[LE1] Lecture 2 Flashcards by Genella Alessandra Roallos

Generation of specialized cells where cells cease to divide and develop specialized structural elements and distinct functional properties

CELL DIFFERENTIATION

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Committed cells are those cells that look the same from neighboring cells, but its developmental fate has already been programmatically restricted

CELL DIFFERENTIATION

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Fate of cells are specified when it are capable of differentiating autonomously when placed in an environment that is neutral with respect to the developmental pathway

CELL FATE MATURATION: SPECIFIED CELLS

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Commitment to cell identity is still ____________

labile

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If a specified cell is transplanted to a population of differently specified cells, the fate of the transplant will be altered by interaction with its new neighbor

Specified Cells

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What is the difference between undifferentiated and committed cells?

Undifferentiated: could become any of the three germ layers: ectoderm, endoderm, or mesoderm

Committed: already ectoderm, mesoderm, and endoderm

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Ability of a single cell to divide and produce all of the differentiated cells in an organism

Ex: Fertilized egg

Totipotent

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Stem cells that has the potential to differentiate into any of the three germ layers

Ex: embryonic stem cells

Pluripotent

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Progenitor cells, which have the gene activation potential to differentiate into multiple but limited cell types

Ex: hematopoietic stem cells

Multipotent

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One stem cell has the capacity to differentiate into only one cell type
Cannot be divided

Ex: muscle stem cell

Unipotent

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Progenitor cells with the ability to differentiate into a few cell types

Ex: myeloid stem cell

Oligopotent

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Cytoplasmic determinants within the egg cytoplasm
Egg cytoplasm is not homogenous but rather than different regions contain different cell fate specifying factors

AUTONOMOUS SPECIFICATION

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In autonomous specification, at the cleavage stage (2 cell stage), if you try to kill one side with a hot needle, the other half would ____________________

still continue to live

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Cells know “very early” what it is to be, even without interacting with other cells

AUTONOMOUS SPECIFICATION

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Cells achieve their respective fates by interacting with other cells
Nervous system of the tunicate

CONDITIONAL SPECIFICATION

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Mechanisms of interactions:

Juxtacrine factors: _____________
Paracrine factors: _____________
Mechanical stress: ____________

cell-to-cell contacts
secrete signals
physical properties of the cell’s local environment

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In conditional specification, even though you transfer the cell, it will _____ because it is already developed

still continue to live

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MAIN DIFFERENCE:

Autonomous: at 2-cell stage, since you killed the other half, it will __________________

Conditional: Even though you transfer the cell, it will ________________ because it is already developed

not regenerate
still continue to live

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Cells use both elements of autonomous and conditional specification

SYNCYTIAL SPECIFICATION

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Nuclei divide 13 cycles without cytoplasmic cleavage in _______________

drosophila

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Leads to the formation of _____________

syncytial blastoderm

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Identity of future cells is achieved simultaneously across the ____________________ of the entire embryo

anterior-posterior axis

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Identity is established without any _______________

membranes

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In cellularization, membranes start to form after _________________

nuclear cycle 13

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Microtubule extensions allow dynamic spacing for each nuclei

Interphase/Cytoskeletal Machinery

- Are there determination factors segregated to discrete locations in the blastoderm? - Eggs contain gradients of positional information that dictate cell fate along their anterior-posterior axis

SYNCYTIAL-AUTONOMOUS SPECIFICATION

Nuclei in the anterior region are exposed to ________________ only found in the anterior region (i.e. vice versa)

cytoplasmic determinants

- Nuclei undergo synchronous waves of ______________ after fertilization - Becomes positioned at specific __________________ and experiences unique concentration of ____________

division, coordinates, gradients

- Specification that predominates in most invertebrates a. Autonomous b. Conditional c. Syncytial

Autonomous specification

Invariant cleavages produce the same lineages in each embryo of the species; blastomere fates are generally invariant a. Autonomous b. Conditional c. Syncytial

Autonomous specification

Specification by differential acquisition of certain cytoplasmic molecules present in the egg a. Autonomous b. Conditional c. Syncytial

Autonomous specification

Specification that predominates in vertebrates and a few invertebrates a. Autonomous b. Conditional c. Syncytial

