Linkage analysis of multiplex Caribbean Hispanic families loaded for unexplained early-onset cases identifies novel Alzheimer's disease loci

Introduction: Less than 10% of early-onset Alzheimer's disease (EOAD) is explained by known mutations. Methods: We conducted genetic linkage analysis of 68 well-phenotyped Caribbean Hispanic families without clear inheritance patterns or mutations in APP, PSEN1, and PSEN2 and with two or more individuals with EOAD. Results: We identified 16 (logarithm of odds > 3.6) linked regions, including eight novel loci for EOAD (2p15, 5q14.1, 11p15.1, 13q21.22, 13q33.1, 16p12.1, 20p12.1, and 20q11.21) and eight regions previously associated with late-onset Alzheimer's disease. The strongest signal was observed at 16p12.1 (25 cM, 33 Mb; heterogeneity logarithm of odds = 5.3), ∼3 Mb upstream of the ceroid lipofuscinosis 3 (CLN3) gene associated with juvenile neuronal ceroid lipofuscinosis (JNCL), which functions in retromer trafficking and has been reported to alter intracellular processing of the amyloid precursor protein. Discussion: This study supports the notion that the genetic architectures of unexplained EOAD and late-onset AD overlap partially, but not fully.