Silkie the "SHH" gene, called the ZPA Regulatory Sequence (ZRS). This causes ectopic "SHH" expression in the anterior of the developing limb bud, leading to increased tissue growth and digits. While the feet of the Silkie display polydactyly, the wings have the standard tridactyly (three digit) arrangement. The Japanese Silkie initially develops additional digits in the wing as an embryo, but these are lost prior to hatching. The genetic cause behind Silkie polydactyly differs from those that cause polydactyly in the Dorking chicken breed, which is due to ectopic "FGF4" expression in the AER, with ectopic "SHH" a secondary effect. The
Blue Bird Micro Bird of a passenger van to a school bus. In another departure from precedent, the MB-series buses utilized aluminum body panels in place of steel. The MB-II was offered with two different entry door configurations: a standard bus door (standard on Ford-chassis buses) and a van-style door (standard on Chevrolet/GMC G-van prior to 1997). In 2009, Girardin Minibus entered its second joint venture with Blue Bird. The partnership, named Micro Bird, Inc., consolidated all Type A school bus production at the Girardin facilities in Drummondville, Quebec, Canada. Under the agreement, Blue Bird shifted production of van-based buses to Girardin (to again