17-18274818-CA-C

Variant names:

• chr17-18274818-CA-C
• rs777850988
• NM_004618.5:c.2989delT

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PVS1_Moderate

The NM_004618.5(TOP3A):​c.2989delT​(p.Cys997ValfsTer11) variant causes a frameshift change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000204 in 1,614,008 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.00016 (0 hom., cov: 30)
  • Exomes 𝑓: 0.0000062 (0 hom.)
• Consequence: TOP3A NM_004618.5 frameshift
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.59
• Publications: 2 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: Ambry Genetics, PanelApp Australia, Labcorp Genetics (formerly Invitae), 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: Uncertain_significance. The variant received 2 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.00566 CDS is truncated, and there are 0 pathogenic variants in the truncated region.

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.2989delT	p.Cys997ValfsTer11	frameshift	Exon 19 of 19	NP_004609.1	Q13472-1
	TOP3A	NM_001320759.2		c.2704delT	p.Cys902ValfsTer11	frameshift	Exon 18 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.2989delT	p.Cys997ValfsTer11	frameshift	Exon 19 of 19	ENSP00000321636.5	Q13472-1
	TOP3A	ENST00000580095.5	TSL:1	c.2914delT	p.Cys972ValfsTer5	frameshift	Exon 19 of 19	ENSP00000462790.1	Q13472-2
	TOP3A	ENST00000924978.1		c.3145delT	p.Cys1049ValfsTer11	frameshift	Exon 20 of 20	ENSP00000595037.1

Frequencies

GnomAD3 genomes AF: 0.000158 AC: 24 AN: 152182 Hom.: 0 Cov.: 30

Gnomad AFR AF: 0.000555

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

GnomAD2 exomes AF: 0.0000398 AC: 10 AN: 251346 AF XY: 0.0000147

Gnomad AFR exome AF: 0.000554

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.00

Gnomad EAS 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: 0.00000616 AC: 9 AN: 1461826 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 727216

African (AFR) AF: 0.000239 AC: 8 AN: 33480

American (AMR) AF: 0.0000224 AC: 1 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26128

East Asian (EAS) AF: 0.00 AC: 0 AN: 39696

South Asian (SAS) AF: 0.00 AC: 0 AN: 86244

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53416

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111984

Other (OTH) AF: 0.00 AC: 0 AN: 60390

GnomAD4 genome AF: 0.000158 AC: 24 AN: 152182 Hom.: 0 Cov.: 30 AF XY: 0.000161 AC XY: 12 AN XY: 74338

African (AFR) AF: 0.000555 AC: 23 AN: 41440

American (AMR) AF: 0.0000654 AC: 1 AN: 15284

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5196

South Asian (SAS) AF: 0.00 AC: 0 AN: 4832

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10610

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

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68032

Other (OTH) AF: 0.00 AC: 0 AN: 2090

Alfa AF: 0.0000712 Hom.: 0

Bravo AF: 0.000159

ClinVar

ClinVar submissions

Significance: Uncertain significance

Revision: criteria provided, single submitter

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

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		8.6
Mutation Taster		=24/176	disease causing (ClinVar)

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: rs777850988; hg19: chr17-18178132;