T. Eggert et al., ISOLATION OF A DROSOPHILA HOMOLOG OF THE VERTEBRATE HOMEOBOX GENE RX AND ITS POSSIBLE ROLE IN BRAIN AND EYE DEVELOPMENT, Proceedings of the National Academy of Sciences of the United Statesof America, 95(5), 1998, pp. 2343-2348
Vertebrate and invertebrate eye development require the activity of se
veral evolutionarily conserved genes, Among these the Pax-6 genes play
a major role in the genetic control of eye development, Mutations in
Pax-6 genes affect eye development in humans, mice, and Drosophila, an
d misexpression of Pax-6 genes in Drosophila can induce ectopic eyes,
Here we report the identification of a paired-like homeobox gene, DRx,
which is also conserved from flies to vertebrates, Highly conserved d
omains in the Drosophila protein are the octapeptide, the identical ho
meodomain, the carboxyl-terminal OAR domain, and a newly identified Rx
domain, DRx is expressed in the embryo in the procephalic region and
in the clypeolabrum from stage 8 on and later in the brain and the cen
tral nervous system, Compared with eyeless, the DRx expression in the
embryo starts earlier, similar to the pattern in vertebrates, where Rx
expression precedes Pax-6 expression, Because the vertebrate Rx genes
have a function during brain and eye development, it was proposed tha
t DRx has a similar function, The DRx expression pattern argues for a
conserved function at least during brain development, but we could not
detect any expression in the embryonic eye primordia or in the larval
eye imaginal discs, Therefore DRx could be considered as a homolog of
vertebrate Rx genes, The Rx genes might be involved in brain patterni
ng processes and specify eye fields in different phyla.