15-48613009-C-A

Variant names:

• chr15-48613009-C-A
• rs25404
• NM_000138.5:c.247+1G>T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000138.5(FBN1):​c.247+1G>T variant causes a splice donor, intron 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. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: FBN1 NM_000138.5 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 7.30

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 Pathogenic. Variant got 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 15-48613009-C-A is Pathogenic according to our data. Variant chr15-48613009-C-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 549086.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
FBN1	NM_000138.5	c.247+1G>T		splice_donor_variant, intron_variant	Intron 3 of 65	ENST00000316623.10	NP_000129.3
FBN1	NM_001406716.1	c.247+1G>T		splice_donor_variant, intron_variant	Intron 2 of 64		NP_001393645.1
FBN1	NM_001406717.1	c.247+1G>T		splice_donor_variant, intron_variant	Intron 3 of 8		NP_001393646.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
FBN1	ENST00000316623.10	c.247+1G>T		splice_donor_variant, intron_variant	Intron 3 of 65	1	NM_000138.5	ENSP00000325527.5
FBN1	ENST00000559133.6	n.247+1G>T		splice_donor_variant, intron_variant	Intron 3 of 66	1		ENSP00000453958.2
FBN1	ENST00000537463.6	n.247+1G>T		splice_donor_variant, intron_variant	Intron 3 of 30	5		ENSP00000440294.2
FBN1	ENST00000674301.2	n.247+1G>T		splice_donor_variant, intron_variant	Intron 3 of 67			ENSP00000501333.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Marfan syndrome Pathogenic:1

Nov 07, 2017

Center for Medical Genetics Ghent, University of Ghent

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Familial thoracic aortic aneurysm and aortic dissection Pathogenic:1

Feb 15, 2023

Ambry Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.247+1G>T intronic variant results from a G to T substitution one nucleotide after coding exon 2 of the FBN1 gene. This alteration has been reported in individuals with Marfan syndrome (Baudhuin LM et al. J Hum Genet, 2015 May;60:241-52; Ambry internal data). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice donor site and may result in the creation or strengthening of a novel splice donor site. In addition to the clinical data presented in the literature, alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. As such, this alteration is classified as likely pathogenic. -

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

Aug 05, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects a donor splice site in intron 3 of the FBN1 gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in FBN1 are known to be pathogenic (PMID: 17657824, 19293843). This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individuals with Marfan syndrome (PMID: 25652356). ClinVar contains an entry for this variant (Variation ID: 549086). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.44
CADD	Pathogenic	35
DANN	Uncertain	1.0
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.98	D
GERP RS		5.1

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.39		Position offset: -3
DS_DL_spliceai		1.0		Position offset: 1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs25404; hg19: chr15-48905206;