In this issue of Gut, Domon-Dell and colleagues¹ report the influence of butyrate on the intestinal homeobox gene Cdx2 [see page 525]. Butyrate is a byproduct of fibre fermentation by colonic bacteria and is known to be a substrate for colonocytes. Over the last few years there has been increasing interest in the function of genes involved in controlling the anatomical relationships between various organs. This article therefore touches on the role of homeobox genes and dietary factors in gut growth and differentiation.

The development of multicellular animals is dependent on expression of a hierarchy of genes that sequentially provide increasingly detailed positional information. Many of these genes contain a highly preserved “homeobox” sequence that codes for a DNA binding homeo domain. In insects, a group of such genes—specifying the individual characteristics of body segments and known as homeotic selector genes of the Antp-type (the defining gene is named Antennapaedia)—are clustered in a complex known as the HOM cluster. These are expressed topographically in the same order as they occupy in chromosomal DNA. They are conserved strongly during evolution so that their homologues appear as four paraologous gene complexes known as Hox complexes which specify positional information in mammalian embryos.

Other homeobox genes are scattered in …