rs1555685182

Positions:

• chr18-51048816-G-A
• chr18-51048816-G-C
• chr18-51048816-G-T

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1 PM2 PP2 PP3_Strong PP5

The NM_005359.6(SMAD4):​c.380G>A​(p.Cys127Tyr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 33)
• Consequence: SMAD4 NM_005359.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 10.0

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 Pathogenic. Variant got 10 ACMG points.

• PM1: In a binding_site (size 0) in uniprot entity SMAD4_HUMAN
• 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.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.989
• PP5: Variant 18-51048816-G-A is Pathogenic according to our data. Variant chr18-51048816-G-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 460549.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Uncertain_significance=2}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SMAD4	NM_005359.6	c.380G>A	p.Cys127Tyr	missense_variant	3/12	ENST00000342988.8	NP_005350.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SMAD4	ENST00000342988.8	c.380G>A	p.Cys127Tyr	missense_variant	3/12	5	NM_005359.6	ENSP00000341551	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

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

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 03, 2023

The p.C127Y variant (also known as c.380G>A), located in coding exon 2 of the SMAD4 gene, results from a G to A substitution at nucleotide position 380. The cysteine at codon 127 is replaced by tyrosine, an amino acid with highly dissimilar properties. This alteration has been observed in at least one individual with a personal and/or family history that is consistent with juvenile polyposis syndrome (Ambry internal data). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Juvenile polyposis syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 19, 2019

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 disruptive, 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 conditions. ClinVar contains an entry for this variant (Variation ID: 460549). This variant is not present in population databases (ExAC no frequency). This sequence change replaces cysteine with tyrosine at codon 127 of the SMAD4 protein (p.Cys127Tyr). The cysteine residue is highly conserved and there is a large physicochemical difference between cysteine and tyrosine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	32
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.97	D;D;D;D;D
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.96
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	.;D;D;D;D
M_CAP	Pathogenic	0.83	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.6	H;.;.;H;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.96	D
PROVEAN	Pathogenic	-10	D;.;.;D;.
REVEL	Pathogenic	0.98
Sift	Pathogenic	0.0	D;.;.;D;.
Sift4G	Pathogenic	0.0010	D;D;D;D;D
Polyphen		1.0	D;.;.;D;.
Vest4		0.97
MutPred		0.89		Gain of phosphorylation at C127 (P = 0.0337);Gain of phosphorylation at C127 (P = 0.0337);Gain of phosphorylation at C127 (P = 0.0337);Gain of phosphorylation at C127 (P = 0.0337);Gain of phosphorylation at C127 (P = 0.0337);
MVP		0.99
MPC		4.1
ClinPred		1.0	D
GERP RS		5.3
Varity_R		0.99
gMVP		0.99

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: rs1555685182; hg19: chr18-48575186;