ApoE4-expressing mice has an elevated ratio of Aβ40:42 in brain extracellular pools and a lower Aβ40:42 ratio in CSF, which suggests that ApoE4 leads to the altered transport and clearance of Aβ proteins by LDLR in different brain compartments [42], a possible explanation for the lower Aβ levels in CSF of AD patients with cortical microbleeds [43]. The gene discussed is APOE; the disease is Alzheimer disease.