Fig 2. SCaMC is a Ca²⁺-regulated protein required for sperm storage in Drosophila.

(A) D. melanogaster TRPP2 mutants (amo¹) were male sterile (*P = 9 × 10⁻¹¹). (B) Homozygous Z3-2147 males and males with Z3-2147 over a third-chromosomal deficiency deleting CG32103, Df(3L)BSC380, were infertile (both *P = 0.003). Z3-2147/+ heterozygous males showed normal fertility. One copy of the CG32103 cDNA fully rescued the fertility defect in Z3-2147 homozygous males (CG32103/+;Z3-2147). (C) Sequencing chromatogram of SCaMC¹ (Z3-2147) flies. Mutant flies presented with a point mutation on the third chromosome at position 3L:12,405,022, causing a change of thymine to adenine. (D) This missense mutation translates into replacement of basic arginine (R) 308 to nonpolar tryptophan (W) in the evolutionarily highly conserved first mitochondrial carrier domain of SCaMC (CG32103). (E) Mutations in the EF-hand domains of SCaMC (CG32103) impaired its function. SCaMC variants were tested in SCaMC¹ (CG32103^R308W) mutant background. While transgenic rescue with SCaMC wt cDNA (+SCaMC) behaved like wt males, transgenes lacking the N-terminal EF-hands (+SCaMC^Δ1–268) or transgenes comprising missense mutations inactivating the Ca²⁺-binding EF-hand domains (+SCaMC^EF) barely rescued SCaMC¹ male fertility (both *P = 0.0009; compared to wt rescue). (F) Human SLC25A25 cDNA rescued infertility in SCaMC¹ homozygous males (SLC25A25/+; SCaMC¹) (*P = 0.0001). For numerical values, see S1 Data. SLC25A25, solute carrier 25 A 25; TRPP2, transient receptor potential channel polycystin-2; wt, wild-type.