The Groucho/Tle family of corepressor proteins has important roles in 
development and in adult tissue in both Protostomes and Deuterostomes. In 
Drosophila, a single member of this family has been identified. Unlike in 
Protostomes, most Deutrostomes contain more than two full-length Tle genes. In 
this study, I analyse the genomic organization and phylogenetic relationship 
between the long and short forms of the Groucho/Tle family members in Chordata. 
The genomic location and sequence similarities suggest that Aes/Grg5 and 
Tle6/Grg6 arose from duplication of the Tle2 gene; each evolved independently 
and acquired new functions as negative regulators of the other Tle proteins. 
Based on these data, a model for Groucho/Tle gene evolution is proposed.