Lecture 2/11

Introduction to Proliferative Phase and Cell Tracking

  • Discussion focuses on proliferative phase processes in cells, particularly neurons.

    • Mention of genetic tools: GFP (Green Fluorescent Protein).

Genetic Engineering in Neurons

  • Genetic engineering used to study proteins in newborn neurons.

    • GFP: Green Fluorescent Protein.

    • GFP linked to the gene for doublecortin (DCX), which is specific to neurons in early development.

    • DCX is expressed only in neurons up to 15 days post-cell birth.

    • Cells expressing GFP indicate newborn neurons due to inherent expression of DCX.

Mechanism of Gene Expression with GFP

  • Genetic engineering steps:

    • Insertion of GFP gene into the target gene.

    • This combination allows scientists to visualize when and where specific proteins are expressed in living cells.

    • Promoter: Controls the expression of DCX and, consequently, GFP.

    • The promoter region must interact with binding proteins for gene transcription.

Use of Retroviruses in Gene Delivery

  • Retrovirus is a viral mechanism used to introduce the GFP-DCX construct into target cells.

    • Infection allows the inserted DNA to integrate into the host genome, thus facilitating the expression of GFP along with the target protein (DCX).

    • If the specific promoter is present, the targeted cells express GFP, marking them as newborn neurons.

Comparison of GFP and BrdU for Cell Tracking

  • GFP Advantage: Specific to certain types of cells, allowing targeted studies.

  • BrdU (Bromodeoxyuridine): Non-specific tracking tool.

    • Incorporates into the DNA of all proliferating cells.

    • Useful for measuring overall proliferation rates but lacks specificity compared to GFP.

Progenitor and Differentiation Mechanisms

  • Progenitor cells can develop into various types of neurons and glial cells depending on the differentiation signals received.

  • Asymmetrical Division: A progenitor cell produces one progenitor and one differentiated cell.

  • Symmetrical Division: A progenitor cell produces two identical progenitor cells.

    • This process is crucial for maintaining the progenitor pool while generating specialized cells.

Factors Influencing Neurogenesis

  • Extrinsic and intrinsic factors regulate cell division and differentiation.

    • Examples of external factors include signaling molecules responsible for guiding differentiation and migration.

    • Key signaling pathways, such as those mediated by glial cells and growth factors, play roles in determining cell fate.

Development of Radial Glial Cells

  • Discusses radial glial cells, which serve as structural scaffolds during brain development.

    • These cells are essential for the organization of different neuron layers in the cortex.

    • Early stages of development see predominance of neurogenesis (formation of neurons) followed by gliogenesis (formation of glial cells).

Neurogenesis and Gliogenesis

  • Highlights the transition from neurogenesis to gliogenesis.

    • All cortical layers (six distinct layers) arise from initial stem/progenitor cells, structure prioritization starting at the ventricular zone.

    • Different cortical areas are linked to various functions and thickness, affected by developmental factors.

Cavity Structure and Cerebellar Development

  • Describes differences in the development of the cerebellum vs. the cortex.

    • Cerebellar development has opposite migration profiles, with proliferative cells moving from outer to inner layers to form the Purkinje cell layer.

    • The development of Purkinje cells is outlined with guidance from specific signaling pathways.

External Guidance Molecules in Cortical Development

  • Reelin Protein: A key protein involved for guiding migrating neurons in the cerebral cortex.

    • High expression levels in superficial neurons guide newly formed neurons to their intended locations.

    • The differential responses of progenitor cells to reelin determine their migration behavior.

Clinical and Research Applications

  • Importance of understanding developmental stages of neurons as it relates to neurological consequences.

    • Potential projects include evaluating early risk factors influencing neurodevelopmental outcomes, such as ADHD and epilepsy.

    • Proposals for surveys to gather data on protective factors (like folic acid) and risks associated with neurological disorders.

Conclusion

  • The complexity of neural development emphasizes the multifactorial influences acting at various stages, highlighting both intrinsic cellular mechanisms and external signaling pathways guiding neurogenesis and gliogenesis in the developing brain.