Exam 1 Material: History, Genetic Control, Signal Transduction, Epithelial to Mesenchymal, Primary Cilia, Stem Cells

What is developmental biology?

The study of how organisms grow and develop from a single cell into a complex organism

What major fields are included in developmental biology?

Genetics, cell biology, physiology, anatomy, cancer research, neurobiology, immunology, ecology, and evolutionary biology

What are the main stages of animal development?

Fertilization → Cleavage → Blastula → Gastrulation → Organogenesis → Metamorphosis → Gametogenesis

What are the three primary germ layers?

Ectoderm, mesoderm, endoderm

What does the ectoderm form?

Outer structures like skin and nervous system

What does the mesoderm form?

Muscles, bones, circulatory system

What does the endoderm form?

Internal organs like the digestive tract

What are the major questions in developmental biology?

Differentiation, morphogenesis, growth, reproduction, evolution, environmental integration

What are the three main approaches to developmental biology?

Anatomical, experimental, and genetic

What is fate mapping?

Linking regions of an embryo to their future structures

What is "loss-of-function" evidence?

Disabling a gene to see its role in development

What is "gain-of-function" evidence?

Activating or overexpressing a gene to observe effects

What is epigenesis?

Organs develop progressively during development

What is preformation?

Organs are already present in miniature form

What is recapitulation theory?

Ontogeny recapitulates phylogeny (development mirrors evolution)

What is a totipotent cell?

Can form all cells including extra-embryonic tissues

What is a pluripotent cell?

Can form all body cell types

What is a multipotent cell?

Can form multiple related cell types

What is a differentiated cell?

A specialized cell that usually does not divide

What is differential gene expression?

Cells have the same DNA but express different genes

Why is differential gene expression important?

It allows cells to specialize into different types

What are the main levels of gene regulation?

Transcription, RNA processing, translation, and protein modification

What is DNA methylation?

Addition of methyl groups that suppress gene transcription

What are enhancers and silencers?

DNA regions that increase or decrease transcription

What is combinatorial control?

Multiple regulators working together to control gene expression

What must RNA undergo to become functional?

Splicing, capping, poly-A tail addition, and translation

What are microRNAs?

Small RNAs that block translation by binding mRNA

What is signal transduction?

Process where a signal activates a pathway leading to gene expression changes

What is the general pathway?

Ligand → receptor → kinase cascade → transcription factors

What is induction?

One group of cells influencing another's development

What is competence?

Ability of a cell to respond to signals

What is reciprocal induction?

Two tissues signal each other to develop

What are major signaling pathway families?

FGF, Hedgehog, Wnt, TGF-β

What does Sonic Hedgehog (Shh) do?

Controls neural tube and brain patterning

What happens if Shh signaling is reduced?

Brain defects like holoprosencephaly

What does Wnt signaling regulate?

Cell fate, polarity, and proliferation

Key molecule in Wnt pathway?

Beta-catenin activates transcription

What do TGF-β pathways regulate?

Cell division, differentiation, and organ formation

What proteins mediate TGF-β signaling?

SMAD proteins

Can signaling pathways interact?

Yes—signals can enhance, block, or combine with each other

What is the Differential Adhesion Hypothesis?

Cells rearrange to form the most thermodynamically stable configuration based on adhesion properties

Who proposed the Differential Adhesion Hypothesis?

Malcolm Steinberg (1964)

What controls cell adhesion properties?

Changes in gene expression alter cell surface molecules

What are tight junctions?

Junctions that prevent fluid leakage between cells

What are gap junctions?

Channels allowing communication between cells

What are adherens junctions?

Connect actin cytoskeletons between cells

What are desmosomes?

Connect intermediate filaments between cells

What are hemidesmosomes?

Attach cells to the basement membrane

What are cadherins?

Calcium-dependent adhesion molecules important for cell sorting

What determines cell sorting?

Type and amount of cadherins expressed

What is E-cadherin associated with?

Early embryonic cells

What is N-cadherin associated with?

Nervous system development

What are the requirements for cell migration?

Polarization, protrusion, adhesion, and release of adhesion

What proteins regulate cell movement?

Rac and Rho GTP-binding proteins

What structures help cells move?

Pseudopodia and lamellipodia

What is the extracellular matrix?

A network of macromolecules surrounding cells that provides support and signaling

Name key ECM components.

Integrins, fibronectin, laminin, collagen, proteoglycans

What do integrins do?

Connect ECM to the cell and signal to transcription factors

What is EMT?

Process where epithelial cells become motile mesenchymal cells

What changes occur during EMT?

decrease adhesion, decrease communication, increase motility

What are the three types of EMT?

Type I: Development (gastrulation)

Type II: Wound healing

Type III: Cancer/metastasis

What is the cadherin switch?

Decrease in E-cadherin and increase in N-cadherin during EMT

What does decreased E-cadherin cause?

Increased cell movement via cytoskeletal changes

What is apoptosis?

Programmed cell death used to shape tissues

Key molecules in apoptosis pathway?

BAX, BAK, cytochrome c, caspases

What are primary cilia?

Single, non-motile structures involved in signaling and polarity

What are cilia made of?

Microtubules with dynein arms

What pathways involve cilia?

Wnt, Sonic Hedgehog (Shh), growth factor pathways

What is intraflagellar transport (IFT)?

Movement of proteins along cilia using kinesin and dynein

What establishes left-right asymmetry?

Cilia-generated fluid flow (nodal flow)

What molecules regulate asymmetry?

Nodal and Lefty

What happens without Shh?

Gli represses transcription

What happens with Shh present?

Gli activates gene transcription

What is Kartagener syndrome?

Cilia dysfunction causing situs inversus and respiratory issues

What diseases are linked to cilia defects?

Polycystic kidney disease (ADPKD, ARPKD)

What are stem cells?

Cells that self-renew and differentiate into specialized cells

What enzyme do stem cells express?

Telomerase

What is totipotent?

Can form entire organism + extraembryonic tissues

What is pluripotent?

Can form all body tissues

What maintains pluripotency?

LIF (Jak/STAT) and BMP signaling

Key transcription factors for pluripotency?

Sox2, Oct4, Nanos

What induces neuroectoderm?

Wnt signaling

What induces mesoendoderm?

FGF signaling

Sources of stem cells?

Embryonic, adult, cord blood, induced pluripotent stem cells

What are iPS cells?

Reprogrammed adult cells turned pluripotent

How are iPS cells made?

Adding transcription factors via viruses or other methods

What is regenerative medicine?

Using stem cells to repair or replace tissues

Example use of stem cells?

Treating genetic disorders by correcting mutations and transplanting cells

Where are hematopoietic stem cells found?

Bone marrow

What are satellite cells?

Muscle stem cells for repair

What are cancer stem cells?

Cells that drive tumor growth and can self-renew