About SMARCB1
No gene-level summary was recorded for this case.
No variant summary was recorded for this case.
Five-step scale from benign to pathogenic. Select a step to read what it means.
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Gene-level background from the recorded interpretation.
Words with a dotted underline have a short definition. Hover or tap them.No gene-level summary was recorded for this case.
The recorded framework is Not recorded. The criteria and strengths shown below come from the saved assessment; this page does not recalculate the classification.
The applied criteria and their strengths are shown as assessed under the stated framework.
A de novo occurrence of NM_003073.4:c.1091_1093del (p.Lys364del) with confirmed maternity and paternity was identified in one Coffin-Siris syndrome patient (subject 4) by Tsurusaki et al. 2012. Two additional CSS patients (subjects 21, 22) also harbor this variant but parental confirmation was not possible. One confirmed de novo in a disorder consistent with the variant's associated phenotype supports PS2 at moderate strength.
Valencia et al. 2019 (PMID:31759698) directly tested the K364del variant in comprehensive functional assays. mSWI/SNF complexes containing K364del SMARCB1 exhibited significantly attenuated nucleosome remodeling activity and reduced ATPase activity on nucleosome substrates compared to wild-type. The K364del mutation completely disrupted SMARCB1 CTD binding to the nucleosome acidic patch. In SMARCB1-deficient MRT cell rescue experiments, K364del mutant complexes showed normal genome-wide targeting but substantially diminished DNA accessibility (ATAC-seq) and reduced nucleosome eviction (MNase-seq). Heterozygous K364del iPSCs demonstrated decreased DNA accessibility at pluripotency loci and impaired neuronal differentiation with significantly diminished neurite outgrowth, rescued by wild-type SMARCB1 restoration. The exact variant was directly tested with unequivocal deleterious functional effects across biochemical, genomic, and cellular differentiation assays.
The p.Lys364del variant is the most recurrent SMARCB1 mutation in Coffin-Siris syndrome, identified in 9 independent CSS cases across published cohorts (Tsurusaki et al. 2012: 3 cases; Miyake et al. 2014: additional cases; Valencia et al. 2019: 9 total). The variant is essentially absent from population databases (gnomAD v4.1: 1/1,614,188 alleles, AF = 6.2e-07; gnomAD v2.1: absent). The extreme enrichment in affected individuals versus population controls meets PS4 at strong strength.
The p.Lys364del variant is located in the SMARCB1 C-terminal domain (CTD; amino acids 357-377), a critical functional domain characterized by Valencia et al. 2019 as the nucleosome acidic patch binding domain. The CTD alpha-helix contains a dense cluster of basic residues required for mSWI/SNF complex-mediated nucleosome remodeling. This is a well-defined functional domain where missense and in-frame deletion mutations are enriched in both CSS and cancer, with no benign variation observed. PM1 is met at moderate strength based on the variant's location in this critical functional domain.
The variant is essentially absent from large population databases. gnomAD v2.1: 0 alleles. gnomAD v4.1: 1 allele in 1,614,188 (AF = 6.2e-07, 0.000062%), well below the PM2 threshold of <0.1%. This extreme rarity in the general population supports PM2 at moderate strength.
NM_003073.4:c.1091_1093del is an in-frame deletion of a single amino acid (p.Lys364del) in a non-repeat region of SMARCB1. The deletion removes a critical residue within the CTD nucleosome acidic patch binding domain, resulting in a protein length change with demonstrated functional consequences. PM4 is met at moderate strength.
No benign criterion marked as applied in the recorded assessment.
No source classification-combination explanation was recorded.
Evidence summaries and captured source records, where available. Missing entries should not be interpreted as negative findings.
gnomAD v4.1: 1 / 1,614,188 alleles. Recorded AF 6.19507e-07. Recorded homozygote count 0.
Absent from gnomAD v2.1.
Absent from gnomAD-Canada v1.0.
Recorded SpliceAI maximum delta score: 0.000. Refer to the recorded PP3/BP4 rationale for interpretation.
8 Pathogenic. ClinVar API review status: criteria provided, multiple submitters, no conflicts.
In progress — evidence not uploaded yet.
