The w gene product is highly conserved among many insects and is structurally related to the human protein ABCG1 that is associated with multiple mental health disorders (Kirov et al., 2001; Nakamura et al., 1999). In addition to the Drosophila eye, the w gene is highly expressed in the head outside of the eye (Campbell and Nash, 2001), in the prepupal fat body (functionally analogous to the vertebrate liver), and the adult Malpighian tubules (functionally analogous to the vertebrate kidney) (Chintapalli et al., 2007). The w locus could therefore be important for the function of the brain and other organ systems in addition to the eye in Drosophila. Consistent with this possibility, several studies have shown that endogenous w or mini-w influence multiple non-visual processes. Null mutants for w have altered levels and localization of the biogenic amines dopamine, serotonin, and histamine in heads (Borycz et al., 2008; Sitaraman et al., 2008), are resistant to sedation by volatile anesthetic gases (Campbell and Nash, 2001) and have poor place memory (Diegelmann et al., 2006). Expression of w is found in fly
