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Additional file 2: Supplementary Figure 2. Analysis of synaptic loss in cranial and thoracoabdominal muscles in SMN∆7 mouse model at P12. (A) Schematic diagram of the anatomical locations of cranial muscles (adductor auris longus [AAL] and auricularis superior [AS]) in a dorsally viewed mouse. (B) Schematic diagram of the anatomical locations of thoracic muscles (triangularis sterni [TS]) in a mouse in supine position. (C) Schematic diagram of the anatomical locations of abdominal muscles (external oblique [EO] and rectus abdominis [RA]) in a mouse in supine position. (D-F) Bar charts showing the quantification of percentage of full, partial and vacant endplates in SMN∆7 mice compared to controls in cranial muscles (AAL and AS), thoracic muscles (TS), and abdominal muscles (EO and RA) respectively. Note that all cranial muscles show a significant increase in vacant motor endplates and a significant decrease in fully occupied endplates, whereas non of the thoracic or abdominal muscles show a significant increase in vacant endplates. Two-sided ANOVA with Sidak correction (ns= no significance, *p≤0.05, **p≤0.01, ***p≤0.001 and ****p≤0.0001). n=3 for controls and SMN∆7 mice respectively. Error bars represent mean ± SEM.

Additional file 3: Supplementary Figure 3. Comparison of levels of synaptic loss between the SMN∆7 mouse model and the Smn2B/− mouse model in muscles of three different body regions. (A-C) Bar charts showing the quantification of percentage of full, partial and vacant endplates in SMN∆7 mice compared to Smn2B/− mice in cranial muscles (adductor auris longus and auricularis superior), thoracic muscles (triangularis sterni), and abdominal muscles (external oblique and rectus abdominis) respectively. Note that all SMN∆7 cranial muscles show a significant increase in vacant motor endplates and a significant decrease in fully occupied endplates compared to the Smn2B/− cranial muscles, whereas Smn2B/− thoracic and abdominal muscles are significantly more vulnerable than in SMN∆7 mice. Significance levels indicate the statistical difference between full, partial and vacant endplates when comparing SMN∆7 to Smn2B/− mice. Two-sided ANOVA with Sidak correction (ns= no significance, *p≤0.05, **p≤0.01, ***p≤0.001 and ****p≤0.0001). n=3 for SMN∆7 mice, n=4-5 for Smn2B/− mice. Error bars represent mean ± SEM.

Additional file 1: Supplementary Figure 1. Representative images from Smn2B/- mice. Confocal images from muscles showing NMJs labelled with antibodies against NF (green), SV2 (green) and BTX (red) from control (Smn2B/+) and Smn2B/- mice from muscles located in the head and neck (A,C), thoracoabdominal region (D,F), forelimb (G,I) and hind limb (J,N). Schematic images (B, E, H, K- M) show location of muscles, with colour linking to confocal images from specific muscles. Scale bar = 25um.

Additional file 4: Supplementary Figure 4. Comparison of intrinsic muscle properties in four mouse models of SMA. The colour gradient legend describes seven classification categories of neuromuscular junction pathology according to the percentage of fully occupied motor endplates in a muscle at disease end- stage (see methods section for more details). The tables shows investigated muscles coloured according to its classification categories by percentage of fully occupied endplates in the Smn -/- ;SMN2 (Murray et al., 2008; Murray et al., 2010; Thomson et al., 2012), Taiwanese (Lin et al., 2016), SMN∆7 (Murray et al., 2008; Ling et al., 2012; Comley et al., 2016) and Smn2B/- (Murray et al., 2015) mouse model. (A) The table displays the muscles categorised by delayed synapsing (DeSyn) or fast synapsing (FaSyn). Note that for the LALc muscle, different results were observed in two independent studies (* = (Murray et al., 2008); # = (Thomson et al., 2012)). (B) The table displays the muscles categorised by muscle fibre type (fast-twitch, mixed fibre types and slow-twitch). Note that for the AS, AAL, LALc and lumbrical muscles, different results were observed in two independent studies (* = (Murray et al., 2008); # = (Thomson et al., 2012); + = (Comley et al., 2016); ° = (Ling et al., 2012)).

Comparison between evolutionarily distant receptors can provide critical insights into both structure and function. Sequence comparison between the mineralocorticoid receptors (MR) of the zebrafish (zMR) and human (hMR) reveals a high degree of sequence conservation in the major functional domains. We isolated a zMR cDNA to contrast the transcriptional response to a range of ligands and to establish whether a teleost MR exhibits the amino/carboxyl-terminal interaction (N/C-interaction) previously reported for the hMR. Aldosterone, deoxycorticosterone (DOC) and cortisol induced zMR transcriptional activity with similar efficacy to that observed with the hMR. The hMR antagonist, spironolactone, acted as an agonist with the zMR. The zMR exhibited an N/C-interaction in response to aldosterone but, in contrast to the hMR, cortisol and DOC predominantly stimulated the interaction in the zMR. Conservation of the N/C-interaction between evolutionarily distant MR provides evidence of functional significance.