18-51054786-T-G

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.460T>G(p.Ser154Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 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 (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. S154P) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SMAD4 NM_005359.6 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 1.25

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=0.12836495).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SMAD4	NM_005359.6	c.460T>G	p.Ser154Ala	missense_variant	5/12	ENST00000342988.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SMAD4	ENST00000342988.8	c.460T>G	p.Ser154Ala	missense_variant	5/12	5	NM_005359.6	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

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

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 16, 2020

The p.S154A variant (also known as c.460T>G), located in coding exon 4 of the SMAD4 gene, results from a T to G substitution at nucleotide position 460. The serine at codon 154 is replaced by alanine, an amino acid with similar properties. This amino acid position is poorly 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 this alteration remains unclear. -

Juvenile polyposis syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Sep 05, 2023

This sequence change replaces serine, which is neutral and polar, with alanine, which is neutral and non-polar, at codon 154 of the SMAD4 protein (p.Ser154Ala). 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: 219690). 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. 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	0.056
BayesDel_addAF	Benign	-0.0019	T
BayesDel_noAF	Benign	-0.24
Cadd	Benign	18
Dann	Benign	0.86
DEOGEN2	Uncertain	0.44	T;T;T
Eigen	Benign	-0.61
Eigen_PC	Benign	-0.47
FATHMM_MKL	Uncertain	0.97	D
M_CAP	Uncertain	0.15	D
MetaRNN	Benign	0.13	T;T;T
MetaSVM	Uncertain	0.13	D
MutationAssessor	Benign	0.90	L;L;.
MutationTaster	Benign	1.0	D;N;N;N
PrimateAI	Benign	0.34	T
PROVEAN	Benign	-0.74	N;N;.
REVEL	Benign	0.27
Sift	Benign	0.30	T;T;.
Sift4G	Benign	0.77	T;T;T
Polyphen		0.0	B;B;.
Vest4		0.26
MutPred		0.26		Loss of disorder (P = 0.0449);Loss of disorder (P = 0.0449);Loss of disorder (P = 0.0449);
MVP		0.57
MPC		0.38
ClinPred		0.040	T
GERP RS		3.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.7
Varity_R		0.031
gMVP		0.25

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: rs864622209; hg19: chr18-48581156;