15-48537628-C-T

Position:

• chr15-48537628-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 7P and 4B. PM1 PM5 PP2 PP3_Moderate BS2

The NM_000138.5(FBN1):​c.719G>A​(p.Arg240His) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000805 in 1,614,030 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R240C) has been classified as Pathogenic.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000075 (0 hom.)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:10
• 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 Uncertain_significance. Variant got 3 ACMG points.

• PM1: In a region_of_interest Interaction with MFAP4 (size 210) in uniprot entity FBN1_HUMAN there are 27 pathogenic changes around while only 6 benign (82%) in NM_000138.5
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr15-48537629-G-A is described in Lovd as [Pathogenic].
• 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, 0.843
• BS2: High AC in GnomAdExome4 at 11 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
FBN1	NM_000138.5	c.719G>A	p.Arg240His	missense_variant	7/66	ENST00000316623.10	NP_000129.3
FBN1	NM_001406716.1	c.719G>A	p.Arg240His	missense_variant	6/65		NP_001393645.1
FBN1	NM_001406717.1	c.719G>A	p.Arg240His	missense_variant	7/9		NP_001393646.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
FBN1	ENST00000316623.10	c.719G>A	p.Arg240His	missense_variant	7/66	1	NM_000138.5	ENSP00000325527.5
FBN1	ENST00000559133.6	n.719G>A		non_coding_transcript_exon_variant	7/67	1		ENSP00000453958.2
FBN1	ENST00000674301.2	n.719G>A		non_coding_transcript_exon_variant	7/68			ENSP00000501333.2
FBN1	ENST00000537463.6	n.636+83G>A		intron_variant		5		ENSP00000440294.2

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152144 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000294

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000752 AC: 11 AN: 1461886 Hom.: 0 Cov.: 31 AF XY: 0.00000688 AC XY: 5 AN XY: 727244

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: 0.00000719

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152144 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74312

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000294

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000756

ExAC AF: 0.00000824 AC: 1

Asia WGS AF: 0.000289 AC: 1 AN: 3478

EpiCase AF: 0.000218

EpiControl AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:10

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Familial thoracic aortic aneurysm and aortic dissection Uncertain:3

Uncertain significance, criteria provided, single submitter	clinical testing	CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario	Dec 14, 2017	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Mar 10, 2023	This missense variant replaces arginine with histidine at codon 240 of the FBN1 protein. Computational prediction tool suggests that this variant may have deleterious impact on protein structure and function (internally defined REVEL score threshold >= 0.7, PMID: 27666373). To our knowledge, functional studies have not been performed for this variant. This variant has been reported in two siblings affected with Marfan syndrome, who also carried a pathogenic truncation c.3861delC in the same gene (PMID: 19059503). Their affected mother carried the truncation variant, and this missense variant was inherited from unaffected father. This variant has been identified in 1/245956 chromosomes in the general population by the Genome Aggregation Database (gnomAD). The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Oct 25, 2023	The p.R240H variant (also known as c.719G>A), located in coding exon 6 of the FBN1 gene, results from a G to A substitution at nucleotide position 719. The arginine at codon 240 is replaced by histidine, an amino acid with highly similar properties. In one study, p.R240H was identified in two probands in one family in conjunction with the c.3861delC pathogenic FBN1 mutation. In this family, p.R240H was inherited from the unaffected father, and c.3861delC was inherited from the affected mother; however, the probands appeared to have a more severe clinical phenotype than their mother (Van Dijk FS et al. Eur J Med Genet. 2009;52(1):1-5). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Marfan syndrome Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Mendelics	May 28, 2019	- -
Uncertain significance, criteria provided, single submitter	clinical testing	All of Us Research Program, National Institutes of Health	Nov 30, 2023	This missense variant replaces arginine with histidine at codon 240 of the FBN1 protein. Computational prediction tool suggests that this variant may have deleterious impact on protein structure and function (internally defined REVEL score threshold >=0.7, PMID: 27666373). To our knowledge, functional studies have not been performed for this variant. This variant has been reported in two siblings affected with Marfan syndrome, who also carried a pathogenic truncation c.3861delC in the same gene (PMID: 19059503). Their affected mother carried the truncation variant, and this missense variant was inherited from unaffected father. This variant has been identified in 1/245956 chromosomes in the general population by the Genome Aggregation Database (gnomAD). The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance. -

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Dec 07, 2023	Reported in two siblings with Marfan syndrome who also harbor a frameshift variant on the opposite allele (in trans); the p.(R240H) variant was inherited from the unaffected father (PMID: 19059503); Not observed at significant frequency in large population cohorts (gnomAD); Does not affect a cysteine residue within a calcium-binding EGF-like domain of the FBN1 gene; 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); In silico analysis supports that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 27582083, 27437668, 31098894, 12938084, 34426522, 24941995, 19059503) -
Uncertain significance, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Oct 01, 2023	FBN1: PM2, PP3, PP4 -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Mar 25, 2021

Variant summary: FBN1 c.719G>A (p.Arg240His) results in a non-conservative amino acid change in the encoded protein sequence. Three of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251226 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.719G>A has been reported in the literature in a family with Marfan Syndrome (van Dijk_2009). In this report, the two affected probands carried both the c.719G>A variant (inherited from their unaffected father) as well as the c.3861delC (inherited from their affected mother). While this suggests the truncating variant to be the causitive variant in this family, the authors note the c.719G>A variant may have a potentially modifying effect, as evidence by the probands having a more severe clinical phenotype than their mother (van Dijk_2009). To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Six clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. All laboratories classified the variant as uncertain significance. Based on the evidence outlined above, the variant was classified as uncertain significance. -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 05, 2022

This sequence change replaces arginine, which is basic and polar, with histidine, which is basic and polar, at codon 240 of the FBN1 protein (p.Arg240His). This variant is present in population databases (rs768744583, gnomAD 0.0009%). This missense change has been observed in individual(s) with clinical features of Marfan syndrome. In at least one individual, this variant co-occurred with a pathogenic variant in the FBN1 gene. (PMID: 19059503; Invitae). ClinVar contains an entry for this variant (Variation ID: 449122). 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. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

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 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 13, 2021

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.21
BayesDel_addAF	Pathogenic	0.32	D
BayesDel_noAF	Pathogenic	0.22
CADD	Pathogenic	32
DANN	Pathogenic	1.0
Eigen	Uncertain	0.59
Eigen_PC	Uncertain	0.65
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Benign	0.85	D
M_CAP	Pathogenic	0.33	D
MetaRNN	Pathogenic	0.84	D
MetaSVM	Uncertain	-0.082	T
PrimateAI	Pathogenic	0.90	D
PROVEAN	Benign	-0.86	N
REVEL	Pathogenic	0.72
Sift	Benign	0.37	T
Sift4G	Benign	0.32	T
Vest4		0.92
MVP		0.92
MPC		1.6
ClinPred		0.97	D
GERP RS		5.4

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs768744583; hg19: chr15-48829825; COSMIC: COSV100355194;