rs1555894697

Variant names:

• chr22-50581424-C-T
• rs1555894697
• NM_005198.5:c.577G>A

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_005198.5(CHKB):​c.577G>A​(p.Glu193Lys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,460,938 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: CHKB NM_005198.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.29

Genes affected

CHKB (HGNC:1938): (choline kinase beta) Choline kinase (CK) and ethanolamine kinase (EK) catalyze the phosphorylation of choline/ethanolamine to phosphocholine/phosphoethanolamine. This is the first enzyme in the biosynthesis of phosphatidylcholine/phosphatidylethanolamine in all animal cells. The highly purified CKs from mammalian sources and their recombinant gene products have been shown to have EK activity also, indicating that both activities reside on the same protein. The choline kinase-like protein encoded by CHKL belongs to the choline/ethanolamine kinase family; however, its exact function is not known. Read-through transcripts are expressed from this locus that include exons from the downstream CPT1B locus. [provided by RefSeq, Jun 2009]

CHKB-CPT1B (HGNC:41998): (CHKB-CPT1B readthrough (NMD candidate)) The genes CHKB and CPT1B are adjacent on chromosome 22 and read-through transcripts are expressed that include exons from both loci. The read-through transcripts are candidates for nonsense-mediated mRNA decay (NMD) and are unlikely to express proteins. [provided by RefSeq, Jun 2009]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CHKB	NM_005198.5	c.577G>A	p.Glu193Lys	missense_variant	Exon 4 of 11	ENST00000406938.3	NP_005189.2
CHKB-CPT1B	NR_027928.2	n.795G>A		non_coding_transcript_exon_variant	Exon 4 of 30

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CHKB	ENST00000406938.3	c.577G>A	p.Glu193Lys	missense_variant	Exon 4 of 11	1	NM_005198.5	ENSP00000384400.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1460938 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 726716

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

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

Megaconial type congenital muscular dystrophy Uncertain:1

Jun 27, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated. This sequence change replaces glutamic acid, which is acidic and polar, with lysine, which is basic and polar, at codon 193 of the CHKB protein (p.Glu193Lys). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with CHKB-related conditions. ClinVar contains an entry for this variant (Variation ID: 468475). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.18
BayesDel_addAF	Benign	-0.048	T
BayesDel_noAF	Benign	-0.31
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Benign	0.18	T
Eigen	Benign	0.012
Eigen_PC	Benign	0.16
FATHMM_MKL	Uncertain	0.91	D
LIST_S2	Uncertain	0.95	D
M_CAP	Benign	0.0090	T
MetaRNN	Uncertain	0.54	D
MetaSVM	Benign	-0.98	T
MutationAssessor	Benign	1.1	L
PrimateAI	Uncertain	0.56	T
PROVEAN	Uncertain	-2.4	N
REVEL	Benign	0.093
Sift	Benign	0.14	T
Sift4G	Benign	0.18	T
Polyphen		0.24	B
Vest4		0.64
MutPred		0.52		Gain of MoRF binding (P = 0.003);
MVP		0.74
ClinPred		0.87	D
GERP RS		5.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.58
gMVP		0.55

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: rs1555894697; hg19: chr22-51019853;