WDR79/TCAB1 plays a conserved role in the control of locomotion and ameliorates phenotypic defects in SMA models

Abstract

SMN (Survival Motor Neuron) deficiency is the predominant cause of spinal muscular atrophy (SMA), a severe neurodegenerative disorder that can lead to progressive paralysis and death. Although SMN is required in every cell for proper RNA metabolism, the reason why its loss is especially critical in the motor system is still unclear. SMA genetic models have been employed to identify several modifiers that can ameliorate the deficits induced by SMN depletion. Here we focus on WDR79/TCAB1, a protein important for the biogenesis of several RNA species that has been shown to physically interact with SMN in human cells. We show that WDR79 depletion results in locomotion defects in both Drosophila and Caenorhabditis elegans similar to those elicited by SMN depletion. Consistent with this observation, we find that SMN overexpression rescues the WDR79 loss-of-function phenotype in flies. Most importantly, we also found that WDR79 overexpression ameliorates the locomotion defects induced by SMN depletion in both flies and worms. Our results collectively suggest that WDR79 and SMN play evolutionarily conserved cooperative functions in the nervous system and suggest that WDR79/TCAB1 may have the potential to modify SMA pathogenesis.

Intimate functional interactions between TGS1 and the Smn complex revealed by an analysis of the Drosophila eye development

“…The pan-neuronal drivers elav155-Gal4 and nsyb-Gal4 did not induce lethality or visible . morphological phenotypes ( Figure 4C), such as wing expansion defects, which were instead observed when a UAS-Smn RNAi construct is expressed by the same drivers (Di Giorgio et al, 2017). The results of these RNAi experiments are in line with those previously reported by (Borg et al, 2016).…”

“…Transgenic flies were obtained by injecting the constructs into y 1 v 1 ; P{CaryP}attP40 (2L, 25C6). The tub-Smn-GFP strain used for AP/MS experiments carries a construct the eGFP sequences fused in-frame with the 3′ end of the Smn CDS under control of the tubulin promoter, cloned into the pJZ4 vector (Bruckner et al, 2004;Di Giorgio et al, 2017). All embryo injections were carried out by BestGene (Chino Hills, CA, USA).…”

“…The tub-Smn-FLAG bearing strain was described in (Di Giorgio et al, 2017).The moi + , moi-dTgs1 FL and moi-dTgs1 CD carrying stocks were described in (Raffa et al, 2009). The UAS-dTgs1RNAi stock P{GD14932}v29503, was obtained from the Vienna Drosophila Resource Center (VDRC, www.vdrc.at) (Dietzl et al, 2007).…”

“…Larval locomotion analysis was described previously (Di Giorgio et al, 2017). Briefly, locomotor activity was measured by counting the number of peristaltic contractions per minute of third instar larvae on a surface of a 1% agarose gel in a Petri dish; measurements were repeated ten times.…”

“…Previous studies have shown that loss-of-function mutations in the Drosophila Smn gene result in a variety of phenotypes, including alterations in the sensory-motor neuronal network, abnormal neuromuscular junctions, and defective locomotion (Chang et al, 2008;Imlach et al, 2012;Praveen et al, 2014;Praveen et al, 2012;Sen et al, 2011;Spring et al, 2019). In addition, we have recently shown that Smn depletion in neurons results in unexpanded wings and unretracted ptilinum (Di Giorgio et al, 2017). The ptilinum is a head muscle required to break open the operculum of the puparium, and is normally retracted after fly eclosion.…”