Cell Differentiation Flashcards
Sperm and egg come together to for a ____, a diploid cell.
Zygote
The zygote, then gives rise to a cluster of daughter cells called _____ which are transformed into Totipotent cells
Blastomeres
Three biological processes create the new individual:
Cell proliferation
Cell migration
Cell differentiation
The first observable event were cells begin to adopt different fates during embryogenesis, is the formation of the _____ and ___ ___ ___.
Trophoblast
Inner cell mass
Trophoblast cells will form the ____ membranes and most of the ____.
The inner sell mass cells will proliferate and differentiate to give rise to all of the cells of the ___.
Extraembryonic
Placenta
Body
The central mechanism by which cells adopt distinct fates during embryogenesis involves ____ ___ ____, where genes are turned off or kept active diverge
Differential gene expression
Cells that begin to pursue different fates do this by two general mechanisms: ___ ___ ___ and ____.
Asymmetric cell divisions
Induction
In asymmetric cell division, specific factors, such as mRNAs, and miRNAs are partitioned ____ among daughter cells during cell division. This process leads to a _____ pattern of development.
Unequally
Mosaic
In induction, cells are initially the same, but could be separately influenced by other cells, or other types of ___ ___. Cells are not ‘ born different’ but instead become different by receiving distinct signals. This leads to a _____ pattern of development, which is how most human development occurs.
Environmental signals
Regulative
Diagram of two mechanisms of differentiation:
Monozygotic or identical twins are produced from a ____ fertilized egg. This results when blastomeres exhibit reduced ____ and separate from each other. The later the separation occurs the greater risk for ____ ___.
Single
Adherence
Conjoined twins
The timing of blastomere separation determines whether separate ____ or ____ form, or whether they are shared or not.
Amnions
Chorions
The later, the separation, the more likely, the twins will share the same amnion and chorion. this is referred to as _____/____ pregnancies which is riskier because of the increased possibility of umbilical cords, becoming entangled
Monoamniotic/monochorionic (Mo-Mo)
Monozygotic twinning demonstrates that the fate of cells in the embryo are not determined until after the ____ ___ ___ and ____ ____ stages. This observation leads to the concept of ___ ___.
Inner cell mass
Early epiblast
Cell potency
The inner cell mass cells normally no longer produce trophoblast cells, and are therefore called _____.
Pluripotent
The epiblast forms all of the cells and body parts of the embryo an adult and are therefore also _____
Pluripotent
The process of ____ gives rise to the three basic germ layers, and now each a germ layer is a significantly more restricted in the types of cells and tissues they can form. Cells of each germ layer are referred to as ____.
Gastrulation
Multipotent
Review:
____ cells gain a general type of identification, such as neuromuscular, epidermal, etc. but the precise cell type is not yet defined
Committed
_____: the type of cell is defined, and further development is independent of environmental signals
Determined
Commitment is usually followed by determination, and typically gives rise to a hierarchical pattern of organization. Early development is this characterized by a ___ ____ of cell fate.
Progressive restriction
Somatic cell nuclear transplantation (SCNT) experiments revealed that when you remove the nucleus from an adult cell and place it in activated, cytoplasm and a nucleated egg, a _____ organism could be derived.
Complete
SCNT experiments indicate that each mature differentiated cell contains the complete set of genetic blueprints for ___ ___.
All cells
Differentiation from a pluripotent state, must therefore involved ____ of sets of genes not appropriate to a specific cell type
Inactivation
Factors and conditions exist in an egg that can ____ a fully differentiated cells nucleus to reactivate these genes and re-achieve complete potency
Reprogram
A two-step process is characteristically associated with the cell differentiation:
1. The conversion of environmental signals into selective activation of transcriptional regulators via ___ ____ pathways.
2. ____ modification of chromosomes
Cell signaling
Epigenetic
Interestingly, the induction of over 200 cell types present in the body are instructed by only a ____ signaling pathways, which are used repeatedly throughout embryogenesis.
Few
Major signaling pathways involved in induction:
Epigenetic modification of DNA and histones can promote an ____ (active) configuration or a ___ (repressed) configuration
Open
Closed
Toti potent and pluripotent cells have mostly ___ and ___ chromatin which becomes more closed as differentiation proceeds
Open
Active
Some epithelial cells in an adult can exhibit ____ and change their differentiation in state. ____ ____ attempts to use differentiated cells to produce stem cells for tissue repair.
Plasticity
Regenerative medicine
The ____ model (1950) of cell fate envisions that cells acquire specific fates as they roll down and enter different valleys
Waddington’s
This model has been helpful for regenerative medicine applications, and efforts to directly ____ one type of cell into another.
Transform
Major early developmental cell differentiation events:
Trophoblast versus inner cell mass:
In the morula, asymmetric divisions, during cleavage, concentrate the transcription factor ____ in the outer cells.
CDX2
CDX2 upregulates its own ____. It also promotes the expression of ____ specific genes. It suppresses the expression of ___, ___, and ____ which are transcription factors associated with the maintenance of pluripotency
Expression
Trophoblast
Oct4, Nanog, and Sox2
Oct4, Nanog, and Sox2 suppress the expression of ___. Therefore oct4/Nanog/Sox2 and CDX2 expression become mutually exclusive between ___ and ___ cells due to a double negative feedback loop.
CDX2
Inner
Outer
Tropho blast versus inner cell mass:
End result: outer cells become ____ and enter cells remain pluripotent and give rise to the ____.
Trophoblasts
Embryo
Increased expression of ___ and ___ in the outer cells further activate CDX2
Yap
Tead
Diagram and summary of first decision:
Second decision: formation of epiblast and hypoblast:
Cells of the inner cell mass begin to differentiate and express different sets of ___ ___ through a double negative feedback loop. Differences in the ___ (MAPK) signaling pathway cause ____ to promote hypoblast formation and ___ helps maintain pluripotency and future epiblast fate.
Transcription factors
Erk
Gata6
Nanog
Third decision: formation of ectoderm, mesoderm and endoderm:
The three germ layers differentiate during _____ and appears to result from complex patterns of ____ signaling involving signaling pathway regulation of transcription factor expression.
Gastrulation
Combinatorial
Beyond specific cell fates: establishment of the body axes (dorsal/ventral, cranial/caudal, left/right)
____ genes aka ____ genes are involved in cranial-caudal axis formation. They encode transcription factors that contain DNA binding sequences called ____.
Hox
Homeobox
Homeodomains
Hox genes are regulated by ___ ___ signaling. The longer cells reside in the node, the longer they are exposed to retinoic acid, and the more ____ fate they adopt.
Retinoic acid (RA)
Posterior
___ ___ and ___ signaling is involved in dorsal-ventral axis formation.
Sonic hedgehog (SHH)
BMP
Neural cell differentiation in the neural tube is instructed by opposing gradients of BMP and SHH. SHH develops ____ floor plate and BMP develops ____ floor plate .
Ventral
Dorsal
Left and right asymmetry arises from the ability of ___ ___ ___ to concentrate nodal activity on the ___ side of the embryo, resulting in the regional activation of transcription factors, such as ____.
Primitive node cilia
Left
Ptx2
Key points:
