Molecular genetic analysis of R124H TGFBIp in one family Avellino corneal dystrophy.

Purpose: The mutation of R124H in TGFBIp causes Avellino corneal dystrophy (ACD, GCD II). However, the molecular mechanisms of ACD caused by the p. R124H mutation are not well understood. In our research, we aimed to explain the molecular mechanisms of ACD caused by the R124H mutation.

Methods: The whole blood of a three-generation family having ACD was studied with the whole exome sequencing. Sanger sequencing was used to identify the mutation gene. The mutant structure of R124H TGFBIp was visualized in Pymol, using the PISA server, Coot and the HDOCK automated docking program. The TGFBIp was expressed in mammalian expression system. And size exclusion chromatography (SEC) was used to identify the aggregate state of TGFBIp.

Results: The whole exome sequencing results showed that there was a c.371G>A mutation in the TGFBI gene in one family, including three patients. In biochemical assays, the purified soluble wild-type TGFBIp and R124H TGFBIp formed a homodimer through a novel interface distinct from the previously proposed FAS1-1: FAS1-4 dimer (interface I). R124H TGFBIp is likely to have formed more severe cross-links and aggregation. Therefore, R124H TGFBIp causes homozygous patients to have more serious symptom than heterozygous patients.

Conclusions: In our study, one family having ACD harboring the mutation of R124H TGFBIp was identified. A new homodimerization interface was determined for wild-type TGFBIp and R124H TGFBIp. Besides, we provided a possible molecular explanation for why the symptom of homozygous patients was more severe than those of heterozygous patients. The possible molecular explanation can provide a new insight into the treatment of ACD.