18-51058149-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 3P and 3B. PM2 PP2 BP4_Moderate BP6

The NM_005359.6(SMAD4):c.692G>C(p.Gly231Ala) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign outcome for this variant. 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. G231D) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000059 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: SMAD4 NM_005359.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:2 B:1
• Conservation: PhyloP100: 4.38

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 0 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=0.08838549).
• BP6: Variant 18-51058149-G-C is Benign according to our data. Variant chr18-51058149-G-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 421348.We mark this variant Likely_benign, oryginal submissions are: {Uncertain_significance=2, Likely_benign=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SMAD4	NM_005359.6	c.692G>C	p.Gly231Ala	missense_variant	6/12	ENST00000342988.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SMAD4	ENST00000342988.8	c.692G>C	p.Gly231Ala	missense_variant	6/12	5	NM_005359.6	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AS_VQSR AF: 0.0000589 AC: 86 AN: 1461274 Hom.: 0 Cov.: 33 AF XY: 0.0000647 AC XY: 47 AN XY: 726940

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000447

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00126

Gnomad4 NFE exome AF: 0.00000719

Gnomad4 OTH exome AF: 0.000149

GnomAD4 genome Cov.: 32

ExAC AF: 0.000478 AC: 58

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:2 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Jun 02, 2016

This variant is denoted SMAD4 c.692G>C at the cDNA level, p.Gly231Ala (G231A) at the protein level, and results in the change of a Glycine to an Alanine (GGC>GCC). This variant has not, to our knowledge, been published in the literature as pathogenic or benign. SMAD4 Gly231Ala was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, suggesting it is not a common benign variant in these populations. Since Glycine and Alanine share similar properties, this is considered a conservative amino acid substitution. SMAD4 Gly231Ala occurs at a position where amino acids with properties similar to Glycine are tolerated across species and is not located in a known functional domain (UniProt). In silico analyses are inconsistent regarding the effect this variant may have on protein structure and function. Based on currently available evidence, it is unclear whether SMAD4 Gly231Ala is a pathogenic or benign variant. We consider it to be a variant of uncertain significance. -

Juvenile polyposis syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jun 30, 2023

This variant has not been reported in the literature in individuals affected with SMAD4-related conditions. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This sequence change replaces glycine, which is neutral and non-polar, with alanine, which is neutral and non-polar, at codon 231 of the SMAD4 protein (p.Gly231Ala). ClinVar contains an entry for this variant (Variation ID: 421348). 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. 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. -

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

Likely benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 23, 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	0.077
BayesDel_addAF	Benign	-0.082	T
BayesDel_noAF	Benign	-0.36
Cadd	Benign	22
Dann	Benign	0.80
DEOGEN2	Uncertain	0.43	T;T
Eigen	Benign	-0.29
Eigen_PC	Benign	-0.084
FATHMM_MKL	Uncertain	0.89	D
M_CAP	Benign	0.055	D
MetaRNN	Benign	0.088	T;T
MetaSVM	Benign	-0.89	T
MutationAssessor	Benign	1.0	L;L
MutationTaster	Benign	1.0	D;N;N
PrimateAI	Uncertain	0.52	T
PROVEAN	Benign	-0.23	N;N
REVEL	Benign	0.12
Sift	Benign	0.74	T;T
Sift4G	Benign	0.33	T;T
Polyphen		0.0	B;B
Vest4		0.33
MVP		0.65
MPC		0.49
ClinPred		0.012	T
GERP RS		4.9
Varity_R		0.082
gMVP		0.41

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: rs759679579; hg19: chr18-48584519;