15-48434661-A-T

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP2 PP3_Strong

The NM_000138.5(FBN1):c.6549T>A(p.Asn2183Lys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. N2183N) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.595

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 Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 5 uncertain in NM_000138.5
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, FBN1
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.981

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.6549T>A	p.Asn2183Lys	missense_variant	54/66	ENST00000316623.10
FBN1	NM_001406716.1	c.6549T>A	p.Asn2183Lys	missense_variant	53/65

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.6549T>A	p.Asn2183Lys	missense_variant	54/66	1	NM_000138.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Aug 19, 2019

In summary, this variant has uncertain impact on FBN1 function. The available evidence is currently insufficient to determine its role in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with a FBN1-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces asparagine with lysine at codon 2183 of the FBN1 protein (p.Asn2183Lys). The asparagine residue is highly conserved and there is a moderate physicochemical difference between asparagine and lysine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.19	D
BayesDel_noAF	Uncertain	0.040
Cadd	Benign	21
Dann	Uncertain	1.0
Eigen	Uncertain	0.32
Eigen_PC	Uncertain	0.24
FATHMM_MKL	Uncertain	0.90	D
LIST_S2	Uncertain	0.96	D
M_CAP	Pathogenic	0.78	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.82	D
PROVEAN	Uncertain	-4.3	D
REVEL	Pathogenic	0.88
Sift	Uncertain	0.0030	D
Sift4G	Uncertain	0.0030	D
Vest4		0.84
MutPred		0.85		Gain of methylation at N2183 (P = 0.0041);
MVP		0.94
MPC		1.5
ClinPred		0.99	D
GERP RS		2.6

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: rs752192006; hg19: chr15-48726858;