This report describes choroideremia, an X-linked disease that leads to the degeneration of the choriocapillaris, the retinal pigment epithelium, and the photoreceptor of the eye. The human gene implicated is CHD, which encodes REP1, a subunit of a 2-subunit RAB geranylgeranyl transferase. There is one high-scoring fly ortholog, Dmel\Rep, for which multiple genetic reagents, including classical alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated.
The human gene CHD has not been introduced into flies.
Null alleles of Dmel\Rep are lethal when homozygous. Mutant clones were generated in the developing retina by FLP\FRT recombination; by late pupal stages, most homozygous mutant photoreceptor cells were lost, with some areas of the mosaic retinas containing no photoreceptors. This phenotype could be rescued by expression of wild-type Dmel\Rep. Surviving photoreceptor cells deficient for Rep protein exhibit vesicle clusters instead of Golgi stacks. Aging flies in which the mutant phenotype was partially rescued by transgenic Dmel\Rep exhibit retinal degeneration.
[updated Aug. 2026 by FlyBase; FBrf0222196]
[CHOROIDEREMIA; CHM](https://omim.org/entry/303100)
[CHM RAB ESCORT PROTEIN; CHM](https://omim.org/entry/300390)
Choroideremia (CHM) is an X-linked disease that leads to the degeneration of the choriocapillaris, the retinal pigment epithelium, and the photoreceptor of the eye (Cremers et al., 1990, pubmed:2220804). The characteristic lesion of choroideremia is chorioretinal scalloped atrophy in the midperipheral fundus, with preservation of the macula (Li et al., 2014, pubmed:24913019). [from MIM:303100; 2026.08.07]
Choroideremia (CHM) is caused by mutation in the CHM (REP1) gene on chromosome Xq21. [from MIM:3303100; 2026.08.07]
CHM encodes REP1, a subunit of a 2-subunit RAB geranylgeranyl transferase that attaches 20-carbon isoprenoid groups to cysteine residues in Rab proteins, a family of GTP-binding proteins that regulate vesicular traffic (Seabra et al., 1993, pubmed:8380507). [from MIM:300390; 2026.08,07]
Two to one (2 human to 1 Drosophila); CHM has one moderate-scoring Drosophila ortholog, Rep.
High-scoring ortholog of human CHM and CHML (1 Drosophila to 2 human).
