Developmental regulation of eukaryotic gene loci: which cis-regulatory information is required?

It is becoming increasingly accepted that gene loci comprise an extensive cis-regulatory system that encodes different layers of regulatory information, all of which are necessary to achieve and maintain tissue-specific gene expression in ontogeny. To gain a detailed understanding of developmental processes, it is clearly necessary to unravel the molecular basis behind the different regulatory processes that control gene expression. This information is also of utmost importance for any practical application that uses gene transfer technology.