322: Bi-allelic RNU6ATAC and RNU4ATAC variants cause infancy-onset autoimmune diabetes via minor spliceosome U12 intron retention

Johnson MB et al., The American Journal of Human Genetics - Bi-allelic variants in snRNAs RNU6ATAC and RNU4ATAC cause infancy-onset autoimmune diabetes in humans, with RNA-seq showing U12 intron retention and impaired B cell development. Key terms: RNU6ATAC, RNU4ATAC, minor spliceosome, U12 intron retention, autoimmune diabetes.

Study Highlights:
In human infants with early-onset diabetes and immune dysregulation, the authors used genome sequencing, RNA-seq, DNA methylation deconvolution, WGCNA, Sanger sequencing, and flow cytometry to define a genetic syndrome. They identified 19 individuals with bi-allelic RNU6ATAC or RNU4ATAC variants and RNA-seq revealed significant U12 intron retention in 274 genes, 94% of which are known U12-intron-containing genes. Multi-omic analyses and targeted immune profiling showed reduced naive B cells and abnormal B cell maturation. Half of tested individuals were GADA-positive, supporting an autoimmune mechanism for the diabetes in these snRNA spliceosome disorders.

Conclusion:
Bi-allelic pathogenic variants in RNU6ATAC cause early-onset autoimmune diabetes with immune dysregulation and bi-allelic RNU4ATAC variants extend RNU4ATAC-opathy to include infancy-onset autoimmune diabetes.

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

Article title:
Bi-allelic variants in the non-protein-coding minor spliceosome components RNU6ATAC and RNU4ATAC cause syndromic monogenic autoimmune diabetes

First author:
Johnson MB

Journal:
The American Journal of Human Genetics

DOI:
10.1016/j.ajhg.2026.02.017

Reference:
Johnson MB, Russ-Silsby J, Blair PA, Govier M, Bonfield G, Domingo-Vila C, EXE-T1D consortium, ATAC clinical consortium, Wakeling MN, Oram RA, Flanagan SE, Tree TIM, Patel KA, Hattersley AT, De Franco E. Bi-allelic variants in the non-protein-coding minor spliceosome components RNU6ATAC and RNU4ATAC cause syndromic monogenic autoimmune diabetes. The American Journal of Human Genetics. 2026 Apr 2;113:1–11. https://doi.org/10.1016/j.ajhg.2026.02.017

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/rnu6atac-rnu4atac-minor-spliceosome

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-03-22.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript portions describing (a) minor spliceosome biology and snRNA function, (b) genetic findings in RNU6ATAC and RNU4ATAC, (c) U12 intron retention as a shared mechanism, (d) B cell development impairment and multi-omic immune profiling, (e) autoimmunity evidence (GADA positivity), (f) clinical phenoty
- transcript topics: Minor spliceosome biology and U12 introns; RNU6ATAC bi-allelic variants; RNU4ATAC bi-allelic variants and interaction with RNU6ATAC; RNA-seq intron retention in U12 genes; B cell development and maturation defects; Islet autoantibody positivity in early-onset diabetes

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:
- 19 individuals from 16 families with bi-allelic variants in RNU6ATAC or RNU4ATAC
- RNA-seq shows U12 intron retention in 274 genes (274/258 known U12 genes; 94% overlap with IAOD)
- 50% of tested individuals were GADA-positive
- Reduced naive B cells and impaired B cell maturation validated by DNA methylation deconvolution and flow cytometry
- Infancy-onset insulin-dependent diabetes (median onset ~17–20 weeks)

QC result: Pass.