Animal Development Unit 1 Vocabulary

Early Development

Animal development is broadly conserved, although timing differs between species

Cleavage

rapid mitotic division without growth

Morula

solid ball of 16-32 cells

Blastula

hollow ball surrounding the fluid-filled blastocoel

Gastrula

cells rearrange into 3 germ layers (ecto, meso, edno)

find it

in stitu hybridization, immunohistochemistry, RNA -seq, qPCR, single cell RNA seq, spatial RNA seq

in stitu hybridization

detects RNA in its original location (find it)

Immunohistochemistry

detects proteins in their original location (find it)

RNA seq

measures the complete set of RNA molecules in a sample (find it)

q PCR

amplifies and quantitatively measures specific DNA/RNA sequences (find it)

single cells RNA seq

idnetifies cell tyes based on gene expression marker clusters (find it)

spatial RNA seq

measures gene expression while preserving its location in tissue (find it)

move it

change the location or amount of developmental factors (cell transplantation, mRNA injection, implanting protein soaked beads)

Lose it/Gain it

remove, block, or overexpress a gene or signal (cell removal, ENU induced mutagenesis, CRISPR CAS 9, antibodies or negative regulators to block a signal, extra mRNA/protein to increase activity)C

Crispr Cas 9

uses guide RNA and the Cas9 enzyme to cut DNA at a targeted location, allowing specific genetic modifications (lose it/gain it)

General principles of development

1. Timing and location matter

2. Cells neighbor can impact cells fate through cell-cell signaling 

3. Responses depend on signal level, other signals, tissue type, neighboring cells, and cells competency to respond

4. Small local changes can produce large effects throughout the embryo 

5. Cell fate is multifactorial 

cell fate

what a cell will eventually become

commitment

 Specification, Determination, Differentiation 

Specification

fate options are limited but labile, adopts fate in neutral environment, commitment reversible

Determination

 fate restricted, fate remains in non neutral environment, commitment irreversible

Differentiation

cell is specialized, structure, function, and phenotype change

Stem Cells

partly undifferentiated, self renew, produce daughter cells that can differentiate

totipotent

any type of cell including placenta

Pluripotent

any of the 3 germ layers

Multipotent

limited range of cell types in one lineage

Fate mapping

shows what cells in a region will become and cell lineages and developmental origins, does not show WHEN cells commit

Original painting

type of fate mapping where  you inject dye in early embryonic cells, follow later in development

Modern Fate mapping

cells labeled with GFP on N- terminus or C- terminus, brandbow uses multiple fluorescent proteins to label different neurons in different colors

Transplantation/chimera experiments

type of fate mapping experiment in which donor and accepting embryo cells, transplanted GFP labeled donor cells into unloved embryo cells

Uses of fate maps

Determine cellular fates, Study the timing of commitment, Plan experiments, Interpret mutant and transplantation results. Visualize cell movements and development

Control of Commitment

changes in factors inside cells, communication between neighboring cells 

Types of Specification

Autonomous, Conditional, Syncytial

Autonomous

fate is determined by only factors within the cells, cytoplasmic determinants (asymmetrical cell division)

Asymmetric cell division

type of autonomous specification in which  single cells produce daughter cells with different fates, factors localized to one side before division

mRNA localization

type of autonomous specifcation in which localized mRNA can create different cell fates by restriction the production of particular proteins ( diffusion and local anchoring, localized protection, or active transport)

Master regulator

type of autonomour specification in which expressed when specification begins, controls many genes needed for a specific cell fate, can redirect cells towards fate

Conditional Specification

Fate depends on neighboring cells and cell position and induction

Induction

conditional specification in which one cell influences the development of neighboring cell through local signaling , regional specificity and genetic specificity 

Reciprocal induction

two way signaling

Instructive interaction

signal necessary for fate determination

Permissive interaction

responder is already specified, provides further commitment

Synctial

type of specification where one cell many nuclei (syncytium), internal factors within cells and neighboring nuclei or region

Morphogens

diffusible factor that influences cell fate according to its concentration (Forms concentration gradient, cells respond differntly to different concentration, concentration thresholds determine different fates)

French flag model

Different thresholds of a morphogen gradient specify different cell fates, opposing gradients can help establish different regions (ex: head v tail) high concentration 1 fate, intermediate concentration another fate, low concentration a third fate

Turing mechanism

simple chemical interaction generate complex biological patterns, math models based on reaction diffusion, reaction diffusion and instability in unifrom state

Reaction- diffusion

activator promotes its own activity and inhibitor limits activity

Instability in uniform state

activator conc. Grows, inhibitor restricts surrounding regions, spots or strips, emergent patterns ( system self organizes into repeated structures such as stripes, spots, waves, and concentric rings)