Pax genes and their role in organogenesis

Pax genes have been cloned on the basis of their homology to the Drosophila segmentation gene paired. They share a common domain, the paired domain, t hat is sufficient to mediate sequence-specific DNA binding. Thus far, nine members have been characterized, which exhibit highly restricted temporal a nd spatial expression patterns. The analysis of mouse mutants has revealed their crucial role in the formation of a variety of tissues. In particular, they are involved in the regulation of early steps in organ development. T hey act to define the regional specification of distinct germ layers.