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

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

Ciudad Autónoma de Buenos Aires, Argentina

Congreso; XXII Latin-American and Fisrt Ibero-American Congress of Physiological Science; 2006

Asoc. Latinoamericana de Ciencias Fisiológicas, Soc. Arg. de Fisiología, Soc. Española de Ciencias Fisiológicas

Matrix metalloproteinases (MMPs), a family of extracellular enzymes which participate in processing of extracellular matrix (ECM) components are involved in tissue remodelling 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) was 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 ol MMP2 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 MMP2 activity in the OT, intramolecularly quenched gelatine (DQ) was used as substrate in unfixed cryostat tissue sections. We detected MMP2 but not MMP9 activity in the developing OT. The zimographic activity pattern exhibits a biphasic curve with a significant increase between E12 and E14 and abrupt decrease from E16 until NH in both fractions SN (p=0.001) 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 pf the radial glial cells. These results were confirmed by electron microscopic studies. Temporo-spatial patterns of MMP2 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