17-18302700-G-A

Variant names:

• chr17-18302700-G-A
• rs1163645463
• NM_004618.5:c.523C>T
• TOP3A p.Arg175*

Variant summary

Our verdict is Pathogenic. The variant received 10 ACMG points: 10P and 0B. PVS1 PM2

The NM_004618.5(TOP3A):​c.523C>T​(p.Arg175*) variant causes a stop gained change. The variant allele was found at a frequency of 0.00000434 in 1,613,808 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. R175R) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000041 (0 hom.)
• Consequence: TOP3A NM_004618.5 stop_gained
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 4.00
• Publications: 0 publications found

Genes affected

TOP3A (HGNC:11992): (DNA topoisomerase III alpha) This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This enzyme catalyzes the transient breaking and rejoining of a single strand of DNA which allows the strands to pass through one another, thus reducing the number of supercoils and altering the topology of DNA. This enzyme forms a complex with BLM which functions in the regulation of recombination in somatic cells. Alternative splicing results in multiple transcript variants encoding different isoforms. [provided by RefSeq, Mar 2016]

TOP3A Gene-Disease associations (from GenCC):

• microcephaly, growth restriction, and increased sister chromatid exchange 2

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: PanelApp Australia, Labcorp Genetics (formerly Invitae), Ambry Genetics, G2P
• progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal recessive 5

  Inheritance: AR Classification: STRONG, LIMITED Submitted by: PanelApp Australia, Labcorp Genetics (formerly Invitae)

ACMG classification

Our verdict: Pathogenic. The variant received 10 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_004618.5. 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
	TOP3A	NM_004618.5	MANE Select	c.523C>T	p.Arg175*	stop_gained	Exon 6 of 19	NP_004609.1	Q13472-1
	TOP3A	NM_001320759.2		c.238C>T	p.Arg80*	stop_gained	Exon 5 of 18	NP_001307688.1	Q13472-3

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TOP3A	ENST00000321105.10	TSL:1 MANE Select	c.523C>T	p.Arg175*	stop_gained	Exon 6 of 19	ENSP00000321636.5	Q13472-1
	TOP3A	ENST00000580095.5	TSL:1	c.448C>T	p.Arg150*	stop_gained	Exon 6 of 19	ENSP00000462790.1	Q13472-2
	TOP3A	ENST00000924978.1		c.523C>T	p.Arg175*	stop_gained	Exon 6 of 20	ENSP00000595037.1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152100 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

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: 0.0000147

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000410 AC: 6 AN: 1461708 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727132

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86252

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53396

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000450 AC: 5 AN: 1111872

Other (OTH) AF: 0.0000166 AC: 1 AN: 60384

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152100 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74286

African (AFR) AF: 0.00 AC: 0 AN: 41420

American (AMR) AF: 0.00 AC: 0 AN: 15264

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3464

East Asian (EAS) AF: 0.00 AC: 0 AN: 5178

South Asian (SAS) AF: 0.00 AC: 0 AN: 4824

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10612

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000147 AC: 1 AN: 68022

Other (OTH) AF: 0.00 AC: 0 AN: 2088

Alfa AF: 0.0000283 Hom.: 0

Bravo AF: 0.00000378

ClinVar

ClinVar submissions

Significance: Pathogenic

Revision: criteria provided, single submitter

Pathogenic	VUS	Benign	Condition
1	-	-	not provided (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.61	D
BayesDel_noAF	Pathogenic	0.63
CADD	Pathogenic	37
DANN	Uncertain	1.0
Eigen	Pathogenic	0.69
Eigen_PC	Uncertain	0.55
FATHMM_MKL	Uncertain	0.95	D
PhyloP100		4.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Mutation Taster		=2/198	disease causing (fs/PTC)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.16		Details are displayed if max score is > 0.2

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

MaxEntScan Visualizer can be used to analyze the impact of this mutation on the neighboring sequence.

Other links and lift over

dbSNP: rs1163645463;

hg19: chr17-18206014;

COSMIC: COSV58179529;

COSMIC: COSV58179529;