Tol2 gene trap integrations in the zebrafish amyloid precursor protein genes appa and aplp2 reveal accumulation of secreted APP at the embryonic veins.

The single spanning transmembrane amyloid precursor protein (APP) and its proteolytic product, amyloid-beta (Ab) peptide, have been intensely studied due to their role in the pathogenesis of Alzheimer's disease. However, the biological role of the secreted ectodomain of APP, which is also generated by proteolytic cleavage, is less well understood. Here, we report Tol2 red fluorescent protein (RFP) transposon gene trap integrations in the zebrafish amyloid precursor protein a (appa) and amyloid precursor-like protein 2 (aplp2) genes. The transposon integrations are predicted to disrupt the appa and aplp2 genes to primarily produce secreted ectodomains of the corresponding proteins that are fused to RFP. Our results indicate the Appa-RFP and Aplp2 fusion proteins are likely secreted from the central nervous system and accumulate in the embryonic veins independent of blood flow. The zebrafish appa and aplp2 transposon insertion alleles will be useful for investigating the biological role of the secreted form of APP.