Conditional specification

Specification by interactions among cells. Positions of cells relative to each other are key a. Autonomous b. Conditional c. Syncytial

Conditional specification

Variable cleavages, no invariant state assignment to cells a. Autonomous b. Conditional c. Syncytial

Conditional specification

Capacity for "regulative" development allows cells to acquire different functions as a result of interactions with neighboring cells a. Autonomous b. Conditional c. Syncytial

Conditional specification

Predominates in most insect classes a. Autonomous b. Conditional c. Syncytial

Syncytial specification

Specification of body regions by interactions between cytoplasmic regions prior to cellularization of the blastoderm a. Autonomous b. Conditional c. Syncytial

Syncytial specification

After cellularization, both autonomous and conditional specification are seen a. Autonomous b. Conditional c. Syncytial

Syncytial specification

Three general principles of differentiation

1. Constancy of the genome 2. Cytoplasmic control of nuclear activity 3. Regulation mechanisms Levels of gene expression Mechanisms involved in differential gene expression

Each somatic cell nucleus has the same chromosomes and, therefore, the same set of genes as all other somatic cell nuclei

THE CONCEPT OF GENOMIC EQUIVALENCE

- We have an oocyte, then now nucleus is removed - Now it is called an enucleated cell, the nucleus from blastula cell is transferred to the enucleated oocyte, so they are able to clone cells

BRIGGS AND KING EXPERIMENT

A nobel prize for physiology and medicine, 2013 NOTE: - They use the nucleus of differentiated cell instead of blastula - Cell here is also determined of what type of cell they are - The genes here in nucleus are still complete and capable to develop an adult form

JOHN GURDON'S EXPERIMENT

- The genome of a cell appears to respond to and controlled by substances or determinants in the cytoplasm - Nuclear activity is under the influence of cytoplasmic factors

CYTOPLASMIC CONTROL OF NUCLEAR ACTIVITY

If you remove polar granules and put it in vegetal pole, cytoplasm become _____________ alone in vegetal pole

segregated

Process by which cell become different from each other based on unique combination of genes that are active of expressed

DIFFERENTIAL GENE EXPRESSION

Three postulates of differential gene expression

1. All cells contain the entire genome (genomic equivalence); 2. Unused genes still has the capacity to be expressed (if genes are not used, they can still be expressed but only with determinants) 3. Only a small, specific percentage of the genome is expressed in each cell

Regulation that controls the amount and rate at which mRNA transcripts are produced

TRANSCRIPTION CONTROL

Occurs at the packaging level of DNA changing patterns of _____________________ Occurs due to __________________

chromosomal puffs regulatory proteins

Bonds non-specifically to DNA of chromosome, causing compaction

Histones

Binding to the DNA, it would be compacted to form the chromatin that would become chromatids, leading to formation of chromosome

Histones

- Protect region of DNA from histones - Cells with very active genes tend to have more nonhistone proteins that cells with inactive genes

Nonhistones

You want to uncondense your condensed nucleosomes you need _______________________

histone methyltransferase

Once they are uncondensed, the area can now be transcribed you need __________________

histone acetyltransferase histone deacetylase

Modification of histones signal recruitment of proteins that retain the memory of transcriptional state

HEREDITARY HISTONE METHYLATION

- Genes active - Modify nucleosomes or alter positions on chromatin - Trimethylates histones

HEREDITARY HISTONE METHYLATION

Binds to condensed nucleosomes, genes are in repressed state

Polycomb protein family

- Services as histone methyltransferases - Binds to methylated tails on H3

Polycomb protein family

- Your RNA polymerase 2 are now open so it can bind to the gene and proceed to transcription - If gene is not open due to repression, it would not allow your gene to be expressed

Developmental control genes

- In _________ cells, it is tagged not to be express in life cycle - The only one that can be expressed is after the gene is demethylated

mature

It is assumed that genes are inherited equally from the father and the mother With methylation, expression can either be from egg or sperm, with the help of __________________________

Genomic imprinting

- Sites where RNA polymerase bind to the DNA to initiate transcription - Control whether or not transcription occurs

