ABCD1 and X-linked adrenoleukodystrophy: The biochemical hallmark in patients with X-linked adrenoleukodystrophy (X-ALD) is the accumulation of VLCFAs (C>22), particularly C26:0 (hexacosanoic acid), and to a lesser extent, C24:0 (tetracosanoic acid) and with nominal difference in C22:0 (docosanoic acid, not considered a VLCFA).40 Thus, we assessed for a similar biochemical signature in both the RNAi-mediated knockdown (Abcd1-RNAiGD and Abcd1-RNAiKK) with da-GAL4 and the Abcd1 out-of-frame small deletion (Abcd1Δ4/Δ4) larvae using gas chromatography-mass spectrometry (GCMS) (Figure 3).