# NM_000162.5(GCK):c.917T>A (p.Leu306Gln)

https://sugi.bio/variant/gck-p-leu306gln

## Summary

**GCK p.Leu306Gln (c.917T>A)** is classified **Likely pathogenic** in GCK (ClinVar, Single submitter, 1 submitter; last evaluated 2022-05-04). AlphaMissense: likely pathogenic (0.9779); Absent from gnomAD v4.1; Associated with maturity-onset diabetes of the young type 2.

**At a glance:** Likely pathogenic · review: Single submitter · rsID rs193922337 · 1 submitter · 1 linked condition · AlphaMissense likely pathogenic · absent from gnomAD v4.1

## For patients & families {#patients}

This is a change in the GCK gene that is considered likely disease-causing, submitted by 1 submitter, and is linked to maturity-onset diabetes of the young type 2.

*Reference information, not medical advice, and not a prediction for any individual. A genetic counselor or clinician can interpret what it means for you and your family.*

|  |  |
| --- | --- |
| Typical inheritance (of this condition) | Autosomal dominant, Not applicable |
| Age of onset (of this condition) | Adolescent, Adult, Childhood |
| Prevalence | 1-5 / 10 000 (Europe) |
| Clinical trials | 1 registered for this condition — see ClinicalTrials.gov |
| Diagnostic panels | GCK is a diagnostic-grade gene on 6 Genomics England panels |

**Commonly reported features of MODY** (across patients with this condition; presentation varies — frequencies from Orphanet):

- Glucose intolerance — Frequent (79-30%)
- Hyperglycemia — Frequent (79-30%)
- Glycosuria — Frequent (79-30%)
- Abnormal oral glucose tolerance — Frequent (79-30%)
- Abnormal C-peptide level — Frequent (79-30%)
- Abnormal circulating insulin concentration — Frequent (79-30%)
- Hypoinsulinemia — Frequent (79-30%)
- Elevated hemoglobin A1c — Frequent (79-30%)

**Support & next steps:** [Condition overview & support (NIH GARD)](https://rarediseases.info.nih.gov/diseases/0010657/index) · [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [GCK](https://sugi.bio/atlas/gene/GCK/) |
| Protein change (HGVS p.) | p.Leu306Gln |
| Coding change (HGVS c.) | c.917T>A |
| MANE Select transcript | [NM_000162](https://www.ncbi.nlm.nih.gov/nuccore/NM_000162) |
| dbSNP | [rs193922337](https://www.ncbi.nlm.nih.gov/snp/rs193922337/) |
| Variant type | single nucleotide variant |
| Location | chr7:44146565-44146565 (GRCh38) |
| ClinVar | [VCV1685328](https://www.ncbi.nlm.nih.gov/clinvar/variation/1685328/) |

**All HGVS expressions:** `LRG_1074:g.56606T>A`, `LRG_1074t1:c.917T>A`, `LRG_1074t2:c.920T>A`, `NC_000007.13:g.44186164A>T`, `NC_000007.14:g.44146565A>T`, `NG_008847.2:g.56606T>A`, `NM_000162.5:c.917T>A`, `NM_001354800.1:c.917T>A`, `NM_001354801.1:c.8+54T>A`, `NM_033507.3:c.920T>A`, `NM_033508.3:c.914T>A`

