The developing midbrain-hindbrain boundary contains molecularly distinct cell populations

Area of Science:

• Developmental Biology
• Neuroscience
• Genomics

Background:

• The isthmic region is vital for vertebrate brain development, acting as an organizer at the midbrain-hindbrain boundary.
• Its precise molecular and cellular makeup has remained largely undefined.

Purpose of the Study:

• To molecularly characterize cell populations within the embryonic isthmic region.
• To refine understanding of its cellular organization and subdomains.

Main Methods:

• Combined single-nucleus ATAC-seq and RNA-seq (scMultiome) in zebrafish embryos.
• In vivo validation using RNA fluorescence in situ hybridization.

Main Results:

• Identified two main isthmic cell populations: isthmic midbrain (IsMB) and isthmic hindbrain (IsHB).
• Discovered heterogeneity within IsHB into FGF8-expressing (IsO/r0a) and FGF8-negative (r0p) populations.
• FGF signaling inhibition disrupted isthmic region formation, yielding cells with mixed neural identity.

Conclusions:

• Transcriptional and epigenetic analyses reveal distinct subdomains within the isthmic region.
• Expands understanding of isthmic region cellular organization beyond anatomical and genetic studies.