Orthodenticle

Orthodenticle is a homeobox gene involved in head development. It produces a homeodomain protein which controls the development of cells in the developing head of embryos. It defines the midline of the head, and is involved in the formation of the top side of the head, including the eyes.^[1]

The gene breaks the head down into subdomains; the medial subdomain (contains the ocelli); the mediolaterial ; and the lateral (just above the compound eyes).^[1] If orthodenticle is not expressed, structures from the lateral subdomain will be expressed all the way over the head - meaning that ocelli are not produced.^[2]

References

1. ^ ^{a b} Royet, J; Finkelstein, R (1995), "Pattern formation in Drosophila head development: the role of the orthodenticle homeobox gene", Development 121 (11): 3561–3572, PMID 8582270, http://dev.biologists.org/cgi/reprint/121/11/3561.pdf 
2. ^ Friedrich, M (2006), "Ancient mechanisms of visual sense organ development based on comparison of the gene networks controlling larval eye, ocellus, and compound eye specification in Drosophila", Arthropod Structure and Development 35 (4): 357–378, doi:10.1016/j.asd.2006.08.010, PMID 18089081, http://friedrichlab.googlepages.com/Friedrich2006b.pdf