## Computational & population evidence {#evidence}

**Concordance:** 1 independent predictor **concordant** with the ClinVar classification.

- AlphaMissense **likely pathogenic** (0.9779) — concordant with the pathogenic call
- REVEL 0.991 (strongly pathogenic-leaning) — agrees with AlphaMissense
- SaProt LLR -11.888 (damaging) — agrees with AlphaMissense
- → **In-silico consensus:** AlphaMissense, REVEL and SaProt all call this damaging
- Conservation: phyloP 10.967, GERP 1.84, phastCons 1 — highly conserved (agrees)
- CADD: **PHRED 32.0**. No single ClinGen-calibrated threshold exists and the expert panels that use CADD disagree — GUCY2D/AIPL1 require ≥ 20.0 for an untranslated-region variant, ABCA4 ≥ 28.1 for a synonymous or indel variant, the Pulmonary Hypertension panel imports Pejaver 2022's missense-calibrated numbers, and the Antibody Deficiencies panel declines CADD entirely for PIK3CD. CADD v1.7 also incorporates Zoonomia phyloP, so it partly re-expresses the conservation above. *Descriptive; no threshold applied.*
- Regional missense constraint: **o/e 0.71** across the covering region of the MANE Select transcript (44,145,139–44,152,363), spanning 7,224 bp. Chi-square p 1.1e-11. Describes the region, not this allele; gnomAD v4.1.1's own constrained determination. *Descriptive; no ACMG code applied.*
- SpliceAI: **not assessed** — no allele at this position is in our SpliceAI release, either because it lies outside the scored MANE transcript scope or because every allele is below Δ0.2. We cannot tell which, so this claims neither; absence is not evidence against a splicing effect.
- Population frequency: **absent from gnomAD v4.1** — a rarity signal (ACMG PM2-supporting), not evidence of pathogenicity on its own.

*Computational predictors are not independent (ClinGen Variant Classification guidance): AlphaMissense (Cheng et al. 2023) carries the ACMG weight for missense and conservation (phyloP/GERP/phastCons) for non-missense; REVEL (Pejaver-2022 calibrated strength bands) and SaProt (Su et al. 2023, structure-aware, ClinVar-independent protein language model, raw LLR) are shown as orthogonal agreement signals, not additive. For frequency, the gnomAD v4.1 grpmax filtering allele frequency (FAF95) is ClinGen's designated BA1/BS1 input (gnomAD v4 guidance v3.0, June 2025); BA1/BS1 thresholds are disease-specific, not a blanket 5%. Predictions, not a clinical determination.*

## Gene constraint & dosage {#gene-context}

**GCK** population constraint: LOEUF 0.866, pLI 7.7468e-07, missense-Z 2.7902; ClinGen dosage — haploinsufficiency 3/3, triplosensitivity 0/3. *Lower LOEUF and higher pLI indicate a gene that tolerates loss-of-function poorly; ClinGen dosage is the curated haploinsufficiency call.*

Curated gene–disease validity (ClinGen):

- **monogenic diabetes** — Definitive (SD)
- **hyperinsulinism due to glucokinase deficiency** — Definitive (AD)

## Protein context {#protein}

Residue **306** lies in the hexokinase domain; an α-helix; the 'hexokinase large subdomain' region; a UniProt-annotated variant site (in mody2); a UniProt-annotated variant site (in mody2 and t2d).

AlphaFold model confidence (whole protein): pLDDT 93.87, 85% of residues very-high.

**35 experimental structure(s)** (PDB): [1V4S](https://www.rcsb.org/structure/1V4S), [1V4T](https://www.rcsb.org/structure/1V4T), [3A0I](https://www.rcsb.org/structure/3A0I), [3F9M](https://www.rcsb.org/structure/3F9M), [3FGU](https://www.rcsb.org/structure/3FGU), [3FR0](https://www.rcsb.org/structure/3FR0).

## What this gene does {#gene-function}

*Describes the biological roles of GCK (the gene this variant disrupts) — not effects measured for this specific variant. A damaging variant is expected to affect these functions and pathways; the degree depends on the variant.*

**How this variant is thought to act:** GCK's established molecular role includes glucokinase activity. p.Leu306Gln falls in the hexokinase domain. In Reactome, GCK is annotated in disease pathway(s) including **Defective GCK causes maturity-onset diabetes of the young 2 (MODY2)**, **Defective TPR may confer susceptibility towards thyroid papillary carcinoma (TPC)**.

**Disease mechanism (Reactome):** GCK loss or alteration is curated in [Defective GCK causes maturity-onset diabetes of the young 2 (MODY2)](https://reactome.org/content/detail/R-HSA-5619073), [Defective TPR may confer susceptibility towards thyroid papillary carcinoma (TPC)](https://reactome.org/content/detail/R-HSA-5619107).

