chr9-135778469-C-T

Variant names:

• chr9-135778469-C-T
• rs1554777911
• NM_020822.3:c.2568C>T

Variant summary

Our verdict is Benign. The variant received -9 ACMG points: 2P and 11B. PM2 BP4_Moderate BP6_Very_Strong BP7

The NM_020822.3(KCNT1):​c.2568C>T​(p.Val856Val) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000128 in 1,558,018 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 Likely benign (★★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 33)
  • Exomes 𝑓: 7.1e-7 (0 hom.)
• Consequence: KCNT1 NM_020822.3 synonymous
• Clinical Significance: Likely benign criteria provided, multiple submitters, no conflicts B:2
• Conservation: PhyloP100: 0.685
• Publications: 0 publications found

Genes affected

KCNT1 (HGNC:18865): (potassium sodium-activated channel subfamily T member 1) Potassium channels represent the most complex class of voltage-gated ion channels from both functional and structural standpoints. Their diverse functions include regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction, and cell volume. This gene encodes a sodium-activated potassium channel subunit which is thought to function in ion conductance and developmental signaling pathways. Mutations in this gene cause the early-onset epileptic disorders, malignant migrating partial seizures of infancy and autosomal dominant nocturnal frontal lobe epilepsy. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Dec 2012]

KCNT1 Gene-Disease associations (from GenCC):

• childhood-onset epilepsy syndrome

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• developmental and epileptic encephalopathy, 14

  Inheritance: AD Classification: DEFINITIVE, STRONG, MODERATE Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics, G2P
• malignant migrating partial seizures of infancy

  Inheritance: AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: G2P, Orphanet
• autosomal dominant nocturnal frontal lobe epilepsy 5

  Inheritance: AD Classification: STRONG, MODERATE Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
• autosomal dominant nocturnal frontal lobe epilepsy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Benign. The variant received -9 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.37).
• BP6: Variant 9-135778469-C-T is Benign according to our data. Variant chr9-135778469-C-T is described in ClinVar as Likely_benign. ClinVar VariationId is 540589.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• BP7: Synonymous conserved (PhyloP=0.685 with no splicing effect.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_020822.3. 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
	KCNT1	NM_020822.3	MANE Select	c.2568C>T	p.Val856Val	synonymous	Exon 22 of 31	NP_065873.2
	KCNT1	NM_001272003.2		c.2433C>T	p.Val811Val	synonymous	Exon 21 of 31	NP_001258932.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNT1	ENST00000371757.7	TSL:1 MANE Select	c.2568C>T	p.Val856Val	synonymous	Exon 22 of 31	ENSP00000360822.2
	KCNT1	ENST00000460750.5	TSL:1	n.*2178C>T		non_coding_transcript_exon	Exon 22 of 32	ENSP00000418777.1
	KCNT1	ENST00000460750.5	TSL:1	n.*2178C>T		3_prime_UTR	Exon 22 of 32	ENSP00000418777.1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152214 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

GnomAD4 exome AF: 7.11e-7 AC: 1 AN: 1405804 Hom.: 0 Cov.: 32 AF XY: 0.00000144 AC XY: 1 AN XY: 694200

African (AFR) AF: 0.00 AC: 0 AN: 31926

American (AMR) AF: 0.00 AC: 0 AN: 36276

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25208

East Asian (EAS) AF: 0.00 AC: 0 AN: 36248

South Asian (SAS) AF: 0.00 AC: 0 AN: 80152

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 49326

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5704

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1082684

Other (OTH) AF: 0.0000172 AC: 1 AN: 58280

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152214 Hom.: 0 Cov.: 33 AF XY: 0.0000134 AC XY: 1 AN XY: 74356

⚠️ 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: 41466

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

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

East Asian (EAS) AF: 0.00 AC: 0 AN: 5192

South Asian (SAS) AF: 0.00 AC: 0 AN: 4836

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: 68018

Other (OTH) AF: 0.00 AC: 0 AN: 2094

⚠️ 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: 0.0000340

ClinVar

Significance: Likely benign

Submissions summary: Benign:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Developmental and epileptic encephalopathy, 14;C3554306:Autosomal dominant nocturnal frontal lobe epilepsy 5 Benign:1

Nov 13, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

not provided Benign:1

Breakthrough Genomics, Breakthrough Genomics

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: not provided

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.21
BayesDel_noAF	Benign	-0.37
CADD	Benign	8.2
DANN	Benign	0.85
PhyloP100		0.69

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.070		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: rs1554777911; hg19: chr9-138670315;