rs1555395658

Positions:

• chr15-48444627-C-T

Variant summary

Our verdict is Pathogenic. Variant got 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_000138.5(FBN1):​c.5951G>A​(p.Cys1984Tyr) 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. 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. C1984R) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 7.51

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 Pathogenic. Variant got 19 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 8 uncertain in NM_000138.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr15-48444628-A-G is described in ClinVar as [Pathogenic]. Clinvar id is 549320.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant where missense usually causes diseases, FBN1
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.995
• PP5: Variant 15-48444627-C-T is Pathogenic according to our data. Variant chr15-48444627-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 519792.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.5951G>A	p.Cys1984Tyr	missense_variant	49/66	ENST00000316623.10
FBN1	NM_001406716.1	c.5951G>A	p.Cys1984Tyr	missense_variant	48/65

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.5951G>A	p.Cys1984Tyr	missense_variant	49/66	1	NM_000138.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Marfan syndrome Pathogenic:1

Likely pathogenic, no assertion criteria provided

clinical testing

Center for Medical Genetics Ghent, University of Ghent

Nov 07, 2017

- -

Familial thoracic aortic aneurysm and aortic dissection Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 20, 2017

The p.C1984Y variant (also known as c.5951G>A), located in coding exon 48 of the FBN1 gene, results from a G to A substitution at nucleotide position 5951. The cysteine at codon 1984 is replaced by tyrosine, an amino acid with highly dissimilar properties, and is located in the cbEGF-like #30 domain. This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. The majority of FBN1 mutations identified to date have involved the substitution or generation of cysteine residues within cbEGF domains (Vollbrandt T et al. J Biol Chem. 2004;279(31):32924-32931). Two alterations affecting the same cysteine, C1984R and C1984G, have been reported in individuals with Marfan syndrome (Baetens M et al. Hum. Mutat., 2011 Sep;32:1053-62; Franken R et al. Eur. Heart J., 2016 Nov;37:3285-3290). Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Marfan Syndrome/Loeys-Dietz Syndrome/Familial Thoracic Aortic Aneurysms and Dissections Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

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

May 23, 2022

Variant summary: FBN1 c.5951G>A (p.Cys1984Tyr) results in a non-conservative amino acid change located in the EGF-like domain (IPR000742) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251092 control chromosomes (gnomAD). The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.5951G>A has been reported in at least one individual affected with Marfan Syndrome (UMD-FBN1 database). To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported, however, 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 (Dietz_1992). Therefore, the substitution of a cysteine may disrupt the structure of the FBN1 protein, affecting its function. Two other variants affecting cysteine1984 residue have been classified as pathogenic within ClinVar or reported in HGMD database (c.5950T>C/p.Cys1984Arg, c.5950T>G/p.Cys1984Gly). Two ClinVar submitters have assessed the variant since 2014: both classified the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Marfan syndrome;C4707243:Familial thoracic aortic aneurysm and aortic dissection Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Dec 30, 2022

This missense change has been observed in individuals with Marfan syndrome (Invitae). For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Cys1984Arg amino acid residue in FBN1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 16571647, 16905551, 17701892, 19349279). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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 expected to disrupt FBN1 protein function. ClinVar contains an entry for this variant (Variation ID: 519792). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces cysteine, which is neutral and slightly polar, with tyrosine, which is neutral and polar, at codon 1984 of the FBN1 protein (p.Cys1984Tyr). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.59
CADD	Pathogenic	29
DANN	Uncertain	1.0
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.87	D
M_CAP	Pathogenic	0.95	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	0.97	D
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.76	T
PROVEAN	Pathogenic	-9.5	D
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.011	D
Vest4		0.98
MutPred		0.92		Loss of methylation at K1983 (P = 0.0149);
MVP		0.99
MPC		1.8
ClinPred		1.0	D
GERP RS		6.1

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

Publications

LitVar

Other links and lift over

dbSNP: rs1555395658; hg19: chr15-48736824;