ABCC9/SUR2 has a Complex Expression Pattern in Human Brain Gliovascular Unit Cells, Including Astrocytes

The ABCC9 gene and its cognate protein SUR2 play important roles in neurovascular coupling and are implicated in hippocampal sclerosis of aging (HS-Aging). However, prior studies have not focused on human brain SUR2 expression or SUR2 in glial cells. Here we analyzed cell type-specific ABCC9/SUR2 expression patterns, and correlation with known genetic risk variants, using multiple data sets and a novel antiserum. Existing single-nucleus RNA sequencing data sets and new spatial transcriptomics data indicated that SUR2 transcripts were expressed primarily in human brain pericytes, astrocytes, smooth muscle cells, and endothelial cells. Evaluation of Sur2 expression in a sample of mice brains showed similar results except Sur2 was not detected in the mice astrocytes. In a SUR2-enriched subcluster of human astrocytes, the pattern of transcript expression suggested responsiveness to thyroid hormone signaling: SUR2-correlated gene products were enriched for thyroid hormone-sensitive transcripts and SLCO1C1, the astrocyte thyroid hormone importer, was the transcript with the strongest correlation with SUR2 expression. Cells in the SUR2 + astrocyte cluster tended to have been derived from individuals lacking severe Alzheimer's disease pathology. An ABCC9 single nucleotide variant (rs1914361, also a HS-Aging risk allele) was associated with increased SUR2 expression in astrocytes, but not other cell types. SUR2 mRNA splicing differed between cell types; astrocytes preferentially expressed the SUR2B variant. A novel SUR2 antiserum immunolabeled blood vessel walls and some astrocyte-morphology cells in human brain. Overall, human brain SUR2 expression was enriched among different cell types of the gliovascular unit. A SUR2-enriched, possibly-homeostatic astrocyte subcluster suggested connections to thyroid hormone signaling.