Cell Specification Flashcards
3 types of commitment a cell has to become a certain type of cell:
Specification: Labile commitment
Determination: Stable commitment
Differentiation: Overt change
3 modes of specification:
- Autonomous specification (mosaic) – Transcription factors localized in cytoplasm and are inherited by the cells containing that cytoplasm
- Conditional specification (regulative) – Cells are influenced by their neighbors. Paracrine factors from 1 cell are received by another cell and activate transcription factors in that cell
- Syncytial specification (flies) – Transcription factors form gradients within a large cell that contains many nuclei. The nuclei express genes depending on the ratios of these transcription factors.
The tunicate embryo is an embryo where many of its cell types are specified during cell cleavage and they’re specified by having certain transcription factors present and these transcription factors tell the genes what to express. Which mode of specification?
Autonomous specification
________ are proteins that bind to specific regions of DNA, they regulate the binding of RNA polymerase to the promoter of that gene and they can activate or repress gene transcription.
Transcription factors
Researchers found an mRNA that was only found in those cells that were destined to give rise to the muscle cells. It was originally found in the vegetal pole of the embryo. During fertilization, it migrated up into the B4.1 blastomere and they used the find it, lose it, and move it.
MACHO-1 mRNA
is done not only by transcription factors, it also involves paracrine factors. What mode of specification?
Conditional specification
one cell is telling its neighboring cells what to do
Induction of cells
_______ work by binding to a receptor in their neighboring cell and changing the conformation of that protein on the inside of the cell, giving that protein a new set of properties, often it’s a kinase property, which allows it to phosphorylate a protein, which eventually will phosphorylate or in some ways modify a transcription factor which will then enter the nucleus and turn on or repress of the gene.
Paracrine factors
The ______ is autonomously specified to become the skeletal forming cells of the sea urchin embryo. Their other property is that they induce the cells next to them such as the larger cell that got 95% of the cytoplasm to become the endoderm cells, to become the gut cells. They are specified by a transcription factor called _______. If this transcription factor is removed, hardly any of the cells become skeleton instead they all become skin/ectoderm of the embryo. If it is stabilized in all the cells = a gut with skeleton.
micromere; beta-catenin
________ is a protein that stabilizes beta-catenin so that beta-catenin is everywhere but it’s only stabilized in the bottom of the embryo, in the vegetal portion of the embryo.
Disheveled
_______ induces the development of gut
Micromeres
Syncytial specification in flies begins before fertilization: The sperm enters the egg that already has structure and nuclei divide in 1 big cell (________). Nuclear division without cell division. Cells form later from invaginating cell membrane of egg.
syncytium
4 major mRNAs that develop into an oocyte
2 mRNAs that get localized by their 3’ untranslated regions:
Bicoid mRNA tethered to anterior cytoskeleton
Nanos mRNA tethered to posterior cytoskeleton
4 major mRNAs that develop into an oocyte
2 mRNAs are not localized and disperse throughout the cytoplasm
Hunchback mRNA and Caudal mRNA
Bicoid does not only make the head, but it also inhibits the translation of caudal mRNA, which makes the tail. The nanos protein when it’s made can combine with other proteins and if nanos is present, it blocks the translation of hunchback mRNA, and hunchback mRNA is responsible for the development of the head and thorax.
_______ is needed for head formation and inhibits translation of caudal mRNA, which makes the tail.
Bicoid mRNA
Gradient: Bicoid and hunchback, makes head; Nanos and caudal makes tail.
In medical sciences, how can we utilize our knowledge in the modes of specification for treatment or combatting existing problems in this field?
Applying knowledge of cell specification enables medical advancements in regenerative medicine, cancer therapy, neurodegenerative disease treatment, congenital disorder correction, and infection control. It allows for more precise, targeted, and effective interventions in modern medicine.
these cells make mRNAs that travel though channels and they go into the developing oocyte
ovary cells called nurse cells
Bicoid and nanos can function as regulators of translation and bicoid can also act as a transcription factor.
What other factors exhibit conditional specification aside from paracrine factors?
- Juxtacrine Signaling (Direct Cell-to-Cell Contact)
- Mechanical Forces & Biomechanical Cues
- Cell-Cell Adhesion Molecules (CAMs)
Cadherins & Integrins help cells recognize their environment and differentiate accordingly. - Extracellular Matrix (ECM) Components
- Oxygen & Metabolic Signals
- Electrical Signals (Bioelectricity)
