10-100989382-G-T

Variant names:

• chr10-100989382-G-T
• rs556445621
• NM_021830.5:c.1172G>T

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 5P and 1B. PM1 PM2 PP2 BP4

The NM_021830.5(TWNK):​c.1172G>T​(p.Arg391Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R391C) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TWNK NM_021830.5 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 2.65
• Publications: 16 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]

MRPL43 (HGNC:14517): (mitochondrial ribosomal protein L43) Mammalian mitochondrial ribosomal proteins are encoded by nuclear genes and help in protein synthesis within the mitochondrion. Mitochondrial ribosomes (mitoribosomes) consist of a small 28S subunit and a large 39S subunit. They have an estimated 75% protein to rRNA composition compared to prokaryotic ribosomes, where this ratio is reversed. Another difference between mammalian mitoribosomes and prokaryotic ribosomes is that the latter contain a 5S rRNA. Among different species, the proteins comprising the mitoribosome differ greatly in sequence, and sometimes in biochemical properties, which prevents easy recognition by sequence homology. This gene encodes a 39S subunit protein. This gene and the gene for a semaphorin class 4 protein (SEMA4G) overlap at map location 10q24.31 and are transcribed in opposite directions. Sequence analysis identified multiple transcript variants encoding at least four different protein isoforms. [provided by RefSeq, Jul 2008]

ACMG classification

Our verdict: Uncertain_significance. The variant received 4 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, 7 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.
• BP4: Computational evidence support a benign effect (MetaRNN=0.4134809).

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

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TWNK	NM_021830.5	MANE Select	c.1172G>T	p.Arg391Leu	missense	Exon 1 of 5	NP_068602.2
	TWNK	NM_001163812.2		c.1172G>T	p.Arg391Leu	missense	Exon 1 of 5	NP_001157284.1	Q96RR1-2
	TWNK	NM_001163813.2		c.-119-262G>T		intron	N/A	NP_001157285.1	A0A2R8Y4V4

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TWNK	ENST00000311916.8	TSL:1 MANE Select	c.1172G>T	p.Arg391Leu	missense	Exon 1 of 5	ENSP00000309595.2	Q96RR1-1
	TWNK	ENST00000370228.2	TSL:1	c.1172G>T	p.Arg391Leu	missense	Exon 1 of 5	ENSP00000359248.1	Q96RR1-2
	MRPL43	ENST00000858454.1		c.-306C>A		5_prime_UTR	Exon 1 of 4	ENSP00000528513.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

Alfa AF: 0.00000380 Hom.: 0

Bravo AF: 0.00000756

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.17
BayesDel_addAF	Uncertain	0.097	D
BayesDel_noAF	Benign	-0.10
CADD	Benign	19
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.72	D
Eigen	Benign	-0.31
Eigen_PC	Benign	-0.28
FATHMM_MKL	Uncertain	0.87	D
LIST_S2	Uncertain	0.93	D
M_CAP	Pathogenic	0.53	D
MetaRNN	Benign	0.41	T
MetaSVM	Uncertain	0.25	D
MutationAssessor	Benign	1.8	L
PhyloP100		2.7
PROVEAN	Uncertain	-4.2	D
REVEL	Uncertain	0.52
Sift	Uncertain	0.0050	D
Sift4G	Uncertain	0.0060	D
Polyphen		0.93	P
Vest4		0.34
MVP		0.39
MPC		0.81
ClinPred		0.70	D
GERP RS		3.2
Varity_R		0.23
gMVP		0.63
Mutation Taster		=49/51	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: rs556445621; hg19: chr10-102749139;