126: Smith-Magenis Syndrome: Chromatin Rewiring to Hyperexcitable Neurons

Lee Y et al., The American Journal of Human Genetics - This episode reviews a study using hiPSC-derived 2D cortical neurons and 3D cortical organoids from individuals with del(17)p11.2 (Smith-Magenis syndrome) to map chromatin, transcriptional, developmental, and electrophysiological consequences of the deletion. Key terms: Smith-Magenis syndrome, del(17)p11.2, hiPSC organoids, chromatin topology, neuronal hyperexcitability.

Study Highlights:
The authors show that del(17)p11.2 induces local TAD fusion on chromosome 17 and genome-wide chromatin miswiring in hiPSCs and cortical organoids, with widespread transcriptional dysregulation. SMS organoids display reduced growth, enlarged PAX6+ ventricles, impaired progenitor cell-cycle progression, and accelerated neuronal maturation. In 2D cortical neurons, SMS cells exhibit early accelerated dendritic growth, increased excitatory synapse density, and intrinsic hyperexcitability linked to reduced voltage-gated potassium conductance. Together, the models recapitulate neuroanatomical and neurophysiological features of SMS and identify candidate molecular and cellular mechanisms.

Conclusion:
del(17)p11.2 disrupts 3D chromatin architecture and transcriptional programs, impairing progenitor proliferation and promoting neuronal hyperexcitability, which hiPSC-derived 2D and 3D models faithfully recapitulate and that point to potassium-channel and cell-cycle pathways as potential intervention targets.

Music:
Enjoy the music based on this article at the end of the episode.

Article title:
Molecular and developmental deficits in Smith-Magenis syndrome human stem cell-derived cortical neural models

First author:
Lee Y

Journal:
The American Journal of Human Genetics

DOI:
10.1016/j.ajhg.2025.07.020

Reference:
Lee Y.-J., Chang Y.-T., Cho Y., Kowalczyk M., Dragoiescu A., Pacis A., Kailasam S., Lefebvre F., Zhang Q., Gao X., Huang W.-H. (2025). Molecular and developmental deficits in Smith-Magenis syndrome human stem cell-derived cortical neural models. The American Journal of Human Genetics 112, 1–25. https://doi.org/10.1016/j.ajhg.2025.07.020

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/

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Episode link: https://basebybase.com/episodes/molecular-and-developmental-deficits-in-smith-magenis-syndrome-human-stem-cell-derived-cortical-neural-models

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2025-09-03.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited transcript sections covering human iPSC-based SMS models (2D neurons and 3D organoids), 3D genome topology (Hi-C/TAD fusion), transcriptional changes (snRNA-seq/bulk RNA-seq), organoid growth and ventriculomegaly, NPC proliferation/cell-cycle defects, 2D neuron maturation and hyperexcitability with potassium-ch
- transcript topics: Human iPSC-derived SMS models (2D cortical neurons and 3D cortical organoids); 3D genome architecture and chromatin topology changes (Hi-C, TAD fusion, trans effects); Global transcriptional dysregulation across multiple cortical cell types (snRNA-seq and bulk RNA-seq); Organoid growth impairment and ventriculomegaly-like phenotypes with NPC proliferation defects; NPC cell-cycle perturbations and G1 arrest signatures; Neuron maturation and dendritic expansion with early excitatory synapse changes

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 8
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- del(17)p11.2 in SMS hiPSCs and cortical organoids alters 3D chromatin topology (local TAD fusion and global miswiring)
- Widespread transcriptional dysregulation across multiple cortical cell types (trans effects observed beyond deleted region)
- SMS cortical organoids show reduced growth and ventriculomegaly-like ventricles due to impaired NPC proliferation/cell-cycle progression
- SMS 2D cortical neurons show accelerated dendritic growth followed by neuronal hyperexcitability linked to reduced potassium conductance
- Reduced voltage-gated potassium currents (K fast and K slow) accompany hyperexcitability; SLC family transporters involved
- POTEI and POTEF are primate-specific protocadherin-related genes with altered expression in SMS organoids

QC result: Pass.