Intersecting impact of CAG repeat and Huntingtin knockout in stem cell-derived cortical neurons

Area of Science:

• Neuroscience
• Genetics
• Stem Cell Biology

Background:

• Huntington's Disease (HD) arises from CAG repeat expansion in the Huntingtin (HTT) gene.
• The precise biological mechanisms distinguishing CAG repeat expansion effects from simple HTT loss-of-function remain unclear.

Purpose of the Study:

• To differentiate the biological signatures of CAG repeat expansion from HTT loss-of-function.
• To elucidate the distinct and overlapping pathways affected in Huntington's Disease.

Main Methods:

• Utilized multi-omics, live cell imaging, and survival analysis on human embryonic stem cell-derived cortical neurons (eCNs).
• Applied a novel feature-based pipeline to compare HTT knockout (KO) models with CAG repeat expansion models.
• Analyzed differentially expressed genes and proteins alongside epigenetic motifs.

Main Results:

• Both HTT KO and CAG repeat expansion altered eCN developmental trajectories, exhibiting opposing effects on growth.
• Identified shared subnetworks between CAG repeat expansion and HTT KO, involving neuronal differentiation, cell cycle regulation, and transcriptional repression.
• These commonalities suggest gain-of-function mechanisms beyond simple HTT loss.

Conclusions:

• Aberrant neurodevelopment and neurodegeneration in HD likely result from a combination of dominant and loss-of-function mechanisms.
• Findings provide insights for developing targeted therapeutic strategies for Huntington's Disease.