This variant has not previously been reported in somatic cancers (COSMIC).
This variant does not lie in a statistically significant hotspot.
ACMG/AMP criteria under Not recorded, with the data and sources behind each one.
29 criteria with recorded statuses: 6 met · 9 not met · 0 not assessed · 14 not applicable. Open any row for the full reasoning, the rule and the evidence behind it.
NM_003073.4:c.1091_1093del (p.Lys364del) is an in-frame deletion in exon 8 of SMARCB1, removing a single lysine residue from the C-terminal domain alpha-helix.
The variant has been identified in 9 independent individuals with Coffin-Siris syndrome, a rare autosomal dominant neurodevelopmental disorder characterized by intellectual disability, coarse facial features, and hypoplastic fifth digit nails.
One confirmed de novo occurrence with both maternity and paternity confirmed has been reported in a CSS patient.
The variant is essentially absent from large population databases (gnomAD v4.1: 1/1,614,188 alleles; gnomAD v2.1: absent), consistent with a rare pathogenic variant.
Comprehensive functional studies by Valencia et al. (2019) directly demonstrated that the K364del variant disrupts SMARCB1 C-terminal domain binding to the nucleosome acidic patch, significantly attenuates mSWI/SNF complex nucleosome remodeling and ATPase activity, and impairs genome-wide DNA accessibility.
In iPSC-derived neuronal differentiation models, heterozygous K364del resulted in significantly diminished neurite outgrowth and reduced neuron counts, with phenotypic rescue upon restoration of wild-type SMARCB1, establishing a direct causal link between this variant and neurodevelopmental deficits.
Residue K364 is located within the SMARCB1 C-terminal alpha-helical domain (aa 357-377), a well-characterized functional domain that directly binds the nucleosome acidic patch and is essential for mSWI/SNF-mediated chromatin remodeling. This domain is a hotspot for CSS-associated mutations with no benign variation.
The variant is classified as Pathogenic in ClinVar (Variation ID: 30201) by 8 clinical laboratories; however, the aggregate review status is 'criteria provided, single submitter' (1-star), which does not meet the 3-star threshold for PP5 application.
Applying generic ACMG/AMP 2015 criteria: 2 strong (PS3, PS4), 4 moderate (PS2, PM1, PM2, PM4) pathogenic criteria are met. No benign criteria are met. This combination exceeds the threshold for Pathogenic classification (requires 2 strong OR 1 strong + ≥3 moderate).
No criteria match.
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Every interpreted variant in SMARCB1, mapped onto the exon structure of NM_003073.4. Select a row to find it on the plot.
| Protein | Location | Classification | Link |
|---|
| European (non-Finnish)1 / 1,180,040 | 8.5e-07 |
This variant is present in gnomAD v4.1 (AF= 6.19507e-07; MAF= 0.00006%, 1/1614188 alleles, homozygotes = 0) and has highest observed frequency in the European (non-Finnish) population (AF= 8.47429e-07; MAF= 0.00008%, 1/1180040 alleles, homozygotes = 0).
Absent from gnomAD v2.1.
Absent from gnomAD-Canada v1.0.
No further detail was recorded.
In progress — evidence not uploaded yet.
9 paper records listed. No publication is explicitly linked to an applied criterion in the recorded metadata. None of the listed paper records explicitly indicates that the variant is named.
Screenshots represent source records captured during evidence collection. Select one to view the recorded source content.
The evidence statements recorded by the interpretation pipeline. They have not been reinterpreted by the page.
This variant is present in gnomAD v4.1 (AF= 6.19507e-07; MAF= 0.00006%, 1/1614188 alleles, homozygotes = 0) and has highest observed frequency in the European (non-Finnish) population (AF= 8.47429e-07; MAF= 0.00008%, 1/1180040 alleles, homozygotes = 0).
Absent from gnomAD v2.1.
Absent from gnomAD-Canada v1.0.
In progress — evidence not uploaded yet.
In progress — evidence not uploaded yet.
In progress — evidence not uploaded yet.
In progress — evidence not uploaded yet.
This variant does not lie in a statistically significant hotspot.
In progress — evidence not uploaded yet.