rs1085308004

Positions:

• chr15-48425420-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.7402T>C​(p.Cys2468Arg) 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 Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C2468Y) has been classified as Likely 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: 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 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 12 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 chr15-48425419-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 519787.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), FBN1. . Gene score misZ 5.0644 (greater than the threshold 3.09). Trascript score misZ 8.1787 (greater than threshold 3.09). GenCC has associacion of gene with MASS syndrome, Weill-Marchesani syndrome, geleophysic dysplasia, Shprintzen-Goldberg syndrome, Acromicric dysplasia, familial thoracic aortic aneurysm and aortic dissection, progeroid and marfanoid aspect-lipodystrophy syndrome, ectopia lentis 1, isolated, autosomal dominant, Marfan syndrome, Weill-Marchesani syndrome 2, dominant, isolated ectopia lentis, neonatal Marfan syndrome, stiff skin syndrome.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.995
• PP5: Variant 15-48425420-A-G is Pathogenic according to our data. Variant chr15-48425420-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 427179.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr15-48425420-A-G is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.7402T>C	p.Cys2468Arg	missense_variant	60/66	ENST00000316623.10
FBN1	NM_001406716.1	c.7402T>C	p.Cys2468Arg	missense_variant	59/65

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.7402T>C	p.Cys2468Arg	missense_variant	60/66	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

Pathogenic, criteria provided, single submitter

clinical testing

Petrovsky National Research Centre of Surgery, The Federal Agency for Scientific Organizations

Aug 30, 2019

The p.C2468R variant was found in one individual with MFS and is absent from large population studies (ExAC no frequency). ClinVar has an entry for this variant (Variation ID:427179). There is a known different missense variant at same codon C2468Y (UMD-FBN1 ID: 2517). Cysteine is located cbEGF-like domain and participates Disulfide bonds 2455-2468. Cysteine substitutions in EGF domains are common pathogenic mechanisms of the disease (PMID: 1301946, 15161917, 20591885). In Addition, prediction tools like Provean, SIFT, PolyPhen2, MutationTaster show deleterious effect of the variant. Based on this evidences we classify C2468R variant as Pathogenic. -

Familial thoracic aortic aneurysm and aortic dissection Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Apr 05, 2021

The p.C2468R variant (also known as c.7402T>C), located in coding exon 59 of the FBN1 gene, results from a T to C substitution at nucleotide position 7402. The cysteine at codon 2468 is replaced by arginine, an amino acid with highly dissimilar properties. 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). Based on internal structural analysis, this alteration eliminates a structurally critical disulfide in the structurally sensitive cbEGF-like domain #38 (Ambry internal data). A likely pathogenic alteration (p.C2468Y) has been described in the same codon (Groth KA et al. Genet. Med., 2017 07;19:772-777). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Jan 26, 2022

Has not been previously published as pathogenic or benign to our knowledge; 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; 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); Reported in ClinVar but additional evidence is not available (ClinVar Variant ID #427179); This variant is associated with the following publications: (PMID: 12938084) -

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

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Feb 12, 2020

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. This variant disrupts the p.Cys2468 amino acid residue in FBN1. Other variant(s) that disrupt this residue have been observed in individuals with FBN1-related conditions (PMID: 27906200), which suggests that this may be a clinically significant amino acid residue. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). 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). This variant has been observed in an individual with clinical features of FBN1-related conditions (Invitae). ClinVar contains an entry for this variant (Variation ID: 427179). This variant is not present in population databases (ExAC no frequency). This sequence change replaces cysteine with arginine at codon 2468 of the FBN1 protein (p.Cys2468Arg). The cysteine residue is highly conserved and there is a large physicochemical difference between cysteine and arginine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.59
CADD	Pathogenic	30
DANN	Uncertain	1.0
Eigen	Pathogenic	0.80
Eigen_PC	Pathogenic	0.73
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.91	D
M_CAP	Pathogenic	0.96	D
MetaRNN	Pathogenic	1.0	D
MetaSVM	Pathogenic	0.94	D
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.84	D
PROVEAN	Pathogenic	-10	D
REVEL	Pathogenic	0.94
Sift	Uncertain	0.0010	D
Sift4G	Pathogenic	0.0	D
Vest4		0.99
MutPred		1.0		Gain of ubiquitination at K2472 (P = 0.0898);
MVP		0.98
MPC		1.9
ClinPred		1.0	D
GERP RS		4.7

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: rs1085308004; hg19: chr15-48717617;