15-48415588-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 4P and 4B. PM1 PP2 PP3 BS2

The NM_000138.5(FBN1):c.7999G>A(p.Glu2667Lys) variant causes a missense change. The variant allele was found at a frequency of 0.0000248 in 1,614,068 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 Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.000053 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000022 (0 hom.)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:8
• Conservation: PhyloP100: 4.97

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 0 ACMG points.

• PM1: In a hotspot region, there are 9 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_000138.5
• PP2: Missense variant where missense usually causes diseases, FBN1
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.765
• BS2: High AC in GnomAd at 8 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.7999G>A	p.Glu2667Lys	missense_variant	64/66	ENST00000316623.10
FBN1	NM_001406716.1	c.7999G>A	p.Glu2667Lys	missense_variant	63/65

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.7999G>A	p.Glu2667Lys	missense_variant	64/66	1	NM_000138.5	P1

Frequencies

GnomAD3 genomes AF: 0.0000526 AC: 8 AN: 152188 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000724

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000131

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: 0.0000441

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000200 AC: 5 AN: 250448 Hom.: 0 AF XY: 0.0000221 AC XY: 3 AN XY: 135460

Gnomad AFR exome AF: 0.000123

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.0000544

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000177

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000219 AC: 32 AN: 1461880 Hom.: 0 Cov.: 32 AF XY: 0.0000179 AC XY: 13 AN XY: 727242

Gnomad4 AFR exome AF: 0.0000896

Gnomad4 AMR exome AF: 0.0000224

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000252

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000225

Gnomad4 OTH exome AF: 0.0000331

GnomAD4 genome AF: 0.0000526 AC: 8 AN: 152188 Hom.: 0 Cov.: 33 AF XY: 0.0000672 AC XY: 5 AN XY: 74356

Gnomad4 AFR AF: 0.0000724

Gnomad4 AMR AF: 0.000131

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000441

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000383 Hom.: 0

Bravo AF: 0.0000529

ESP6500AA AF: 0.000227 AC: 1

ESP6500EA AF: 0.000116 AC: 1

ExAC AF: 0.0000330 AC: 4

EpiCase AF: 0.000109

EpiControl AF: 0.00

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:8

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not specified Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	May 22, 2017	Variant classified as Uncertain Significance - Favor Pathogenic. The p.Glu2667Ly s variant in FBN1 has been reported in 1 individual from a consanguineous family with clinical features of Marfan syndrome and segregated with disease in 3 affe cted relatives, one of whom was homozygous for the variant but was not more seve rely affected (Arnaud 2016). This variant has also been reported in ClinVar (Var iation ID 36124). In addition, it has been identified in 1/66690 of European chr omosomes by the Exome Aggregation Consortium (ExAC, http://exac.broadinstitute.o rg; dbSNP rs149062442). Computational prediction tools and conservation analysis do not provide strong support for or against an impact to the protein. In summa ry, while there is some suspicion for a pathogenic role, the clinical significan ce of the p.Glu2667Lys variant is uncertain. -
Uncertain significance, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Feb 05, 2024	Variant summary: FBN1 c.7999G>A (p.Glu2667Lys) results in a conservative amino acid change located in the EGF-like calcium-binding domain of the encoded protein sequence. Three of five in-silico tools predict a benign effect of the variant on protein function.The variant allele was found at a frequency of 2e-05 in 250448 control chromosomes, predominantly at a frequency of 0.00012 within the African or African-American subpopulation in the gnomAD database. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. This variant has been reported in the literature in individuals affected with features suggestive of Marfan Syndrome (Arnaud_2017). It was subsequently reported in individuals with fetal demise/multiple anomalies and short stature, respectively (example, Ahn_2021, Zhao_2021). These report(s) do not provide unequivocal conclusions about association of the variant with Marfan Syndrome. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 34653508, 27582083, 33100332). ClinVar contains an entry for this variant (Variation ID: 36124). Based on the evidence outlined above, the variant was classified as uncertain significance. -

