chr7-44147732-C-G

Variant names:

• chr7-44147732-C-G
• rs104894008
• NM_000162.5:c.781G>C

Variant summary

Our verdict is Pathogenic. Variant got 13 ACMG points: 13P and 0B. PP4_Moderate PM2_Supporting PS3_Moderate PP2 PP3 PS1 PS4_Moderate

This summary comes from the ClinGen Evidence Repository: The c.781G>C variant in the glucokinase gene, GCK, causes an amino acid change of glycine to arginine at codon 261 (p.(Gly261Arg)) of NM_000162.5. GCK is defined by the ClinGen MDEP as a gene that has a low rate of benign missense variation and has pathogenic missense variants as a common mechanism of disease (PP2). This variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.914, which is greater than the MDEP threshold of 0.70 (PP3). 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 negative antibodies) (PP4_Moderate; internal lab contributors). This variant segregated with hyperglycemia with one informative meioses in a single family; however, this does not meet the thresholds for PP1 set by the ClinGen MDEP (PMID:27236918, internal lab contributors). This variant was identified in 5 unrelated individuals with hyperglycemia (PS4_Moderate; internal lab contributors). The nucleotide change c.781G>A, which causes the same amino acid change, has been classified as pathogenic by the ClinGen MDEP (PS1). A kinetic analysis of recombinant wild-type (WT) and mutant glucokinase demonstrated that the wild-type kinetic parameters pass the quality control, the wild-type ATP Km is between 0.4-0.65, and the p.Gly261Arg variant has a relative activity index (RAI) of 0.02, which is less than the MDEP VCEP threshold of 0.50 (PMID:19903754). In summary, the c.781G>C variant meets the criteria to be classified as pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP VCEP (specification version 1.3.0, approved 8/11/2023): PM2_Supporting, PP2, PP3, PS3_Moderate, PS1, PS4_Moderate, PP4_Moderate. LINK:https://erepo.genome.network/evrepo/ui/classification/CA367400571/MONDO:0015967/086

• Frequency: Genomes: not found (cov: 33)
• Consequence: GCK NM_000162.5 missense
• Clinical Significance: Pathogenic reviewed by expert panel P:4
• Conservation: PhyloP100: 7.83

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]

LOC105375258 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 13 ACMG points.

• PS1: For more information check the summary or visit ClinGen Evidence Repository.
• PS3: For more information check the summary or visit ClinGen Evidence Repository.
• PS4: For more information check the summary or visit ClinGen Evidence Repository.
• PM2: For more information check the summary or visit ClinGen Evidence Repository.
• PP2: For more information check the summary or visit ClinGen Evidence Repository.
• PP3: For more information check the summary or visit ClinGen Evidence Repository.
• PP4: For more information check the summary or visit ClinGen Evidence Repository.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GCK	NM_000162.5	c.781G>C	p.Gly261Arg	missense_variant	Exon 7 of 10	ENST00000403799.8	NP_000153.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GCK	ENST00000403799.8	c.781G>C	p.Gly261Arg	missense_variant	Exon 7 of 10	1	NM_000162.5	ENSP00000384247.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: reviewed by expert panel

Submissions by phenotype

Monogenic diabetes Pathogenic:2

Nov 13, 2024

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: GCK c.781G>C (p.Gly261Arg) results in a non-conservative amino acid change located in the Hexokinase domain (IPR001312) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251056 control chromosomes. c.781G>C has been reported in the literature in individuals affected with Monogenic Diabetes (example, Wang_2019). These data indicate that the variant may be associated with disease. A different variant resulting in the same amino acid consequence has been classified as pathogenic by our lab (c.781G>A p.Gly261Arg), supporting the pathogenicity of this variant. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect results in abolished normal activity in vitro (Davis_1999). The following publications have been ascertained in the context of this evaluation (PMID: 10525657, 30592380). ClinVar contains an entry for this variant (Variation ID: 447418). Based on the evidence outlined above, the variant was classified as pathogenic. -

Aug 12, 2023

ClinGen Monogenic Diabetes Variant Curation Expert Panel

Significance: Pathogenic

Review Status: reviewed by expert panel

Collection Method: curation

The c.781G>C variant in the glucokinase gene, GCK, causes an amino acid change of glycine to arginine at codon 261 (p.(Gly261Arg)) of NM_000162.5. GCK is defined by the ClinGen MDEP as a gene that has a low rate of benign missense variation and has pathogenic missense variants as a common mechanism of disease (PP2). This variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.914, which is greater than the MDEP threshold of 0.70 (PP3). 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 negative antibodies) (PP4_Moderate; internal lab contributors). This variant segregated with hyperglycemia with one informative meioses in a single family; however, this does not meet the thresholds for PP1 set by the ClinGen MDEP (PMID: 27236918, internal lab contributors). This variant was identified in 5 unrelated individuals with hyperglycemia (PS4_Moderate; internal lab contributors). The nucleotide change c.781G>A, which causes the same amino acid change, has been classified as pathogenic by the ClinGen MDEP (PS1). A kinetic analysis of recombinant wild-type (WT) and mutant glucokinase demonstrated that the wild-type kinetic parameters pass the quality control, the wild-type ATP Km is between 0.4-0.65, and the p.Gly261Arg variant has a relative activity index (RAI) of 0.02, which is less than the MDEP VCEP threshold of 0.50 (PMID: 19903754). In summary, the c.781G>C variant meets the criteria to be classified as pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP VCEP (specification version 1.3.0, approved 8/11/2023): PM2_Supporting, PP2, PP3, PS3_Moderate, PS1, PS4_Moderate, PP4_Moderate. -

not provided Pathogenic:2

May 19, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glycine, which is neutral and non-polar, with arginine, which is basic and polar, at codon 261 of the GCK protein (p.Gly261Arg). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with autosomal dominant maturity onset diabetes of the young (PMID: 1502186, 30592380, 31291970, 36227502). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 447418). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on GCK protein function. Experimental studies have shown that this missense change affects GCK function (PMID: 10525657). For these reasons, this variant has been classified as Pathogenic. -

Aug 17, 2016

Athena Diagnostics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.53
CADD	Pathogenic	31
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.91	.;D;.;.;.
Eigen	Pathogenic	0.75
Eigen_PC	Pathogenic	0.72
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	0.98	D;D;.;D;D
M_CAP	Pathogenic	0.81	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Uncertain	2.2	.;M;.;.;.
PrimateAI	Pathogenic	0.83	D
PROVEAN	Pathogenic	-7.6	.;D;D;D;D
REVEL	Pathogenic	0.91
Sift	Pathogenic	0.0	.;D;D;D;D
Sift4G	Uncertain	0.010	D;D;D;D;D
Polyphen		1.0	D;D;D;D;.
Vest4		0.97
MutPred		0.94		.;Loss of glycosylation at S263 (P = 0.0679);.;.;.;
MVP		0.97
MPC		2.4
ClinPred		1.0	D
GERP RS		5.2
Varity_R		0.97
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: rs104894008; hg19: chr7-44187331;