Fig3f Ptn +/+ top. Copyright: This image is from [doi:10.1002/gene.10091] Loebel DA, O'Rourke MP, Steiner KA, Banyer J, Tam PP., "Isolation of differentially expressed genes from wild-type and Twist mutant mouse limb buds." Genesis 2002 33(3):103-13. Reprinted with permission of Wiley-Liss Inc. [PMID:12124942]