rs876657811

chr15-48534155-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM1 PM2 PP2

The NM_000138.5(FBN1):c.787A>G(p.Ile263Val) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,744 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★). Synonymous variant affecting the same amino acid position (i.e. I263I) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 5.10

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 5 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 11 uncertain in NM_000138.5
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, FBN1

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.787A>G	p.Ile263Val	missense_variant	8/66	ENST00000316623.10
FBN1	NM_001406716.1	c.787A>G	p.Ile263Val	missense_variant	7/65
FBN1	NM_001406717.1	c.787A>G	p.Ile263Val	missense_variant	8/9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.787A>G	p.Ile263Val	missense_variant	8/66	1	NM_000138.5	P1
FBN1	ENST00000559133.6	c.787A>G	p.Ile263Val	missense_variant, NMD_transcript_variant	8/67	1
FBN1	ENST00000674301.2	c.787A>G	p.Ile263Val	missense_variant, NMD_transcript_variant	8/68
FBN1	ENST00000537463.6	c.636+3556A>G		intron_variant, NMD_transcript_variant		5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461744 Hom.: 0 Cov.: 33 AF XY: 0.00000138 AC XY: 1 AN XY: 727188

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Marfan syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

All of Us Research Program, National Institutes of Health

May 30, 2023

This missense variant replaces isoleucine with valine at codon 263 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 not been reported in individuals affected with FBN1-related disorders in the literature. This variant has not been identified 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 specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Apr 03, 2015

Variant classified as Uncertain Significance - Favor Benign. The p.Ile263Val var iant in FBN1 has not been previously reported in individuals with connective tis sue disease or in large population studies. Isoleucine (Ile) at position 263 is not conserved in evolutionarily distant species and 2 fish species (Mexican tetr a, lamprey) carry a valine (Val) at this position, raising the possibility that this change may be tolerated. In summary, while the clinical significance of the p.Ile263Val is uncertain, the lack of conservation suggests that it is more lik ely to be benign. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.083
BayesDel_addAF	Uncertain	0.080	D
BayesDel_noAF	Benign	-0.12
Cadd	Benign	21
Dann	Uncertain	0.99
Eigen	Benign	-0.23
Eigen_PC	Benign	0.032
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Benign	0.78	T
M_CAP	Benign	0.024	T
MetaRNN	Uncertain	0.47	T
MetaSVM	Benign	-0.36	T
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.81	D
PROVEAN	Benign	-0.29	N
REVEL	Benign	0.25
Sift	Benign	0.54	T
Sift4G	Benign	0.78	T
Vest4		0.45
MutPred		0.52		Loss of catalytic residue at I263 (P = 0.2103);
MVP		0.66
MPC		0.69
ClinPred		0.58	D
GERP RS		5.5

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: rs876657811; hg19: chr15-48826352;