Fig. 1.

Loss of dSms recapitulates polyamine imbalance of SRS and causes survival defects in Drosophila. a Diagram of human SMS gene structure and wild-type/mutant cDNA constructs. Fourteen mutations identified in SRS are indicated. The asterisks indicate new mutations. b Diagram of Drosophila CG4300 gene structure, predicated mRNA transcripts, and cDNA construct. dSms ^e allele has a P element inserted in the opposite direction of the gene (triangle). Capped line under mRNAs indicates qPCR probe. c Homology of SMS proteins across species scored by amino acid identity and similarity. Protein sequence (coded by gray region indicated in a and b) alignment showing evolutionary conservation (gray background). Arrowheads indicate amino acids affected in SRS. d qPCR of dSms normalized to Rp49 in control, dSms ^e/+, and dSms ^e/e fly heads (mean ± S.E.M.; n = 4 extractions, each extraction from 10 fly heads). e Scatter dot plot of viability index (mean ± 95% CI, n = 14 for dSms ^e/e, 12 for dSms ^RA rescue, 11 for hSms ^wt rescue, and 13 for hSms ⁴⁴³ rescue; each data point represents a sample of ≥80 embryos) of control, dSms ^e/e, and dSms ^e/e flies ubiquitously expressing cDNA constructs. f Diagram of polyamine metabolic pathway (Put putrescine, Spd spermidine, Spm spermine, SPDSY spermidine synthase, N¹-AcSpd N¹-acetylspermidine, PAO polyamine oxidase, SSAT spermidine/spermine acetyltransferase, 3-AAP 3-acetoamidopropanal). g Absolute levels (mean ± 95% CI, n = 9/7 for male control/dSms ^e/e and 9/9 for female control/dSms ^e/e spermidine levels; n = 8/7 for male control/dSms ^e/e and 9/9 for female control/dSms ^e/e putrescine levels; each data point represents a sample of ≥20 flies) of polyamines in the whole body of young (2–5 DAE) flies measured by LC-MS/MS. h Climbing performance (mean ± S.E.M.; each data point obtained from a group of 10 individuals, n = 10 experiments) of male and female flies at 2 DAE. i Fly survival curves (n = 109/106 for control male/female, 75/62 for dSms ^e/e male/female, and 130/132 for dSms ^e/e; actin > dSms ^RA male/female flies) determined by the age-specific number of live individuals. d, e, h, One-way ANOVA post hoc Bonferroni test (d) or Tukey test (e, h), and g Student t test; *P < 0.05, **P < 0.01