chr7-44145620-C-A

Position:

• chr7-44145620-C-A

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PS4_Moderate PM5_Supporting PP4_Moderate PP2 PP3 PM2_Supporting

This summary comes from the ClinGen Evidence Repository: The c.1130G>T variant in the glucokinase gene, GCK, causes an amino acid change of arginine to leucine at codon 377 (p.(Arg377Leu)) 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 0.988, 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 five unrelated individuals with hyperglycemia (PS4_Moderate: PMIDs: 21348868, 30245511, internal lab contributors). At least two of these individuals had a clinical history highly specific for GCK-hyperglycemia (FBG 5.5-8 mmol/L and HbA1c 5.6 - 7.6% and OGTT increment < 3.0 mmol/L or negative antibodies) (PP4_Moderate; internal lab contributors). Another missense variant, c.1129C>T p.(Arg377Cys), has been classified as pathogenic by the ClinGen MDEP VCEP but has a greater Grantham distance than p.(Arg377Leu). Another missense variant, c.1129C>A p.Arg377Ser, has been classified as likely pathogenic by the ClinGen MDEP VCEP (PM5_Supporting). 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 1.3.0, approved 8/11/2023) : PS4_Moderate, PP2, PP3, PM2_Supporting, PP4_Moderate, PM5_Supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA367398811/MONDO:0015967/086

• Frequency: Genomes: not found (cov: 33)
• Consequence: GCK ENST00000403799.8 missense
• Clinical Significance: Likely pathogenic reviewed by expert panel P:2 U:1
• Conservation: PhyloP100: 6.10

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 Likely_pathogenic. Variant got 8 ACMG points.

• PS4: For more information check the summary or visit ClinGen Evidence Repository.
• PM2: For more information check the summary or visit ClinGen Evidence Repository.
• PM5: 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/exons	MANE	Protein	UniProt
GCK	NM_000162.5	c.1130G>T	p.Arg377Leu	missense_variant	9/10	ENST00000403799.8	NP_000153.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GCK	ENST00000403799.8	c.1130G>T	p.Arg377Leu	missense_variant	9/10	1	NM_000162.5	ENSP00000384247	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

Monogenic diabetes Pathogenic:1

Likely pathogenic, reviewed by expert panel

curation

ClinGen Monogenic Diabetes Variant Curation Expert Panel

Nov 24, 2023

The c.1130G>T variant in the glucokinase gene, GCK, causes an amino acid change of arginine to leucine at codon 377 (p.(Arg377Leu)) 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 0.988, 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 five unrelated individuals with hyperglycemia (PS4_Moderate: PMIDs: 21348868, 30245511, internal lab contributors). At least two of these individuals had a clinical history highly specific for GCK-hyperglycemia (FBG 5.5-8 mmol/L and HbA1c 5.6 - 7.6% and OGTT increment < 3.0 mmol/L or negative antibodies) (PP4_Moderate; internal lab contributors). Another missense variant, c.1129C>T p.(Arg377Cys), has been classified as pathogenic by the ClinGen MDEP VCEP but has a greater Grantham distance than p.(Arg377Leu). Another missense variant, c.1129C>A p.Arg377Ser, has been classified as likely pathogenic by the ClinGen MDEP VCEP (PM5_Supporting). 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 1.3.0, approved 8/11/2023) : PS4_Moderate, PP2, PP3, PM2_Supporting, PP4_Moderate, PM5_Supporting. -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

CeGaT Center for Human Genetics Tuebingen

Sep 01, 2018

- -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Aug 23, 2023

Variant summary: GCK c.1130G>T (p.Arg377Leu) results in a non-conservative amino acid change located in the Hexokinase, C-terminal domain (IPR022673) 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 234572 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.1130G>T has been reported in the literature in individuals affected with features of Monogenic Diabetes (example, Osbak_2009, Borowiec_2012, Ma_2019, Zhou_2020, unpublished observations from the Clingen MODY expert panel). These data do not allow any conclusion about variant significance. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 21348868, 30245511, 19790256, 32375122). One submitter has cited clinical-significance assessments for this variant to ClinVar after 2014 and has classified the variant as pathogenic without evidence for independent evaluation. Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.57
CADD	Pathogenic	33
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.82	.;D;D;.;.;.
Eigen	Pathogenic	0.87
Eigen_PC	Pathogenic	0.79
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.92	D;D;D;.;D;D
M_CAP	Pathogenic	0.90	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D
MetaSVM	Pathogenic	0.99	D
MutationAssessor	Pathogenic	4.0	.;.;H;.;.;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.87	D
PROVEAN	Pathogenic	-6.8	.;D;D;D;D;D
REVEL	Pathogenic	0.99
Sift	Pathogenic	0.0	.;D;D;D;D;D
Sift4G	Pathogenic	0.0010	D;D;D;D;D;D
Polyphen		1.0	D;.;D;D;D;D
Vest4		0.99
MutPred		0.98		.;.;Loss of disorder (P = 0.0292);.;.;.;
MVP		0.99
MPC		2.5
ClinPred		1.0	D
GERP RS		5.2
Varity_R		0.98
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: rs193922264; hg19: chr7-44185219;