NM_004519.4:c.1045-4C>T

Variant names:

• chr8-132172697-G-A
• rs777650536
• NM_004519.4:c.1045-4C>T

Variant summary

Our verdict is Benign. The variant received -16 ACMG points: 0P and 16B. BP4_Strong BP6_Very_Strong BS1

The NM_004519.4(KCNQ3):​c.1045-4C>T variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000149 in 1,611,396 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Likely benign (★★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000016 (0 hom.)
• Consequence: KCNQ3 NM_004519.4 splice_region, intron
• Scores: Splicing: ADA: 0.00005839
• Clinical Significance: Likely benign criteria provided, multiple submitters, no conflicts B:2
• Conservation: PhyloP100: -0.102
• Publications: 0 publications found

Genes affected

KCNQ3 (HGNC:6297): (potassium voltage-gated channel subfamily Q member 3) This gene encodes a protein that functions in the regulation of neuronal excitability. The encoded protein forms an M-channel by associating with the products of the related KCNQ2 or KCNQ5 genes, which both encode integral membrane proteins. M-channel currents are inhibited by M1 muscarinic acetylcholine receptors and are activated by retigabine, a novel anti-convulsant drug. Defects in this gene are a cause of benign familial neonatal convulsions type 2 (BFNC2), also known as epilepsy, benign neonatal type 2 (EBN2). Alternative splicing of this gene results in multiple transcript variants. [provided by RefSeq, May 2014]

KCNQ3 Gene-Disease associations (from GenCC):

• seizures, benign familial neonatal, 2

  Inheritance: AD Classification: STRONG, MODERATE Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
• benign familial infantile epilepsy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• benign neonatal seizures

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• genetic developmental and epileptic encephalopathy

  Inheritance: AR Classification: LIMITED Submitted by: Ambry Genetics

ACMG classification

Our verdict: Benign. The variant received -16 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.72).
• BP6: Variant 8-132172697-G-A is Benign according to our data. Variant chr8-132172697-G-A is described in ClinVar as Likely_benign. ClinVar VariationId is 413256.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• BS1: Variant frequency is greater than expected in population amr. GnomAdExome4 allele frequency = 0.0000158 (23/1459162) while in subpopulation AMR AF = 0.000492 (22/44720). AF 95% confidence interval is 0.000333. There are 0 homozygotes in GnomAdExome4. There are 10 alleles in the male GnomAdExome4 subpopulation. Median coverage is 31. This position passed quality control check.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_004519.4. 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
	KCNQ3	NM_004519.4	MANE Select	c.1045-4C>T		splice_region intron	N/A	NP_004510.1
	KCNQ3	NM_001204824.2		c.685-4C>T		splice_region intron	N/A	NP_001191753.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNQ3	ENST00000388996.10	TSL:1 MANE Select	c.1045-4C>T		splice_region intron	N/A	ENSP00000373648.3
	KCNQ3	ENST00000519445.5	TSL:5	c.1045-4C>T		splice_region intron	N/A	ENSP00000428790.1
	KCNQ3	ENST00000521134.6	TSL:2	c.685-4C>T		splice_region intron	N/A	ENSP00000429799.1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152234 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

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: 0.0000801 AC: 20 AN: 249800 AF XY: 0.0000592

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000549

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: 0.000164

GnomAD4 exome AF: 0.0000158 AC: 23 AN: 1459162 Hom.: 0 Cov.: 31 AF XY: 0.0000138 AC XY: 10 AN XY: 726054

African (AFR) AF: 0.00 AC: 0 AN: 33446

American (AMR) AF: 0.000492 AC: 22 AN: 44720

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26130

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

South Asian (SAS) AF: 0.00 AC: 0 AN: 86218

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 52320

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

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1110538

Other (OTH) AF: 0.0000166 AC: 1 AN: 60326

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152234 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74374

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 41468

American (AMR) AF: 0.0000654 AC: 1 AN: 15290

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3470

East Asian (EAS) AF: 0.00 AC: 0 AN: 5186

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

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10626

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

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68042

Other (OTH) AF: 0.00 AC: 0 AN: 2092

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.0000264

Asia WGS AF: 0.000289 AC: 1 AN: 3478

ClinVar

ClinVar submissions as Germline

Significance: Likely benign

Revision: criteria provided, multiple submitters, no conflicts

Pathogenic	VUS	Benign	Condition
-	-	1	Benign neonatal seizures (1)
-	-	1	not specified (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.72
CADD	Benign	4.1
DANN	Benign	0.72
PhyloP100		-0.10

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.000058
dbscSNV1_RF	Benign	0.012
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: rs777650536; hg19: chr8-133184944;