rs1286804191

Positions:

• chr7-44145212-G-A
• chr7-44145212-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM5_Supporting PP2 PP3 PP4 PM2_Supporting

This summary comes from the ClinGen Evidence Repository: The c.1322C>T variant in the glucokinase gene, GCK, causes an amino acid change of glycine to asparagine at codon 441 (p.(Ser441Leu)) of NM_000162.5. This variant has a non-calculable Popmax filtering allele frequency, with absence in the gnomAD v2.1.1 European non-Finnish population and one copy in the African/African American subpopulation, which is less than the ClinGen MDEP threshold for PM2_Supporting (ENF Popmax FAF <= 0.000003 and <= 2 copies in ENF and <=1 copy in any other subpopulation) (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). The variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.984, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant was identified in an individual with a clinical history highly specific for GCK-MODY (FBG 5.5-8 mmol/L and HbA1c 5.6 - 7.6%) (PP4; PMID:28726111). Another missense variant, c.1322C>G p.(Ser441Trp), has been classified as pathogenic by the ClinGen MDEP but has a greater Grantham distance than p.(Ser441Leu) (PM5_Supporting). In summary, c.1322C>T meets the criteria to be classified as uncertain significance for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.2.0, approved 6/7/2023): PM2_Supporting, PP3, PP2, PP4, PM5_Supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA367397015/MONDO:0015967/086

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: GCK NM_000162.5 missense
• Clinical Significance: Uncertain significance reviewed by expert panel P:3 U:2
• Conservation: PhyloP100: 6.37

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 Uncertain_significance. Variant got 5 ACMG points.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GCK	NM_000162.5	c.1322C>T	p.Ser441Leu	missense_variant	10/10	ENST00000403799.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GCK	ENST00000403799.8	c.1322C>T	p.Ser441Leu	missense_variant	10/10	1	NM_000162.5	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000410 AC: 1 AN: 243630 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 132780

Gnomad AFR exome AF: 0.0000637

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000206 AC: 3 AN: 1459672 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 726142

Gnomad4 AFR exome AF: 0.0000299

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: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:3 Uncertain:2

Revision: reviewed by expert panel

Submissions by phenotype

Maturity-onset diabetes of the young type 2 Pathogenic:3

Likely pathogenic, criteria provided, single submitter	clinical testing	Genetic Services Laboratory, University of Chicago	Oct 13, 2016	- -
Likely pathogenic, criteria provided, single submitter	research	Geisinger Clinic, Geisinger Health System	Aug 02, 2022	PM2, PP3, PP2, PP4, PM5_Supporting -
Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Apr 01, 2021	Variant summary: GCK c.1322C>T (p.Ser441Leu) 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 allele was found at a frequency of 4.1e-06 in 243630 control chromosomes (gnomAD). c.1322C>T has been reported in the literature as homozygous occurrence in at least one individual affected with Permanent Neonatal Diabetes Mellitus (e.g. Flanagan_2014, Raimondo_2014) and as heterozygous occurrence in one family with clinical features of Maturity Onset Diabetes Of The Young (Aloi_2017). These data indicate that the variant may be associated with disease. Experimental evidence evaluating an impact on protein function demonstrated the variant to confer decreased enzyme activity and thermostability (Raimondo_2014). One ClinVar submitter (evaluation after 2014) cites the variant as likely pathogenic while another ClinVar submitter (evaluation after 2014) cites it as uncertain significance. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Monogenic diabetes Uncertain:1

Uncertain significance, reviewed by expert panel

curation

ClinGen Monogenic Diabetes Variant Curation Expert Panel

Jun 25, 2023

The c.1322C>T variant in the glucokinase gene, GCK, causes an amino acid change of glycine to asparagine at codon 441 (p.(Ser441Leu)) of NM_000162.5. This variant has a non-calculable Popmax filtering allele frequency, with absence in the gnomAD v2.1.1 European non-Finnish population and one copy in the African/African American subpopulation, which is less than the ClinGen MDEP threshold for PM2_Supporting (ENF Popmax FAF <= 0.000003 and <= 2 copies in ENF and <=1 copy in any other subpopulation) (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). The variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.984, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant was identified in an individual with a clinical history highly specific for GCK-MODY (FBG 5.5-8 mmol/L and HbA1c 5.6 - 7.6%) (PP4; PMID: 28726111). Another missense variant, c.1322C>G p.(Ser441Trp), has been classified as pathogenic by the ClinGen MDEP but has a greater Grantham distance than p.(Ser441Leu) (PM5_Supporting). In summary, c.1322C>T meets the criteria to be classified as uncertain significance for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.2.0, approved 6/7/2023): PM2_Supporting, PP3, PP2, PP4, PM5_Supporting. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Athena Diagnostics

Jan 02, 2024

Available data are insufficient to determine the clinical significance of the variant at this time. The frequency of this variant in the general population is uninformative in assessment of its pathogenicity (http://gnomad.broadinstitute.org). This variant has been identified in at least one individual with MODY and at least one individual with permanent neonatal diabetes mellitus. One other missense mutation found at the same codon position is classified as pathogenic. Assessment of experimental evidence suggests this variant results in abnormal protein function. (PMID: 37101203) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.88
BayesDel_addAF	Pathogenic	0.43	D
BayesDel_noAF	Pathogenic	0.57
CADD	Pathogenic	33
DANN	Pathogenic	1.0
DEOGEN2	Uncertain	0.75	.;D;D;.;.;.
Eigen	Pathogenic	0.81
Eigen_PC	Pathogenic	0.73
FATHMM_MKL	Uncertain	0.91	D
LIST_S2	Pathogenic	1.0	D;D;D;.;D;D
M_CAP	Pathogenic	0.71	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.6	.;.;H;.;.;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Uncertain	0.71	T
PROVEAN	Pathogenic	-5.8	.;D;D;D;D;D
REVEL	Pathogenic	0.98
Sift	Pathogenic	0.0	.;D;D;D;D;D
Sift4G	Pathogenic	0.0	D;D;D;D;D;D
Polyphen		1.0	D;.;D;D;D;D
Vest4		0.82
MutPred		0.84		.;.;Loss of disorder (P = 0.012);.;.;.;
MVP		0.96
MPC		2.1
ClinPred		1.0	D
GERP RS		4.9
Varity_R		0.96
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: rs1286804191; hg19: chr7-44184811;