rs794728326

Positions:

• chr15-48515429-A-C
• chr15-48515429-A-G

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.1426T>G​(p.Cys476Gly) 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. 11/18 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C476R) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 9.32

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 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 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 chr15-48515429-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 406325.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, 0.993
• PP5: Variant 15-48515429-A-C is Pathogenic according to our data. Variant chr15-48515429-A-C is described in ClinVar as [Pathogenic]. Clinvar id is 200179.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr15-48515429-A-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.1426T>G	p.Cys476Gly	missense_variant	12/66	ENST00000316623.10
FBN1	NM_001406716.1	c.1426T>G	p.Cys476Gly	missense_variant	11/65

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.1426T>G	p.Cys476Gly	missense_variant	12/66	1	NM_000138.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Nov 15, 2016

- -

Marfan syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Apr 17, 2019

The p.Cys476Gly variant in FBN1 has been identified in at least 4 individuals with Marfan syndrome, segregated in 33 affected relatives from one family, and was absent in 19 unaffected family members from that same family (Piersall 1994, Somers 2016, Vatti 2017). In addition, this variant was absent from large population studies. Two other variants at the same position (p.Cys476Arg and p.Cys476Ser) have also been identified in individuals with Marfan syndrome, suggesting that changes at this position are not tolerated. Studies provide some evidence that this variant impacts protein function (Schrijver 1999). Furthermore, this variant affects a highly conserved cysteine residue in the EGF-like domains, which is a common finding in individuals with Marfan syndrome (Schrijver 1999). In summary, this variant meets criteria to be classified as pathogenic for autosomal dominant Marfan syndrome. ACMG/AMP Criteria applied: PP1_Strong; PM1; PM2; PS4_Moderate; PP3, PS3_Supporting. -

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

Pathogenic, criteria provided, single submitter

clinical testing

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

Oct 12, 2016

Variant summary: The FBN1 c.1426T>G (p.Cys476Gly) variant located in an EGF-like domain (via InterPro) alters a cysteine, which plays a key role in disulfide binding, important for proper fibrillin function. 4/4 in silico tools (SNPs&GO not captured here due to low reliability index) predict a damaging outcome, which is supported by a functional study, Schrijver_1999. The variant of interest was not observed in controls (ExAC, 1000 Gs, ESP, or publication controls) and has been reported in multiple affected individuals including a large family that segregates with disease, Piersall_1994. Multiple reputable clinical diagnostic laboratories/databases cite the variant as "pathogenic." Therefore, the variant of interest has been classified as Pathogenic. -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Aug 22, 2022

Affects a cysteine residue within a calcium-binding EGF-like domain of the FBN1 gene, which may affect disulfide bonding and is predicted to alter the structure and function of the protein; cysteine substitutions in the calcium-binding EGF-like domains represent the majority of pathogenic missense changes associated with FBN1-related disorders (Collod-Beroud et al., 2003); Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 7951214, 10486319, 27112580, 28941062) -

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

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Dec 20, 2023

This sequence change replaces cysteine, which is neutral and slightly polar, with glycine, which is neutral and non-polar, at codon 476 of the FBN1 protein (p.Cys476Gly). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with Marfan syndrome (PMID: 7951214, 10486319, 27112580). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 200179). 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 with a positive predictive value of 95%. This variant affects a cysteine residue in the EGF-like, TGFBP or hybrid motif domains of FBN1. Cysteine residues are believed to be involved in intramolecular disulfide bridges and have been shown to be important for FBN1 protein structure (PMID: 16905551, 19349279). In addition, missense substitutions affecting cysteine residues within these domains are significantly overrepresented among patients with Marfan syndrome (PMID: 16571647, 17701892). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	32
DANN	Uncertain	0.99
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.91	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.0	D
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.87	D
PROVEAN	Pathogenic	-11	D
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Vest4		0.98
MutPred		0.91		Loss of stability (P = 0.0021);
MVP		1.0
MPC		2.4
ClinPred		1.0	D
GERP RS		5.9

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: rs794728326; hg19: chr15-48807626;