chr7-44151075-G-T

Position:

• chr7-44151075-G-T

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM5_Supporting PP4_Moderate PM2 PP2 PP3

This summary comes from the ClinGen Evidence Repository: The c.364C>A variant in the glucokinase gene, GCK, causes an amino acid change of leucine to isoleucine at codon 122 (p.(Leu122Ile)) 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 0.91, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant is absent in gnomAD v2.1.1 (PM2_Supporting). 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 antibody negative) (PP4_Moderate; internal lab contributors). Another missense variant, c.364C>T, p.Leu122Phe, has been classified as likely pathogenic by the ClinGen MDEP (PM5_Supporting). Taken together, this evidence supports the classification of c.364C>A as likely pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.3.0, approved 8/11/2023): PP4_Moderate, PM2_Supporting, PM5_Supporting, PP2, PP3. LINK:https://erepo.genome.network/evrepo/ui/classification/CA367402232/MONDO:0015967/086

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: GCK ENST00000403799.8 missense, splice_region
• Scores: Splicing: ADA: 0.9267
• Clinical Significance: Likely pathogenic reviewed by expert panel P:4 U:1
• Conservation: PhyloP100: 5.88

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 7 ACMG points.

• 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.364C>A	p.Leu122Ile	missense_variant, splice_region_variant	4/10	ENST00000403799.8	NP_000153.1
GCK	NM_033507.3	c.367C>A	p.Leu123Ile	missense_variant, splice_region_variant	4/10		NP_277042.1
GCK	NM_033508.3	c.361C>A	p.Leu121Ile	missense_variant, splice_region_variant	5/11		NP_277043.1
GCK	NM_001354800.1	c.364C>A	p.Leu122Ile	missense_variant, splice_region_variant	4/11		NP_001341729.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GCK	ENST00000403799.8	c.364C>A	p.Leu122Ile	missense_variant, splice_region_variant	4/10	1	NM_000162.5	ENSP00000384247	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461602 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727104

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: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:4 Uncertain:1

Revision: reviewed by expert panel

Submissions by phenotype

not provided Pathogenic:1 Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 26, 2023	In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. This variant disrupts the p.Leu122 amino acid residue in GCK. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 32468610). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). ClinVar contains an entry for this variant (Variation ID: 435307). This missense change has been observed in individual(s) with clinical features of autosomal dominant GCK-related conditions (PMID: 31063852). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces leucine, which is neutral and non-polar, with isoleucine, which is neutral and non-polar, at codon 122 of the GCK protein (p.Leu122Ile). -
Likely pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Mar 31, 2022	This variant was not reported in large, multi-ethnic, general populations (http://gnomad.broadinstitute.org). This variant has been identified in at least one individual with clinical features of MODY. Multiple individuals have been identified with clinical features associated with this gene who also carry missense variants affecting this codon. At least one of those variants is considered to be likely pathogenic, suggesting this variant may also cause disease. -

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

Likely pathogenic, criteria provided, single submitter

clinical testing

Genetic Services Laboratory, University of Chicago

Oct 12, 2016

- -

Monogenic diabetes Pathogenic:1

Likely pathogenic, reviewed by expert panel

curation

ClinGen Monogenic Diabetes Variant Curation Expert Panel

Mar 07, 2024

The c.364C>A variant in the glucokinase gene, GCK, causes an amino acid change of leucine to isoleucine at codon 122 (p.(Leu122Ile)) 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 0.91, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant is absent in gnomAD v2.1.1 (PM2_Supporting). 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 antibody negative) (PP4_Moderate; internal lab contributors). Another missense variant, c.364C>T, p.Leu122Phe, has been classified as likely pathogenic by the ClinGen MDEP (PM5_Supporting). Taken together, this evidence supports the classification of c.364C>A as likely pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.3.0, approved 8/11/2023): PP4_Moderate, PM2_Supporting, PM5_Supporting, PP2, PP3. -

Maturity onset diabetes mellitus in young Pathogenic:1

Likely risk allele, criteria provided, single submitter

research

Clinical Genomics, Uppaluri K&H Personalized Medicine Clinic

-

Potent mutations in GCK gene is associated with poor secretion of insulin. Its associated with milder forms of diabetes, which can be controlled by diet . However, there is no sufficient evidence to ascertain the significance of rs1554335616 in MODY, yet. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.76
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.34
CADD	Pathogenic	29
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.85	.;D;.;.
Eigen	Pathogenic	0.86
Eigen_PC	Pathogenic	0.77
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.97	D;D;.;D
M_CAP	Pathogenic	0.83	D
MetaRNN	Pathogenic	0.98	D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	3.5	.;M;.;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.89	D
PROVEAN	Benign	-2.0	.;N;N;N
REVEL	Pathogenic	0.91
Sift	Pathogenic	0.0	.;D;D;D
Sift4G	Pathogenic	0.0	D;D;D;D
Polyphen		0.98	D;D;D;D
Vest4		0.76
MutPred		0.88		.;Loss of catalytic residue at L122 (P = 0.0152);.;.;
MVP		0.97
MPC		2.3
ClinPred		0.99	D
GERP RS		5.0
Varity_R		0.88
gMVP		0.95

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.93
dbscSNV1_RF	Pathogenic	0.82
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: rs1554335616; hg19: chr7-44190674;