rs193922185

Positions:

• chr15-48505037-G-A

Variant summary

Our verdict is Pathogenic. Variant got 15 ACMG points: 15P and 0B. PM1 PM2 PP2 PP3_Moderate PP5_Very_Strong

The NM_000138.5(FBN1):​c.1948C>T​(p.Arg650Cys) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,860 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/18 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. R650H) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:10
• Conservation: PhyloP100: 8.06

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 15 ACMG points.

• PM1: In a hotspot region, there are 2 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
• 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, 0.912
• PP5: Variant 15-48505037-G-A is Pathogenic according to our data. Variant chr15-48505037-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 36042.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr15-48505037-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.1948C>T	p.Arg650Cys	missense_variant	16/66	ENST00000316623.10
FBN1	NM_001406716.1	c.1948C>T	p.Arg650Cys	missense_variant	15/65

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.1948C>T	p.Arg650Cys	missense_variant	16/66	1	NM_000138.5	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461860 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727226

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:10

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Marfan syndrome Pathogenic:3

Likely pathogenic, criteria provided, single submitter	clinical testing;curation	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Aug 18, 2011	- -
Likely pathogenic, no assertion criteria provided	clinical testing	Center for Medical Genetics Ghent, University of Ghent	Nov 07, 2017	- -
Likely pathogenic, criteria provided, single submitter	research	Centre of Medical Genetics, University of Antwerp	Mar 01, 2021	PM2, PS5, PP4 -

Familial thoracic aortic aneurysm and aortic dissection Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Ambry Genetics	Feb 24, 2021	The c.1948C>T (p.R650C) alteration is located in exon 16 (coding exon 15) of the FBN1 gene. This alteration results from a C to T substitution at nucleotide position 1948, causing the arginine (R) at amino acid position 650 to be replaced by a cysteine (C). Based on data from the Genome Aggregation Database (gnomAD), the FBN1 c.1948C>T alteration was not observed, with coverage at this position. This alteration has been reported in individuals and families with ectopia lentis, some of whom also had aortic findings (Zadeh, 2011; Zhang, 2015; Vatti, 2017). This amino acid position is highly conserved in available vertebrate species. The majority of FBN1 mutations identified to date have involved the substitution or generation of cysteine residues within cbEGF domains (Vollbrandt, 2004). The p.R650C alteration is predicted to be deleterious by in silico analysis. Based on the available evidence, this alteration is classified as likely pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario	May 08, 2019	- -

not provided Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Clinical Genetics and Genomics, Karolinska University Hospital	Feb 23, 2017	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Mar 21, 2022	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; Introduces a new 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 FBN-related disorders (Collod-Beroud et al., 2003); This variant is associated with the following publications: (PMID: 27353645, 17701892, 15161917, 21932315, 25900864, 29376001, 16677079, 4750422, 33844962, 12938084, 28941062) -

not specified Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Sep 19, 2016

- -

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

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Jan 05, 2024

This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 650 of the FBN1 protein (p.Arg650Cys). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with ectopia lentis (PMID: 21932315, 25900864). ClinVar contains an entry for this variant (Variation ID: 36042). 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%. For these reasons, this variant has been classified as Pathogenic. -

Marfan syndrome;C0265287:Acromicric dysplasia;C1858556:MASS syndrome;C1861456:Stiff skin syndrome;C1869115:Weill-Marchesani syndrome 2, dominant;C3280054:Geleophysic dysplasia 2;C3541518:Ectopia lentis 1, isolated, autosomal dominant;C4310796:Progeroid and marfanoid aspect-lipodystrophy syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 31, 2018

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.50	D
BayesDel_noAF	Pathogenic	0.49
CADD	Pathogenic	34
DANN	Pathogenic	1.0
Eigen	Pathogenic	0.91
Eigen_PC	Pathogenic	0.86
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.38	D
MetaRNN	Pathogenic	0.91	D
MetaSVM	Pathogenic	0.97	D
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.85	D
PROVEAN	Pathogenic	-7.0	D
REVEL	Pathogenic	0.94
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0010	D
Vest4		0.85
MutPred		0.67		Gain of catalytic residue at V651 (P = 0.2219);
MVP		0.99
MPC		2.4
ClinPred		1.0	D
GERP RS		5.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs193922185; hg19: chr15-48797234; COSMIC: COSV100353754;