-1 and increased beta-amyloid production. We conclude that ETS2 is a transcriptional regulator of beta-APP and that overexpression of ETS2 in DS may play a role in the pathogenesis of the brain abnormalities in DS and possibly AD.
Subject(s)
Amyloid beta-Protein Precursor/genetics , Chromosomes, Human, Pair 21/genetics , DNA-Binding Proteins , Down Syndrome/genetics , Proto-Oncogene Proteins/physiology , Repressor Proteins , Trans-Activators/physiology , Transcription Factors , 3T3 Cells , Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor/biosynthesis , Animals , Binding Sites , Brain/metabolism , Humans , Membrane Proteins/metabolism , Mice , Mice, Transgenic , Presenilin-1 , Promoter Regions, Genetic , Proto-Oncogene Protein c-ets-2 , Proto-Oncogene Proteins/biosynthesis , Trans-Activators/biosynthesis , Transcription Factor AP-1/metabolism , Transcriptional ActivationABSTRACT
We have cloned and characterized a novel murine DNA-binding protein Desrt, with a motif characteristic of the ARID (A-T rich interaction domain) family of transcription factors. The Desrt gene encodes an 83-kD protein that is shown to bind DNA and is widely expressed in adult tissues. To examine the in vivo function of Desrt, we have generated mice with a targeted mutation in the ARID domain of Desrt. Homozygous mutants have reduced viability, pronounced growth retardation, and a high incidence of abnormalities of the female and male reproductive organs including cryptorchidism. This may thus serve as a model to dissect the mechanisms involved in the development of the reproductive tract including testicular descent. Gene-targeted mice also display a reduction in the thickness of the zona reticularis of the adrenal gland and transient aberrations of the T and B cell compartments of primary lymphoid organs. These data show that this novel DNA-binding protein, Desrt, has a nonredundant function during growth and in the development of the reproductive system.
