Normal development of spinal axons in early embryo stages and posterior locomotor function is independent of GAL‐1

Abstract

It was recently described that Galectin-1 (Gal-1) promotes axonal growth after spinal cord injury. This effect depends on protein dimerization, since monomeric Gal-1 fails to stimulate axonal re-growth. Gal-1 is expressed in vivo at concentrations that favor the monomeric species. The aim of the present study is to investigate whether endogenous Gal-1 is required for spinal axon development and normal locomotor behavior in mice. In order to characterize axonal development, we used a novel combination of 3-DISCO technique with 1-photon microscopy and epifluorescence microscopy under high power LED illumination, followed by serial image section deconvolution and 3-D reconstruction. Cleared whole lgals-1 embryos were used to analyze the 3-D cytoarchitecture of motor, commissural, and sensory axons. This approach allowed us to evaluate axonal development, including the number of fibers, fluorescence density of the fiber tracts, fiber length as well as the morphology of axonal sprouting, deep within the tissue. Gal-1 deficient embryos did not show morphological/anatomical alterations in any of the axonal populations and parameters analyzed. In addition, specific guidance receptor PlexinA4 did not change its axonal localization in the absence of Gal-1. Finally, Gal-1 deficiency did not change normal locomotor activity in post-natal animals. Taken together, our results show that development of spinal axons as well as the locomotor abilities observed in adult mice are independent of Gal-1. Supporting our previous observations, the present study further validates the use of lgals-1 mice to develop spinal cord- or traumatic brain injury models for the evaluation of the regenerative action of Gal-1.

BrainFilm, a novel technique for physical compression of 3D brain slices for efficient image acquisition and post-processing

“…Tissue shrinkage may cause distortion of the sample structure and reduce spatial resolution/accuracy of the images, thus the application of this technique is limited to non-quantitative morphometric analyses 11 – 13 . However, mechanical compression has been proposed to increase the depth acquisition from a cleared embryo 14 , which also shortens the duration of imaging 3D axonal projections. To further reduce the burden of data collection, a version of iDISCO, uDISCO, has recently been developed to achieve isotropic shrinkage (30–55%) of the sample 15 .…”