rs863223923

Variant names:

• chr10-100990461-G-A
• rs863223923
• NM_021830.5:c.1510G>A

Your query was ambiguous. Multiple possible variants found:

• chr10-100990461-G-A
• chr10-100990461-G-T

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM1 PM2 PP2 PP3_Moderate

The NM_021830.5(TWNK):​c.1510G>A​(p.Ala504Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000186 in 1,613,872 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. A504V) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TWNK NM_021830.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 9.92
• Publications: 1 publications found

Genes affected

TWNK (HGNC:1160): (twinkle mtDNA helicase) This gene encodes a hexameric DNA helicase which unwinds short stretches of double-stranded DNA in the 5' to 3' direction and, along with mitochondrial single-stranded DNA binding protein and mtDNA polymerase gamma, is thought to play a key role in mtDNA replication. The protein localizes to the mitochondrial matrix and mitochondrial nucleoids. Mutations in this gene cause infantile onset spinocerebellar ataxia (IOSCA) and progressive external ophthalmoplegia (PEO) and are also associated with several mitochondrial depletion syndromes. Alternative splicing results in multiple transcript variants encoding distinct isoforms.[provided by RefSeq, Aug 2009]

TWNK Gene-Disease associations (from GenCC):

• progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 3

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• mitochondrial DNA depletion syndrome 7 (hepatocerebral type)

  Inheritance: AR Classification: STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae)
• autosomal dominant progressive external ophthalmoplegia

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• mitochondrial DNA depletion syndrome, hepatocerebrorenal form

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Perrault syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 7 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 4 uncertain in NM_021830.5
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 36 curated pathogenic missense variants (we use a threshold of 10). The gene has 6 curated benign missense variants. Gene score misZ: 1.6071 (below the threshold of 3.09). Trascript score misZ: 2.58 (below the threshold of 3.09). GenCC associations: The gene is linked to progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 3, mitochondrial DNA depletion syndrome 7 (hepatocerebral type), Perrault syndrome, autosomal dominant progressive external ophthalmoplegia, mitochondrial DNA depletion syndrome, hepatocerebrorenal form.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.901

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TWNK	NM_021830.5	c.1510G>A	p.Ala504Thr	missense_variant	Exon 3 of 5	ENST00000311916.8	NP_068602.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TWNK	ENST00000311916.8	c.1510G>A	p.Ala504Thr	missense_variant	Exon 3 of 5	1	NM_021830.5	ENSP00000309595.2

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152202 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000483

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461670 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727150

⚠️ 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: 33476

American (AMR) AF: 0.0000224 AC: 1 AN: 44718

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: 86240

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53402

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111844

Other (OTH) AF: 0.00 AC: 0 AN: 60390

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152202 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74354

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

African (AFR) AF: 0.0000483 AC: 2 AN: 41436

American (AMR) AF: 0.00 AC: 0 AN: 15280

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5202

South Asian (SAS) AF: 0.00 AC: 0 AN: 4830

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10624

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68038

Other (OTH) AF: 0.00 AC: 0 AN: 2092

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0.00233887), which strongly suggests a high chance of mosaicism in these individuals.

Alfa AF: 0.0000155 Hom.: 0

Bravo AF: 0.0000151

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:3

Oct 03, 2022

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. This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 504 of the TWNK protein (p.Ala504Thr). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This variant has not been reported in the literature in individuals affected with TWNK-related conditions. ClinVar contains an entry for this variant (Variation ID: 214188). 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 TWNK protein function. -

Mar 17, 2021

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at a significant frequency in large population cohorts (Lek et al., 2016); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Has not been previously published as pathogenic or benign to our knowledge -

Dec 29, 2017

Athena Diagnostics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.52
BayesDel_addAF	Pathogenic	0.52	D
BayesDel_noAF	Pathogenic	0.50
CADD	Pathogenic	30
DANN	Pathogenic	1.0
DEOGEN2	Uncertain	0.78	.;D;.;.
Eigen	Pathogenic	0.91
Eigen_PC	Pathogenic	0.88
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	0.98	D;D;D;D
M_CAP	Pathogenic	0.50	D
MetaRNN	Pathogenic	0.90	D;D;D;D
MetaSVM	Pathogenic	0.93	D
MutationAssessor	Pathogenic	3.1	.;M;M;.
PhyloP100		9.9
PROVEAN	Uncertain	-3.6	.;D;D;.
REVEL	Pathogenic	0.88
Sift	Pathogenic	0.0	.;D;D;.
Sift4G	Uncertain	0.0050	.;D;D;.
Polyphen		1.0, 1.0	.;D;D;.
Vest4		0.96, 0.96
MVP		0.97
MPC		1.4
ClinPred		1.0	D
GERP RS		5.7
Varity_R		0.82
gMVP		0.81
Mutation Taster		=37/63	disease causing

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: rs863223923; hg19: chr10-102750218;