ClinVar Genomic variation as it relates to human health

The c.1372_1373del variant in the glucokinase gene, GCK, causes a frameshift in the protein at codon 458 (NM_000162.6), adding 75 novel amino acids before encountering a stop codon (p.(Lys458GlufsTer75)). This variant, located in exon 10 of 10, is predicted to cause loss of a stop codon and result in an elongated protein. The additional residues are expected to cause improper folding, resulting in loss of function in a gene in which loss-of-function is an established disease mechanism (PVS1; PMID 19790256). Additionally, this variant is absent in gnomAD v.2.1.1 (PM2_Supporting). This variant was identified in 2 unrelated individuals with a clinical picture consistent with non-autoimmune/insulin-deficient diabetes, however PS4 cannot be applied because this number is below the MDEP threshold (internal lab contributors). This variant was identified in a case consistent with GCK-hyperglycemia but there was insufficient clinical information to evaluate for PP4 (internal lab contributors). This variant segregated with disease with one informative meiosis in a family with MODY, however this does not meet the thresholds for PP1 set by Jarvik and Browning (PMID 27236918) (internal lab contributors). In summary, c.1372_1373del meets the criteria to be classified 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): PVS1, PM2_Supporting.

Converted during submission to Likely pathogenic.

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 well. However, there is no sufficient evidence to assertain the significance of rs193922284 in MODY, yet. This variant is shown to be potentially damaging by insilico analysis.