Single-cell multiomic and spatial landscape of the primate pineal gland reveals circadian and melatonin regulatory architecture.

Abstract

The mammalian pineal gland maintains normal circadian rhythms and homeostasis by secreting melatonin. However, the lack of a single-cell-resolved regulatory map limits our understanding of how these neuroendocrine functions are orchestrated. Here, we constructed a multiomics atlas of the pineal gland from <i>Macaca fascicularis</i> by integrating snRNA-seq, snATAC-seq, and spatial transcriptomics. We identified pinealocytes as the predominant cell type, alongside six glial and vascular lineages. Chromatin accessibility analysis delineated cell-type-specific regions enriched for melatonin synthesis and phototransduction genes. Notably, we resolved a dual-layer regulatory architecture: While melatonin synthesis programs are robustly organized, circadian clock regulators exhibit a distinct, sparse spatial pattern. Coexpression networks further identified core modules and regulatory hubs-including CRX/OTX2, LHX4, and RORA-that integrate these circadian and light-responsive signals. Cell-cell communication analysis identified signaling axes, such as <i>PTN</i>-<i>ALK</i>/<i>SDC2</i>, <i>RA</i>-<i>RORB</i>, and <i>NRG1</i>-<i>ERBB4</i>, that potentially coordinate this spatial functional organization. Integrating genetic traits showed that sleep and neuropsychiatric risk variants preferentially map to these pineal regulatory modules. Specifically, sleep-associated loci converged on <i>MEIS1</i>-linked elements, while bipolar disorder-associated loci highlighted candidate genes of <i>RDH12</i> and <i>SDK2</i>. Overall, this study reveals the cellular diversity and spatial regulatory logic of the primate pineal gland, providing a physiological foundation for investigating circadian and neuroendocrine regulation in healthy and disease models.