CG13494 encodes a 120-residue protein found only in the Drosophila melanogaster species group, with orthologs in close relatives such as D. simulans, D. yakuba, D. erecta and D. suzukii. It has a Ser/Thr-rich N-terminal segment, a single predicted transmembrane helix (residues 37-61), and a low-complexity C-terminal tail rich in glycine, cysteine and aspartate (20 cysteines in total). It has no recognised protein family or domain and no characterised homolog in any species. Its transcript is reported mainly in testis, in elongating spermatids. Nothing is known experimentally about its molecular activity, subcellular location or biological role; the transmembrane helix suggests a membrane-anchored protein.
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Download this section (compressed HTML)Q: Is CG13494 a de novo or rapidly evolving testis gene of the melanogaster group, and does its Gly/Cys-rich tail point to a structural role in the spermatid or sperm (for example, a disulfide-crosslinked component like the cysteine-rich sperm and keratin-associated proteins it resembles only in composition)?
Q: Should a membrane (GO:0016020) annotation be made from the Phobius transmembrane prediction alone, given that the 25-residue hydrophobic segment carries four cysteines and sits between two low-complexity regions?
Experiment: Tag endogenous CG13494 (CRISPR knock-in) and image it in testes to find where in the spermatid it localises, with membrane fractionation to test whether the predicted helix anchors it.
Type: Endogenous tagging, microscopy and fractionation
Experiment: Make a CRISPR null allele and test male fertility and sperm development (sperm counts, sperm storage, competition), with genomic rescue to rule out effects on neighbouring genes.
Type: CRISPR knockout and fertility assays
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The molecular activity, subcellular location and biological role of CG13494 are entirely unknown. It is a young, melanogaster-group-restricted gene with no recognised domain, so no function can be transferred from a characterised homolog. Whether the predicted transmembrane helix is a real membrane anchor, and on which membrane, has not been tested.
BIOLOGY WHOLLY_DARK
What is known: Established: a 120-residue product with one Phobius-predicted transmembrane helix (37-61), a Gly/Cys-rich C-terminal tail, orthologs only within the melanogaster species group (OMA), no InterPro signature, and testis/spermatid-enriched transcript expression (Bgee). No gene-specific publication exists.
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