18-51078354-C-CA

Position:

• chr18-51078354-C-CA

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PVS1_Strong PM2 PP5_Very_Strong

The NM_005359.6(SMAD4):​c.1547dup​(p.Ser517GlufsTer10) variant causes a frameshift change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SMAD4 NM_005359.6 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 9.17

Genes affected

SMAD4 (HGNC:6770): (SMAD family member 4) This gene encodes a member of the Smad family of signal transduction proteins. Smad proteins are phosphorylated and activated by transmembrane serine-threonine receptor kinases in response to transforming growth factor (TGF)-beta signaling. The product of this gene forms homomeric complexes and heteromeric complexes with other activated Smad proteins, which then accumulate in the nucleus and regulate the transcription of target genes. This protein binds to DNA and recognizes an 8-bp palindromic sequence (GTCTAGAC) called the Smad-binding element (SBE). The protein acts as a tumor suppressor and inhibits epithelial cell proliferation. It may also have an inhibitory effect on tumors by reducing angiogenesis and increasing blood vessel hyperpermeability. The encoded protein is a crucial component of the bone morphogenetic protein signaling pathway. The Smad proteins are subject to complex regulation by post-translational modifications. Mutations or deletions in this gene have been shown to result in pancreatic cancer, juvenile polyposis syndrome, and hereditary hemorrhagic telangiectasia syndrome. [provided by RefSeq, May 2022]

ACMG classification

Verdict is Pathogenic. Variant got 14 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. There are 7 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 18-51078354-C-CA is Pathogenic according to our data. Variant chr18-51078354-C-CA is described in ClinVar as [Pathogenic]. Clinvar id is 156513.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SMAD4	NM_005359.6	c.1547dup	p.Ser517GlufsTer10	frameshift_variant	12/12	ENST00000342988.8	NP_005350.1
SMAD4	NM_001407041.1	c.1547dup	p.Ser517GlufsTer10	frameshift_variant	12/12		NP_001393970.1
SMAD4	NM_001407042.1	c.1547dup	p.Ser517GlufsTer10	frameshift_variant	12/12		NP_001393971.1
SMAD4	NR_176265.1	n.2198dup		non_coding_transcript_exon_variant	13/13

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SMAD4	ENST00000342988.8	c.1547dup	p.Ser517GlufsTer10	frameshift_variant	12/12	5	NM_005359.6	ENSP00000341551	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Aug 02, 2022

Frameshift variant predicted to result in protein truncation, as the last 36 amino acids are replaced with 9 different amino acids, and other loss-of-function variants have been reported downstream in HGMD; Not observed at significant frequency in large population cohorts (gnomAD); Has not been previously published as pathogenic or benign to our knowledge; This variant is associated with the following publications: (PMID: 18823382) -

Hereditary cancer-predisposing syndrome;C4707243:Familial thoracic aortic aneurysm and aortic dissection Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 08, 2014

The c.1547dupA pathogenic mutation, located in coding exon 11 of the SMAD4 gene, results from a duplication of A at nucleotide position 1547, causing a translational frameshift with a predicted alternate stop codon. Since frameshifts are typically deleterious in nature, this alteration is interpreted as a disease-causing mutation (ACMG Recommendations for Standards for Interpretation and Reporting of Sequence Variations. Revision 2007. Genet Med. 2008;10:294). -

Generalized juvenile polyposis/juvenile polyposis coli Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

Pathway Genomics

Jul 24, 2014

- -

Juvenile polyposis syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 25, 2018

This variant has not been reported in the literature in individuals with SMAD4-related disease. ClinVar contains an entry for this variant (Variation ID: 156513). For these reasons, this variant has been classified as Pathogenic. A different truncation (p.His530Thrfs*47) that lies downstream of this variant has been determined to be pathogenic (PMID: 18178612, Invitae). This suggests that deletion of this region of the SMAD4 protein is causative of disease. This variant is not present in population databases (ExAC no frequency). This sequence change results in a premature translational stop signal in the SMAD4 gene (p.Ser517Glufs*10). While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 36 amino acids of the SMAD4 protein. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs587783060; hg19: chr18-48604724;