rs1064794204

chr18-51047227-A-Cchr18-51047227-A-Gchr18-51047227-A-T

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP2

The NM_005359.6(SMAD4):c.181A>C(p.Ile61Leu) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. 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. I61V) 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: 6.36

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 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, SMAD4

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SMAD4	NM_005359.6	c.181A>C	p.Ile61Leu	missense_variant	2/12	ENST00000342988.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SMAD4	ENST00000342988.8	c.181A>C	p.Ile61Leu	missense_variant	2/12	5	NM_005359.6	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

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 26, 2016

The p.I61L variant (also known as c.181A>C), located in coding exon 1 of the SMAD4 gene, results from an A to C substitution at nucleotide position 181. The isoleucine at codon 61 is replaced by leucine, 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 0.001% (greater than 85000 alleles tested) in our clinical cohort. This amino acid position is highly 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

Aug 16, 2017

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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has not been reported in the literature in individuals with SMAD4-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces isoleucine with leucine at codon 61 of the SMAD4 protein (p.Ile61Leu). The isoleucine residue is highly conserved and there is a small physicochemical difference between isoleucine and leucine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.92
BayesDel_addAF	Uncertain	0.097	D
BayesDel_noAF	Benign	-0.10
Cadd	Pathogenic	27
Dann	Uncertain	0.99
DEOGEN2	Uncertain	0.59	D;D;D;D;D;D;D;D
Eigen	Uncertain	0.42
Eigen_PC	Uncertain	0.50
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.97	D;.;D;D;D;D;D;D
M_CAP	Benign	0.034	D
MetaRNN	Uncertain	0.71	D;D;D;D;D;D;D;D
MetaSVM	Benign	-0.48	T
MutationTaster	Benign	0.99	D;D;D;D
PrimateAI	Pathogenic	0.89	D
Sift4G	Benign	0.44	T;T;T;T;T;T;T;T
Polyphen		0.92	.;P;.;.;.;P;.;.
Vest4		0.48, 0.48, 0.51
MutPred		0.57		Gain of disorder (P = 0.1088);Gain of disorder (P = 0.1088);Gain of disorder (P = 0.1088);Gain of disorder (P = 0.1088);Gain of disorder (P = 0.1088);Gain of disorder (P = 0.1088);Gain of disorder (P = 0.1088);Gain of disorder (P = 0.1088);
MVP		0.82
MPC		2.0
ClinPred		0.95	D
GERP RS		5.6
Varity_R		0.63
gMVP		0.79

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: rs1064794204; hg19: chr18-48573597;