Promoters

_______________ is where the RNA polymerase attaches

TATA box

Controls the efficiency and rate of transcription of a specific promoter

Enhancers

If a gene is off and you have a ligand, the ligand will bounce to repressor protein, and it will ________________________________ If you have an activator protein with the attachment of ligand, it will have a signal RNA polymerase, and the transcription will ___________

not repress your gene now start

Proteins that bind DNA with precise sequence recognition for specific promoters, enhancers, or silencers

TRANSCRIPTION FACTORS

Functions of Transcription Factors: recruit _________________ to make chromatin more accessible for RNA polymerase II

nucleosome-modifying proteins

Functions of Transcription Factors: Recruit _________________________ to form bridges

transcriptional co-regulators

Target Genes of GTF and TAR: GTF: TAR:

GTF: Most genes TAR: Selected genes

Occurence of GTF and TAR: GTF: TAR:

GTF: All cells TAR: Certain cells

GTF or TAR? TBP (TATA binding protein) TAFs (TATA ass'td factors)

GTF

GTF or TAR? Bicoid proteins, steroid receptors

TAR

Representative transcription factors of HOX family

Hoxa1, Hoxb2, etc.

Some functions of HOX

Axis Formation

Representative transcription factors of LIM family

Lim1, Forkhead

Some functions of LIM

Head Development

Representative transcription factors of PAX family

Pax 1,2,3,6,7,etc

Some functions of PAX

Neural specification; eye and muscle development

Representative transcription factors of SRY-SOX family

Sry, SoxD, Sox2

Some functions of Sry-Sox

Bend DNA; mammalian primary sex determination; ectoderm diferentiation

MITF binds to histone acetyltransferases Pax7 recruits histone methyltransferase Trithorax - trimethylated (active state)

Recruit histone-modifying enzyme

MITF binds to ______ Pax7 recruits _______ - trimethylated (active state)

histone acetyltransferases histone methyltransferase Trithorax

MyoD stabilizes TFIIB which supports RNA polymerase II

Stabilizes polymerase

Pax6 coordinates lens genes expression

Coordinates timex expression of genes

Uniquely bind DNA tightly wrapped around nucleosomes and heterochromatic areas

PIONEER TRANSCRIPTION FACTORS

___________ for liver development binds to liver-promoting enhancers and opens up the chromatin

FoxA1

__________ supports muscle specification by recruiting trithorax

Pax7

These mediators could actually enhance, silence and stop the transcriptions

THE MEDIATOR COMPLEX

_____________ allow mRNA to be expressed in your brain and limb

enhancers

Embryonic development is an enormous informational transaction in which _______________________ generate and guides the system-wide development of specific cellular functions

DNA sequence data

Cell produces different types of _____________ factors to produce different types of genes leading to differential expression

splicing

_____- you remove only 1 part _____ - could be large or small

[A] Cassette axon [C] Alternative splicing

mRNA TRANSLATION 1. Differential mRNA ___________ 2. Selective ___________ of mRNA translation 3. Selective ___________ of mRNA translation 4. Specific regulation of mRNA _____________ and ______________ 5. Control of RNA expression by __________________

1. longevity 2. inhibition 3. activation 4. translation, transcription 5. cytoplasmic localization

The longer the mRNA persists, the _______ protein it can synthesize

____________________ for nervous system development stabilizes two groups of mRNA

Hu proteins (HuA, HuB, HuC, HuD)

Group 1 - encodes for proteins that ________ neuronal precursor cells from diving Group 2 encodes for proteins that ________ neuronal differentiation

stop initiate

MATERNAL TO ZYGOTIC TRANSITION: (A) Numerous mRNAs derived from maternal contributions fuel development during the _____________________ stages, but transitioning into the gastrula requires active transcription of the _______________. ______________ plays a major role in clearing these maternally derived transcripts during this transition.

cleavage zygotic genome miRNAs

MATERNAL TO ZYGOTIC TRANSITION: (B) __________ has been discovered to play a major role in the interference of a majority of maternal transcripts in the zebrafish blastula as it transitions to zygotic control during ________________.

miR430 gastrulation

[LE1] Lecture 2 Flashcards

(97 cards)