22-50579209-T-G

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_005198.5(CHKB):c.1160A>C(p.Gln387Pro) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000274 in 1,461,618 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/20 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: CHKB NM_005198.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.49

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:):

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.34584087).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CHKB	NM_005198.5	c.1160A>C	p.Gln387Pro	missense_variant	11/11	ENST00000406938.3
CHKB-CPT1B	NR_027928.2	n.1378A>C		non_coding_transcript_exon_variant	11/30

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CHKB	ENST00000406938.3	c.1160A>C	p.Gln387Pro	missense_variant	11/11	1	NM_005198.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461618 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 727090

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: 0.0000187

Gnomad4 NFE exome AF: 0.00000270

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

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jan 06, 2020

This sequence change replaces glutamine with proline at codon 387 of the CHKB protein (p.Gln387Pro). The glutamine residue is moderately conserved and there is a moderate physicochemical difference between glutamine and proline. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with CHKB-related conditions. 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, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Benign	0.0017	T
BayesDel_noAF	Benign	-0.24
Cadd	Uncertain	24
Dann	Uncertain	0.99
DEOGEN2	Benign	0.15	T
Eigen	Benign	0.037
Eigen_PC	Benign	0.10
FATHMM_MKL	Uncertain	0.91	D
LIST_S2	Benign	0.70	T
M_CAP	Benign	0.068	D
MetaRNN	Benign	0.35	T
MetaSVM	Benign	-0.79	T
MutationAssessor	Benign	2.0	M
MutationTaster	Benign	0.77	N;D
PrimateAI	Benign	0.36	T
PROVEAN	Benign	-1.4	N
REVEL	Benign	0.15
Sift	Uncertain	0.028	D
Sift4G	Benign	0.19	T
Polyphen		0.53	P
Vest4		0.46
MutPred		0.45		Gain of glycosylation at Q387 (P = 0.0405);
MVP		0.78
ClinPred		0.56	D
GERP RS		3.3
Varity_R		0.67
gMVP		0.55

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1389494045; hg19: chr22-51017638;