chr7-44150990-A-T

Variant names:

• chr7-44150990-A-T
• rs193922297
• NM_000162.5:c.449T>A

Variant summary

Our verdict is Pathogenic. The variant received 13 ACMG points: 13P and 0B. PP1_Moderate PP2 PP3 PS3_Moderate PM2_Supporting PP4_Moderate PS4

This summary comes from the ClinGen Evidence Repository: The c.449T>A variant in the glucokinase gene, GCK, causes an amino acid change of phenylalanine to tyrosine at codon 150 (p.(Phe150Tyr)) 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 0.962, 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 10 unrelated individuals with hyperglycemia (PS4; PMIDs: 25306193, 19564454, 32086287, 30663027, 28726111, 22761713, internal lab contributors). One 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 negative antibodies) (PP4_Moderate; PMID:28726111). This variant segregated with hyperglycemia, with 3 informative meioses in 2 families (PP1_Moderate; internal lab contributors). MDEP wild type quality control measures were met, and the relative activity Index (RAI) of this variant was found to be 0.014, which is below the MDEP cutoff (<0.5) (PS3_Moderate, PMID:22761713). In summary, c.449T>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): PS4, PP1_Moderate, PP4_Moderate, PS3_Moderate, PP2, PP3, PM2_Supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA231135/MONDO:0015967/086

• Frequency: Genomes: not found (cov: 32)
• Consequence: GCK NM_000162.5 missense
• Clinical Significance: Pathogenic reviewed by expert panel P:4 U:1
• Conservation: PhyloP100: 9.25
• Publications: 18 publications found

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]

GCK Gene-Disease associations (from GenCC):

• hyperinsulinism due to glucokinase deficiency

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), Ambry Genetics, Orphanet
• maturity-onset diabetes of the young type 2

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp, Ambry Genetics
• monogenic diabetes

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• diabetes mellitus, noninsulin-dependent

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
• permanent neonatal diabetes mellitus 1

  Inheritance: AR Classification: STRONG, MODERATE Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), Ambry Genetics
• transient neonatal diabetes mellitus

  Inheritance: AR Classification: STRONG Submitted by: Genomics England PanelApp
• maturity-onset diabetes of the young

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• permanent neonatal diabetes mellitus

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ENSG00000300758 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 13 ACMG points.

• 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.
• 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.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000162.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GCK	NM_000162.5	MANE Select	c.449T>A	p.Phe150Tyr	missense	Exon 4 of 10	NP_000153.1
	GCK	NM_033507.3		c.452T>A	p.Phe151Tyr	missense	Exon 4 of 10	NP_277042.1
	GCK	NM_033508.3		c.446T>A	p.Phe149Tyr	missense	Exon 5 of 11	NP_277043.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GCK	ENST00000403799.8	TSL:1 MANE Select	c.449T>A	p.Phe150Tyr	missense	Exon 4 of 10	ENSP00000384247.3
	GCK	ENST00000395796.8	TSL:1	n.*447T>A		non_coding_transcript_exon	Exon 5 of 11	ENSP00000379142.4
	GCK	ENST00000395796.8	TSL:1	n.*447T>A		3_prime_UTR	Exon 5 of 11	ENSP00000379142.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4 Uncertain:1

Revision: reviewed by expert panel

Submissions by phenotype

not provided Pathogenic:2 Uncertain:1

Sep 25, 2024

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Published in vitro functional studies suggest a damaging effect on enzymatic activity (PMID: 22761713); Not observed at 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 a common cause of disease and they are underrepresented in the general population; This variant is associated with the following publications: (PMID: 19564454, 22761713, 30663027, 25306193, 28726111, 36836406, 32086287, 34440516)

Apr 08, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces phenylalanine, which is neutral and non-polar, with tyrosine, which is neutral and polar, at codon 150 of the GCK protein (p.Phe150Tyr). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with autosomal dominant GCK-related conditions (PMID: 19564454, 32086287, 33477506; Invitae). ClinVar contains an entry for this variant (Variation ID: 129142). 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: 22761713). This variant disrupts the p.Phe150 amino acid residue in GCK. Other variant(s) that disrupt this residue have been observed in individuals with GCK-related conditions (PMID: 12627330), which suggests that this may be a clinically significant amino acid residue. 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.

Feb 21, 2013

Genetic Services Laboratory, University of Chicago

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Monogenic diabetes Pathogenic:2

Jan 06, 2024

ClinGen Monogenic Diabetes Variant Curation Expert Panel

Significance: Pathogenic

Review Status: reviewed by expert panel

Collection Method: curation

The c.449T>A variant in the glucokinase gene, GCK, causes an amino acid change of phenylalanine to tyrosine at codon 150 (p.(Phe150Tyr)) 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 0.962, 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 10 unrelated individuals with hyperglycemia (PS4; PMIDs: 25306193, 19564454, 32086287, 30663027, 28726111, 22761713, internal lab contributors). One 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 negative antibodies) (PP4_Moderate; PMID: 28726111). This variant segregated with hyperglycemia, with 3 informative meioses in 2 families (PP1_Moderate; internal lab contributors). MDEP wild type quality control measures were met, and the relative activity Index (RAI) of this variant was found to be 0.014, which is below the MDEP cutoff (<0.5) (PS3_Moderate, PMID: 22761713). In summary, c.449T>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): PS4, PP1_Moderate, PP4_Moderate, PS3_Moderate, PP2, PP3, PM2_Supporting.

Mar 23, 2023

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.449T>A (p.Phe150Tyr) results in a conservative amino acid change located in the Hexokinase, N-terminal domain (IPR022672) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251462 control chromosomes. c.449T>A has been reported in the literature in settings of individuals affected with incidental hyperglycemia, MODY, gestational/monogenic diabetes and laboratory testing cohorts (example, Lorini_2009, Capuano_2012, Alkorta-Aranburu_2014, Aloi_2017, Zubkova_2019, Stankute_2020, Ivanoshchuk_2021). Of these, only the subset of individuals/cohorts reporting diagnostic findings supportive of MODY/monogenic diabetes were captured in this ascertainment (example, Aloi_2017, Stankute_2020, Ivanoshchuk_2021). These data indicate that the variant is likely to be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function (example, Capuano_2012). The most pronounced variant effect results in <10% of normal GCK activity in-vitro. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as pathogenic.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.89
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.59
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	D
Eigen	Pathogenic	0.92
Eigen_PC	Pathogenic	0.86
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Pathogenic	0.98	D
M_CAP	Pathogenic	0.79	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	0.99	D
MutationAssessor	Pathogenic	3.8	H
PhyloP100		9.2
PrimateAI	Pathogenic	0.93	D
PROVEAN	Uncertain	-3.0	D
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.92
MutPred		0.98		Gain of phosphorylation at F150 (P = 0.1295)
MVP		0.96
MPC		2.4
ClinPred		1.0	D
GERP RS		5.2
Varity_R		0.93
gMVP		0.98
Mutation Taster		=5/95	disease causing

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

Other links and lift over

dbSNP: rs193922297; hg19: chr7-44190589;