Imai A et al., Proceedings of the National Academy of Sciences (PNAS) - This paper shows that alternative splicing of a 12-nt microexon (meB) in Ptprd is regulated by a genetic intronic enhancer and an activity-dependent intronic silencer to set region- and age-specific ratios of PTPRD splice variants. Manipulating these intronic elements in mice changes the proportion of meB-containing isoforms without altering total PTPRD protein and produces distinct behavioral consequences. Key terms: microexon, alternative splicing, PTPRD, synaptogenesis, behavior.

Study Highlights:
The authors mapped eight Ptprd splice variants across brain regions and ages and found neuronal activity induces rapid meB skipping. They identified a 316-bp intronic splicing enhancer (ISE) whose heterozygous deletion reduced meB selection by ~25% and caused broad sensory, motor, social, and emotional deficits. They also identified a 420-bp intronic splicing silencer (ISS) required for activity-dependent meB skipping; deletion of the ISS produced selective impairments in motor learning and remote cued fear memory. These results indicate that the spatiotemporal and activity-dependent AS code of a four–amino-acid microexon sculpts synaptogenic properties and behavioral development.

Conclusion:
Spatiotemporal and activity-dependent alternative splicing of a single four–amino-acid microexon in Ptprd controls the balance of PTPRD splice variants and is essential for normal behavioral development in mice.

Music:
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Article title:
Alternative microexon splicing code for a four - amino acid peptide of PTPRD governs behavioral development

First author:
Imai A

Journal:
Proceedings of the National Academy of Sciences (PNAS)

DOI:
10.1073/pnas.2515310123

Reference:
Imai A, Izumi H, Ito N, et al. Alternative microexon splicing code for a four-amino acid peptide of PTPRD governs behavioral development. Proc Natl Acad Sci U S A. 2026;123(15):e2515310123. doi:10.1073/pnas.2515310123

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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QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-04-12.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the scientific narrative in the transcript related to Ptprd microexon meB regulation, the regulatory elements ISE and ISS, bead-coculture experiments, in vivo CRISPR mouse models (ISE and ISS mutations), activity-dependent skipping, and the resulting behavioral and learning/memory phenotypes, as well as the pro
- transcript topics: Ptprd microexon meA3, meA6, meB and eight splice variants; Bead coculture assay to test synaptogenicity and ligand interactions (Shank2, gephyrin, NLGN3); Genetic regulation of meB: intronic splicing enhancer (ISE); Activity-dependent regulation of meB: intronic splicing silencer (ISS); In vivo CRISPR mouse models: Ptprd+/dISE, PtprddISE/dISE, PtprddISS/dISS; Neuronal activity and rapid meB skipping (1 hour after KCl)

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 6
- 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:
- Eight Ptprd splice variants arise from combinations of meA3, meA6, and meB, with region- and age-specific distributions
- An upstream intronic splicing enhancer (ISE) of Ptprd meB regulates inclusion; its deletion reduces meB selection by about 25% with no change to total PTPRD
- An activity-dependent intronic splicing silencer (ISS) regulates meB skipping; deletion increases meB exclusion to near 100% and impairs motor learning and remote fear memory
- Neuronal activity (KCl) rapidly increases meB skipping within 1 hour
- A 50% reduction in total PTPRD with normal splice ratios yields fewer behavioral abnormalities than a 25% shift in splice ratio
- Dysregulation of Ptprd microexons is linked to ASD-like phenotypes and may be therapeutically targetable via splicing ratio modulation

QC result: Pass.