A genetic modifier links integrin α5 to the phenotypic variation in fibronectin 1a mutant zebrafish.

Phenotypic variation is often observed in individuals with the same mutation. However, the mechanisms that contribute to this variation remain largely unknown. Fibronectin mutants in both mouse and zebrafish fail to form a functional cardiovascular system, although the penetrance and expressivity of this phenotype vary depending on the genetic background.