rs757702252

Positions:

• chr18-51047054-A-G
• chr18-51047054-A-T

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_005359.6(SMAD4):​c.8A>G​(p.Asn3Ser) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,240 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Synonymous variant affecting the same amino acid position (i.e. N3N) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: SMAD4 NM_005359.6 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: 2.46

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 Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, SMAD4
• BP4: Computational evidence support a benign effect (MetaRNN=0.07283887).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SMAD4	NM_005359.6	c.8A>G	p.Asn3Ser	missense_variant	2/12	ENST00000342988.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SMAD4	ENST00000342988.8	c.8A>G	p.Asn3Ser	missense_variant	2/12	5	NM_005359.6	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461240 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 726968

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.00e-7

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Feb 01, 2022

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant does not alter protein structure/function; Has not been previously published as pathogenic or benign to our knowledge -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 22, 2015

The p.N3S variant (also known as c.8A>G), located in coding exon 1 of the SMAD4 gene, results from an A to G substitution at nucleotide position 8. The asparagine at codon 3 is replaced by serine, an amino acid with highly similar properties. This variant was not reported in population based cohorts in the following databases: Database of Single Nucleotide Polymorphisms (dbSNP), NHLBI Exome Sequencing Project (ESP), and 1000 Genomes Project. In the ESP, this variant was not observed in 6503 samples (13006 alleles) with coverage at this position. To date, this alteration has been detected with an allele frequency of approximately 0.003% (greater than 30000 alleles tested) in our clinical cohort. This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of p.N3S remains unclear. -

Juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

All of Us Research Program, National Institutes of Health

Dec 18, 2023

This missense variant replaces asparagine with serine at codon 3 of the SMAD4 protein. Computational prediction suggests that this variant may not impact protein structure and function (internally defined REVEL score threshold <= 0.5, PMID: 27666373). To our knowledge, functional studies have not been reported for this variant. This variant has not been reported in individuals affected with SMAD4-related disorders in the literature. This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance. -

Juvenile polyposis syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Feb 01, 2024

This sequence change replaces asparagine, which is neutral and polar, with serine, which is neutral and polar, at codon 3 of the SMAD4 protein (p.Asn3Ser). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with SMAD4-related conditions. ClinVar contains an entry for this variant (Variation ID: 580768). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt SMAD4 protein function with a negative predictive value of 95%. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.060
BayesDel_addAF	Benign	-0.057	T
BayesDel_noAF	Benign	-0.32
CADD	Benign	17
DANN	Benign	0.86
DEOGEN2	Benign	0.22	T;T;T;T;T;T;T;T
Eigen	Benign	-0.64
Eigen_PC	Benign	-0.41
FATHMM_MKL	Uncertain	0.88	D
LIST_S2	Benign	0.85	D;.;D;D;D;D;D;D
M_CAP	Benign	0.082	D
MetaRNN	Benign	0.073	T;T;T;T;T;T;T;T
MetaSVM	Uncertain	-0.24	T
MutationTaster	Benign	0.98	N;N;N;N
PrimateAI	Uncertain	0.57	T
Sift4G	Benign	0.78	T;T;T;T;T;T;T;T
Polyphen		0.0	.;B;.;.;.;B;.;.
Vest4		0.12, 0.079, 0.17
MutPred		0.056		Gain of phosphorylation at N3 (P = 0.0588);Gain of phosphorylation at N3 (P = 0.0588);Gain of phosphorylation at N3 (P = 0.0588);Gain of phosphorylation at N3 (P = 0.0588);Gain of phosphorylation at N3 (P = 0.0588);Gain of phosphorylation at N3 (P = 0.0588);Gain of phosphorylation at N3 (P = 0.0588);Gain of phosphorylation at N3 (P = 0.0588);
MVP		0.52
MPC		1.2
ClinPred		0.12	T
GERP RS		3.4
Varity_R		0.023
gMVP		0.44

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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: rs757702252; hg19: chr18-48573424;