Marfan syndrome Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	MGZ Medical Genetics Center	Aug 16, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	All of Us Research Program, National Institutes of Health	Nov 30, 2023	This missense variant replaces glutamic acid with lysine at codon 2667 of the FBN1 protein. Computational prediction suggests that this variant may not impact protein structure and function (internally defined REVEL score threshold <= 0.5, PMID: 27666373). To our knowledge, functional studies have not been reported for this variant. This variant has been reported in homozygosity in an individual from a consanguineous Algerian family, who had clinical features of Marfan syndrome (PMID: 27582083). The proband's heterozygous father and daughter had aortic dilation, while the heterozygous mother was unaffected (PMID: 27582083). This variant has also been reported in a case of fetal demise with multiple anomalies (PMID: 33100332). This variant has been identified in 9/281854 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. -

Familial thoracic aortic aneurysm and aortic dissection Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Dec 23, 2019	The c.7999G>A (p.E2667K) alteration is located in exon 64 (coding exon 63) of the FBN1 gene. This alteration results from a G to A substitution at nucleotide position 7999, causing the glutamic acid (E) at amino acid position 2667 to be replaced by a lysine (K). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -
Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Dec 16, 2022	This missense variant replaces glutamic acid with lysine at codon 2667 of the FBN1 protein. Computational prediction suggests that this variant may not impact protein structure and function (internally defined REVEL score threshold <= 0.5, PMID: 27666373). To our knowledge, functional studies have not been reported for this variant. This variant has been reported in homozygosity in an individual from a consanguineous Algerian family, who had clinical features of Marfan syndrome (PMID: 27582083). The proband's heterozygous father and daughter had aortic dilation, while the heterozygous mother was unaffected (PMID: 27582083). This variant has also been reported in a case of fetal demise with multiple anomalies (PMID: 33100332). This variant has been identified in 9/281854 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. -

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

Likely pathogenic, criteria provided, single submitter

clinical testing

Invitae

Jan 28, 2024

This sequence change replaces glutamic acid, which is acidic and polar, with lysine, which is basic and polar, at codon 2667 of the FBN1 protein (p.Glu2667Lys). This variant is present in population databases (rs149062442, gnomAD 0.02%). This missense change has been observed in individuals with clinical features of Marfan syndrome and/or aortic dissection (PMID: 27582083; Invitae). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 36124). 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 not expected to disrupt FBN1 protein function with a negative predictive value of 95%. 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. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Sep 24, 2021

Has been reported as a variant of uncertain significance in a 22+ week fetus with multiple anomalies (Zhao et al., 2020); In silico analysis supports that this missense variant does not alter protein structure/function; Although located in a calcium-binding EGF-like domain of the FBN1 gene, it does not affect a cysteine residue within this domain; 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 as a variant of uncertain significance (ClinVar Variant ID# 36124; Landrum et al., 2016); This variant is associated with the following publications: (PMID: 27582083, 33100332, 26582918) -

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

Dec 17, 2021

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.28
BayesDel_addAF	Benign	-0.015	T
BayesDel_noAF	Uncertain	-0.080
Cadd	Uncertain	25
Dann	Uncertain	0.99
Eigen	Benign	0.064
Eigen_PC	Benign	0.22
FATHMM_MKL	Uncertain	0.88	D
LIST_S2	Uncertain	0.96	D
M_CAP	Benign	0.049	D
MetaRNN	Pathogenic	0.77	D
MetaSVM	Benign	-0.31	T
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.62	T
PROVEAN	Benign	-1.9	N
REVEL	Uncertain	0.45
Sift	Benign	0.69	T
Sift4G	Benign	0.61	T
Vest4		0.86
MVP		0.85
MPC		0.93
ClinPred		0.15	T
GERP RS		5.8

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: rs149062442; hg19: chr15-48707785; COSMIC: COSV57312867;