rs111033573

Positions:

• chr10-100989285-G-A
• chr10-100989285-G-T

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PM1 PM2 PP3_Strong PP5_Very_Strong

The NM_021830.5(TWNK):​c.1075G>A​(p.Ala359Thr) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,461,860 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 Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TWNK NM_021830.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 4.22

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 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 16 ACMG points.

• PM1: In a region_of_interest Required for hexamers formation and DNA helicase activity (size 251) in uniprot entity PEO1_HUMAN there are 18 pathogenic changes around while only 2 benign (90%) in NM_021830.5
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.966
• PP5: Variant 10-100989285-G-A is Pathogenic according to our data. Variant chr10-100989285-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 4618.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TWNK	NM_021830.5	c.1075G>A	p.Ala359Thr	missense_variant	1/5	ENST00000311916.8	NP_068602.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TWNK	ENST00000311916.8	c.1075G>A	p.Ala359Thr	missense_variant	1/5	1	NM_021830.5	ENSP00000309595.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461860 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727230

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000252

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 3 Pathogenic:3

Pathogenic, no assertion criteria provided	literature only	OMIM	Sep 24, 2010	- -
Pathogenic, criteria provided, single submitter	clinical testing	Suma Genomics	-	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	3billion	Jan 03, 2022	Same nucleotide change resulting in same amino acid change has been previously reported to be associated with TWNK related disorder (ClinVar ID: VCV000004618, PMID:11431692, PS1_P). The variant is located in a well-established functional domain or exonic hotspot, where pathogenic variants have frequently reported (PM1_M). In silico tool predictions suggest damaging effect of the variant on gene or gene product (REVEL: 0.806, 3CNET: 0.904, PP3_P). A missense variant is a common mechanism associated with Progressive external ophthalmoplegia with mitochondrial DNA deletions (PP2_P). It is not observed in the gnomAD v2.1.1 dataset (PM2_M). Therefore, this variant is classified as likely pathogenic according to the recommendation of ACMG/AMP guideline. -

Mitochondrial disease Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

Wellcome Centre for Mitochondrial Research, Newcastle University

Apr 07, 2017

- -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 10, 2023

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 359 of the TWNK protein (p.Ala359Thr). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with autosomal dominant progressive external ophthalmoplegia (PMID: 11431692, 24076137). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 4618). 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 with a positive predictive value of 95%. Experimental studies have shown that this missense change affects TWNK function (PMID: 20659899). This variant disrupts the p.Ala359 amino acid residue in TWNK. Other variant(s) that disrupt this residue have been determined to be pathogenic (Invitae). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.24
BayesDel_addAF	Pathogenic	0.38	D
BayesDel_noAF	Pathogenic	0.31
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.52	D;.
Eigen	Uncertain	0.68
Eigen_PC	Pathogenic	0.67
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Uncertain	0.88	D;D
M_CAP	Pathogenic	0.64	D
MetaRNN	Pathogenic	0.97	D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	3.3	M;M
PrimateAI	Uncertain	0.49	T
PROVEAN	Uncertain	-3.2	D;D
REVEL	Pathogenic	0.81
Sift	Uncertain	0.0030	D;D
Sift4G	Uncertain	0.0060	D;D
Polyphen		0.99	D;D
Vest4		0.49
MutPred		0.83		Gain of relative solvent accessibility (P = 0.0249);Gain of relative solvent accessibility (P = 0.0249);
MVP		0.98
MPC		1.4
ClinPred		0.97	D
GERP RS		5.9
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.40
gMVP		0.93

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: rs111033573; hg19: chr10-102749042; COSMIC: COSV52966945; COSMIC: COSV52966945;