BIO 448 Exam 1: Cell fate maps and cell identity

fate map

Cells of the early embryo are not static and do not stay put.​.. They MOVE and CHANGE SHAPE​

How do cells know they are going to be endoderm, ectoderm, or mesoderm?? ​

technique that is used to know which cells become which cell type, which is called a _____​

Fate Maps

______: A technique to map larval or adult structures onto the region of the embryo from which they arose. Cell fate refers to what cells will become. ​

***What do these cells become and can we map it??? ​

***fate maps are really important in development, because it helps us know what fate those early embryonic cells will become​

Direct observation

______: visually follow cells to see what they will become. In the roundworm C. elegans, the cell lineage of EVERY cell is known using direct observation in part because the embryo is very transparent. ​

• Watch the cells divide and follow them with your eye to see where they go to and what cell types they become ​

• Really hard to do! Takes a lot of time and patience ​

• Works really well in organisms that are transparent since you need to directly see the cells ​

• the first organism that actually had all of its cells fate mapped was, the roundworm C. elegans, because C. elegans is a transparent organism, C. elegans is a worm. And because of that, they were able to actually look at every single cell type​

• celligans are unique in that, the cells are… will always become the same cell type, so it's very, it's highly patterned, and it doesn't really deviate from one embryo to another​

• because it's transparent, we can follow and trace where all of these cells become… where all of these cells will be​

• Effective technique but you have to be able to see the cells ​​

John Sulston

_____ spent over 18 months watching C. elegans embryonic cells and mapping their fate. ​

• he's one of the major proponents back in the 80s that fought for free exchange of scientific information and against patenting of genes​

Fluorescence molecule

_______: Inject a few cells with a fluorescent dye. The dye will stay in those cells and willbe passed on to the new cells after cell division. ​

Green Fluorescent Protein (GFP)

• tissue-specific promoter

• neural

GFP

cell type

The _______ gene can be placed by a promoter that is only active in specific cells.​

• The arrow is a _____ that isonly active in neural tissues/neural crest.​

• This allows a research to fate map only the ___ cells. ​

• This is a type of cell fate mapping of specific cell fates.​

____ - it's a gene that produces a protein that fluoresces​

Driven by a promoter that is expressed a specific type of ____ (ecto, meso, or endoderm) ​

Can follow where these cells would be because only cells that had that promoter turned on should express the fluorescent protein

Different promoters can be used to drive (turn on) expression of florescence protein in many different tissue types. (Can use different reporters for different things!!) ​

Direct Observation

Dye/GFP Maker

Pros and cons:

________:​

• Pro: Does not require much technology and effective. ​

• Cons: Requires an embryo that is very transparent. If embryos are opaque, it is harder to see the cells. ​

• Cons: Very difficult to follow cells without a marker.​

_______:​

• Pro: This can be performed with either transparent or opaque cells, because the fluorescence is very bright.​

• Pro: Can label specific cell types ​

• Cons: Is technically more advanced​

• Cons: Sometimes, hard to mark a single cell​

read and comprehend

Why would researchers create a fate map?​

​By understanding which early embryonic cells give rise to later developmental tissues, developmental biologists can perform more targeted experiments on that specific cell. ​

• determine what cells develop into the different parts of the organism​

• if you want to study how a brain forms, you have to first know which cells become the brain, right? You have to know that question if you really want to study how a brain forms.​

• undifferentiated

• differentiates

Cell Differentiation​

• The orange,embryonic cell begins as an _____ cell. This means it does not yet have a cell identity. ​

• The orange cell can undergo different cell fate decisions so that it _____ into either mesoderm or endoderm tissue. ​

at this stage, it can become anything it wants. It can become endoderm, or ectoderm, or mesoderm, or even a germ cell. ​

that cell decides to become the endoderm or whatever else it becomes, why did it make that choice to travel down this path of endoderm specification? ​

Functional difference: neurons provide signals and skin cells provide protection. One conducts signals and the other acts as a protective barrier ​

Same genome, but how are they different: that different genes are expressed, even though they are the same. all share the same DNA, but again, since only certain genes are expressed.​

• it's not the fact that, of course, they have different genes, they have the same genes, but it's really which genes are expressed and made into proteins that then make those cells so different from each other. ​

A skin cell and a neuron are both derived from ectoderm yet have very different functions. ​

• What is one functional difference between a skin celland a neuron?​

• If a skin cell and neuron have the same genome, why arethese cells different? ​

• Brainstorm a mechanism by which an ectoderm celldetermines to become either a skin cell or a neuron. ​