rs878854765

Variant names:

• chr18-51067083-C-CT
• rs878854765
• NM_005359.6:c.1206dupT

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_005359.6(SMAD4):​c.1206dupT​(p.Ser403fs) variant causes a frameshift, stop gained 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 (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SMAD4 NM_005359.6 frameshift, stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 7.93

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 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 18-51067083-C-CT is Pathogenic according to our data. Variant chr18-51067083-C-CT is described in ClinVar as [Pathogenic]. Clinvar id is 240143.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SMAD4	NM_005359.6	c.1206dupT	p.Ser403fs	frameshift_variant, stop_gained	Exon 10 of 12	ENST00000342988.8	NP_005350.1
SMAD4	NM_001407041.1	c.1206dupT	p.Ser403fs	frameshift_variant, stop_gained	Exon 10 of 12		NP_001393970.1
SMAD4	NM_001407042.1	c.1206dupT	p.Ser403fs	frameshift_variant, stop_gained	Exon 10 of 12		NP_001393971.1
SMAD4	NR_176265.1	n.1744dupT		non_coding_transcript_exon_variant	Exon 10 of 13

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SMAD4	ENST00000342988.8	c.1206dupT	p.Ser403fs	frameshift_variant, stop_gained	Exon 10 of 12	5	NM_005359.6	ENSP00000341551.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

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

Nov 08, 2017

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.1206dupT pathogenic mutation, located in coding exon 9 of the SMAD4 gene, results from a duplication of T at nucleotide position 1206, causing a translational frameshift with a predicted alternate stop codon (p.S403*). This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation. -

Juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome Pathogenic:1

Feb 09, 2024

Myriad Genetics, Inc.

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is considered pathogenic. This variant creates a termination codon and is predicted to result in premature protein truncation. -

Juvenile polyposis syndrome Pathogenic:1

Dec 11, 2016

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. While this particular variant has not been reported in the literature, loss-of-function variants in SMAD4 are known to be pathogenic (PMID: 22810475, 16152648). This sequence change inserts 1 nucleotide in exon 10 of the SMAD4 mRNA (c.1206dupT), causing a frameshift at codon 403. This creates a premature translational stop signal (p.Ser403*) and is expected to result in an absent or disrupted protein product. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs878854765; hg19: chr18-48593453;