NOG and corneal ulcer: Our data have demonstrated that many Boxer dogs with superficial nonhealing corneal ulcers have a genetic defect in the NOG gene (a 30 base pair deletion at a splice site in NOG [Chromosome 9:31,453,999-31,454,029]), which encodes the protein noggin, a constitutively-secreted, 46 kDa, disulfide-linked homodimer consisting of two, 206 amino acid polypeptide chains [30].