Characterization of the adenosine deaminase-related growth factor (ADGF) gene family in Drosophila

A novel family of growth factors, with sequence similarity to adenosine deaminase, has been identified in various organisms including flesh fly, tsetse fly, sand fly, mollusk and human. The human homologue, CECR1, is a candidate gene for the genetic disorder cat eye syndrome. Here, we describe six members of this growth factor family in Drosophila and two in vertebrates. The six Drosophila genes, named adenosine deaminase-related growth factors (ADGF), are found at three different chromosomal locations, with one singleton, two in an inverted orientation, and three in a tandem arrangement. These genes show distinct patterns of expression as measured by RT-PCR and Northern blots, indicating gene-specific function. The presence of six ADGF genes in the Drosophila genome suggests that gene duplication and divergence has been important for these growth factors in insect development. Phylogenetic analysis of the 14 extant ADGF-like gene products shows there are at least three major groups, two of which are found in Drosophila. The third appears specific to the vertebrate line. Seven gene duplications are inferred among the ADGF-like genes, most of which occurred long before the origin of Drosophila. Our analysis predicts the existence of several other unsampled ADGF-like genes, both within the species examined here, and in other related invertebrates.