ClinVar

Description

The c.1102C>T variant in MYOC is predicted to cause a change in the length of the protein due to the insertion of a terminating codon instead of the usual Glutamine at amino acid 368 (p.Gln368Ter). This variant is predicted to cause a deletion of >= 10% of the protein within the conserved olfactomedin domain, meeting PM4. Although this variant had a minor allele frequency of 0.003344 in the European (Finnish) population of gnomAD (84 alleles out of 25,118), which meets the >= 0.001 threshold for BS1, Gln368Ter is exempt from this criterion due to its incomplete penetrance and the presence of a common disease haplotype in all carriers. There was no computational evidence predicting a damaging or benign impact of this variant on MYOC function. This variant is exempt from the rule which normally does not allow the application of PS4 unless PM2_Supporting is met. 23 probands with juvenile or primary open angle glaucoma (JOAG or POAG) have been reported carrying this variant (PMIDs: 11535458, 11004290, 10815160, 22736945, 11803488, 12189160), which met PS4 (>= 15 probands). As this variant is exempt from the application of BS1, PP1 has been applied. 52 segregations in 10 families, with JOAG or POAG, have been reported (PMIDs: 11004290, 10815160, 11535458), which fulfilled PP1_Strong (>= 7 meioses in > 1 family). There were many more probands and family studies published than presented here. A previous study (PMID: 16466712) demonstrated that the Gln368Ter protein had reduced secretion levels compared to wild type myocilin protein and met the OddsPath threshold for PS3_Moderate (> 4.3), indicating that this variant did impact protein function. In summary, this variant met the criteria to receive a score of 12 and to be classified as pathogenic (pathogenic classification >= 10) for juvenile open angle glaucoma based on the ACMG/AMP criteria met, as specified by the ClinGen Glaucoma VCEP (v1, 12 Oct 2021): PS4, PP1_Strong, PM4, PS3_Moderate.