Caratterizzazione molecolare e funzionale di una nuova linea di topi transgenici per l'analisi in vivo degli esoni di BDNF (BLEV)

Brain-derived neurotrophic factor (BDNF) is a key neurotrophin which plays an important role in the alteration of synaptic efficacy, the balance between inhibition and excitation and the activity-dependent plasticity (Mandas et al. 2009; Reichardt 2006). BDNF possesses a characteristic gene structure: a common protein-encoding exon (IX), which can be alternatively spliced to any of the eight non-coding upstream exons (I-VIII). This results in different BDNF transcripts which lead to only one protein (Aid et al. 2007; Timmusk et al. 1993) The role of the differential usage of the untranslated BDNF exons during plasticity changes is still unknown (Chiaruttini et al. 2008; Pattabirmaman et al. 2005; Rich and Wenner 2007). In this study we focused on BDNF exon IV and VI, which have been demonstrated to be differentially targeted in an activity dependent manner into a neuron´s soma and its dendrites (Tongiorgi 2008; Chiaruttini et al. 2007; Baj et al. 2011). A construct was designed for the generation of a transgenic mouse line in which the transcription of BDNF exon IV and VI can be visualized in parallel via either a cyan (BDNF exon IV) or a yellow (BDNF exon VI) fluorescent protein, without affecting the basal BDNF expression. In the present study, this newly generated mouse line called BLEV (BDNF Live Exon Viewing) was analyzed for the first time in order to describe its usefulness for the analysis of the untranslated BDNF exon IV and VI. Therefore, the basic phenotype of the mouse line was analyzed, as well as the basal BDNF expression. Furthermore, the activity-dependent usage of the BDNF promoters IV and VI was detected. In a subsequent step, special focus was laid on the auditory system by analyzing the hearing function and the inner hair cell physiology of the BLEV mice. The heterozygous and homozygous BLEV mice were found to have in all analyzed functional and molecular aspects a similar phenotype as the Wild Type animals, meaning that this mouse line is a useful model organism for future studies.