RNU12-related Minor Spliceopathy Manual Deep-Research Note

Scope

• Parent curation frame: local mechanism-defined umbrella disease for RNU12-related minor spliceopathy
• MONDO status: umbrella concept tracked as MONDO NTR #9963, not yet a stable local MONDO term
• Reported clinical presentations currently within scope:
• MONDO:0011287 craniosynostosis-anal anomalies-porokeratosis syndrome (CDAGS)
• MONDO:0859360 spinocerebellar ataxia, autosomal recessive 33 (SCAR33)
• Shared molecular mechanism in scope:
• biallelic RNU12 variation
• minor spliceosome dysfunction
• impaired U12-type intron splicing / minor intron retention

Primary Sources Used

• PMID:34085356
• Defines the CDAGS presentation and establishes biallelic RNU12 variants with transcriptome/splicing abnormalities in lymphoblastoid cells.
• PMID:27863452
• Defines the SCAR33 presentation and demonstrates selective disruption of U12-type intron splicing with minor intron retention in affected individuals.

Core Curation Decisions

Disease framing

• The two disease papers support a broader shared-disorder frame rather than two fully unrelated single-presentation entries, because both presentations are caused by biallelic RNU12 disruption and converge on defective minor spliceosome function.
• The YAML therefore uses a mechanism-defined umbrella root with explicit has_subtypes entries for CDAGS and SCAR33.

Initial phenotype scope

• This first-pass PR intentionally models one high-signal anchor phenotype per subtype:
• CDAGS -> craniosynostosis
• SCAR33 -> early-onset cerebellar ataxia
• The purpose of this minimal phenotype set is to establish the umbrella entry and subtype foreign-key structure without over-claiming frequency or phenotype completeness from only two primary abstracts.

Additional subtype features identified but deferred

• CDAGS features explicitly named in PMID:34085356 and suitable for later phenotype expansion:
• delayed closure of the fontanelles
• cranial defects
• clavicular hypoplasia
• anal malformations
• genitourinary malformations
• skin manifestations including porokeratosis
• SCAR33 features named in the disease report / summary framing and suitable for later phenotype expansion:
• delayed motor development
• hypotonia
• tremor
• nystagmus
• dysarthria
• cerebellar hypoplasia or degeneration

Evidence-Type Decision

• The transcriptome / alternative splicing result from PMID:34085356 comes from lymphoblastoid cells and should be treated as IN_VITRO, not HUMAN_CLINICAL, even though the variants were discovered in human families.

Ontology Anchors Used

• Disease / subtype terms:
• MONDO:0011287 craniosynostosis-anal anomalies-porokeratosis syndrome
• MONDO:0859360 spinocerebellar ataxia, autosomal recessive 33
• Gene:
• hgnc:19380 RNU12
• Biological process:
• GO:0000398 mRNA splicing, via spliceosome
• Phenotypes:
• HP:0001363 Craniosynostosis
• HP:0001251 Ataxia, rendered with preferred term Cerebellar ataxia because the local HPO snapshot does not provide the reviewer-suggested HP:0002070 label for this concept.

Follow-up Work Deferred Beyond This PR

• Expand subtype phenotype coverage using exact abstract-backed evidence items for additional CDAGS and SCAR33 manifestations.
• Revisit whether a more specific GO term for minor/U12 spliceosome function is available and preferable to GO:0000398.
• Add phenotype-targeted downstream links if the entry is expanded into a denser connected pathograph.