Regulatory Mechanisms Orchestrating Cellular Diversity in Cd36+ Olfactory Sensory Neurons Revealed by Single-Cell Multi-omics Analysis.

The olfactory system relies on the precise expression of olfactory receptor (OR) genes in individual olfactory sensory neurons (OSNs) to detect and discriminate a vast array of odorants. Recent discoveries have revealed remarkable complexity and diversity within OSNs, including the existence of two distinct OSN populations based on high-affinity receptor Cd36 expression. However, the regulatory mechanisms governing this cellular diversity in the same cell type remain elusive. To address these questions, we conducted single-cell multi-omics analyses of mature OSNs in the mouse olfactory epithelium. Firstly, we systematically revealed the transcriptome diversity and spatial distribution of Cd36+ OSNs and found a specific subset of olfactory receptors co-expressed with Cd36 in a deterministic manner. scATAC-seq profiling of chromatin landscape demonstrated a divergence between Cd36+ OSNs and Cd36- OSNs, including differential accessibility of cis-elements. By integrating transcriptome and epigenome profiling of OSN lineage-associated cell types, we revealed that the processes governing this diversity are initiated at the immature OSNs stage, where cellular diversity was first set by the lineage-specific binding of Lhx2 at Hdac9 enhancer. Hdac9, which is specifically expressed in the Cd36- OSN lineage, functions as a histone deacetylase and may repress the transcription of Mef2-dependent genes that contribute to Cd36+ OSN diversity. By gene regulation network analysis, we revealed Mef2a and Tshz1 as the key transcription factors, orchestrating the transcriptome diversity of Cd36+ OSNs. Remarkably, we identified and confirmed Tshz1 as a critical transcription factor that directly promotes Cd36 expression in OSNs through enhancer binding. Our study unravels the intricate regulatory landscape and principles governing cellular diversity in the olfactory system. These findings provide valuable insights into the regulation principles underlying neuronal heterogeneity and its functional implications.