The identification and functional characterisation of conserved regulatory elements in developmental genes

Understanding the mechanisms that govern the expression of genomes is one of the major challenges of the post-genomic era. Phylogenetic footprinting, which identifies genomic regions under evolutionary constraints, has proven helpful in finding cis-regulatory elements of transcription; however, this method may not be applicable across all evolutionary distances and for all types of genes. Recent results from vertebrate comparisons indicate that strong conservation of cis-regulatory regions may occur more frequently in developmental regulator genes. This paper reviews methods of identifying conserved regulatory elements of developmental genes by comparative genomics, including new attempts to detect conserved features beyond simple sequence similarities. The results obtained are outlined and the authors comment on their functional and evolutionary implications. Finally, an evaluation of currently available methods of characterising the function of presumed conserved regulatory regions is presented, and problems such as promoter compatibility, assigning distant elements to their cognate genes and multifunctionality of elements, discussed.