REQUIREMENT FOR BMP SIGNALING IN INTERDIGITAL APOPTOSIS AND SCALE FORMATION

Interdigital cell death leads to regression of soft tissue between emb ryonic digits in many vertebrates. Although the signals that regulate interdigital apoptosis are not known, BMPs-signaling molecules of the transforming growth factor-beta superfamily-are expressed interdigital ly. A dominant negative type I BMP receptor (dnBMPR-IB) was used here to block BMP signaling. Expression of dnBMPR in chicken embryonic hind limbs greatly reduced interdigital apoptosis and resulted in webbed f eet. In addition, scales were transformed into feathers. The similarit y of the webbing to webbed duck feet led to studies that indicate that BMPs are not expressed in the duck interdigit. These results indicate BMP signaling actively mediates cell death in the embryonic limb.