To clarify the in vivo effect of LRP1 on Aβ production/clearance, mice expressing a mutant LRP1 protein, with impaired endocytosis and transcytosis activity, were crossed with a mouse model for Alzheimer disease (which were transgenic mice expressing mutant human APP with both the Swedish (K670N/M671L) and London (V717I) mutations) [3]. The gene discussed is APP; the disease is early-onset autosomal dominant Alzheimer disease.