Exam 2: Embryology Flashcards
Functional Differentiation
Series of regulatory steps that determine the “when, where, and how” a gene that produces a functional protein is expressed.
Embryonic Developmental
Processes
- Cell proliferation
- Cell specialization
- Cell-to-cell interactions
- Cell movement
Differentiation
The transition of cells from pluripotency to its specific functional state.
Induction
One population of cells produces signal molecules to guide the development of a neighboring population of cells into a specific tissue or organ.
Inductor ⇒ cell or tissue producing the signal molecule
Competent tissue ⇒ responding group of cells or tissues
Fate
When a specific region of the embryo regularly gives rise to the same tissue or structure.
Cells commit to a particular fate based on their location within the embryo and stage of development ⇒ developmental field.
Chemical communication between cells ensures that all fates are properly allocated and pattern of allocation is coherent.
Divergent Developmental Pathways
Simple binary options ⇒ cells become comitted to one of two fates
Multiple fate options ⇒ intricate branching patterns
Simple Binary Developmental Pathway
Concentration of regulatory molecules determines on/off switch.
Above a threshold level, the “on” path is taken ⇒ alternative pathway
“Off” path implies that developmental pathways will proceed along the path that had been determined by previous decisions ⇒ default pathway
Forming Complex
Patterns
Developmental responses more finely graded by the concentration fo a signal molecule.
Usually involves generation of the molecule from a localized source and allowing simple diffusion to create a gradient.
Morphogenesis
The process where a 3D structure is formed through changes in cell shape, cell adhesion, and/or cell death.
Morphogens
Diffusible molecules through which one group of cells influences neighboring group of cells to follow a developmental route.
Intracellular Gradients
- Promotes cellular polarity and asymmetrical cell division
- Can be composed of mRNA, proteins, or other intracellular components
- Allows events to occur differently within regions of the cell
Extracellular Gradients
- External morphogen gradients can influence cell development
- Able to regulate whole fields of cells to develop into specific tissues and organs
- Regions with multiple gradients originating from different sources
- Allows cells within the field to judge their position
- Very small differences in morphogen concentration can lead to distinct fates
Positional Information
Utilization
Cells must be there to respond to the positional information provided by extracellular gradients.
Requires that competent cells respond by making one or more specific transcription factors.
Nature and concentration of the transcription factors regulate cellular protein production in a coordinated fashion.
Developmental Gene
Classes
-
Gene regulatory proteins
- promote or inhibit gene expression
- control protein modification
- determines the functional protein profile in the cell
-
Communication proteins
- used for cell signaling and cellular adhesion
- soluble mediators
- membrane-bound ligands
- receptors
Together allow organism’s cells to behave independently while promoting development in an organized, integrated manner.
HOX Genes
Encodes transcription factors that act as “master switches”
-
Regulate the expression of a large set of downstream genes
- Critical for the morphogenesis of different body parts
-
Important in establishment of the cranio-caudal axis
- somites, limbs, vertebrae, and craniofacial structures
- 39 HOX genes expressed sequentially throughout embryo
- Starts during embryogenesis and continues throughout
- Regulated by DNA-binding proteins that alter chromatin