Modification of SMN2 exon 7 (E7) splicing is a validated therapeutic strategy against spinal muscular atrophy (SMA). However, a target-based approach to identify small-molecule E7 splicing modifiers has not been attempted, which could reveal novel therapies with improved mechanistic insight. Here, we chose as a target the stem-loop RNA structure TSL2, which overlaps with the 5′ splicing site of E7. A small-molecule TSL2-binding compound, homocarbonyltopsentin (PK4C9), was identified that increases E7 splicing to therapeutic levels and rescues downstream molecular alterations in SMA cells. High-resolution NMR combined with molecular modelling revealed that PK4C9 binds to pentaloop conformations of TSL2 and promotes a shift to triloop conformations that display enhanced E7 splicing. Collectively, our study validates TSL2 as a target for small-molecule drug discovery in SMA, identifies a novel mechanism of action for an E7 splicing modifier, and sets a precedent for other splicing-mediated diseases where RNA structure could be similarly targeted.
Obesity and depression are major public health concerns, and there is increasing evidence that they share etiological mechanisms. CREB-regulated transcription coactivator 1 (CRTC1) participates in neurobiological pathways involved in both mood and energy balance regulation. Crtc1
−/− mice rapidly develop a depressive-like and obese phenotype in early adulthood, and are therefore a relevant animal model to explore possible common mechanisms underlying mood disorders and obesity. Here, the obese phenotype of male and female Crtc1
−/− mice was further characterized by investigating CRTC1’s role in the homeostatic and hedonic regulation of food intake, as well as its influence on daily locomotor activity. Crtc1
−/− mice showed a strong gender difference in the homeostatic regulation of energy balance. Mutant males were hyperphagic and rapidly developed obesity on normal chow diet, whereas Crtc1
−/− females exhibited mild late-onset obesity without hyperphagia. Overeating of mutant males was accompanied by alterations in the expression of several orexigenic and anorexigenic hypothalamic genes, thus confirming a key role of CRTC1 in the central regulation of food intake. No alteration in preference and conditioned response for saccharine was observed in Crtc1
−
/− mice, suggesting that mutant males’ hyperphagia was not due to an altered hedonic regulation of food intake. Intriguingly, mutant males exhibited a hyperphagic behavior only during the resting (diurnal) phase of the light cycle. This abnormal feeding behavior was associated with a higher diurnal locomotor activity indicating that the lack of CRTC1 may affect circadian rhythmicity. Collectively, these findings highlight the male-specific involvement of CRTC1 in the central control of energy balance and circadian locomotor activity.
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