Role of MMP2 in postmitotic neuronal migration in the developing chick optic tectum.

DI GUILMI M; SANCHEZ V; SCICOLONE G; RAPACIOLI M; FLORES V

Buenos Aires

Congreso; XII Congreso Latinoamericano y 1ro IberoAmericano de Cs Fisiológicas.; 2006

Asociacion IberoAmericana de Ciencias Fisiológicas, Sociedad Argentina de Fisiologia

Role of MMP2 in postmitotic neuronal migration in the developing chick optic tectum. M Di Guilmi1, V Sanchez1, G Scicolone1, M Rapacioli1, V Flores1,2 1Inst Biologia Celular y Neurocien, Facultad Med UBA, Buenos Aires 2Interdisciplinary Group in Theorical Biolology, Favaloro University, Buenos Aires. Matrix metalloproteinases (MMPs), a family of extracellular enzymes which participate in processing of extracellular matrix (ECM) components are involved in tissue remodeling during the SNC development. This work investigates the pattern of MMP2 activity in the developing optic tectum (OT), a cortical structure organized in alternating neuronal and fibrous laminae. OTs from different embryonic ages (E) from E8 to newly hatched chicks (NH) were used. Tissue homogenates were ultracentrifugated to separate a soluble fraction (SF) and a pellet that was resuspended in buffer containing 0.5% Triton X-100 and then ultracentrifuged to obtain a second supernatant (E1). MMP-2 activity was determinate by SDS-PAGE gelatine zimography. Tissue localization of MMP-2 was detected by immunohistochemical assay in E12. The same method was used to study the subcellular localization of this enzyme by electron microscopy. To determine the localization of MMP-2 activity in the OT, intramolecularly quenched gelatine (DQ) was used as substrate in unfixed cryostat tissue sections. We detected MMP-2 but not MMP-9 activity in the developing OT. The zimographic activity pattern exhibits a biphasic curve with a significant increase between E12 and E14 and an abrupt decrease from E16 until NH in both fractions SN (p=0,0010) and E1 (p= 0,0021). The maximal activity was observed at E12. High activity was detected in layers composed of neurons that are migrating towards their definitive location into a defined specific layer. In situ MMP2 activity mainly localizes at the ventricular zone and also in migrating neurons attached to the basal processes of the radial glial cells. These results were confirmed by electron microscopic studies. Temporo-spatial patterns of MMP-2 expression and activity suggest that MMP2 is involved in regulating the neuronal migration during the OT lamination. Supported by grants from UBACYT and CONICET. Argentina.