18-51058125-G-T

Position:

• chr18-51058125-G-T

Variant summary

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

The NM_005359.6(SMAD4):​c.668G>T​(p.Ser223Ile) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SMAD4 NM_005359.6 missense, splice_region
• Scores: Splicing: ADA: 0.9996
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.30

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 in gene, where missense usually causes diseases (based on misZ statistic), SMAD4. . Gene score misZ 4.1308 (greater than the threshold 3.09). Trascript score misZ 4.9346 (greater than threshold 3.09). GenCC has associacion of gene with familial thoracic aortic aneurysm and aortic dissection, generalized juvenile polyposis/juvenile polyposis coli, hereditary hemorrhagic telangiectasia, Myhre syndrome, pulmonary arterial hypertension, juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome, juvenile polyposis syndrome.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SMAD4	NM_005359.6	c.668G>T	p.Ser223Ile	missense_variant, splice_region_variant	6/12	ENST00000342988.8	NP_005350.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SMAD4	ENST00000342988.8	c.668G>T	p.Ser223Ile	missense_variant, splice_region_variant	6/12	5	NM_005359.6	ENSP00000341551	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Juvenile polyposis syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 16, 2022

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. ClinVar contains an entry for this variant (Variation ID: 240152). This variant has not been reported in the literature in individuals affected with SMAD4-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces serine, which is neutral and polar, with isoleucine, which is neutral and non-polar, at codon 223 of the SMAD4 protein (p.Ser223Ile). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.17
BayesDel_addAF	Pathogenic	0.33	D
BayesDel_noAF	Pathogenic	0.24
CADD	Pathogenic	32
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.68	D;D
Eigen	Uncertain	0.26
Eigen_PC	Uncertain	0.42
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Benign	0.82	.;T
M_CAP	Uncertain	0.10	D
MetaRNN	Uncertain	0.63	D;D
MetaSVM	Benign	-0.75	T
MutationAssessor	Uncertain	2.0	M;M
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Uncertain	0.61	T
PROVEAN	Benign	-1.6	N;N
REVEL	Uncertain	0.33
Sift	Benign	0.14	T;T
Sift4G	Benign	0.15	T;T
Polyphen		0.50	P;P
Vest4		0.79
MutPred		0.26		Loss of glycosylation at S223 (P = 0.0278);Loss of glycosylation at S223 (P = 0.0278);
MVP		0.92
MPC		0.55
ClinPred		0.69	D
GERP RS		5.8
Varity_R		0.35
gMVP		0.67

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.45		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.45		Position offset: 0

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs774334251; hg19: chr18-48584495;