Type XVIII collagen
The endostatin is from the c terminus end of the collagen XVIII, and is known to have an inhibitory effect on the growth of blood vessels.[4] It is speculated that the mutation of type XVIII collagen that occurs in Knobloch syndrome can be located in several variants of endostatin, a gene that interacts with type XVIII collagen to not only develop the ocular system, but to also maintain its visual functionality.This amino acid substitution is deleterious because it blocks the endostatin variant from interacting with laminin.[6] This discovery was significant in that it provided a new genetic locus for Knobloch syndrome, which helped to explain the development of the disease from genomes free of mutation in the COL18A1 gene.The mutations in type XVIII collagen result in a multitude of abnormalities in vision and eye structure, some of which include high myopia, vitreoretinal degeneration, retinal detachment, macular abnormalities, and occipital encephalocele.