Nell-1 transgenic mice compared with nontransgenic littermates. (a) Transgene copy number. The founders (FA and FB) and their progeny (TF₂A1, TF₂A2, and TF₂B1) have copy numbers between 50 and 100. TF₂A1 and TF₂A2 are from the founder A line. TF₂B1, TF₂B2, and TF₂B3 are from the founder B line. (b) RT-PCR analyses of Nell-1 RNA expression in both founders. C, control Nell-1 plasmid; M, muscle; H, heart; B, bone; K, kidney; L, liver. (c) Whole body (without head) RNA of newborn progeny. TF₂A1 and TF₂A2 express different levels of Nell-1. TF₂B1 expresses Nell-1 weakly, while TF₂B2 and TF₂B3 have no Nell-1 expression. (d) Left panels, immunolocalization of Nell-1 protein in newborn NF₂ epithelium, muscle, and calvarial bone. There is no detectable Nell-1 expression (brown staining indicates the presence of Nell-1) except some staining in the calvarial bone. Right panels, immunolocalization of Nell-1 protein in TF₂A2 epithelium, muscle, and calvarial bone. Abundant Nell-1 expression is present throughout all soft tissue layers as well as in bone. Bar represents 50 μm.