18-51058128-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.671A>T(p.Gln224Leu) variant causes a missense change. The variant allele was found at a frequency of 0.00000342 in 1,461,806 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. Q224E) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: SMAD4 NM_005359.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:9 B:1
• Conservation: PhyloP100: 5.13

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.671A>T	p.Gln224Leu	missense_variant	6/12	ENST00000342988.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SMAD4	ENST00000342988.8	c.671A>T	p.Gln224Leu	missense_variant	6/12	5	NM_005359.6	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.0000119 AC: 3 AN: 251320 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135848

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000867

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1461806 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727208

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000671

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: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:9 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome Uncertain:3

Uncertain significance, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Apr 10, 2023	This variant is classified as a variant of uncertain significance as there is insufficient evidence to determine its impact on protein function and/or cancer risk. -
Uncertain significance, criteria provided, single submitter	clinical testing	All of Us Research Program, National Institutes of Health	Oct 23, 2023	This missense variant replaces glutamine with leucine at codon 224 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 been identified in 3/251320 chromosomes 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. -
Uncertain significance, criteria provided, single submitter	clinical testing	Baylor Genetics	Oct 02, 2023	- -

SMAD4-related disorder Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

PreventionGenetics, part of Exact Sciences

Mar 31, 2023

The SMAD4 c.671A>T variant is predicted to result in the amino acid substitution p.Gln224Leu. To our knowledge, this variant has not been reported in the literature. This variant is reported in 0.0087% of alleles in individuals of Latino descent in gnomAD (http://gnomad.broadinstitute.org/variant/18-48584498-A-T) and has been interpreted as likely benign and variant of uncertain significance in Clinvar (https://www.ncbi.nlm.nih.gov/clinvar/variation/136077/). At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Nov 04, 2022

To the best of our knowledge, the variant has not been reported in the published literature. The frequency of this variant in the general population, 0.000087 (3/34586 chromosomes in Latino/Admixed American subpopulation, http://gnomad.broadinstitute.org), is higher than would generally be expected for pathogenic variants in this gene. Analysis of this variant using bioinformatics tools for the prediction of the effect of amino acid changes on protein structure and function yielded predictions that this variant is benign. Based on the available information, we are unable to determine the clinical significance of this variant. -

Carcinoma of pancreas;C0345893:Juvenile polyposis syndrome;C0796081:Myhre syndrome;C1832942:Juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Sep 23, 2021

- -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Color Diagnostics, LLC DBA Color Health

May 30, 2023

This missense variant replaces glutamine with leucine at codon 224 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 been identified in 3/251320 chromosomes 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. -

Generalized juvenile polyposis/juvenile polyposis coli Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Counsyl

Oct 27, 2017

- -

Juvenile polyposis syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jan 30, 2024

This sequence change replaces glutamine, which is neutral and polar, with leucine, which is neutral and non-polar, at codon 224 of the SMAD4 protein (p.Gln224Leu). This variant is present in population databases (rs587780793, gnomAD 0.009%). 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: 136077). 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. -

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

Likely benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Aug 29, 2022

This alteration is classified as likely benign based on a combination of the following: population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.11
BayesDel_addAF	Uncertain	0.089	D
BayesDel_noAF	Uncertain	0.090
Cadd	Uncertain	23
Dann	Benign	0.97
DEOGEN2	Uncertain	0.60	D;D
Eigen	Benign	-0.019
Eigen_PC	Benign	0.19
FATHMM_MKL	Pathogenic	0.98	D
M_CAP	Benign	0.068	D
MetaRNN	Uncertain	0.53	D;D
MetaSVM	Benign	-0.73	T
MutationAssessor	Benign	1.4	L;L
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Uncertain	0.51	T
PROVEAN	Benign	-1.4	N;N
REVEL	Uncertain	0.32
Sift	Benign	0.64	T;T
Sift4G	Benign	0.36	T;T
Polyphen		0.039	B;B
Vest4		0.68
MutPred		0.26		Gain of glycosylation at S223 (P = 0.0746);Gain of glycosylation at S223 (P = 0.0746);
MVP		0.94
MPC		0.45
ClinPred		0.28	T
GERP RS		5.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.12
gMVP		0.54

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: rs587780793; hg19: chr18-48584498;