Effect of TTC8
on the protein. A) The normal retina-specific and ubiquitous isoforms encode 515 and 505 amino acids respectively. The proteins differ only with the presence or absence of 10 amino acids unique to the retina-specific isoform (grey). The remainder of the protein is identical in both isoforms. B) Both isoforms are affected by the c.669delA variant. 233 amino acids at the N-terminus of the retina-specific protein and 223 of the ubiquitous isoform are normal. However the deletion causes a shift in the reading frame of 15 amino acids, leading to a premature termination codon. This results in a truncated protein product, lacking 267 residues of the C-terminus of both isoforms. More than half of the protein is therefore absent.