7-44147745-C-G

Variant names:

• chr7-44147745-C-G
• rs193922328
• NM_000162.5:c.768G>C

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5

The NM_000162.5(GCK):​c.768G>C​(p.Glu256Asp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. E256Q) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: GCK NM_000162.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 O:1
• Conservation: PhyloP100: 1.35
• Publications: 5 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

LOC105375258 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 27 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 9 uncertain in NM_000162.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr7-44147747-C-G is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 421063.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 274 curated pathogenic missense variants (we use a threshold of 10). The gene has 10 curated benign missense variants. Gene score misZ: 3.069 (below the threshold of 3.09). Trascript score misZ: 2.7821 (below the threshold of 3.09). GenCC associations: The gene is linked to transient neonatal diabetes mellitus, monogenic diabetes, permanent neonatal diabetes mellitus 1, diabetes mellitus, noninsulin-dependent, maturity-onset diabetes of the young type 2, hyperinsulinism due to glucokinase deficiency, permanent neonatal diabetes mellitus, maturity-onset diabetes of the young.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.994
• PP5: Variant 7-44147745-C-G is Pathogenic according to our data. Variant chr7-44147745-C-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 36255.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GCK	NM_000162.5	c.768G>C	p.Glu256Asp	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.768G>C	p.Glu256Asp	missense_variant	Exon 7 of 10	1	NM_000162.5	ENSP00000384247.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Other:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

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

Jul 09, 2024

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

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: GCK c.768G>C (p.Glu256Asp) results in a 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 was absent in 251142 control chromosomes (gnomAD). c.768G>C has been reported in the literature in at least an individual affected with autosomal dominant maturity onset diabetes of the young 2/neonatal diabetes mellitus (examples: Garin_2008, Aykut_2018). These data indicate that the variant is likely associated with disease. A different variant affecting the same codon has been classified as pathogenic by our lab (c.766G>A, p.Glu256Lys), supporting the critical relevance of codon 256 to GCK protein function. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 29056535, 18248649). ClinVar contains an entry for this variant (Variation ID: 36255). Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Maturity onset diabetes mellitus in young Other:1

-

Clinical Genomics, Uppaluri K&H Personalized Medicine Clinic

Significance: Uncertain risk allele

Review Status: criteria provided, single submitter

Collection Method: research

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 rs193922328 in MODY, yet. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.51	D
BayesDel_noAF	Pathogenic	0.50
CADD	Benign	23
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.96	.;D;.;.;.
Eigen	Benign	0.023
Eigen_PC	Benign	-0.063
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Pathogenic	1.0	D;D;.;D;D
M_CAP	Pathogenic	0.85	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.0	.;H;.;.;.
PhyloP100		1.4
PrimateAI	Uncertain	0.74	T
PROVEAN	Uncertain	-2.8	.;D;D;D;D
REVEL	Pathogenic	0.92
Sift	Uncertain	0.0010	.;D;D;D;D
Sift4G	Uncertain	0.0040	D;D;D;D;D
Polyphen		0.98	D;D;D;D;.
Vest4		0.98
MutPred		0.98		.;Loss of sheet (P = 0.1907);.;.;.;
MVP		0.95
MPC		2.0
ClinPred		0.99	D
GERP RS		2.4
Varity_R		0.94
gMVP		1.0
Mutation Taster		=4/96	disease causing (ClinVar)

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: rs193922328; hg19: chr7-44187344;