rs778258207

Variant names:

• chr15-48495253-G-C
• rs778258207
• NM_000138.5:c.2547C>G

Variant summary

Our verdict is Uncertain significance. The variant received 0 ACMG points: 3P and 3B. PM1 PP2 BP4_Moderate BP6

The NM_000138.5(FBN1):​c.2547C>G​(p.Ile849Met) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000595 in 1,613,968 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. I849V) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.000026 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000063 (0 hom.)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:7 B:4
• Conservation: PhyloP100: 0.187
• Publications: 4 publications found

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 Gene-Disease associations (from GenCC):

• familial thoracic aortic aneurysm and aortic dissection

  Inheritance: AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: ClinGen, Orphanet
• Marfan syndrome

  Inheritance: AD, AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp, ClinGen, G2P, PanelApp Australia, Orphanet, Ambry Genetics
• Acromicric dysplasia

  Inheritance: AD Classification: STRONG, SUPPORTIVE Submitted by: Orphanet, Ambry Genetics
• progeroid and marfanoid aspect-lipodystrophy syndrome

  Inheritance: AD Classification: STRONG, MODERATE, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics, Orphanet
• stiff skin syndrome

  Inheritance: AD Classification: STRONG, LIMITED Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
• Weill-Marchesani syndrome 2, dominant

  Inheritance: AD Classification: STRONG Submitted by: G2P, Labcorp Genetics (formerly Invitae)
• geleophysic dysplasia

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• isolated ectopia lentis

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• neonatal Marfan syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Weill-Marchesani syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• ectopia lentis 1, isolated, autosomal dominant

  Inheritance: AD Classification: LIMITED Submitted by: G2P
• Shprintzen-Goldberg syndrome

  Inheritance: AD, Unknown Classification: LIMITED, NO_KNOWN Submitted by: ClinGen, Labcorp Genetics (formerly Invitae)

ACMG classification

Our verdict: Uncertain_significance. The variant received 0 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 14 uncertain in NM_000138.5
• PP2: Missense variant in the FBN1 gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 1311 curated pathogenic missense variants (we use a threshold of 10). The gene has 112 curated benign missense variants. Gene score misZ: 5.0644 (above the threshold of 3.09). Trascript score misZ: 8.1787 (above the threshold of 3.09). GenCC associations: The gene is linked to Marfan syndrome, Weill-Marchesani syndrome 2, dominant, progeroid and marfanoid aspect-lipodystrophy syndrome, geleophysic dysplasia, Shprintzen-Goldberg syndrome, stiff skin syndrome, familial thoracic aortic aneurysm and aortic dissection, isolated ectopia lentis, ectopia lentis 1, isolated, autosomal dominant, Acromicric dysplasia, neonatal Marfan syndrome, Weill-Marchesani syndrome.
• BP4: Computational evidence support a benign effect (MetaRNN=0.22711003).
• BP6: Variant 15-48495253-G-C is Benign according to our data. Variant chr15-48495253-G-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 406321.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
FBN1	NM_000138.5	c.2547C>G	p.Ile849Met	missense_variant	Exon 22 of 66	ENST00000316623.10	NP_000129.3
FBN1	NM_001406716.1	c.2547C>G	p.Ile849Met	missense_variant	Exon 21 of 65		NP_001393645.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
FBN1	ENST00000316623.10	c.2547C>G	p.Ile849Met	missense_variant	Exon 22 of 66	1	NM_000138.5	ENSP00000325527.5

Frequencies

GnomAD3 genomes AF: 0.0000263 AC: 4 AN: 152186 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

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: 0.0000294

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.0000358 AC: 9 AN: 251344 AF XY: 0.0000368

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000116

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000440

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000629 AC: 92 AN: 1461782 Hom.: 0 Cov.: 32 AF XY: 0.0000578 AC XY: 42 AN XY: 727202

African (AFR) AF: 0.00 AC: 0 AN: 33474

American (AMR) AF: 0.000134 AC: 6 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86254

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53418

Middle Eastern (MID) AF: 0.000878 AC: 5 AN: 5696

European-Non Finnish (NFE) AF: 0.0000585 AC: 65 AN: 1111998

Other (OTH) AF: 0.000265 AC: 16 AN: 60382

GnomAD4 genome AF: 0.0000263 AC: 4 AN: 152186 Hom.: 0 Cov.: 33 AF XY: 0.0000269 AC XY: 2 AN XY: 74342

African (AFR) AF: 0.00 AC: 0 AN: 41436

American (AMR) AF: 0.000131 AC: 2 AN: 15286

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5196

South Asian (SAS) AF: 0.00 AC: 0 AN: 4826

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10610

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000294 AC: 2 AN: 68044

Other (OTH) AF: 0.00 AC: 0 AN: 2088

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.0000453

TwinsUK AF: 0.000270 AC: 1

ALSPAC AF: 0.00 AC: 0

ExAC AF: 0.0000165 AC: 2

EpiCase AF: 0.000218

EpiControl AF: 0.000178

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:7 Benign:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Marfan syndrome Uncertain:3 Benign:1

Mar 01, 2021

Centre of Medical Genetics, University of Antwerp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: research

