Genomic evolution reshapes cell-type diversification in the amniote brain

Area of Science:

• Evolutionary biology
• Neuroscience
• Genomics

Background:

• Amniotes evolved complex brains and cognition over 320 million years.
• Genetic and gene expression mechanisms underlying these changes remain largely unexplored.

Purpose of the Study:

• To create a comprehensive single-cell atlas of the amniote telencephalon and cerebellum.
• To identify species-specific variations, conservation, and diversification of cell types across evolution.
• To investigate genetic mechanisms driving brain evolution and adaptation.

Main Methods:

• Generated a single-cell atlas of over 1.3 million cells from turtles, birds (zebra finches, pigeons), mice, and macaques.
• Utilized single-cell resolution spatial transcriptomics to analyze gene expression patterns.
• Performed comparative analysis of cell types and gene expression across species.

Main Results:

• Identified significant species-specific variations in telencephalon excitatory neurons (EXs) and cerebellar cell types.
• Observed distinct gene expression patterns (SLC17A6 vs. SLC17A7) in bird and mammal EXs.
• Discovered a bird-specific Purkinje cell subtype (SVIL+) linked to the KDM1A pathway and positively selected genes.

Conclusions:

• Species-specific cell types and gene expression contribute to amniote brain evolution and cognitive diversity.
• The KDM1A pathway and positively selected genes in bird Purkinje cells suggest evolutionary optimization for adaptation.
• Genetic diversification plays a crucial role in developing specialized cell types for ecological and behavioral adaptation.