15-48483890-T-C

Position:

• chr15-48483890-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 7P and 4B. PM1 PP2 PP3_Strong BS2

The NM_000138.5(FBN1):​c.3766A>G​(p.Asn1256Asp) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000151 in 1,461,366 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000015 (0 hom.)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:5
• 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 Uncertain_significance. Variant got 3 ACMG points.

• PM1: In a disulfide_bond (size 14) in uniprot entity FBN1_HUMAN there are 8 pathogenic changes around while only 0 benign (100%) in NM_000138.5
• 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, 0.945
• BS2: High AC in GnomAdExome4 at 22 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
FBN1	NM_000138.5	c.3766A>G	p.Asn1256Asp	missense_variant	31/66	ENST00000316623.10	NP_000129.3
FBN1	NM_001406716.1	c.3766A>G	p.Asn1256Asp	missense_variant	30/65		NP_001393645.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
FBN1	ENST00000316623.10	c.3766A>G	p.Asn1256Asp	missense_variant	31/66	1	NM_000138.5	ENSP00000325527.5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251136 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135728

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000151 AC: 22 AN: 1461366 Hom.: 0 Cov.: 31 AF XY: 0.0000165 AC XY: 12 AN XY: 727022

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.0000113

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:5

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Familial thoracic aortic aneurysm and aortic dissection Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Feb 11, 2019	Variant of Uncertain Significance due to insufficient evidence: This missense variant replaces asparagine with aspartic acid at codon 1256 of the FBN1 protein. Computational prediction tools and conservation analyses suggest that this variant may have deleterious impact on the protein function. Computational splicing tools suggest that this variant may not impact RNA splicing. To our knowledge, functional assays have not been performed for this variant nor has this variant been reported in individuals affected with cardiovascular disorders in the literature. This variant has been identified in 1/245904 chromosomes in the general population by the Genome Aggregation Database (gnomAD). Available evidence is insufficient to determine the role of this variant in disease conclusively. -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Apr 14, 2019	The p.N1256D variant (also known as c.3766A>G), located in coding exon 30 of the FBN1 gene, results from an A to G substitution at nucleotide position 3766. The asparagine at codon 1256 is replaced by aspartic acid, an amino acid with highly similar properties. This variant was reported in an individual with Marfan-like features; however, clinical details were limited (Seo GH et al. Medicine (Baltimore), 2018 May;97:e10767). This amino acid position is highly conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

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

Oct 29, 2023

This sequence change replaces asparagine, which is neutral and polar, with aspartic acid, which is acidic and polar, at codon 1256 of the FBN1 protein (p.Asn1256Asp). This variant is present in population databases (rs772890884, gnomAD 0.0009%). This missense change has been observed in individual(s) with clinical features of FBN1-related conditions (PMID: 29768367; Invitae). ClinVar contains an entry for this variant (Variation ID: 921344). 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 with a positive predictive value of 95%. This variant disrupts the p.Asn1256His amino acid residue in FBN1. Other variant(s) that disrupt this residue have been determined to be pathogenic (Invitae). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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. -

Marfan syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

All of Us Research Program, National Institutes of Health

Aug 15, 2023

Variant of Uncertain Significance due to insufficient evidence: This missense variant replaces asparagine with aspartic acid at codon 1256 of the FBN1 protein. Computational prediction tools and conservation analyses suggest that this variant may have deleterious impact on the protein function. Computational splicing tools suggest that this variant may not impact RNA splicing. To our knowledge, functional assays have not been performed for this variant nor has this variant been reported in individuals affected with cardiovascular disorders in the literature. This variant has been identified in 1/245904 chromosomes in the general population by the Genome Aggregation Database (gnomAD). Available evidence is insufficient to determine the role of this variant in disease conclusively. -

Geleophysic dysplasia 2 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Molecular Lab, Department of Haematology, Christian Medical College

May 20, 2022

- -

Acromicric dysplasia Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Molecular Lab, Department of Haematology, Christian Medical College

May 20, 2022

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.25	D
BayesDel_noAF	Uncertain	0.13
CADD	Pathogenic	28
DANN	Uncertain	1.0
Eigen	Pathogenic	0.82
Eigen_PC	Pathogenic	0.82
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.95	D
M_CAP	Uncertain	0.12	D
MetaRNN	Pathogenic	0.95	D
MetaSVM	Pathogenic	1.1	D
PrimateAI	Uncertain	0.76	T
PROVEAN	Pathogenic	-4.7	D
REVEL	Pathogenic	0.83
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.018	D
Vest4		0.85
MutPred		0.83		Loss of catalytic residue at N1256 (P = 0.0481);
MVP		0.95
MPC		1.4
ClinPred		0.99	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: rs772890884; hg19: chr15-48776087;