NM_021830.5:c.1084G>C

Variant names:

• chr10-100989294-G-C
• rs1554887075
• NM_021830.5:c.1084G>C

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.1084G>C​(p.Ala362Pro) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: TWNK NM_021830.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.95
• Publications: 0 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 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 8 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, 0.876

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_021830.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TWNK	NM_021830.5	MANE Select	c.1084G>C	p.Ala362Pro	missense	Exon 1 of 5	NP_068602.2
	TWNK	NM_001163812.2		c.1084G>C	p.Ala362Pro	missense	Exon 1 of 5	NP_001157284.1
	TWNK	NR_160738.1		n.1752G>C		non_coding_transcript_exon	Exon 1 of 5

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TWNK	ENST00000311916.8	TSL:1 MANE Select	c.1084G>C	p.Ala362Pro	missense	Exon 1 of 5	ENSP00000309595.2
	TWNK	ENST00000370228.2	TSL:1	c.1084G>C	p.Ala362Pro	missense	Exon 1 of 5	ENSP00000359248.1
	TWNK	ENST00000643860.1		n.1084G>C		non_coding_transcript_exon	Exon 1 of 5	ENSP00000494389.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Apr 14, 2017

Athena Diagnostics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.41
BayesDel_addAF	Pathogenic	0.51	D
BayesDel_noAF	Pathogenic	0.50
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Benign	0.32	T
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.86
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.92	D
M_CAP	Pathogenic	0.39	D
MetaRNN	Pathogenic	0.88	D
MetaSVM	Pathogenic	0.95	D
MutationAssessor	Uncertain	2.9	M
PhyloP100		9.9
PROVEAN	Uncertain	-2.9	D
REVEL	Pathogenic	0.79
Sift	Benign	0.046	D
Sift4G	Uncertain	0.050	T
Polyphen		1.0	D
Vest4		0.94
MutPred		0.54		Gain of helix (P = 0.0082)
MVP		0.98
MPC		1.0
ClinPred		0.98	D
GERP RS		5.9
Varity_R		0.86
gMVP		0.96
Mutation Taster		=12/88	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1554887075; hg19: chr10-102749051;