Stability of the mutant ARR4 protein
The human ARR4 protein is composed of 388 amino acids and contains two arrestin-like domains in the N- and C-terminals (Figure 2B). There is only one peer-reviewed report describing three pathogenic ARR4 variants. However, it is still unclear how the variants affect protein function or which pathways play a role in regulating the stability of the protein. In order to observe the effect of the identified variant on protein expression, the mutant and wild-type proteins were labeled with tag flags, transfected into APRE19 cells, and cultured for 48 hours. The mRNA expression of the mutant gene was significantly lower than that of the wild type (Figure 3A). The result showed that ARR4 mutants had significantly lower protein expression than their wild-type counterparts (Figure 3B).