Transcriptional regulation of the gene encoding the amyloid precursor protein (APP) may play an important role in the formation of the amyloid depositions observed in Alzheimer disease and Down syndrome patients.
The amyloid precursor protein (APP) is thought to be processed aberrantly to yield the major constituent of the amyloid plaques observed in the brains of patients with Alzheimer disease and Down syndrome.
The localization of the Alzheimer amyloid protein precursor (APP) gene on chromosome 21, along with its overexpression in Down's syndrome brain compared with normal brain, suggests that alterations in APP gene expression may play a role in the development of the neuropathology common to the two diseases.
Whereas in Down's syndrome, over-expression of the gene coding for PreA4 is likely to be responsible for the premature development of cerebral amyloidosis, a similar mechanism is yet to be demonstrated in Alzheimer's disease.
Here we show, by using a somatic-cell/hybrid-cell mapping panel, in situ hybridization, and transverse-alternating-field electrophoresis, that the beta-amyloid precursor protein gene is located on chromosome 21 very near the 21q21/21q22 border and probably within the region of chromosome 21 that, when trisomic, results in Down syndrome.
Transgenic mice overexpressing the three major neuronal isoforms of the human amyloid precursor protein (APP), APP695, APP751, APP770 may provide an animal model for the analysis of the mechanisms and risk factors leading to amyloid deposition in Alzheimer's disease (AD) and Downs syndrome (DS).
Overexpression of the APP gene may also be responsible for increased production of paired helical filaments (PHF) and result in enhanced formation of primitive beta/A4 deposits in DS.
This may be the case during pathological evolution of AD and DS when beta/A4 derived from synaptic APP is converted to beta/A4 amyloid by radical generation.
Recombinant beta-APP was generated by a vaccinia virus expression system in CV-1 monkey fibroblasts; endogenous beta-APP was obtained using a fibroblast line derived from an individual with Down's syndrome.
A four- to fivefold overexpression of the gene for the Alzheimer amyloid precursor protein (APP) in individuals with Down's syndrome (DS) appears to be responsible for the fifty year earlier onset of Alzheimer's disease pathology in DS compared to the normal population.
Aberrant expression of the amyloid precursor protein (APP) gene may contribute to the beta-amyloid deposition seen in Alzheimer's disease and Down syndrome patients.
Therefore, (one of) the effects of the mutations in the presenilin 1:PS-1 (S182) gene may be to cause or at least promote an early and excessive deposition of Abeta42(43) within the brain, a property shared with other inherited forms of AD, such as those due to amyloid precursor protein mutations, and Down's syndrome (trisomy 21).
Using carboxyl end-terminal specific antibodies to A beta peptides, we examined the immunocytochemical distribution of A beta 40 and A beta 42 species in brain tissue from a Swedish subject with familial AD (FAD) bearing the double mutation at codons 670/671 in the amyloid beta precursor protein (A beta PP), and from subjects with Down's syndrome and sporadic AD.
In delaying the age of onset, the epsilon2 allele would have a similar action in AD-type dementia in DS and in AD families with amyloid precursor protein (APP) mutations.
Maternal serum markers of human chorionic gonadotrophin unconjugated estriol and amyloid precursor protein, nuchal skinfold on ultrasound and new genetic probes are developed to allow better detection of Down syndrome.
Patients with trisomy 21 [Down syndrome (DS)] progressively develop amyloid beta-protein (A beta) deposits and then other features of Alzheimer's disease (AD), apparently due to increased gene dosage and thus expression of the beta-amyloid precursor protein.
The presence of this PS1 mutation has an even greater effect on both vascular and parenchymal amyloid deposition, than the overexpression of the amyloid beta precursor protein present in DS patients, suggesting that PS mutations can be a critical factor determining amyloid deposition.
Further, the manifestation and time course of behavioral yet not neuropathological symptoms in betaAPP mutant mice resemble in some aspects those of the human Down's syndrome.
These observations suggest that the development of pathological changes in DS brains does not parallel that observed in AD, which might be attributable to different causes in the pathogenesis of betaA4 formation.