An integrated transcriptomic approach for identifying enhancers in limb motor pools

Area of Science:

• Neuroscience
• Genomics
• Developmental Biology

Background:

• Motor neurons (MNs) are crucial for body movement, with distinct pools targeting specific muscles.
• Understanding MN subtypes requires knowledge of their unique gene expression patterns.

Purpose of the Study:

• To identify cis-regulatory elements (CREs) specific to different motor neuron subtypes.
• To investigate the role of transcription factors (TFs) in MN identity specification.
• To functionally validate predicted enhancers in motor neuron gene regulation.

Main Methods:

• Integrated single-cell transcriptomics (scRNA-seq) and epigenomics (scATAC-seq, histone modifications).
• Bioinformatic analysis to identify MN-lineage clusters and associated CREs.
• Computational identification of TF binding motifs within CREs.
• Functional validation of candidate enhancers using electroporation in chicken neural tubes.

Main Results:

• Identified five distinct MN-lineage clusters with unique gene ontology terms, TF motifs, and disease associations.
• Found differential enrichment of LIM-homeodomain (LIM-HD) TF motifs, including Isl1/Lhx3, in specific motor column CREs.
• Discovered and functionally validated three novel enhancers within the Etv4 locus, active in limb motor pools.

Conclusions:

• Integrated in silico analysis of single-cell epigenetic and transcriptomic data can predict CREs governing MN subgroup identity.
• This approach provides insights into the genetic regulation of motor pool diversification.
• The findings highlight the importance of specific TF motifs and enhancers in defining MN subtypes.