Biomaterial matrices presenting extracellular matrix (ECM) components in a controlled three-dimensional configuration provide a unique system to study neural stem cell (NSC)-ECM interactions. We cultured primary murine neurospheres in a methylcellulose (MC) scaffold functionalized with laminin-1 (MC-x-LN1) and monitored NSC survival, apoptosis, migration, differentiation, and matrix production. Overall, MC-x-LN1 enhanced both NSC survival and maturation compared with MC controls. Significantly lower levels of apoptotic activity were observed in MC-x-LN1 than in MC controls, as measured by bcl-2/bax gene expression and tetramethylrhodamine-dUTP nick end labeling. A higher percentage of NSCs extended neurites in a β₁-integrin-mediated fashion in MC-x-LN1 than in MC controls. Further, the differentiation profiles of NSCs in MC-x-LN1 exhibited higher levels of neuronal and oligodendrocyte precursor markers than in MC controls. LN1 production and co-localization with α₆β₁ integrins was markedly increased within MC-x-LN1, whereas the production of fibronectin was more pronounced in MC controls. These findings demonstrate that NSC microenvironments modulate cellular activity throughout the neurosphere, contributing to our understanding of ECM-mediated NSC behavior and provide new avenues for developing rationally designed couriers for neurotransplantation.

29Leucine-rich repeat extensins (LRXs)

Leucine-rich repeat extensins (LRXs) are chimeric proteins containing an N-terminal leucine-rich repeat (LRR) and a C-terminal extensin domain. LRXs are involved in cell wall formation in vegetative tissues and required for plant growth. However, the nature of their role in these cellular processes remains to be elucidated. Here, we used a combination of molecular techniques, light microscopy, and transmission electron microscopy to characterize mutants of pollen-expressed LRXs in Arabidopsis thaliana.Mutations in multiple pollen-expressed lrx genes causes severe defects in pollen germination and pollen tube (PT) growth, resulting in a reduced seed set. Physiological experiments demonstrate that manipulating Ca 2+ availability partially suppresses the PT growth defects, suggesting that LRX proteins influence Ca 2+ -related processes.