APP and Alzheimer disease: While CTSB KO in human AβPP-695/Wtβ-Lonγ AD mice resulted in lowered Aβ species [7, 10, 15], CTSB KO in hAβPP-751/770/Wt mice had no effect on hippocampal Aβ42 and increased Aβ1 - x by 18% above controls, and resulted in small increases in Aβ42 and Aβ1 - x in brain cortex of 20% and 24% above controls [17].