Finessing the details: subclasses of LGN neurons and the richness of spatial transcriptomics

Massachusetts General Hospital, Boston MA

Investigators

Abstract

PROJECT SUMMARY / ABSTRACT Evidence is slowly building for a more nuanced and complex architecture within human and macaque lateral geniculate nucleus (LGN) than the classic view of three cell classes separated into six laminae. Exhaustive investigations in primate retina have revealed a highly diverse set of retinal ganglion cell (RGC) types that project to the LGN; while the majority of projections by fiber count are from the primary classes of RGCs (midget and parasol) that target the magno- (M) and parvocellular (P) layers in LGN, many of the classes with sparser fiber count (bistratified, thorny, sparse, monostratified, etc.) project to the koniocellular (K) layers, or have undescribed targets in the LGN. Recent single cell RNA sequencing (scRNA-seq) results on neuronal nuclei microdissected from differ- ent layers of LGN suggest a broader diversity than currently understood by classical anatomical and funct- ional results, with eight cell types identified in macaque: four GABAergic cells (presumably interneurons), M, P, and two kinds of K cells. Our analysis of data from the literature, presented here, suggests that additional sub-classes can be identified. But the spatial distribution of those cell types, specifically the multiple GABAergic and K classes, and the novel sub-classes we have found, is as-yet unknown. We will fill that gap by applying the recently available tools of spatial transcriptomics to analyze the layout of geneticaly-defined cell classes across the LGN, creating data sets from human autopsy tissue. These data will be generated in collaboration with the UCLA Technology Center for Genomics and Bioin- formatics on their NanoString CosMx SMI instrument. Human tissue will be obtained in collaboration with the MGH Pathology Department through an unrelated program that requires rapid autopsy following death. These data will allow us to test hypotheses about the spatial distribution of the factors that determine the cellular subtypes above, such the NOTCH developmental pathway, NDUF, COX, and ATP metabolic pathways, STX1A signaling pathway, and others. We will test whether different LGN laminae within the M, P, and K pathways are genetically differentiated, along with variation along eccentricity through anterior vs posterior sections, or along projection columns. The results from this initial project will be used as preliminary data in support of obtaining funding for a larger, more extensive study that will look for variation within and across individuals, asking questions about cell type distribution across the visual field, within and across laminae, then between sexes, through age, and finally about changes due to retinal or other blinding diseases.