PP4 -

Nov 07, 2017

Center for Medical Genetics Ghent, University of Ghent

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Aug 31, 2023

Clinical Genomics Laboratory, Stanford Medicine

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.Ile849Met variant in the FBN1 gene has been previously reported in 1 individual with Marfan syndrome. This individual also had a co-occurring likely pathogenic variant in FBN1 (p.Gly1838Cys) (Proost et al., 2015; Groth et al., 2017; Meester et al., 2022). This variant has been identified in 4/34590 Latino/Admixed American chromosomes (9/251344 chromosomes overall) by the Genome Aggregation Database (http://gnomad.broadinstitute.org/). This allele frequency is higher than expected for a pathogenic variant. This variant is present in ClinVar (Variation ID: 406321). The FBN1 gene has fewer missense variants in the general population than expected. A low rate of missense variation may suggest that this gene is intolerant to missense variation. Computational tools predict that this variant is neither deleterious nor benign; however, the accuracy of in silico algorithms is limited. These data were assessed using the ACMG/AMP variant interpretation guidelines. In summary, the significance of the p.Ile849Met variant is uncertain. Additional information is needed to resolve the significance of this variant. [ACMG evidence codes used: BS1; PP2] -

Dec 01, 2023

All of Us Research Program, National Institutes of Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense variant replaces isoleucine with methionine at codon 849 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 an individual affected with Marfan syndrome; this individual also carried a different likely pathogenic missense variant in the same gene (PMID: 25907466). This variant has been identified in 9/251344 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 Benign:1

Jul 26, 2024

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.I849M variant (also known as c.2547C>G), located in coding exon 21 of the FBN1 gene, results from a C to G substitution at nucleotide position 2547. The isoleucine at codon 849 is replaced by methionine, an amino acid with highly similar properties. This variant was reported in one individual from a Marfan syndrome cohort; however, an additional FBN1 variant was also detected, and clinical information was not provided (Proost D et al. Hum. Mutat., 2015 Aug;36:808-14). This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Based on the available evidence, the clinical significance of this variant remains unclear. -

Sep 19, 2019

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Apr 23, 2024

Color Diagnostics, LLC DBA Color Health

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided Uncertain:1

Jun 29, 2023

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Identified in a patient with bicuspid aortic valve and TAAD phenotype in published literature (Proost et al., 2015); this patient also harbored a second variant in the FBN1 gene; Does not affect a cysteine residue within a calcium-binding EGF-like domain or a TGF-binding protein domain of the FBN1 gene; 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); In silico analysis supports that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 27906200, 12938084, 25907466) -

FBN1-related disorder Uncertain:1

Mar 12, 2024

PreventionGenetics, part of Exact Sciences

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

The FBN1 c.2547C>G variant is predicted to result in the amino acid substitution p.Ile849Met. This variant has been reported, along with another missense variant p.Gly1838Cys in FBN1, in one individual with Marfan syndrome (Table S2, Proost et al. 2015. PubMed ID: 25907466). This variant is reported in 0.012% of alleles in individuals of Latino descent in gnomAD. At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

not specified Benign:1

Apr 30, 2024

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: FBN1 c.2547C>G (p.Ile849Met) results in a conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 3.6e-05 in 251344 control chromosomes, predominantly at a frequency of 0.00012 within the Latino subpopulation in the gnomAD database. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.2547C>G has been reported in the literature in an individual affected with Marfan Syndrome, however this patient also carried a likely pathogenic FBN1 variant (Proost_2015), suggesting that our variant of interest is in the benign spectrum. In addition, a co-occurrence with another likely pathogenic variant has been reported (FBN1 c.6871+1G>T; in an internal LCA sample), providing further evidence in support of a benign role. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. A recent study combining ACMG criteria with FBN1 gene-specific knowledge (i.e. considering critical FBN1 regions and appropriate minor allele frequency cutoffs), classified the variant as likely benign (Baudhuin_2019).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: 31227806, 27906200, 25907466). ClinVar contains an entry for this variant (Variation ID: 406321). Based on the evidence outlined above, the variant was classified as likely benign. -

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

Dec 10, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.087
BayesDel_addAF	Benign	-0.19	T
BayesDel_noAF	Benign	-0.28
CADD	Benign	22
DANN	Benign	0.96
Eigen	Benign	-0.25
Eigen_PC	Benign	-0.083
FATHMM_MKL	Uncertain	0.83	D
LIST_S2	Benign	0.79	T
M_CAP	Benign	0.057	D
MetaRNN	Benign	0.23	T
MetaSVM	Benign	-0.40	T
PhyloP100		0.19
PrimateAI	Uncertain	0.50	T
PROVEAN	Benign	-0.070	N
REVEL	Benign	0.17
Sift	Benign	0.19	T
Sift4G	Benign	0.24	T
Vest4		0.35
MutPred		0.40		Loss of methylation at K850 (P = 0.0238);
MVP		0.58
MPC		1.3
ClinPred		0.058	T
GERP RS		3.5
Mutation Taster		=81/19	polymorphism

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

Other links and lift over

dbSNP: rs778258207; hg19: chr15-48787450;