chr18-51067027-T-G

Variant names:

• chr18-51067027-T-G
• rs377767355
• NM_005359.6:c.1148T>G

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Moderate

The NM_005359.6(SMAD4):​c.1148T>G​(p.Ile383Arg) 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. 13/22 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. I383T) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SMAD4 NM_005359.6 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.93
• Publications: 8 publications found

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]

SMAD4 Gene-Disease associations (from GenCC):

• juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), ClinGen, Genomics England PanelApp, G2P, PanelApp Australia
• Myhre syndrome

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, Orphanet, G2P, Labcorp Genetics (formerly Invitae)
• generalized juvenile polyposis/juvenile polyposis coli

  Inheritance: AD Classification: STRONG, SUPPORTIVE Submitted by: Orphanet, Genomics England PanelApp
• juvenile polyposis syndrome

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• familial thoracic aortic aneurysm and aortic dissection

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• hereditary hemorrhagic telangiectasia

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• pulmonary arterial hypertension

  Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 25 uncertain in NM_005359.6
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr18-51067027-T-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 629126.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.992
• PP5: Variant 18-51067027-T-G is Pathogenic according to our data. Variant chr18-51067027-T-G is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 652013.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SMAD4	NM_005359.6	c.1148T>G	p.Ile383Arg	missense_variant	Exon 10 of 12	ENST00000342988.8	NP_005350.1
SMAD4	NM_001407041.1	c.1148T>G	p.Ile383Arg	missense_variant	Exon 10 of 12		NP_001393970.1
SMAD4	NM_001407042.1	c.1148T>G	p.Ile383Arg	missense_variant	Exon 10 of 12		NP_001393971.1
SMAD4	NR_176265.1	n.1686T>G		non_coding_transcript_exon_variant	Exon 10 of 13

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SMAD4	ENST00000342988.8	c.1148T>G	p.Ile383Arg	missense_variant	Exon 10 of 12	5	NM_005359.6	ENSP00000341551.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Generalized juvenile polyposis/juvenile polyposis coli Pathogenic:1

Dec 24, 2019

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces isoleucine with arginine at codon 383 of the SMAD4 protein (p.Ile383Arg). The isoleucine residue is highly conserved and there is a moderate physicochemical difference between isoleucine and arginine. This variant is not present in population databases (ExAC no frequency). This variant has been observed in individual(s) with juvenile polyposis and hereditary hemorrhagic telangiectasia (PMID: 30251589, Invitae). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 652013). 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. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.59	D
BayesDel_noAF	Pathogenic	0.61
CADD	Pathogenic	31
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	1.0	D;D;D
Eigen	Pathogenic	0.96
Eigen_PC	Pathogenic	0.89
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.93	.;D;D
M_CAP	Pathogenic	0.89	D
MetaRNN	Pathogenic	0.99	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.0	H;H;.
PhyloP100		7.9
PrimateAI	Pathogenic	0.89	D
PROVEAN	Pathogenic	-6.9	D;D;.
REVEL	Pathogenic	0.98
Sift	Pathogenic	0.0	D;D;.
Sift4G	Uncertain	0.027	D;D;D
Polyphen		1.0	D;D;.
Vest4		0.94
MutPred		0.91		Gain of disorder (P = 0.0179);Gain of disorder (P = 0.0179);.;
MVP		1.0
MPC		4.3
ClinPred		1.0	D
GERP RS		5.7
PromoterAI		0.0086	Neutral
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.96
gMVP		1.0
Mutation Taster		=8/92	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.040		Details are displayed if max score is > 0.2

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

Other links and lift over

dbSNP: rs377767355; hg19: chr18-48593397; COSMIC: COSV61684469; COSMIC: COSV61684469;