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Questions and Answers
What is the primary role of the Activin subfamily in cellular processes?
Which of the following is NOT a function of the TGF-β subfamily?
Which Smad protein is considered a cofactor in the Smad signaling pathway?
In the context of the Wnt signaling pathway, what is the main function of the β-catenin pathway?
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What inhibits the activity of Smads in the signaling pathways?
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Which BMP subfamily is primarily associated with osteogenic differentiation?
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What role does BMP-4 play in development?
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What is the primary receptor family that BMP proteins bind to?
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What role does the inner cell mass (ICM) play in early embryonic development?
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At which stage are the fates of the cells determined in mammalian cleavage?
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Which characteristic of mammalian patterning distinguishes it from other species?
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What is the significance of the zona pellucida in embryonic development?
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What defines the morphology of a blastula during early cleavage?
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In terms of pluripotency, what is a primary characteristic of embryonic stem cells (ESCs)?
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What is a key function of the trophoblast during early embryonic development?
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Which of the following correctly describes cleavage in amphibians?
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Which type of stem cell can differentiate into any cell type in the body?
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What defines pluripotent stem cells?
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Which stem cell type is typically derived from fetal tissues and can differentiate into several but not all cell types?
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Which characteristic is NOT associated with mammalian embryos during development?
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Which stem cell is primarily found in adult organisms and can only differentiate along one specific lineage?
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What process represents the development stage where the three germ layers are formed in the mammalian embryo?
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What signaling pathway is crucial for regulating pluripotency in stem cells?
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Which of the following statements accurately describes mesoderm induction during embryonic development?
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Study Notes
Pattern Formation
- Development of body orientation requires cells to obtain a ‘pattern’
- Cells signal differently within themselves, resulting in molecular regulators
- Mechanisms for pattern formation vary across organisms
- Early stages of patterning are more flexible in mammals
- Patterning influences cell decisions
Cleavage
- Egg divides into smaller cells.
- No net growth during cleavage - cells alternate between DNA synthesis and mitosis.
- Amphibians depend on RNA, protein, membrane, and materials from oogenesis for transcription.
- Cells form a hollow ball (blastula) or a flattened two-layer structure (discoblastula).
- Fate of cells at the 8-cell stage is not yet determined.
- Cells become polarized at the 16-cell stage.
Morula
- The 16-cell stage is called morula.
- Cells achieve a predetermined fate at the 16-cell stage.
- Trophectoderm develops into extraembryonic structures.
- Inner cell mass forms the embryo proper and contains totipotent cells, including embryonic stem cells (ESCs).
- Zona pellucida allows the embryo to escape and implant after a few days.
- The morula remains adaptable in mammals.
ESCs
- ESCs come from the inner cell mass of the blastocyst.
- ESCs can be cultured in vitro.
- ESCs are pluripotent, meaning they can differentiate into many cell types, but not all.
BMP
- Bone morphogenic protein (BMP) is a member of the TGF-B family superfamily.
- BMPs are proteins with 110-140 amino acids.
- BMPs bind to TGFB receptors.
TGF-B Subfamilies
- Activin subfamily functions include FSH production, erythroid cell differentiation, and mesoderm induction in frogs.
- TGF- subfamily functions include cell cycle arrest, mesenchymal cell proliferation and differentiation, wound healing, ECM modulation, angiogenesis, chemotaxis, immunosuppression, apoptosis, and inflammation.
- BMP2 subfamily functions include gastrulation, neurogenesis, chondrogenesis, interdigital apoptosis, and mesoderm patterning.
- BMP5 subfamily functions include development and neurogenesis.
- BMP3 subfamily functions include osteogenic differentiation and monocyte chemotaxis.
- GDF5 subfamily functions include chondrogenesis in developing limbs.
BMP-4
- BMP-4 is a key player in pluripotency and is involved in differentiation and D-V axis formation.
Smad Pathway
- The Smad pathway has three classes:
- Receptor-Associated Smads:
- TGF-ß: Smad2/3
- BMP: Smad1/5 and 8
- Cofactor Smad: Smad 4
- Inhibitory Smads: Smad 6, 7
- Receptor-Associated Smads:
- Smurfs (Smad ubiquitination regulatory factors) inhibit the Smad pathway.
- Smurf 1 targets BMP Smads.
- Smurf 2 degrades Smad 1 and 2.
- Smurf 1/2 degrade the TGF-ß receptor with Smad 7.
Smad Domains and their Functions
- Smad, a combination of Drosophilia MAD and C. elegans sma, has Mad homology domains (MH domains).
Activin/Nodal
- Activin/Nodal signaling plays a role in development.
Wnt Signaling Pathway
- Wnt signaling regulates proliferation and differentiation.
- Wnts are secreted glycoproteins.
- Wnts bind to Frizzled cell surface receptors and lipoprotein receptor-related protein 5 and 6 (LRP-5/6).
- Wnt signaling has three pathways:
- The –catenin pathway
- The planar cell polarity pathway
- The Wnt/Ca2+ pathway
- Wnt promotes self-renewal of ESCs and induces epiblast to adopt a mesodermal fate.
Wnt/β–Catenin Pathway
- LRP stands for LDL-related protein.
- APC stands for adenomatous polyposis coli (not to be confused with anaphase promoting complex).
- In the absence of Wnt, β–catenin either binds to cadherin proteins (transmembrane adhesion proteins) or is degraded.
Origins of Stem Cells
- Stem cells are derived from various sources such as:
- Blastocysts:
- Parthenote stem cells
- Embryonic stem cells (ESCs)
- Nuclear Transplant Blastocysts: Derived from eggs stimulated to divide following complete exchange of genetic material.
- Differentiated Cells: Cells that are “dedifferentiated.”
- Fetal Tissues:
- Found in growing organs, include germ cell precursors, and trophoblast cells.
- Adult Organs:
- Liver, bones, bone marrow, lining of gut, spermatozoa.
- Blastocysts:
Stem Cell ‘Potency’
- Zygote: Totipotent
- Pluripotent: ESCs
- Multipotent: Fetal Tissue Stem Cells (FTSCs) & Adult Stem Cells (ASCs)
- **
Totipotent Stem Cell
- A single cell that can become any type of cell.
Pluripotent Stem Cell
- A cell that can give rise to the types of cells that develop from any one of the three germ layers: mesoderm, endoderm, and ectoderm.
Multipotent Stem Cell
- A cell that can differentiate into more than one cell type, but not all.
- Usually refers to differentiation within a germ layer.
Unipotent Stem Cell
- A cell that can differentiate along only one lineage.
Various Stem Cell Types
Stages of Development
- Fertilization
- Cleavage
- Gastrulation
- Neurulation
- Organogenesis
- Gametogenesis
Day 0
- Fertilization of the oocyte in the oviduct.
3rd Week
- Gastrulation
Specializations in Mammalian Development
- Mammalian embryos are protected by the uterus, which delays early development.
- Placenta development quickly provides nutrients from the mother, eliminating the need for large yolk stores.
- Mammalian eggs are smaller and divide slower than other organisms (difficult to study).
- Gene transcription begins early, by the 2-cell stage in mammals.
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Description
This quiz explores key concepts in embryology, focusing on pattern formation, cleavage, and the morula stage. Understand how cells communicate and organize themselves during early development stages, and the significance of cell fate determination. Targeted for students studying developmental biology.
