A MOLECULAR MARKER FOR TECTORECIPIENT NEURONS IN THE DORSAL LATERAL GENICULATE NUCLEUS OF THE MOUSE (<EM>MUS MUSCULUS</EM>) AND TREE SHREW (<EM>TUPAIA BELANGERI</EM>)

Information in the primate visual system is projected from the retina to the thalamus and relayed to the visual cortex along the magnocellular (M), parvocellular (P), and koniocellular (K) pathways. Homologous organization is found across mammalian species, such as X, Y, and W pathways in carnivores. The contribution to vision of the K-pathway and its homologues remains poorly understood, but features atypical response properties and input from the superior colliculus (SC) at specific locations within the dorsal lateral geniculate nucleus (dLGN) of the thalamus. Although there have been morphological characterizations of cells in these regions, molecular definitions remain elusive. While the mouse serves as neuroscience’s primary model organism due to its abundant experimental tools, its evolutionary distance from primates limits direct comparisons. To address this, the tree shrew provides a valuable intermediary between rodents and primates. In mice, SC inputs are restricted to the dorsal-most “shell” of the dLGN, which lacks lamination, whereas in tree shrews, SC inputs are distributed in specific layers of the dLGN, homologous to the K-layers of primates. Here, we present a molecular marker candidate for tectogeniculate neurons in both the mouse and tree shrew dLGN. Identified via single-cell RNA sequencing, and validated through retrograde and transsynaptic anterograde viral tracing combined with immunohistochemistry and RNA fluorescent in situ hybridization, our findings indicate that tectogeniculate neurons express this candidate marker gene. These results provide a molecular definition for K-pathway homologues in mouse and tree shrew, enabling more precise study of the parallel processing of visual information.