Aggrecan regulates telencephalic neuronal aggregation in culture.
Proteoglycans have been suggested to play roles in pattern formation in the developing central nervous system. In the chick embryo, aggrecan, a chondroitin sulfate proteoglycan, has a regionally-specific and developmentally-regulated expression profile. Telencephalic neuronal cultures, when aggregated, exhibit aggrecan expression patterns comparable to those observed in vivo. The chicken mutation nanomelia produces a truncated aggrecan species that cannot be processed further and is not secreted. Neurons from normal and nanomelic chick embryo telencephalon were scored for aggregate formation and analyzed for distribution of aggrecan protein and expression of aggrecan mRNA. Distinctly different pattern formation, with respect to aggregate size (smaller) and number (fewer) were observed in poly-L-lysine plated neuronal cultures derived from nanomelic embryos when compared to those derived from normal embryos. Significantly, the nanomelic phenotype was subsequently rescued upon addition of the brain-specific form of aggrecan. Modulation of neuronal aggregate formation was mimicked by treatment with chondroitinase ABC but not other glycanases, and was rescued by addition of chondroitin 6-sulfate to the culture media. Lastly, although broad and diffuse distribution of aggrecan among the cell aggregates in the culture paradigm was observed by immunocytochemistry, mRNA in situ hybridization revealed that only a small population of cells in the center of the aggregates was responsible for the production of the secreted aggrecan found associated with neuronal aggregates. These studies suggest a function for aggrecan as a diffusible signal in CNS histomorphogenesis.
Domowicz
Miriam S
MS
Departments of Pediatrics and Biochemistry & Molecular Biology, Committee on Developmental Biology, The University of Chicago, 5841 S. Maryland Avenue, MC 5058, Chicago, IL 60637, USA. mdxx@midway.uchicago.edu
Mangoura
Dimitra
D
Schwartz
Nancy B
NB
D053674:Aggrecans; D000818:Animals; D002449:Cell Aggregation / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D019765:Chondroitin ABC Lyase / Q000378:metabolism; D002809:Chondroitin Sulfates / Q000378:metabolism; D016326:Extracellular Matrix Proteins; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D037181:Lectins, C-Type; D009154:Mutation; D009474:Neurons / Q000378:metabolism*; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D013687:Telencephalon / Q000254:growth & development*
D053674:Aggrecans; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D011509:Proteoglycans; D012333:RNA, Messenger; D002809:Chondroitin Sulfates; D019765:Chondroitin ABC Lyase