FGF4 and intervertebral disk degenerative disorder: Genome-wide studies of chondrodystrophic dogs have identified a significant association between disc degeneration, namely with calcification and a polymorphism causing overexpression of FGF4 associated with insertion of FGF4 retrogene on domestic dog (Canis familiaris, CFA) chromosome 12 and 18 - CFA12 and CFA18.140 However, other models have not explored the molecular basis of this phenomenon.