rs8192303

Variant names:

• chr1-12004099-C-T
• rs8192303
• NM_014874.4:c.1268C>T

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 3P and 0B. PM2 PP2

The NM_014874.4(MFN2):​c.1268C>T​(p.Thr423Met) variant causes a missense change. The variant allele was found at a frequency of 0.00000205 in 1,461,812 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. T423A) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: MFN2 NM_014874.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.80
• Publications: 5 publications found

Genes affected

MFN2 (HGNC:16877): (mitofusin 2) This gene encodes a mitochondrial membrane protein that participates in mitochondrial fusion and contributes to the maintenance and operation of the mitochondrial network. This protein is involved in the regulation of vascular smooth muscle cell proliferation, and it may play a role in the pathophysiology of obesity. Mutations in this gene cause Charcot-Marie-Tooth disease type 2A2, and hereditary motor and sensory neuropathy VI, which are both disorders of the peripheral nervous system. Defects in this gene have also been associated with early-onset stroke. Two transcript variants encoding the same protein have been identified. [provided by RefSeq, Jul 2008]

MFN2 Gene-Disease associations (from GenCC):

• neuropathy, hereditary motor and sensory, type 6A

  Inheritance: AD Classification: DEFINITIVE Submitted by: G2P
• Charcot-Marie-Tooth disease, axonal, autosomal recessive, type 2a2b;

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P
• axonal hereditary motor and sensory neuropathy

  Inheritance: SD Classification: DEFINITIVE Submitted by: ClinGen
• Charcot-Marie-Tooth disease type 2A2

  Inheritance: AD Classification: STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae)
• hereditary motor and sensory neuropathy type 6

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• multiple symmetric lipomatosis

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• severe early-onset axonal neuropathy due to MFN2 deficiency

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the MFN2 gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 123 curated pathogenic missense variants (we use a threshold of 10). The gene has 23 curated benign missense variants. Gene score misZ: 1.6575 (below the threshold of 3.09). Trascript score misZ: 3.2174 (above the threshold of 3.09). GenCC associations: The gene is linked to Charcot-Marie-Tooth disease type 2A2, Charcot-Marie-Tooth disease, axonal, autosomal recessive, type 2a2b;, severe early-onset axonal neuropathy due to MFN2 deficiency, hereditary motor and sensory neuropathy type 6, axonal hereditary motor and sensory neuropathy, multiple symmetric lipomatosis, neuropathy, hereditary motor and sensory, type 6A.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MFN2	NM_014874.4	c.1268C>T	p.Thr423Met	missense_variant	Exon 12 of 19	ENST00000235329.10	NP_055689.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MFN2	ENST00000235329.10	c.1268C>T	p.Thr423Met	missense_variant	Exon 12 of 19	1	NM_014874.4	ENSP00000235329.5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461812 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727222

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33478

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86252

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53406

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5730

European-Non Finnish (NFE) AF: 0.00000270 AC: 3 AN: 1111994

Other (OTH) AF: 0.00 AC: 0 AN: 60394

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.00131091), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Charcot-Marie-Tooth disease type 2 Uncertain:1

Oct 13, 2020

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C15"). This variant has not been reported in the literature in individuals with MFN2-related conditions. ClinVar contains an entry for this variant (Variation ID: 221059). This variant is not present in population databases (ExAC no frequency). This sequence change replaces threonine with methionine at codon 423 of the MFN2 protein (p.Thr423Met). The threonine residue is highly conserved and there is a moderate physicochemical difference between threonine and methionine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.39
BayesDel_addAF	Pathogenic	0.26	D
BayesDel_noAF	Uncertain	0.13
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.45	T;T
Eigen	Uncertain	0.60
Eigen_PC	Uncertain	0.61
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	0.98	D;.
M_CAP	Uncertain	0.11	D
MetaRNN	Uncertain	0.74	D;D
MetaSVM	Uncertain	0.28	D
MutationAssessor	Uncertain	2.3	M;M
PhyloP100		5.8
PrimateAI	Uncertain	0.75	T
PROVEAN	Benign	-2.0	N;N
REVEL	Uncertain	0.56
Sift	Uncertain	0.010	D;D
Sift4G	Uncertain	0.030	D;D
Polyphen		0.97	D;D
Vest4		0.73
MutPred		0.43		Loss of helix (P = 0.0104);Loss of helix (P = 0.0104);
MVP		0.83
MPC		0.61
ClinPred		0.96	D
GERP RS		5.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.14
gMVP		0.89
Mutation Taster		=74/26	polymorphism

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: rs8192303; hg19: chr1-12064156; COSMIC: COSV99336578;