GNPAT and rhizomelic chondrodysplasia punctata: In humans, mutations in the GNPAT gene have been associated with rhizomelic chondrodysplasia punctata, a condition characterized by severely impaired endochondral bone formation, rhizomelic shortening of the femur and humerus, vertebral disorders, dwarfism, cataract, cutaneous lesions, facial dysmorphism and severe mental retardation with spasticity.31 Consistent with its important role in development, deleting Gnpat expression in mice gives rise to a variety of postnatal defects, including impaired growth.