ACCUMULATION OF BETA-IG-H3 GENE-PRODUCT IN CORNEAS WITH GRANULAR DYSTROPHY

We isolated and identified the major protein present in corneas with g ranular dystrophy (GCD). We compared Coomassie-blue-stained protein ba nds obtained on sodium dodecyl sulfate polyacrylamide gel electrophore sis (SDS-PAGE) from the extracts of corneas with GCD, corneas with oth er disorders, and normal human corneal tissue. After SDS-PAGE and tran sfer to a polyvinylidene difluoride membrane, bands of interest were a nalyzed by amino acid sequencing and by Western blotting. Corneas with GCD were also examined immunohistochemically. On SDS-PAGE a 63-kd ban d just below albumin was present in extracts of all corneas. The album in/63-kd ratio was normally approximately 3:1, suggesting that the pro tein is a dominant constituent of the cornea. This band was much more plentiful than normal in corneas with GCD. Amino-terminal sequence ana lysis of the protein revealed a la-Lys-Ser-Pro-Tyr-Gln-Leu-Val-Leu-Gln -His-Ser-Arg sequence indistinguishable from an amino-terminal protein sequence deduced from a cDNA clone designated beta ig-h3, and it as w ell as the abnormal accumulations in GCD crossreacted with beta ig-h3 antiserum. The presence of excessive beta ig-h3 in human corneas with GCD together with reported mutations in the beta ig-h3 gene in GCD sug gests that the mutated gene product is a fundamental constituent of th e characteristic corneal accumulations in GCD.