rs1555686608

Variant names:

• chr18-51067105-TAC-T
• rs1555686608
• NM_005359.6:c.1228_1229delCA

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.1228_1229delCA​(p.Gln410GlufsTer18) 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 (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SMAD4 NM_005359.6 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 7.82

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 18-51067105-TAC-T is Pathogenic according to our data. Variant chr18-51067105-TAC-T is described in ClinVar as [Pathogenic]. Clinvar id is 460532.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr18-51067105-TAC-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SMAD4	NM_005359.6	c.1228_1229delCA	p.Gln410GlufsTer18	frameshift_variant	Exon 10 of 12	ENST00000342988.8	NP_005350.1
SMAD4	NM_001407041.1	c.1228_1229delCA	p.Gln410GlufsTer18	frameshift_variant	Exon 10 of 12		NP_001393970.1
SMAD4	NM_001407042.1	c.1228_1229delCA	p.Gln410GlufsTer18	frameshift_variant	Exon 10 of 12		NP_001393971.1
SMAD4	NR_176265.1	n.1766_1767delCA		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.1228_1229delCA	p.Gln410GlufsTer18	frameshift_variant	Exon 10 of 12	5	NM_005359.6	ENSP00000341551.3

Frequencies

GnomAD3 genomes Cov.: 32

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

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

Jul 20, 2017

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.1228_1229delCA pathogenic mutation, located in coding exon 9 of the SMAD4 gene, results from a deletion of two nucleotides at nucleotide positions 1228 to 1229, causing a translational frameshift with a predicted alternate stop codon (p.Q410Efs*18). This mutation has been identified in 24-year-old man who presented with features of both juvenile polyposis syndrome (JPS) and hereditary hemorrhagic telangiectasia (HHT) (Iyer NK et al. Thorax, 2010 Aug;65:745-6). In addition to the clinical data presented in the literature, 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 syndrome Pathogenic:1

Jan 31, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Gln410Glufs*18) in the SMAD4 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in SMAD4 are known to be pathogenic (PMID: 16152648, 16436638, 22810475). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with juvenile polyposis syndrome and hemorrhagic telanciectasia (PMID: 20685751). ClinVar contains an entry for this variant (Variation ID: 460532). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		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: rs1555686608; hg19: chr18-48593475;