rs1375656631

Variant names:

• chr7-44147738-C-T
• rs1375656631
• NM_000162.5:c.775G>A

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PS4 PM2_Supporting PP1_Strong PP2 PP3 PM5_Supporting PP4_Moderate

This summary comes from the ClinGen Evidence Repository: The c.775G>A variant in the glucokinase gene, GCK, causes an amino acid change of alanine to threonine at codon 259 (p.(Ala259Thr)) of NM_000162.5. This variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.948, which is greater than the MDEP VCEP threshold of 0.70 (PP3) and is absent from gnomAD v2.1.1 (PM2_Supporting). 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). Another missense variant, c.776C>T, p.Ala259Val, has been classified as pathogenic by the ClinGen MDEP but has a greater Grantham distance than p.Ala259Thr (PM5_Supporting). This variant was identified in 12 unrelated individuals with hyperglycemia (PS4; internal lab contributors). Additionally, this variant segregated with diabetes/hyperglycemia, with 7 informative meioses in 6 families (PP1_Strong; internal lab contributors). 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 a 3-generation family history of diabetes) (PP4_Moderate; internal lab contributors). In summary, c.775G>A meets the criteria to be classified as pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.3.0, approved 8/11/2023): PP3, PP2, PM5_Supporting, PS4, PP1_Strong, PP4_Moderate, PM2_Supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA367400584/MONDO:0015967/086

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: GCK NM_000162.5 missense
• Clinical Significance: Pathogenic reviewed by expert panel P:5
• 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 14 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.
• PP1: 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.775G>A	p.Ala259Thr	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.775G>A	p.Ala259Thr	missense_variant	Exon 7 of 10	1	NM_000162.5	ENSP00000384247.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251056 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135790

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000327

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461214 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 726938

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: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: reviewed by expert panel

Submissions by phenotype

Monogenic diabetes Pathogenic:2

Aug 18, 2022

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.775G>A (p.Ala259Thr) results in a non-conservative amino acid change located in the Hexokinase, C-terminal domain (IPR022673) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 4e-06 in 251106 control chromosomes. c.775G>A has been reported in the literature in multiple individuals affected with Monogenic Diabetes, specifically features of Maturity Onset Diabetes of the Young (MODY2) (example, Hattersley_1998, Matyka_1998, Thomson_2003, Lukasova_208, Capuano_2012, Tatsi_2020). These data indicate that the variant is very likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Three clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. 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.775G>A variant in the glucokinase gene, GCK, causes an amino acid change of alanine to threonine at codon 259 (p.(Ala259Thr)) of NM_000162.5. This variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.948, which is greater than the MDEP VCEP threshold of 0.70 (PP3) and is absent from gnomAD v2.1.1 (PM2_Supporting). 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). Another missense variant, c.776C>T, p.Ala259Val, has been classified as pathogenic by the ClinGen MDEP but has a greater Grantham distance than p.Ala259Thr (PM5_Supporting). This variant was identified in 12 unrelated individuals with hyperglycemia (PS4; internal lab contributors). Additionally, this variant segregated with diabetes/hyperglycemia, with 7 informative meioses in 6 families (PP1_Strong; internal lab contributors). 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 a 3-generation family history of diabetes) (PP4_Moderate; internal lab contributors). In summary, c.775G>A meets the criteria to be classified as pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.3.0, approved 8/11/2023): PP3, PP2, PM5_Supporting, PS4, PP1_Strong, PP4_Moderate, PM2_Supporting. -

not provided Pathogenic:2

Jun 23, 2022

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at a significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Missense variants in this gene are often considered pathogenic (HGMD); This variant is associated with the following publications: (PMID: 14517956, 25414397, 18271687, 34956103, 29056535, 26875109, 31604004, 9662401, 26287533, 29927023, 9713013, 22761713, 31638168, Sangwoo-2022[Article], 34101350, 35029855) -

Jan 25, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 259 of the GCK protein (p.Ala259Thr). This variant is present in population databases (no rsID available, gnomAD 0.003%). This missense change has been observed in individuals with clinical features of autosomal dominant maturity onset diabetes of the young (PMID: 9713013, 22761713, 25414397, 26287533, 31638168; Invitae). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 435302). 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. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Maturity-onset diabetes of the young type 2 Pathogenic:1

Jan 11, 2017

Genetic Services Laboratory, University of Chicago

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	0.68
BayesDel_addAF	Pathogenic	0.46	D
BayesDel_noAF	Pathogenic	0.51
CADD	Pathogenic	30
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.94	.;D;.;.;.
Eigen	Pathogenic	0.70
Eigen_PC	Pathogenic	0.67
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.97	D;D;.;D;D
M_CAP	Pathogenic	0.84	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.6	.;H;.;.;.
PrimateAI	Benign	0.47	T
PROVEAN	Uncertain	-3.5	.;D;D;D;D
REVEL	Pathogenic	0.90
Sift	Uncertain	0.0010	.;D;D;D;D
Sift4G	Pathogenic	0.0010	D;D;D;D;D
Polyphen		0.90	P;P;P;P;.
Vest4		0.94
MutPred		0.94		.;Loss of stability (P = 0.0611);.;.;.;
MVP		0.98
MPC		1.8
ClinPred		0.99	D
GERP RS		5.2
Varity_R		0.92
gMVP		0.99

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: rs1375656631; hg19: chr7-44187337; COSMIC: COSV60787622; COSMIC: COSV60787622;