NM_000138.5:c.3G>A

Variant names:

• chr15-48644767-C-T
• rs886039072
• NM_000138.5:c.3G>A

Variant summary

Our verdict is Pathogenic. The variant received 20 ACMG points: 20P and 0B. PVS1 PS1_Moderate PM2 PP5_Very_Strong

The NM_000138.5(FBN1):​c.3G>A​(p.Met1?) variant causes a start lost change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: FBN1 NM_000138.5 start_lost
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 2.47
• Publications: 6 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: Pathogenic. The variant received 20 ACMG points.

• PVS1: Start lost variant, next in-frame start position is after 86 pathogenic variants. Next in-frame start position is after 99 codons. Genomic position: 48610779. Lost 0.034 part of the original CDS.
• PS1: Another start lost variant in NM_000138.5 (FBN1) was described as [Pathogenic] in ClinVar
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 15-48644767-C-T is Pathogenic according to our data. Variant chr15-48644767-C-T is described in ClinVar as Pathogenic. ClinVar VariationId is 488792.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.3G>A	p.Met1?	start_lost	Exon 2 of 66	ENST00000316623.10	NP_000129.3
FBN1	NM_001406716.1	c.3G>A	p.Met1?	start_lost	Exon 1 of 65		NP_001393645.1
FBN1	NM_001406717.1	c.3G>A	p.Met1?	start_lost	Exon 2 of 9		NP_001393646.1
FBN1	NM_001406718.1	c.3G>A	p.Met1?	start_lost	Exon 2 of 3		NP_001393647.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
FBN1	ENST00000316623.10	c.3G>A	p.Met1?	start_lost	Exon 2 of 66	1	NM_000138.5	ENSP00000325527.5

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1

Dec 13, 2016

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.3 G>A pathogenic variant has been identified in the FBN1 gene. This variant has not been published as a pathogenic variant, nor has it been reported as a benign variant to our knowledge. However, it has been observed in two other individuals referred for Marfan/TAAD testing at GeneDx. This variant is predicted to alter the initiator Methionine codon, and the resultant protein would be described as p.Met1?" using a question mark to signify that it is not known if the loss of Met1 means that all protein translation is completely prevented or if an abnormal protein is produced using an alternate Methionine. Other nucleotide substitutions affecting the initiator Methionine have been reported in association with FBN1-related disorders, including the c.1 A>T pathogenic variant reported by Rybczynski et al. (2008), and the c.2 T>G pathogenic variant reported at GeneDx. Moreover, the c.3 G>A variant was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations.In summary, c.3 G>A in the FBN1 gene is interpreted as a pathogenic variant." -

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

Dec 06, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects the initiator methionine of the FBN1 mRNA. The next in-frame methionine is located at codon 99. This variant is not present in population databases (gnomAD no frequency). Disruption of the initiator codon has been observed in individual(s) with clinical features of Marfan syndrome (PMID: 28973303, 29357934). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 488792). 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). 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	0.27
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Benign	0.34	.;T
Eigen	Uncertain	0.19
Eigen_PC	Uncertain	0.28
FATHMM_MKL	Uncertain	0.82	D
LIST_S2	Uncertain	0.90	D;D
M_CAP	Pathogenic	0.91	D
MetaRNN	Pathogenic	0.99	D;D
MetaSVM	Uncertain	-0.0034	T
PhyloP100		2.5
PROVEAN	Benign	-1.1	N;D
REVEL	Uncertain	0.34
Sift	Uncertain	0.028	D;D
Sift4G	Uncertain	0.046	D;D
Vest4		0.74
MutPred		0.98		Gain of catalytic residue at M1 (P = 0.027);Gain of catalytic residue at M1 (P = 0.027);
MVP		0.97
ClinPred		0.99	D
GERP RS		4.6
Mutation Taster		=2/198	disease causing (ClinVar)

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: rs886039072; hg19: chr15-48936964;