To correct genetic defects in GCD patient cells, we designed a disease-specific guide RNA (gRNA) targeting the R124H mutation of TGFBI, which causes GCD type 2 (GCD2).
Typical corneal non-amyloid deposits from GCD type 2 (R124H), amyloid from a variant of LCD type 1 (V624M) and disease-free tissue controls were procured by laser capture microdissection and analyzed by tandem mass spectrometry.
We identified the following mutations: lattice corneal dystrophy--R124C and A546T; Reis-Bücklers corneal dystrophy--R555Q and R124L; granular corneal dystrophy--R555W and Avellino dystrophy--R555W.
In GCD, 18 patients with GCD type I had a mutation of arginine 555-to-tryptophan (Arg555Trp) and 1 patient with GCD type III (Reis-Bucklers dystrophy), had the Arg124Leu mutation.
In 68 unrelated patients who had been diagnosed with GCD, 62 patients (91%) were found to have the R124H mutation, which has been reported to cause ACD, whereas only six patients (9%) had the R555W mutation.
All 34 patients with the R124L mutation displayed the clinical, histologic, and electron microscopic features of the dystrophy previously described as a superficial variant of corneal granular dystrophy.
The homozygous R124H keratoepithelin mutations are the cause of the severe variant of GCD characterized by juvenile-onset and confluent superficial opacity.