GDF6 and Klippel-Feil syndrome 1, autosomal dominant: Of those, one of particular interest was Growth differentiation factor 6 (GDF6) which is a member of the bone morphogenetic protein (BMP) sub-family and has been previously associated with a wide range of phenotypes including ocular, such as microphthalmia and coloboma, as well as skeletal, such as Klippel-Feil syndrome (KFS) which is characterized by fusion of any two of the seven cervical vertebrae [67], [68].