Transcriptional programs controlling lineages specification of mandibular epithelium during tooth initiation

Tooth development starts with formation of the dental lamina, a localized thickening of the maxillary and mandibular epithelium, at specific location of oral cavity. How this dental lamina is specified within the continuous naive maxillary and mandibular epithelium, remains as a critical and unresolved question. To identify potential genes and transcriptional regulatory networks that controlling dental lamina formation, we utilized single-cell Multiome-seq and Laser Microdissection coupled RNA-seq to profile gene expression and open chromatin of mandibular epithelium during tooth initiation. We comprehensively identified transcription factors (TFs) and signaling pathways that are differentially expressed among different domains (including dental lamina) along dorsal-ventral axis of mandibular epithelium. Specifically, we found Sox2 and Tfap2a/Tfap2b forming two complementary domains along the dorsal-ventral axis of mandibular epithelium. Furthermore, dental lamina specific or enriched TFs such as Pitx1, Pitx2 and Zfp536 are presented around the interface of Sox2 and Tfap2a/Tfap2b. We also identified correlation between signaling pathways and domain specific TFs. Through computational analysis of single-cell Multiome-seq dataset, we identified potential key/driver TFs and core transcriptional regulatory networks (TRNs) for lineages (oral, dental, skin) specification during tooth initiation. Our computational analysis also reveals a potential cross repression interactions between different groups of TFs (i.e. Pitx1/Pitx2 and Tfap2a/Tfap2b) that might be essential for dental lamina specification.