15-48644769-T-A

Variant names:

• chr15-48644769-T-A
• rs730880097
• NM_000138.5:c.1A>T

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.1A>T​(p.Met1?) variant causes a initiator codon change. 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 initiator_codon
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 3.95
• Publications: 20 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 15-48644769-T-A is Pathogenic according to our data. Variant chr15-48644769-T-A is described in ClinVar as Pathogenic. ClinVar VariationId is 577426.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000138.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	FBN1	NM_000138.5	MANE Select	c.1A>T	p.Met1?	initiator_codon	Exon 2 of 66	NP_000129.3
	FBN1	NM_001406716.1		c.1A>T	p.Met1?	initiator_codon	Exon 1 of 65	NP_001393645.1
	FBN1	NM_001406717.1		c.1A>T	p.Met1?	initiator_codon	Exon 2 of 9	NP_001393646.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	FBN1	ENST00000316623.10	TSL:1 MANE Select	c.1A>T	p.Met1?	initiator_codon	Exon 2 of 66	ENSP00000325527.5
	FBN1	ENST00000560355.1	TSL:1	c.1A>T	p.Met1?	initiator_codon	Exon 2 of 2	ENSP00000453901.1
	FBN1	ENST00000559133.6	TSL:1	n.1A>T		non_coding_transcript_exon	Exon 2 of 67	ENSP00000453958.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Familial thoracic aortic aneurysm and aortic dissection Pathogenic:1

Sep 05, 2025

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.M1? pathogenic mutation (also known as c.1A>T) is located in coding exon 1 of the FBN1 gene and results from a A to T substitution at nucleotide position 1. This alters the methionine residue at the initiation codon (ATG). This variant was reported in individual(s) with features consistent with Marfan syndrome (Rybczynski M, et al. Am J Med Genet A. 2008 Dec 15;146A(24):3157-66; Söylen B, et al. Clin Genet. 2009 Mar;75(3):265-70. Epub 2009 Jan 20).This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This amino acid position is highly conserved in available vertebrate species. In addition to the clinical data presented in the literature, sequence variations that modify the initiation codon are expected to result in either loss of translation initiation, N-terminal truncation, or cause a shift in the mRNA reading frame. Based on the supporting evidence, this variant is interpreted as a disease-causing mutation.

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

Jun 27, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Cys89Tyr amino acid residue in FBN1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 19293843, 19720936; Invitae). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. ClinVar contains an entry for this variant (Variation ID: 577426). Disruption of the initiator codon has been observed in individuals with Marfan syndrome (PMID: 19012347; 19159394. 27906200). This variant is not present in population databases (gnomAD no frequency). This sequence change affects the initiator methionine of the FBN1 mRNA. The next in-frame methionine is located at codon 99.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.38	D
BayesDel_noAF	Pathogenic	0.30
CADD	Uncertain	23
DANN	Benign	0.93
DEOGEN2	Benign	0.33	T
Eigen	Benign	-0.024
Eigen_PC	Benign	0.097
FATHMM_MKL	Uncertain	0.83	D
LIST_S2	Uncertain	0.90	D
M_CAP	Pathogenic	0.77	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Benign	-0.44	T
PhyloP100		4.0
PROVEAN	Benign	-0.50	N
REVEL	Uncertain	0.36
Sift	Benign	0.65	T
Sift4G	Benign	0.40	T
Vest4		0.85
MutPred		0.98		Loss of MoRF binding (P = 0.0662)
MVP		0.97
ClinPred		0.93	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: rs730880097; hg19: chr15-48936966;