7-44145637-G-C

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_000162.5(GCK):c.1113C>G(p.Cys371Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C371F) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: GCK NM_000162.5 missense
• Clinical Significance: Likely pathogenic reviewed by expert panel P:2 U:1
• Conservation: PhyloP100: 0.0240

Genes affected

GCK (HGNC:4195): (glucokinase) This gene encodes a member of the hexokinase family of proteins. Hexokinases phosphorylate glucose to produce glucose-6-phosphate, the first step in most glucose metabolism pathways. In contrast to other forms of hexokinase, this enzyme is not inhibited by its product glucose-6-phosphate but remains active while glucose is abundant. The use of multiple promoters and alternative splicing of this gene result in distinct protein isoforms that exhibit tissue-specific expression in the pancreas and liver. In the pancreas, this enzyme plays a role in glucose-stimulated insulin secretion, while in the liver, this enzyme is important in glucose uptake and conversion to glycogen. Mutations in this gene that alter enzyme activity have been associated with multiple types of diabetes and hyperinsulinemic hypoglycemia. [provided by RefSeq, Aug 2017]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PM1: In a hotspot region, there are 9 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 5 uncertain in NM_000162.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr7-44145638-C-A is described in ClinVar as [Pathogenic]. Clinvar id is 129140.Status of the report is reviewed_by_expert_panel, 3 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.993
• PP5: Variant 7-44145637-G-C is Pathogenic according to our data. Variant chr7-44145637-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 447379.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr7-44145637-G-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GCK	NM_000162.5	c.1113C>G	p.Cys371Trp	missense_variant	9/10	ENST00000403799.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GCK	ENST00000403799.8	c.1113C>G	p.Cys371Trp	missense_variant	9/10	1	NM_000162.5	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2 Uncertain:1

Revision: reviewed by expert panel

Submissions by phenotype

not provided Pathogenic:1 Uncertain:1

Likely pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Jul 16, 2019	Not found in the total gnomAD dataset, and the data is high quality (0/265258 chr). Found in at least one symptomatic patient. Predicted to have a damaging effect on the protein. One de novo case with parental identity confirmed. -
Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	May 04, 2021	This variant has been observed in individual(s) with autosomal dominant maturity-onset diabetes of the young (PMID: 19790256). ClinVar contains an entry for this variant (Variation ID: 447379). This variant is not present in population databases (ExAC no frequency). This sequence change replaces cysteine with tryptophan at codon 371 of the GCK protein (p.Cys371Trp). The cysteine residue is highly conserved and there is a large physicochemical difference between cysteine and tryptophan. 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 disruptive, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. -

Monogenic diabetes Pathogenic:1

Likely pathogenic, reviewed by expert panel

curation

ClinGen Monogenic Diabetes Variant Curation Expert Panel

Aug 09, 2023

The c.1113C>G variant in the glucokinase gene, GCK, causes an amino acid change of cysteine to tryptophan at codon 371 (p.(Cys371Trp)) of NM_000162.5. GCK is defined by the ClinGen MDEP VCEP as a gene that has a low rate of benign missense variation and where pathogenic missense variants are a common mechanism of disease (PP2). This variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.891, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant is absent from gnomAD v2.1.1 (PM2_Supporting). This variant was identified in an individual with a clinical history highly specific for GCK-hyperglycemia (FBG 5.5-8 mmol/L and HbA1c 5.6 - 7.6% and OGTT increment < 3 mmol/L and a 3-generation family history of diabetes) (PP4_Moderate; internal lab contributors). This variant was identified in three unrelated individuals with a clinical picture consistent with monogenic diabetes; however, PS4_Moderate cannot be applied because this number is below the MDEP threshold (internal lab contributors). This variant segregated with diabetes with one informative meiosis in a single family; however, this does not meet the thresholds for PP1 set by the ClinGen MDEP (PMID: 27236918; internal lab contributors). Another missense variant, c.1112G>T p.(Cys371Phe), has been interpreted as pathogenic by the ClinGen MDEP VCEP and p.Cys371Trp has a greater Grantham distance. (PM5). In summary, this variant meets the criteria to be classified as likely pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP VCEP (specification version 1.2.0 approved 6/7/2023): PP2, PP3, PM2_Supporting, PP4_Moderate, PM5 . -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.50	D
BayesDel_noAF	Pathogenic	0.49
Cadd	Uncertain	25
Dann	Uncertain	0.99
Eigen	Benign	0.18
Eigen_PC	Benign	0.0078
FATHMM_MKL	Uncertain	0.87	D
LIST_S2	Uncertain	0.94	D;D;D;.;D;D
M_CAP	Pathogenic	0.96	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.91	D
Sift4G	Pathogenic	0.0	D;D;D;D;D;D
Polyphen		1.0	D;.;D;D;D;D
Vest4		0.96
MutPred		0.96		.;.;Gain of MoRF binding (P = 0.0093);.;.;.;
MVP		0.97
MPC		2.6
ClinPred		1.0	D
GERP RS		0.73
Varity_R		0.99
gMVP		1.0

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: rs556581174; hg19: chr7-44185236;