chr7-44147737-G-T

Variant names:

• chr7-44147737-G-T
• rs1554335132
• NM_000162.5:c.776C>A

Variant summary

Our verdict is Pathogenic. The variant received 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP2 PP3_Strong

The NM_000162.5(GCK):​c.776C>A​(p.Ala259Asp) variant causes a missense change. 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 Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A259S) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: GCK NM_000162.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.79
• Publications: 0 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 11 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 chr7-44147738-C-A is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 2578354.Status of the report is reviewed_by_expert_panel, 3 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, 0.983

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.776C>A	p.Ala259Asp	missense	Exon 7 of 10	NP_000153.1
	GCK	NM_033507.3		c.779C>A	p.Ala260Asp	missense	Exon 7 of 10	NP_277042.1
	GCK	NM_033508.3		c.773C>A	p.Ala258Asp	missense	Exon 8 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.776C>A	p.Ala259Asp	missense	Exon 7 of 10	ENSP00000384247.3
	GCK	ENST00000395796.8	TSL:1	n.*774C>A		non_coding_transcript_exon	Exon 8 of 11	ENSP00000379142.4
	GCK	ENST00000395796.8	TSL:1	n.*774C>A		3_prime_UTR	Exon 8 of 11	ENSP00000379142.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Uncertain:1

Oct 07, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces alanine with aspartic acid at codon 259 of the GCK protein (p.Ala259Asp). The alanine residue is highly conserved and there is a moderate physicochemical difference between alanine and aspartic acid. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals affected with GCK-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. 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.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.89
BayesDel_addAF	Pathogenic	0.52	D
BayesDel_noAF	Pathogenic	0.51
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.91	D
Eigen	Uncertain	0.58
Eigen_PC	Uncertain	0.53
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.96	D
M_CAP	Pathogenic	0.82	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	3.3	M
PhyloP100		6.8
PrimateAI	Uncertain	0.57	T
PROVEAN	Pathogenic	-4.8	D
REVEL	Pathogenic	0.93
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0010	D
Polyphen		0.90	P
Vest4		0.91
MutPred		0.86		Gain of disorder (P = 0.0353)
MVP		0.98
MPC		2.3
ClinPred		1.0	D
GERP RS		4.3
Varity_R		0.96
gMVP		1.0
Mutation Taster		=0/100	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: rs1554335132; hg19: chr7-44187336;