Evidence for the Role of the Glycoprotein M6a in Dendritic Spine Formation and Synaptogenesis.

KARINA FORMOSO; GARCIA, MICAELA D; APARICIO GABRIELA; ALBERTO C C FRASCH; CAMILA SCORTICATI

Congreso; Congreso FALAN; 2016

Membrane glycoprotein M6a has been related to neuronal development in different experimental models. M6a induces neurite, axon and filopodia outgrowth in neurons whereas its role in spinogenesis and synaptogenesis remains unknown. To test this, cultured hippocampal neurons at 14-16 days expressing GFP or M6a fused to GFP were labeled with synaptophysin (pre-synaptic marker) and NMDA-R1 (post-synaptic marker). The number of synapses (points of double colocalization) in M6a expressing neurons was significantly higher compared with GFP-expressing neurons. Spine density was measured from three-dimensional visualizations of 10 micrometres segments of second or third order dendrite branches from a minimal of 3 segments per neuron. Additionally, spines were categorized in filopodia, long thin, stubby, mushroom and cup-shaped based on their morphological features. Here we showed that M6a-expressing neurons display a significant increase in dendritic spine density associated with an increase in filopodia and mushroom shaped compared with control neurons. We also analyzed whether 2 non-synonymous polymorphisms (nsSNPs) present in the coding region of the human M6a´s transmembrane domains affect synapse and spine formation. Neurons expressing M6a´s mutants showed similar levels of number of synapses and spine density to control neurons. Together, our results situate glycoprotein M6a as a regulator of spine number/shape and synapse formation.