rs1555395015

Positions:

• chr15-48434707-T-C

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.6503A>G​(p.Asp2168Gly) 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. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 8.02

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]

FBN1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 15 ACMG points.

• PM1: In a domain EGF-like 37; calcium-binding (size 39) in uniprot entity FBN1_HUMAN there are 9 pathogenic changes around while only 1 benign (90%) 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, 0.883
• PP5: Variant 15-48434707-T-C is Pathogenic according to our data. Variant chr15-48434707-T-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 449437.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
FBN1	NM_000138.5	c.6503A>G	p.Asp2168Gly	missense_variant	54/66	ENST00000316623.10	NP_000129.3
FBN1	NM_001406716.1	c.6503A>G	p.Asp2168Gly	missense_variant	53/65		NP_001393645.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
FBN1	ENST00000316623.10	c.6503A>G	p.Asp2168Gly	missense_variant	54/66	1	NM_000138.5	ENSP00000325527.5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Mar 20, 2017

The D2168G likely pathogenic variant in the FBN1 gene has been previously reported in one individual with suspected Marfan syndrome (Howarth et al., 2007). Although one of the two family members also found to carry D2168G was unaffected, no additional clinical information was provided. This variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The D2168G variant results in a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties, and in silico analysis predicts this variant is probably damaging to the protein structure/function. In addition, this substitution affects an aspartic acid residue within the consensus sequence of a calcium-binding EGF-like domain at a position that is occupied exclusively by either aspartic acid (Asp) or asparagine (Asn). Substitution of conserved residues within the consensus sequence is a recognized mechanism of disease and is included in the criteria to consider for pathogenicity in the revised Ghent nosology (Loeys et al., 2010). Finally, D2168 is conserved across mammals. In summary, D2168G in the FBN1 gene is interpreted as a likely pathogenic variant. -

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

Jan 22, 2021

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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site, but this prediction has not been confirmed by published transcriptional studies. 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: "Tolerated"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). This variant has been observed in individual(s) with clinical features of Marfan syndrome (PMID: 17627385, 31751304, Invitae). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 449437). This variant is not present in population databases (ExAC no frequency). This sequence change replaces aspartic acid with glycine at codon 2168 of the FBN1 protein (p.Asp2168Gly). The aspartic acid residue is moderately conserved and there is a moderate physicochemical difference between aspartic acid and glycine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.86
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.35
CADD	Pathogenic	29
DANN	Uncertain	1.0
Eigen	Pathogenic	0.74
Eigen_PC	Pathogenic	0.77
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.97	D
M_CAP	Pathogenic	0.45	D
MetaRNN	Pathogenic	0.88	D
MetaSVM	Pathogenic	0.94	D
PrimateAI	Uncertain	0.60	T
PROVEAN	Uncertain	-3.6	D
REVEL	Pathogenic	0.84
Sift	Uncertain	0.016	D
Sift4G	Uncertain	0.015	D
Vest4		0.48
MutPred		0.91		Loss of stability (P = 0.0924);
MVP		0.96
MPC		1.1
ClinPred		0.98	D
GERP RS		6.2

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: rs1555395015; hg19: chr15-48726904;