Alzheimer's disease risk single nucleotide polymorphism rs11218343 is linked to functional expression of SORL1 in microglia

INTRODUCTION: The rs11218343 is a non-coding variant of genome-wide significance for sporadic Alzheimer's disease (AD) with one of the most protective effects known to date. It localizes to SORL1, encoding the AD risk factor Sortilin-related receptor with A type repeats (SORLA). Still, the functional significance of rs11218343 for AD-related processes remains unclear. METHODS: We used induced pluripotent stem cell (iPSC) lines from donors, or genome-engineered to carry major and minor rs11218343 alleles, to study the impact of rs11218343 on cellular activities. RESULTS: We show that rs11218343 is uniquely linked to functional expression of SORLA in microglia, with increased expression in the protective allele correlating with reduced pro-inflammatory responses. These anti-inflammatory effects are seen in donor lines but not in single nucleotide polymorphism (SNP) -engineered isogenic lines, arguing that this polymorphism alone is insufficient but acting context-dependent. DISCUSSION: Our data infer genetically defined expression of SORL1 in microglia as a determinant of protection from pro-inflammatory stimulation, a function likely encoded by a haplotype linked to rs11218343.