Digit ratio in birds.

The Homeobox (Hox) genes direct the development of tetrapod digits. The expression of Hox genes may be influenced by endogenous sex steroids during development. Manning (Digit ratio.

Down-regulation of class II phosphoinositide 3-kinase alpha expression below a critical threshold induces apoptotic cell death.

Members of the phosphoinositide 3-kinase (PI3K) family collectively control multiple cellular responses, including proliferation, growth, chemotaxis, and survival. These diverse effects can partly be attributed to the broad range of downstream effectors being regulated by the products of these lipid kinases, the 3'-phosphoinositides. However, an additional layer of complexity is introduced by the existence of multiple PI3K enzyme isoforms.