Mechanisms of microtubule-mediated cranial neural crest EMT and differentiation

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Project Summary/Abstract Defective development of neural crest (NC) cells can cause structural and neurological disorders that have long-term deleterious effects on human health. NC cells form the neurons and glia of the peripheral and en- teric nervous systems in addition to craniofacial bone and cartilage. Early formation and separation of NC cells from the adherent neural tube is a process tightly regulated by cell signaling, epigenetic and transcrip- tional changes, and altered cell-cell adhesion via changing cadherin protein localization. Structurally, as the neural folds rise to meet in the center of the embryo to create the neural tube, non-neural ectodermal cells meet and cover the embryo, eventually differentiating into epidermis and placodes. After neural tube clo- sure, NC cells undergo an epithelial to mesenchymal transition (EMT), leave their neuroepithelial neigh- bors, and migrate throughout the embryo, invading various tissues, and creating diverse derivatives. Rapid changes at transcriptional, translational, and post-translational levels allow for dynamic transitions in cell polarity, adhesion, and migration. Several transcription factors function as regulators of genes encoding cadherin proteins during NC cell development, but there is a critical lack of information about the more rapid processes that alter cadherin protein localization during NC EMT. Specifically, we aim to understand how microtubules and related cytoskeletal factors regulate cell-cell adhesion at this developmental stage. Based on our published work and preliminary data, -III tubulin (TUBB3) is upregulated in NC cells at the onset of NC EMT. Our objective is to understand the complex mechanisms that control NC EMT and subsequent NC differentiation by defining how the microtubule element, TUBB3, regulates cadherin protein localization during NC cell EMT and differentiation in vivo. Further, we will identify how perturbation of TUBB3 affects the structure of other cytoskeletal elements during NC EMT. In Aim 1 we will perform gain and loss of TUBB3 experiments followed by quantitative analyses of changes in the expression and localization of epi- thelial and migratory cadherins (CDH2, CDH1, and CDH11), tissue-specific markers (NC and neural tube), cell migration and cranial NC differentiation using quantitative spatial approaches at the transcript and pro- tein levels in the chicken (Gallus gallus), which mirrors human development at early stages. In Aim 2, we will perform perturbations of TUBB3 to determine how defective TUBB3-mediated microtubule assembly affects the localization of microtubules, intermediate filaments, and actin filaments during NC EMT. With these experiments, we expect to integrate both traditional and novel approaches to understanding the com- plex links between cell adhesion and cytoskeletal arrangements during NC EMT. We hope to contribute a missing, fundamental element to our knowledge of the protein network that drives the development of NC cells, which is crucial for the identification of novel markers of normal and abnormal development of NC- derived adult cell types.