Single-cell transcriptomics of ventral forebrain progenitors identifies Evf2 enhancer lncRNA-enhancer gene guidance through direct RNA binding and RNP recruitment domains

During mouse embryonic brain development, the Evf2 ultraconserved enhancer (UCE) lncRNA guides the Dlx5/6UCE to ~129 sites across chr6. However, previous work identified only 4 transcriptionally regulated targets associated with Evf2-Dlx5/6UCE-gene guidance, raising questions about the significance of Evf2-regulated Dlx5/6UCE-gene interactions. Here, single-cell transcriptomics reveal far greater alignment between Evf2-Dlx5/6UCE-gene guidance and transcriptional regulation than previously reported. Evf2 divides chr6 into short-range ( <10 Mb distant), activated genes, and long/super-long-range (10-129 Mb distant), repressed genes, identifying seizure regulating genes in the embryonic subventricular zone that predict adult phenotypes. Evf2-regulated Dlx5/6UCE-gene distances and directions (closer to or further from gene targets) can be decoupled from gene target transcriptional effects. Evf2 regulates Evf2-ribonucleoprotein (RNP) binding in a combinatorial manner to key regulatory sites, including chr6 Evf2-Dlx5/6UCE-gene guided sites, Evf1/2 RNA-directly bound sites (RBSs), and inter-chromosomal HiC looping interactions. RBSs divide chromosomes into multi-megabase domains enriched for Evf2-regulated RNP recruitment, transcription factor motifs, and HiC looping interactions. Together with Evf2-controlled homeobox motif recognition at Evf2-RNP recruitment sites and transcription factor motif enrichment in RBSs with DNA identity, this work supports direct roles for Evf2 in enhancer-gene guidance and transcriptional regulation, with the potential for both site-specific and chromosomal domain specific RNP recruitment.