When these ROCK2–/– mice were backcrossed into a C57BL/6 genetic background, they exhibit not only the placental phenotype but also perinatal EOB and omphalocele phenotype (Thumkeo et al. 2005), indicating that genetic background affects the EOB and omphalocele phenotype in ROCK2–/– mice. Here, ROCK2 is linked to omphalocele.