Endophenotypic Effects of the SORL1 Variant rs2298813 on Regional Brain Volume in Patients with Alzheimer’s Disease

Background: Two common variants of sortilin-related receptor 1 gene ( SORL1 ), rs2298813 and rs1784933, have been associated with late-onset Alzheimer’s disease (AD) in the Han Chinese population in Taiwan. However, neuroimaging correlates of these two SORL1 variants remain unknown. We aimed to determine whether the two SORL1 polymorphisms were associated with any volumetric differences in brain regions in AD patients. Methods: We recruited 200 patients with late-onset AD from Taipei Veterans General Hospital. All patients received a structural magnetic resonance imaging brain scan and completed a battery of neurocognitive tests at enrollment. We followed up to assess changes in Mini-Mental State Examination (MMSE) scores in 155 patients (77.5%) at an interval of 2 years. Volumetric measures and cortical thickness of various brain regions were performed using FreeSurfer. Regression analysis controlled for apolipoprotein E status. Multiple comparisons were corrected for using the false discovery rate. Results: The rs2298813 and rs1783933 genotypes were not associated with cognitive test performance or clinical progression. The homozygous major allele of rs2298813 was associated with larger volumes in the right putamen (p = 0.0442) and right pallidum (p = 0.0346). There was no link of the rs1784933 genotypes with any of the imaging measures. In the rs2298813 homozygous major allele carriers, the right putaminal volume was associated with verbal fluency (p = 0.008) and clinical progression (p = 0.020). In the minor allele carriers, the right putaminal and right pallidal volumes were not significantly related to cognitive test scores or clinical progression. Conclusions: The major and minor alleles of rs2298813 had differential effects on the right lentiform nucleus volume and distinctively modulated the association between the regional volume and cognitive function in patients with Alzheimer’s disease.