Identification of rare coding EFEMP1 variants in three
families with JOAG.
Whole exome sequencing was completed for selected affected and
unaffected family members, and exome data was filtered to retain rare
variants (MAF < 0.1%) that were protein altering and
predicted to be pathogenic using in silico programs. Mutations were
identified in known disease-causing genes in 4 families, three withMYOC mutations (p.Ter505Trpext*42; p.Gln337Arg; p.Thr438Ile) and
one with a PAX6 mutation (p.Tyr296*). Novel variants of interest (Table
S2) were further evaluated for co-segregation with disease in each
pedigree using Sanger sequencing. Rare EFEMP1 (MIM: 601548)
coding variants (GenBank: NM_001039348.3) were identified in all
affected individuals of 3 of the remaining families as follows:
(c.238A>T, p. Asn80Tyr) in 16 affected individuals of
Family A and not in 18 unaffected family members older than age 18;
(c.1480T>C, p. Ter494Glnext*29) was identified in 17
affected family members in family B and not in any family members older
than age 18. One Family A member (age 13) and 4 Family B members (ages
7-12) were identified as mutation carriers, but are likely to be too
young to manifest disease. Additionally, a third variant
(c.1429C>T, p.Arg477Cys) was identified in a single case
(Family C) (Figure 1A).
Patients with EFEMP1 variants (N= 34 in total for all three
families) exhibited severe disease with average age of disease onset of
16 years (range 3-43). Affected individuals had much higher than average
IOP (28mmHg) and 76% were blind in at least one eye (Table 1). The
majority of patients required surgical treatment for IOP elevation,
however not all patients had access to clinical care. Retinal
examination did not reveal evidence of subretinal deposits (drusen)
characteristic of MLVT/DHRD in affected individuals (Figure 2).
The three variants p.Asn80Tyr, p.Ter494Glnext*29, and p.Arg477Cys,
identified in affected individuals are not present in population
databases including gnomAD and TOPMed and have not been previously
reported (the stop loss variant, p.Ter494Glnext*29 is not the same
variant as reported in a small Chinese adult onset glaucoma family) (Liu
et al., 2020). All three variants are predicted to be deleterious by in
silico programs SIFT and Polyphen2 (Table S3). p.Asn80Tyr is located
within the first EGF-domain, while p.Arg477Cys and p.Ter494GLNext*29 are
within the terminal fibulin-like carboxy terminal domain.
p.Ter494GLNext*29 results from replacement of the wild type stop codon
with a glutamine residue and the addition of 29 amino acid residues to
the polypeptide before a stop codon is encountered (Figure 1B).