chr18-51058180-ATCAGGGCC-A

Position:

• chr18-51058180-ATCAGGGCC-A

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.728_735del​(p.Gly243AlafsTer18) variant causes a frameshift change. 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 U:1
• Conservation: PhyloP100: 5.79

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 18-51058180-ATCAGGGCC-A is Pathogenic according to our data. Variant chr18-51058180-ATCAGGGCC-A is described in ClinVar as [Pathogenic]. Clinvar id is 405500.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SMAD4	NM_005359.6	c.728_735del	p.Gly243AlafsTer18	frameshift_variant	6/12	ENST00000342988.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SMAD4	ENST00000342988.8	c.728_735del	p.Gly243AlafsTer18	frameshift_variant	6/12	5	NM_005359.6	P1

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 Uncertain:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1 Uncertain:1

Uncertain significance, no assertion criteria provided	clinical testing	Department of Pathology and Laboratory Medicine, Sinai Health System	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Jul 20, 2015	The c.728_735delGGCCTCAG deletion in the SMAD4 gene has been reported previouslyin two patients with combined juvenile polyposis syndrome and hereditary hemorrhagictelangiectasia (Schwenter et al., 2012). This deletion causes a frameshift starting withcodon Glycine 243, changes this amino acid to an Alanine residue and creates a prematureStop codon at position 18 of the new reading frame, denoted p.Gly243AlafsX18. It ispredicted to cause loss of normal protein function either through protein truncation ornonsense-mediated mRNA decay. Therefore, we consider the c.728_735delGGCCTCAG deletion in SMAD4 to be a pathogenic variant. -

Juvenile polyposis syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 28, 2021

This sequence change deletes 8 nucleotides from exon 6 of the SMAD4 mRNA (c.728_735del), causing a frameshift at codon 243. This creates a premature translational stop signal (p.Gly243Alafs*18) and is expected to result in an absent or disrupted protein product. Loss-of-function variants in SMAD4 are known to be pathogenic. This particular variant has been reported in individuals affected with an overlapping spectrum of juvenile polyposis and hereditary hemorrhagic telangiectasia (PMID: 22331366). It is also known as c.724_731delTCAGGGCC in the literature. For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Splicing

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

Publications

LitVar

Other links and lift over

dbSNP: rs1060500742; hg19: chr18-48584550;