Probable regulator of osteoblast differentiation. Plays essential roles in both eye and limb development. In or around the basement membrane. Widely expressed in many tissues with a strongest signal in ovary. Found in the forebrain, midbrain, hindbrain, pharyngeal arch, somites, and forelimb buds at day 9.5 dpc. At day 10.5 dpc, strongly expressed in dorsal neural tube, developing pharyngeal arches and frontonasal region with low expression in the ectoderm overlying the developing optic vesicle, expression can be observed in the optic stalk. At 11.5 dpc it is localized to the closure site of the optic cup. In developing limbs between days 10.5 dpc and 11.5 dpc, it is found in both dorsal and ventral regions, but expression is predominant dorsal in hindlimb bud and not detected in the most anterior, posterior, and distal parts of limb buds. Expression coinciding with chondrogenic condensation can be observed at 12.5 dpc. Expression is restricted to future synovial joint regions at day 13.5 dpc. Glycosylated. Null mice present with a phenotype resembling human microphthalmia with limb anomalies. The phenotype includes aplasia or hypoplasia of optic nerves, hypoplastic fibula and bowed tibia, and syndactyly in limbs. A thinned and irregular ganglion cell layer and atrophy of the anteroventral part of the retina is observed.