title: Developmental expression of matrix metalloproteinases 2 and 9 and their potential role in the histogenesis of the cerebellar cortex.
abstract: The development of the cerebellar cortex depends on intrinsic genetic programs and orchestrated cell-cell/cell-matrix interactions. Matrix metalloproteinases (MMPs) are proteolytic enzymes that play an important role in these interactions. MMP-2 and MMP-9 are involved in diverse neuronal functions including migration, process extension, and synaptic plasticity. We investigated the spatiotemporal pattern of expression/activity of MMP-2/MMP-9 in the developing cerebellum and their role in the histogenesis of the cerebellar cortex. The levels of transcripts of MMP-2/MMP-9 were measured with real-time quantitative polymerase chain reaction. An initial decrease in MMP-2/MMP-9 transcripts was observed between postnatal days 3 (PD3) and PD6, and the mRNA levels remained relatively constant thereafter. Zymographic analysis revealed that the expression/activity of MMP-2/MMP-9 persisted longer than their transcripts; the downregulation occurred around PD9, suggesting a mechanism of translational or post-translational regulation. The gelatinase activity was localized in the external granule layer (EGL) and the internal granule layer during PD3-PD12. The immunoreactivity of MMP-2 was mainly localized in the EGL, the Bergmann glial fibers, and the Purkinje cell layer (PCL), whereas MMP-9 immunoreactivity was detected intensively in the PCL and the extracellular space of the molecular layer. Expression of MMP-9 was relatively weak in the EGL. The immunoreactivity of MMP-2/MMP-9 became undetectable after PD21. A similar expression pattern of MMP-2/MMP-9 was observed in organotypic cerebellar slice cultures. Exposure of organotypic slices to a specific MMP-2/MMP-9 inhibitor significantly increased the thickness of the EGL and concurrently decreased the number of migrating granule neurons in the molecular layer. Thus, MMP-2 and MMP-9 play a role in the postnatal cerebellar morphogenesis.
authors.affiliation: Department of Neurobiology and Anatomy, West Virginia University School of Medicine, Robert C. Byrd Health Sciences Center, Morgantown, West Virginia 26506, USA.
authors.forename: Albert E
authors.initials: AE
authors.lastname: Ayoub
authors.forename: Tian-Quan
authors.initials: TQ
authors.lastname: Cai
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Kaplan
authors.forename: Jia
authors.initials: J
authors.lastname: Luo
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002525:Cerebellar Cortex / Q000166:cytology / Q000196:embryology / Q000201:enzymology*; D005109:Extracellular Matrix / Q000201:enzymology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism*; D009924:Organ Culture Techniques; D038081:Organogenesis / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution
chemical_list: D012333:RNA, Messenger; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9