Figure 2

Over-expression of STRAD isoforms leads to the initiation of multiple axons. Multiple splice variants of each STRAD gene were tested for their ability to elicit supernumerary axons alone or with LKB1. Wild-type E15.5 cortices were electroporated with designated constructs and axon number, as determined by MAP2/Tau immuno-labeling, was quantified in GFP⁺ cortical neurons after five days in vitro. Representative neurons from each condition are shown. Neither LKB1 nor individual STRADα splice forms exhibit a significant increase in multi-axon cells (A-G). When co-expressed with LKB1, all forms of STRAD are sufficient to significantly drive the formation of multiple axons (B’-F’) except the truncated form of STRADβ, (G, G’). Scale bar = 50 μm. ***P <0.001 (two-way ANOVA with Bonferroni’s post-test comparing the STRAD isoform + LKB1 with the STRAD isoform + GFP). (H) Quantification of N = 3 to 6 independent experiments for each set of constructs. >300 GFP⁺ cells counted in each condition. ANOVA, analysis of variance; E, embryonic day; MAP2, microtubule associated protein 2.