10-100988239-C-A

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_021830.5(TWNK):c.29C>A(p.Pro10His) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000031 in 1,614,064 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 12/20 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. P10P) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 33)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: TWNK NM_021830.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.916

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.19667143).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TWNK	NM_021830.5	c.29C>A	p.Pro10His	missense_variant	1/5	ENST00000311916.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TWNK	ENST00000311916.8	c.29C>A	p.Pro10His	missense_variant	1/5	1	NM_021830.5	P1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152248 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0000654

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

GnomAD3 exomes AF: 0.00000796 AC: 2 AN: 251348 Hom.: 0 AF XY: 0.0000147 AC XY: 2 AN XY: 135898

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000578

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461816 Hom.: 0 Cov.: 32 AF XY: 0.00000413 AC XY: 3 AN XY: 727210

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000894

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 AF: 0.00000657 AC: 1 AN: 152248 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74378

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.0000654

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000378

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jun 20, 2023

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. 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 not expected to disrupt TWNK protein function. This sequence change replaces proline, which is neutral and non-polar, with histidine, which is basic and polar, at codon 10 of the TWNK protein (p.Pro10His). This variant is present in population databases (rs777222632, gnomAD 0.006%). This variant has not been reported in the literature in individuals affected with TWNK-related conditions. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.14
BayesDel_addAF	Benign	-0.024	T
BayesDel_noAF	Benign	-0.10
Cadd	Benign	19
Dann	Benign	0.97
DEOGEN2	Benign	0.067	T;.
Eigen	Benign	-0.20
Eigen_PC	Benign	-0.16
FATHMM_MKL	Uncertain	0.76	D
LIST_S2	Benign	0.67	T;T
M_CAP	Uncertain	0.098	D
MetaRNN	Benign	0.20	T;T
MetaSVM	Uncertain	0.24	D
MutationAssessor	Uncertain	2.1	M;M
MutationTaster	Benign	0.98	N;N
PROVEAN	Benign	-0.070	N;N
REVEL	Uncertain	0.40
Sift	Benign	0.041	D;T
Sift4G	Benign	0.19	T;T
Polyphen		0.61	P;P
Vest4		0.47
MutPred		0.39		Loss of disorder (P = 0.047);Loss of disorder (P = 0.047);
MVP		0.31
MPC		1.3
ClinPred		0.34	T
GERP RS		3.9
Varity_R		0.058
gMVP		0.54

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: rs777222632; hg19: chr10-102747996;