SPECIFIC ORGANIZATION OF EXTRACELLULAR MATRIX IN THE OLFACTORY BULB: MOLECULAR COMPOSITION OF AXONAL COAT
Andrea Hunyadi1, Zoltán Mészár1, Alán Alpár2, Dávid Lendvai2, Klára Matesz1, Botond Gaál1, Éva Rácz1
Distribution of extracellular matrix (ECM) molecules shows regional differences in the central nervous system. The ECM molecules are organized into diffuse network in the neuropil or appear in a highly condensed form as the perineuronal net (PNN) around the perikarya, proximal dendrites and axon initial segments, as the nodal ECM surrounding the Ranvier nodes or small, ring-like structures of 2–4 µm representing the axonal coats (AC) around the axon terminals. Previously we described the distribution of ECM molecules in the neuropil of the olfactory bulb (OB). The aim of our study was to examine the molecular composition of the highly condensed AC around the axon terminals. The experiments were performed on adult female Wistar rats and human OB. Hyaluronan (HA) was detected with biotinylated Hyaluronan Binding Protein. WFA histochemistry was performed using biotinylated Wisteria floribunda agglutinin as a general marker of PNN. Lecticans (aggrecan, brevican, versican and neurocan) were detected with antibodies. Double fluorescent labeling was made using neurofilament antibodies. Our results showed that the AC like structures were positive with aggrecan, brevican and HAPLN1 antibodies in the glomeruli of rat and human OB. This expression pattern was similar to those described in other parts of central nervous system. We can suppose that the possible role of this condensed type of ECM is stabilization of synaptic contacts between the olfactory axon terminals and dendrites of periglomerular cells. Support: EFOP-3.6.3-VEKOP-16-2017-00009, OTKA K115471 and MTA TKI355.