rs1555394580

Positions:

• chr15-48427755-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PP2 PP3 PM1 PM5 PS4_Supporting PM2_Supporting

This summary comes from the ClinGen Evidence Repository: NM_00138 c. 7016G>A is a missense variant in FBN1 predicted to cause a substitution of cysteine by tyrosine at amino acid 2339 (p.Cys2339Tyr). This variant has been identified in one individual with clinical features of Marfan syndrome (PS4_Sup). This variant has been reported 1 time in ClinVar as Likely pathogenic and 1 time as uncertain significance (VariationID:495644).This variant is not present in gnomAD (PM2_Sup; https://gnomad.broadinstitute.org/ v4.0.0). This variant affects a cysteine residue in a TB domain. Cysteine residues are believed to be involved in the formation of disulfide bridges which are essential for the protein structure (PM1). The constraint z-score for missense variants affecting FBN1 is 8.18 (PP2; https://gnomad.broadinstitute.org/ v4.0.0). Computational prediction tools and conservation analysis suggest that this variant may impact the protein (REVEL: 0.992, PP3). In summary, this variant meets criteria to be classified as likely pathogenic for Marfan syndrome based on the ACMG/AMP criteria applied, as specified by the ClinGen FBN1 VCEP: PM1, PM5, PS4_Sup, PM2_Sup, PP2, PP3. LINK:https://erepo.genome.network/evrepo/ui/classification/CA392330332/MONDO:0007947/022

• Frequency: Genomes: not found (cov: 33)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 7.91

Genes affected

FBN1 (HGNC:3603): (fibrillin 1) This gene encodes a member of the fibrillin family of proteins. The encoded preproprotein is proteolytically processed to generate two proteins including the extracellular matrix component fibrillin-1 and the protein hormone asprosin. Fibrillin-1 is an extracellular matrix glycoprotein that serves as a structural component of calcium-binding microfibrils. These microfibrils provide force-bearing structural support in elastic and nonelastic connective tissue throughout the body. Asprosin, secreted by white adipose tissue, has been shown to regulate glucose homeostasis. Mutations in this gene are associated with Marfan syndrome and the related MASS phenotype, as well as ectopia lentis syndrome, Weill-Marchesani syndrome, Shprintzen-Goldberg syndrome and neonatal progeroid syndrome. [provided by RefSeq, Apr 2016]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.7016G>A	p.Cys2339Tyr	missense_variant	58/66	ENST00000316623.10
FBN1	NM_001406716.1	c.7016G>A	p.Cys2339Tyr	missense_variant	57/65

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.7016G>A	p.Cys2339Tyr	missense_variant	58/66	1	NM_000138.5	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

Marfan syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Feb 08, 2018

The p.Cys2339Tyr variant in FBN1 has been reported in 1 individual with clinical features of Marfan syndrome (Katzke 2002) and was absent from large population studies. Computational prediction tools and conservation analysis suggest that t he p.Cys2339Tyr variant may impact the protein. Two other variants at this amino acid position (p.Cys2239Gly, p.Cys2239arg) have also been reported in individua ls with Marfan syndrome (Rybczynski 2008, Ogawa 2011), suggesting that changes a t this position may not be tolerated. In addition, the p.Cys2339Tyr variant affe cts a cysteine residue; cysteine substitutions are a common finding in individua ls with Marfan syndrome (Schrijver 1999). In summary, although additional studie s are required to fully establish its clinical significance, the p.Cys2339Tyr va riant is likely pathogenic. ACMG/AMP Criteria applied (Richards 2015): PM1; PM2; PP3; PS4_supporting. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Feb 17, 2017

Variant summary: The FBN1 c.7016G>A (p.Cys2339Tyr) variant causes a missense change involving the alteration of a conserved nucleotide. 4/4 in silico tools predict a damaging outcome for this variant (SNPs&GO not captured due to low reliability index) although these predictions have yet to be functionally assessed. This variant is absent in 119,502 control chromosomes. The variant of interest lies in a conserved region within a TGF-beta binding (TB) domain. Many manifestations of Marfan syndrome relate to excess activation and signaling by the growth factor TGF-beta (Dietz_2005)." This variant determines the substitution of cysteine with tyrosine. The sulfhydryl group of cysteine is unique in its ability to participate in disulfide covalent cross-linkage. In fact, two thirds of fibrillin cysteine residues exist in the half-cystinyl form, suggesting their participation in intramolecular disulfide linkage. Therefore, alteration of cysteine in this domain could disrupt disulfide binding, effecting secondary or tertiary structure or possibly impairing fibrillin interactions. Additionally, this variant was reported in a patient with Marfan syndrome. No clinical laboratories cite the variant of interest. Therefore, taking all available lines of evidence, the variant of interest is classified as VUS-possibly pathogenic until additional information becomes available. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	29
DANN	Uncertain	1.0
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.93
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.94	D
M_CAP	Pathogenic	0.88	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.78	T
PROVEAN	Pathogenic	-9.6	D
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.0060	D
Vest4		1.0
MutPred		0.86		Loss of disorder (P = 0.0603);
MVP		1.0
MPC		1.9
ClinPred		1.0	D
GERP RS		5.4

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: rs1555394580; hg19: chr15-48719952;