In situ hybridization analyses of claustrum‐enriched genes in marmosets

The claustrum/endopiriform nucleus is a unique structure that sits between the striatum and the cerebral cortex. Recent genome‐wide mapping of gene expression in mice identified various genes concentrated in this structure, suggesting a requirement for a special set of genes for its function. In situ hybridization histochemistry was performed for such “claustrum‐enriched” genes in the marmoset brain. In marmosets, nurr1 and netrinG2 genes exhibited highly concentrated expression in the claustrum and endopiriform nucleus, as well as in a subpopulation of layer 6 neurons across the entire cortex, consistent with their expression patterns as described in macaques. Cux2 showed enriched expression in the upper layers (layers 2–4) and the claustrum/endopiriform nucleus. GNG2 was expressed strongly in the claustrum/endopiriform nucleus, but was abundant across cortical areas in a ventral high‐dorsal low gradient. Latexin was detected in the claustrum and dorsal endopiriform nucleus, but not in cortical regions. GNB4 and Tmem163 genes were both concentrated in the claustrum/endopiriform nucleus, as reported in mice, but their cortical expression in the marmoset differed from the mouse pattern. Thus, the gene set required for the claustrum appears to be broadly conserved across species, despite various differences that suggest species‐specific differentiation of brain architecture. J. Comp. Neurol. 525:1442–1458, 2017. © 2016 Wiley Periodicals, Inc.