chr15-48596324-C-T

Position:

• chr15-48596324-C-T

Variant summary

Our verdict is Pathogenic. Variant got 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_000138.5(FBN1):​c.497G>A​(p.Cys166Tyr) 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. 11/18 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C166F) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 7.57

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 19 ACMG points.

• PM1: In a disulfide_bond (size 12) in uniprot entity FBN1_HUMAN there are 8 pathogenic changes around while only 0 benign (100%) in NM_000138.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chrnull-null-null-null is described in UniProt as null.
• 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, 0.995
• PP5: Variant 15-48596324-C-T is Pathogenic according to our data. Variant chr15-48596324-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 1331456.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.497G>A	p.Cys166Tyr	missense_variant	6/66	ENST00000316623.10	NP_000129.3
FBN1	NM_001406716.1	c.497G>A	p.Cys166Tyr	missense_variant	5/65		NP_001393645.1
FBN1	NM_001406717.1	c.497G>A	p.Cys166Tyr	missense_variant	6/9		NP_001393646.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
FBN1	ENST00000316623.10	c.497G>A	p.Cys166Tyr	missense_variant	6/66	1	NM_000138.5	ENSP00000325527.5
FBN1	ENST00000559133.6	n.497G>A		non_coding_transcript_exon_variant	6/67	1		ENSP00000453958.2
FBN1	ENST00000537463.6	n.497G>A		non_coding_transcript_exon_variant	6/31	5		ENSP00000440294.2
FBN1	ENST00000674301.2	n.497G>A		non_coding_transcript_exon_variant	6/68			ENSP00000501333.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

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

Likely pathogenic, criteria provided, single submitter

clinical testing

Juno Genomics, Hangzhou Juno Genomics, Inc

-

PM2_Supporting+PP3_Strong+PP2+PS4_Supporting+PP4 -

Marfan Syndrome/Loeys-Dietz Syndrome/Familial Thoracic Aortic Aneurysms and Dissections Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

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

Dec 20, 2021

Variant summary: FBN1 c.497G>A (p.Cys166Tyr) results in a non-conservative amino acid change located in the EGF-like domain (IPR000742) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. "The sulfhydryl group of cysteine is unique in its ability to participate in disulfide covalent cross-linkage. In fact, two-thirds of fibrillin cysteine residues exist in the half-cystinyl form, suggesting their participation in intramolecular disulfide linkage (Dietz_1992)". Therefore, the substitution of a cysteine may disrupt the structure of the FBN1 protein, affecting its function. The variant was absent in 251386 control chromosomes, however the available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.497G>A has been reported in the literature in an individual affected with Marfan Syndrome (example: Li_2019). Other variants at Cys166 have been reported in HGMD in association with Marfan Syndrome (C166R, C166F, C166S). To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. No ClinVar submitters have assessed this variant since 2014. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

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

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 22, 2021

This sequence change replaces cysteine with tyrosine at codon 166 of the FBN1 protein (p.Cys166Tyr). The cysteine residue is highly conserved and there is a large physicochemical difference between cysteine and tyrosine. This variant is not present in population databases (ExAC no frequency). This missense change has been observed in individual(s) with clinical features of Marfan syndrome (PMID: 31098894). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt FBN1 protein function. This variant affects a cysteine residue in the EGF-like, TGFBP or hybrid motif domains of FBN1. Cysteine residues are believed to be involved in intramolecular disulfide bridges and have been shown to be important for FBN1 protein structure (PMID: 16905551, 19349279). In addition, missense substitutions affecting cysteine residues within these domains are significantly overrepresented among patients with Marfan syndrome (PMID: 16571647, 17701892). This variant disrupts the p.Cys166 amino acid residue in FBN1. Other variant(s) that disrupt this residue have been observed in individuals with FBN1-related conditions (PMID: 7611299, 14695540), which suggests that this may be a clinically significant amino acid residue. For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	32
DANN	Uncertain	1.0
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.89	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	0.91	D
PrimateAI	Pathogenic	0.90	D
PROVEAN	Pathogenic	-9.6	D
REVEL	Pathogenic	0.98
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Vest4		0.98
MutPred		0.96		Loss of stability (P = 0.2165);
MVP		1.0
MPC		1.9
ClinPred		1.0	D
GERP RS		5.9

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

No publications associated with this variant yet.

Other links and lift over

hg19: chr15-48888521;