Expression of the human beta-amyloid precursor protein gene from a yeast artificial chromosome in transgenic mice.

Abstract

One hallmark of Alzheimer disease is the formation in the brain of amyloid plaques containing a small peptide derived from the fi-amyloid precursor protein (APP).The APP gene exhibits a complex pattern of expression in peripheral tissues and in the brain. The entire human APP gene was introduced into embryonic stem (ES) cells by co-lipofection of a 650-kb yeast artificial chromosome (YAC). Three ES lines containing an essentiafly intact YAC were isolated, and expression of human APP mRNAs at levels comparable to those of endogenous mouse APP transcripts was obtained. A transgenic mouse line was established by germ-line transmission of the APP YAC. RNase protection analysis of human APP mRNAs demonstrated appropriate splicing of the primary APP transcript in ES cells and in the brain of a transgenic animal. These mice may be useful for elucidating the function of the various APP isoforms in vivo.The senile plaques characteristic of Alzheimer disease (AD) consist of abnormal neurites around an amyloid core primarily composed of a 4-kDa polypeptide, /3-amyloid. The 3-amyloid peptide is derived from the cellular processing of ,B-amyloid precursor protein (APP). Mutations in the APP gene have been identified in certain cases of familial AD, suggesting a causal role for ,B-amyloid deposition in at least some forms of AD (1, 2). The human APP gene is located on chromosome 21, and Down syndrome (DS) individuals overexpress the wild-type APP protein (3). Those who survive past their thirties invariably develop an AD neuropathology (4), and immunoreactive f-amyloid depositions can be found prior to any detectable neuronal degeneration in the DS brain (5). Although APP is expressed at normal levels in non-DS cases of AD, the phenotype seen in DS individuals suggests that AD may be initiated or accelerated by overexpression of APP.The APP gene is composed of 18 exons distributed over several hundred kilobases (6). Alternative splicing of the primary transcript results in the production of at least five distinct transcripts. Of the three predominant APP isoforms, APP770 and APP751 contain a Kunitz-type protease inhibitor (KPI) domain, and are found at varying levels in many tissues (7,8). APP695, lacking the KPI domain, is the predominant splice form in the brain and is less abundant in the periphery (7). Other APP variants have been detected at lower levels (9-11). A possible role for the various isoforms in the progression of AD is suggested by changes in AD brains of the ratio of the KPI-containing APP variants to . However, it is clear that the APP gene exhibits complex tissue-and cell type-specific expression in human (10) and mouse (16) brain.The lack of a small-animal model for AD has hampered investigation of the early events in the progression of AD.

Twofold overexpression of human ?-amyloid precursor proteins in transgenic mice does not affect the neuromotor, cognitive, or neurodegenerative sequelae following experimental brain injury

“…In the present study, we employed this model of brain injury in APP-YAC transgenic mice that contain the entire WT h-APP gene cloned into a YAC, and these mice overexpress h-APPs at levels twofold higher than endogenous mouse APPs. Notably, similar elevations in APP expression levels are also seen in Down's syndrome patients, all of whom develop extensive AD brain lesions by about the age of 40 years (Buxbaum et al, 1993;Pearson and Choi, 1993). Although the APP-YAC mice do not develop AD-like amyloid plaques even at an advanced age (i.e., 2 years old), we asked whether the overexpression of h-APPs in APP-YAC transgenic mice might lead to the induction of AD-like neuropathological changes or acute deposits of A␤ in the injured brain following TBI as well as an exacerbation of posttraumatic cognitive and neurobehavioral dysfunction.…”

“…The generation of the APP-YAC mouse line was established by germ-line transmission of the APP-YAC. The tissuespecific doubling of the concentration of the APPs in these heterozygous transgenic mice has been reported previously (Buxbaum et al, 1993;Pearson and Choi, 1993;Loring et al, 1996). In the present study, both female and male APP-YAC heterozygous transgenic mice (both thirdand fourth-generation animals bred to C57Bl/6 mice) were used.…”

“…The APP-YAC transgenic mice were bred and genetically characterized as described previously (Buxbaum et al, 1993;Pearson and Choi, 1993;Loring et al, 1996). Briefly, APP-YAC mice were generated by introducing the entire h-APP gene into 129SV embryonic stem (ES) cells by lipofection of a 650-kb YAC containing the APP gene.…”

A Review and Rationale for the Use of Genetically Engineered Animals in the Study of Traumatic Brain Injury

“…The CNS of these APP-YAC mice overexpresses APP twofold when compared with normal mice (Pearson and Choi, 1993). Murai et al (1998) subjected APP-YAC mice to CCI brain injury and failed to observe any differences in posttraumatic cognitive function, neurologic motor deficits, APP expression, reactive astrocytosis, or cell loss between brain-injured TG mice and injured WT littermates.…”

Traumatic brain injury in young, amyloid‐β peptide overexpressing transgenic mice induces marked ipsilateral hippocampal atrophy and diminished Aβ deposition during aging

“…Moreover, traumatic brain injury (TBI) induces accumulations of APP in the central nervous system (CNS; Sherriff et al, 1994;Lewen et al, 1995;Pierce et al, 1996;Murai et al, 1998), and the consequences of head trauma appear to be more severe in APOE4-positive patients (Jordan et al, 1997;Teasdale et al, 1997). Although head trauma may initiate neurodegenerative cascades (for reviews, see Maxwell et al, 1997;McIntosh et al, 1998), TBI does not induce A␤ deposits in WT rodents or in the APP-yeast artificial chromosome (YAC) transgenic mice (Murai et al, 1998) that overexpress human APP (Buxbaum et al, 1993;Pearson and Choi, 1993;Loring et al, 1996).…”