chr7-44149834-A-G

Position:

• chr7-44149834-A-G

Variant summary

Our verdict is Pathogenic. Variant got 13 ACMG points: 13P and 0B. PS4 PP1_Strong PP4_Moderate PP2 PP3 PM2_Supporting

This summary comes from the ClinGen Evidence Repository: The c.605C>T variant in the glucokinase gene, GCK, causes an amino acid change of methionine to threonine at codon 202 (p.(Met202Thr)) of NM_000162.5. This variant segregated with diabetes/hyperglycemia, with 6 informative meioses in 4 families (PP1_Strong; internal lab contributors). This variant was identified in 12 unrelated individuals with hyperglycemia (PS4; PMID:17573000, internal lab contributors). This variant was identified in two individuals 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). 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 0.917, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant has a gnomAD v2.1.1 Popmax filtering allele frequency of 0.000002920 (below the MDEP threshold of 0.000003) and 2 copies observed in the European non-Finnish population and 0 copies in any other subpopulation, thereby meeting the ClinGen MDEP criteria for PM2_Supporting (PM2_Supporting). In summary, c.605C>T 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): PP1_Strong, PS4, PP4_Moderate, PP2, PP3, PM2_Supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA213810/MONDO:0015967/086

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: GCK NM_000162.5 missense
• Clinical Significance: Pathogenic reviewed by expert panel P:2 U:1
• Conservation: PhyloP100: 9.32

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.

• 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.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GCK	NM_000162.5	c.605T>C	p.Met202Thr	missense_variant	6/10	ENST00000403799.8	NP_000153.1
LOC105375258	XR_927223.3	n.365A>G		non_coding_transcript_exon_variant	3/3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GCK	ENST00000403799.8	c.605T>C	p.Met202Thr	missense_variant	6/10	1	NM_000162.5	ENSP00000384247	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000795 AC: 2 AN: 251450 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135912

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: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000176

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461852 Hom.: 0 Cov.: 33 AF XY: 0.00000275 AC XY: 2 AN XY: 727226

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000824 AC: 1

EpiCase AF: 0.00

EpiControl AF: 0.0000593

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2 Uncertain:1

Revision: reviewed by expert panel

Submissions by phenotype

Monogenic diabetes Pathogenic:1

Pathogenic, reviewed by expert panel

curation

ClinGen Monogenic Diabetes Variant Curation Expert Panel

Dec 01, 2023

The c.605C>T variant in the glucokinase gene, GCK, causes an amino acid change of methionine to threonine at codon 202 (p.(Met202Thr)) of NM_000162.5. This variant segregated with diabetes/hyperglycemia, with 6 informative meioses in 4 families (PP1_Strong; internal lab contributors). This variant was identified in 12 unrelated individuals with hyperglycemia (PS4; PMID: 17573000, internal lab contributors). This variant was identified in two individuals 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). 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 0.917, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant has a gnomAD v2.1.1 Popmax filtering allele frequency of 0.000002920 (below the MDEP threshold of 0.000003) and 2 copies observed in the European non-Finnish population and 0 copies in any other subpopulation, thereby meeting the ClinGen MDEP criteria for PM2_Supporting (PM2_Supporting). In summary, c.605C>T 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): PP1_Strong, PS4, PP4_Moderate, PP2, PP3, PM2_Supporting. -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Athena Diagnostics

May 09, 2019

The best available variant frequency is uninformative because it is below the disease allele frequency. Statistically enriched in patients compared to ethnically matched controls. Found in at least one symptomatic patient. Predicted to have a damaging effect on the protein. One de novo case without parental identity confirmed. -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Jan 30, 2019

Variant summary: The variant, GCK c.605T>C (p.Met202Thr) results in a non-conservative amino acid change located in the Hexokinase, N-terminal of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function consistent with an ExAC z score of 4.39 indicative of a gene relatively intolerant to benign missense variation (ACMG PP3, PP2). The variant allele was found at a frequency of 8.1e-06 in 246536 control chromosomes (gnomAD). The variant, c.605T>C has been reported in the literature in individuals affected with Maturity Onset Diabetes of the Young 2 (Chambers_2016, Estalella_2007, Gozalan_2012). In one of these reports, this variant was reported as a de-novo occurrence however the data provided does not confirm this finding (Gozalan_2012; ACMG PM6). Furthermore, one of these reports reflects a conflicting classification of this variant relative to its latest ClinVar submission by the same testing laboratory (Chambers_2016). These data indicate that the variant is likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation and has classified the variant as uncertain significance. This variant was previously classified as a VUS-possibly pathogenic variant that was converted during ClinVar submission to likely pathogenic in 2011. As summarized above, at-least three new reports indicating its presence in individuals diagnosed with MODY2 or a related diabetic phenotype have emerged since its original classification. Based on the evidence outlined above, until additional functional impact and unequivocal co-segregation with disease in additional families/individuals with MODY2 is obtained the variant was classified as VUS Possibly Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.89
BayesDel_addAF	Pathogenic	0.52	D
BayesDel_noAF	Pathogenic	0.52
CADD	Pathogenic	27
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.80	.;D;.;.;.
Eigen	Pathogenic	0.69
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.93	D;D;.;D;D
M_CAP	Pathogenic	0.34	D
MetaRNN	Pathogenic	0.97	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Benign	1.8	.;L;.;.;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.85	D
PROVEAN	Benign	-2.3	.;N;N;N;N
REVEL	Pathogenic	0.92
Sift	Uncertain	0.0010	.;D;D;D;D
Sift4G	Uncertain	0.0030	D;D;D;D;D
Polyphen		1.0	D;D;D;B;.
Vest4		0.90
MutPred		0.91		.;Loss of stability (P = 0.0088);.;.;.;
MVP		0.98
MPC		2.4
ClinPred		0.89	D
GERP RS		6.0
Varity_R		0.90
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: rs193922311; hg19: chr7-44189433;