NM_021830.5:c.-622C>T

Variant names:

• chr10-100987589-C-T
• rs993449080
• NM_021830.5:c.-622C>T

Variant summary

Our verdict is Likely benign. The variant received -4 ACMG points: 0P and 4B. BP4_Strong

The NM_021830.5(TWNK):​c.-622C>T variant causes a 5 prime UTR premature start codon gain change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000547 in 1,096,914 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000055 (0 hom.)
• Consequence: TWNK NM_021830.5 5_prime_UTR_premature_start_codon_gain
• Clinical Significance: Uncertain significance criteria provided, single submitter U:4
• Conservation: PhyloP100: -0.350
• 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]

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: Likely_benign. The variant received -4 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.92).

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.-622C>T		5_prime_UTR_premature_start_codon_gain	Exon 1 of 5	NP_068602.2
	TWNK	NM_021830.5	MANE Select	c.-622C>T		5_prime_UTR	Exon 1 of 5	NP_068602.2
	TWNK	NM_001163812.2		c.-622C>T		5_prime_UTR_premature_start_codon_gain	Exon 1 of 5	NP_001157284.1	Q96RR1-2

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TWNK	ENST00000311916.8	TSL:1 MANE Select	c.-622C>T		5_prime_UTR_premature_start_codon_gain	Exon 1 of 5	ENSP00000309595.2	Q96RR1-1
	TWNK	ENST00000370228.2	TSL:1	c.-622C>T		5_prime_UTR_premature_start_codon_gain	Exon 1 of 5	ENSP00000359248.1	Q96RR1-2
	TWNK	ENST00000311916.8	TSL:1 MANE Select	c.-622C>T		5_prime_UTR	Exon 1 of 5	ENSP00000309595.2	Q96RR1-1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000547 AC: 6 AN: 1096914 Hom.: 0 Cov.: 15 AF XY: 0.00000742 AC XY: 4 AN XY: 538982

African (AFR) AF: 0.00 AC: 0 AN: 24792

American (AMR) AF: 0.00 AC: 0 AN: 20928

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 18014

East Asian (EAS) AF: 0.00 AC: 0 AN: 34234

South Asian (SAS) AF: 0.00 AC: 0 AN: 59542

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 30462

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 3250

European-Non Finnish (NFE) AF: 0.00000699 AC: 6 AN: 858568

Other (OTH) AF: 0.00 AC: 0 AN: 47124

GnomAD4 genome Cov.: 33

ClinVar

ClinVar submissions

Significance: Uncertain significance

Revision: criteria provided, single submitter

Pathogenic	VUS	Benign	Condition
-	1	-	Autosomal recessive cerebellar ataxia (1)
-	1	-	Infantile onset spinocerebellar ataxia (1)
-	1	-	Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 3 (1)
-	1	-	Sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.92
CADD	Benign	5.8
DANN	Benign	0.96
PhyloP100		-0.35
PromoterAI		0.00050	Neutral

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs993449080; hg19: chr10-102747346;