### Pathways affected {#pathways}

GCK participates in **6 Reactome pathways** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| ⚕ [Defective GCK causes maturity-onset diabetes of the young 2 (MODY2)](https://reactome.org/content/detail/R-HSA-5619073) | curated |
| ⚕ [Defective TPR may confer susceptibility towards thyroid papillary carcinoma (TPC)](https://reactome.org/content/detail/R-HSA-5619107) | curated |
| [Glycolysis](https://reactome.org/content/detail/R-HSA-70171) | curated |
| [Regulation of Glucokinase by Glucokinase Regulatory Protein](https://reactome.org/content/detail/R-HSA-170822) | curated |
| [FOXO-mediated transcription of oxidative stress, metabolic and neuronal genes](https://reactome.org/content/detail/R-HSA-9615017) | electronic |
| [Regulation of gene expression in beta cells](https://reactome.org/content/detail/R-HSA-210745) | electronic |

### Molecular function & processes (GO — experimentally supported) {#go}

**Molecular function:** glucokinase activity, ATP binding, D-glucose binding.

**Biological process:** glucose catabolic process, positive regulation of insulin secretion, glucose homeostasis, negative regulation of gluconeogenesis, positive regulation of glycogen biosynthetic process, regulation of insulin secretion.

## Clinical significance {#significance}

**Likely pathogenic** — review status Single submitter *(criteria provided, single submitter)*, last evaluated 2022-05-04.

**Submitter consensus:** unanimous (1/1 Likely pathogenic).

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| Mendelics | Likely pathogenic | criteria provided, single submitter | clinical testing | 2022-05-04 |

## Associated conditions {#conditions}

[maturity-onset diabetes of the young type 2](https://sugi.bio/atlas/disease/maturity-onset-diabetes-of-the-young-type-2/).

**Reported phenotype names (ClinVar):** Maturity-onset diabetes of the young type 2, Diabetes mellitus, type II, autosomal dominant, MODY type 2, Diabetes mellitus MODY type 2, MODY glucokinase-related.

## Similar variants {#similar}

Related GCK variant pages (same residue, condition, or type): [GCK p.Leu306Arg](/variant/gck-p-leu306arg), [GCK p.Leu306Pro](/variant/gck-p-leu306pro), [GCK c.1020-10C>A](/variant/gck-c-1020-minus-10c-a), [GCK c.1020-1G>C](/variant/gck-c-1020-minus-1g-c), [GCK c.679+1G>C](/variant/gck-c-679-plus-1g-c), [GCK c.680-2A>G](/variant/gck-c-680-minus-2a-g), [GCK c.863+1G>A](/variant/gck-c-863-plus-1g-a), [GCK c.864-1G>A](/variant/gck-c-864-minus-1g-a).

### Data sources & attribution {#sources}

ClinVar (NCBI — public domain, built 2026-10-14); gnomAD v4.1 (Broad Institute, built 2026-10-06); AlphaMissense (Cheng et al. 2023, © Google DeepMind — CC BY 4.0, built 2026-01-27); REVEL (Ioannidis et al. 2016 — ODbL, built 2026-07-13); SaProt (Su et al. 2023 — MIT, built 2026-10-14); SpliceAI (Illumina — free for non-commercial use, built 2026-10-13); CADD (Rentzsch et al. 2019, University of Washington — free for non-commercial use, built 2026-10-10); Conservation (phyloP/phastCons/GERP) (UCSC hg38 470-way mammal (Hiller Lab) + Ensembl Compara, built 2026-07-12); gnomAD Non-coding Constraint (Gnocchi) (Chen et al. 2024, Broad Institute — CC0, built 2026-10-11); gnomAD Regional Missense Constraint (Broad Institute — CC0, built 2026-10-13); Pangolin (Zeng & Li 2022 — CC BY 4.0, built 2026-10-11); Repeat regions (UCSC — RepeatMasker, TRF, segmental duplications, built 2026-10-11); ClinGen (ClinGen, built 2026-09-22); UniProt (CC BY 4.0); Reactome / GO (CC BY 4.0, built 2026-09-23); MaveDB (per-record license, built 2026-10-11); CIViC (CC0, built 2026-09-22); Orphanet (Orphanet, built 2026-06-12)

*Primary record: NCBI ClinVar (variation 1685328). Classifications reflect these databases as of the page's build date and may change. Free reference use — not medical advice; consult the primary submitters and a clinician.*