[Dorso-ventral patterning of the vertebrate limb and dermatoglyphs with special reference to the pad pattern of mice]

The proximo-distal (P-D), antero-posterior (A-P) and dorso-ventral (D-V) axes are important for normal limb development in vertebrates. It has been reported that D-V axis is decided by Wnt-7a, Lmx-1 and Engrailed-1 (En-1) which are expressed in the limb bud along D-V axis. These factors are thought to be required for formation of the apical ectodermal ridge (AER) which is necessary for outgrowth of the limb. The results from spontaneous mutant mice meromelia (mem), which exhibits double-dorsality of the distal limb, suggested that other factors, not only En-1 and Wnt-7a are required for decision of AER, and mem was probed to be novel gene regulating En-1 and Wnt-7a directly or indirectly. The dorsalized ventral structures in meromelia were found by observation of the pad pattern. Pad pattern is always constant in normal mice, and each pad indicates particular part of the limb. So pad pattern is useful to detect and describe anomalies even in the limbs without skeletal defects. The process of pad development is associated with the limb patterning, and abnormal pad pattern may indicate pathogenesis of abnormal limb development. The mouse pad pattern is usable as the model for human dermatoglyphs, and it is also important to investigate mechanisms of human diseases.