chr8-72936274-C-T

Position:

• chr8-72936274-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 6P and 4B. PM2 PP3_Strong BS2

The NM_004770.3(KCNB2):​c.919C>T​(p.Arg307Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000342 in 1,461,856 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: KCNB2 NM_004770.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.16

Genes affected

KCNB2 (HGNC:6232): (potassium voltage-gated channel subfamily B member 2) Voltage-gated potassium (Kv) 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. Four sequence-related potassium channel genes - shaker, shaw, shab, and shal - have been identified in Drosophila, and each has been shown to have human homolog(s). This gene encodes a member of the potassium channel, voltage-gated, shab-related subfamily. This member is a delayed rectifier potassium channel. The gene is expressed in gastrointestinal smooth muscle cells. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.978
• BS2: High AC in GnomAdExome4 at 5 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KCNB2	NM_004770.3	c.919C>T	p.Arg307Cys	missense_variant	3/3	ENST00000523207.2	NP_004761.2
KCNB2	XM_017013982.2	c.184C>T	p.Arg62Cys	missense_variant	2/2		XP_016869471.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KCNB2	ENST00000523207.2	c.919C>T	p.Arg307Cys	missense_variant	3/3	1	NM_004770.3	ENSP00000430846.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1461856 Hom.: 0 Cov.: 33 AF XY: 0.00000413 AC XY: 3 AN XY: 727230

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.0000383

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000360

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

May 26, 2023

The c.919C>T (p.R307C) alteration is located in exon 3 (coding exon 2) of the KCNB2 gene. This alteration results from a C to T substitution at nucleotide position 919, causing the arginine (R) at amino acid position 307 to be replaced by a cysteine (C). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.52
CADD	Pathogenic	27
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.92	D
Eigen	Pathogenic	0.77
Eigen_PC	Uncertain	0.64
FATHMM_MKL	Uncertain	0.84	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.83	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	0.97	D
MutationAssessor	Pathogenic	3.8	H
PrimateAI	Pathogenic	0.94	D
PROVEAN	Pathogenic	-8.0	D
REVEL	Pathogenic	0.90
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.95
MutPred		0.80		Loss of MoRF binding (P = 0.0922);
MVP		1.0
MPC		1.8
ClinPred		1.0	D
GERP RS		3.8
Varity_R		0.85
gMVP		0.99

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

Publications

LitVar

Other links and lift over

dbSNP: rs867030236; hg19: chr8-73848509; COSMIC: COSV73049898;