neural crest and neurogenesis from lecture

Overview of Neural Crest and Neurogenesis

Neural Crest Cells

  • Definition: A population of migratory cells that originate from the neural tube during embryonic development.

  • Significance: They contribute to the formation of various tissues and structures, including the face, skull, and nervous system.

  • Common Symptoms: Associated with various conditions, sometimes referred to as "false jaundice."

Migration of Neural Crest Cells

  • Process of Migration:

    • Begins post-neural tube formation as neural crest cells delaminate and migrate from the dorsal aspect of the neural tube.

    • Initially guided by cues along the interleucosidymaxies leading to extensive differentiation.

  • Differentiation of Serotypes:

    • Neural crest cells differentiate into various cell types, influenced by local signaling cues.

Neural Crest Cell Types

  • Classification Based on Body Axis Location:

    • Cranial Neural Crest:

    • Located in the anterior region; migrates to form facial structures, such as the jaws and facial skeleton.

    • Trunk Neural Crest:

    • Migrates laterally and ventrally, with distinct pathways.

    • Forms sensory neurons, autonomic neurons, and melanocytes.

  • Specific Pathways for Trunk Neural Crest Cells:

    • Ventral Pathway:

    • Leads to the development of sensory and autonomic neurons, adrenal medullary cells.

    • Dorsolateral Pathway:

    • Leads to the formation of melanocytes.

Mechanisms of Migration

  • Delamination Process:

    • Neurocrest cells lose adhesion to the epithelium and delaminate to migrate.

    • Important signaling pathways, involving small GTPases such as RhoA, Rac1, and Cdc42, regulate cytoskeletal dynamics during migration.

  • Cellular Protrusions Initiation:

    • Cell migration is facilitated by the assembly of actin and myosin into protrusions.

    • Types of Protrusions:

    • Filopodia:

      • Thin, search-like extensions that probe the environment.

    • Lamelipodia:

      • Broad, sheet-like extensions driving cell movement.

Collective Migration

  • Contact Inhibition:

    • Mechanism where cells avoid clustering, promoting directional movement through maintaining contact with each other while migrating collectively.

  • Collective Migration Dynamics:

    • End result is the alignment and directional movement of cells in response to cues and environmental signals.

Sclerotome Interaction

  • Sclerotome Definition:

    • Blocks of paraxial mesodermal tissue that undergo further differentiation to support neural crest migration.

  • Sclerotome Composition:

    • Anterior and posterior halves, each influencing the fate of migrating neural crest cells differently due to varying expression of factors like Lewis.

  • Neuropresent Cell Migration:

    • Cells migrate through anterior half, influenced by local cell signaling and adhesive properties of surrounding tissue.

Axon Guidance

  • Axon Exploration Strategies:

    • Neurons utilize specific proteins to find their target sites, often guided by attractive and repulsive cues.

  • Role of Chemorepellents and Attractants:

    • Neurons rely on cues like semaphorins and netrins during migration and interaction with target tissues.

  • Commissural Neurons:

    • Special class of neurons that cross the midline.

    • Utilize distinct mechanisms involving the floor plate of the spinal cord to facilitate their crossing and appropriate targeting of the opposite side.

Neuronal Development and Synaptogenesis

  • Forming the Synapse:

    • Lesions result in programmed cell death (apoptosis) when proper synaptic connections are not formed.

    • Neurons adapt their connection properties based on environmental cues leading to synapse formation or elimination.

  • Neurotransmitter Release:

    • Presynaptic neurons release neurotransmitters to either depolarize or hyperpolarize the postsynaptic target cells, initiating signal transmission.

Summary of Functions and Pathways

  • Collectively, neural crest cells play crucial roles in various developmental processes, such as:

    • Bone formation (jaw and face structures).

    • Creation of the peripheral nervous system components.

    • Melanocyte development contributing to skin pigmentation.

  • Mechanisms Including:

    • Regulation by signaling pathways (e.g., Rho GTPases) that maintain cytoskeletal arrangements.

    • Interaction between cell populations leading to collective migration and target recognition.

  • Impact of Genetic Mutations:

    • Altered migration and differentiation due to mutations in critical genes can lead to developmental disorders affecting the neural crest-derived structures.