rs749196340

chr15-48474302-C-Achr15-48474302-C-Gchr15-48474302-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate

The NM_000138.5(FBN1):c.4163G>T(p.Arg1388Leu) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,792 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 Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R1388H) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 4.77

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 Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 10 uncertain 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 chr15-48474302-C-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 495605.We mark this variant Likely_pathogenic, oryginal submissions are: {Pathogenic=1, Uncertain_significance=1}.
• PP2: Missense variant where missense usually causes diseases, FBN1
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.919

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FBN1	NM_000138.5	c.4163G>T	p.Arg1388Leu	missense_variant	34/66	ENST00000316623.10
FBN1	NM_001406716.1	c.4163G>T	p.Arg1388Leu	missense_variant	33/65

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FBN1	ENST00000316623.10	c.4163G>T	p.Arg1388Leu	missense_variant	34/66	1	NM_000138.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461792 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727204

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Marfan syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Victorian Clinical Genetics Services, Murdoch Childrens Research Institute

Feb 02, 2022

Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as VUS-3B. Following criteria are met: 0103 - Dominant negative and loss of function are known mechanisms of disease in this gene and are associated with FBN1 -related disease. Variants predicted to result in nonsense mediated decay cause loss of function effects, and are more commonly associated with severe Marfan syndrome (MIM#154700). Missense variants with both dominant negative and loss of function effects on protein function, are associated with Marfan syndrome and ectopia lentis (MIM#129600) (OMIM, PMID: 29357934). The exact genotype-phenotype correlation for this gene is still unclear, and is compounded by variable expressivity (PMID: 20301510). (I) 0107 - This gene is predominantly associated with autosomal dominant disease; autosomal recessive forms of Marfan syndrome have been reported infrequently (PMID: 27274304; 31950671). 0115 - Variants in this gene are known to have variable expressivity. The genotype-phenotype correlations for this gene are unclear, with single variants reported in patients with a range of phenotypes (PMID: 20301510, OMIM). (I) 0200 - Variant is predicted to result in a missense amino acid change from arginine to leucine. (I) 0251 - This variant is heterozygous. (I) 0301 - Variant is absent from gnomAD (both v2 and v3). (SP) 0309 - Alternative amino acid changes at the same position have been observed in gnomAD (v2, v3) (6 heterozygotes, 0 homozygotes). (I) 0501 - Missense variant consistently predicted to be damaging by multiple in silico tools or highly conserved with a major amino acid change. (SP) 0600 - Variant is located in the annotated EGF-like repeat domain 23 (UniProt, NCBI). (I) 0710 - Other missense variants comparable to the one identified in this case have inconclusive previous evidence for pathogenicity. These alternative changes (p.(Arg1388Cys), p.(Arg1388His), p.(Arg1388Pro)) have been reported as VUS, and observed in an individual with sudden unexplained death and another individual with Stanford type A aortic dissection (ClinVar, PMID: 34422331, PMID: 27930701)] (I) 0809 - Previous evidence of pathogenicity for this variant is inconclusive. This variant has been reported as a VUS (ClinVar). (I) 0905 - No published segregation evidence has been identified for this variant. (I) 1007 - No published functional evidence has been identified for this variant. (I) 1208 - Inheritance information for this variant is not currently available in this individual. (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -

Familial thoracic aortic aneurysm and aortic dissection Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Color Diagnostics, LLC DBA Color Health

May 15, 2019

- -

Marfan syndrome;C0265287:Acromicric dysplasia;C1858556:MASS syndrome;C1861456:Stiff skin syndrome;C1869115:Weill-Marchesani syndrome 2, dominant;C3280054:Geleophysic dysplasia 2;C3541518:Ectopia lentis 1, isolated, autosomal dominant;C4310796:Progeroid and marfanoid aspect-lipodystrophy syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 12, 2021

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.35
BayesDel_addAF	Pathogenic	0.30	D
BayesDel_noAF	Pathogenic	0.20
Cadd	Pathogenic	29
Dann	Benign	0.95
Eigen	Uncertain	0.35
Eigen_PC	Uncertain	0.40
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.88	D
M_CAP	Uncertain	0.24	D
MetaRNN	Pathogenic	0.92	D
MetaSVM	Uncertain	0.48	D
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.62	T
PROVEAN	Pathogenic	-5.5	D
REVEL	Pathogenic	0.79
Sift	Uncertain	0.0040	D
Sift4G	Uncertain	0.040	D
Vest4		0.88
MutPred		0.70		Gain of ubiquitination at K1392 (P = 0.0754);
MVP		0.96
MPC		0.71
ClinPred		0.98	D
GERP RS		4.4

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: rs749196340; hg19: chr15-48766499;