Molecular regulation of neural diversity Flashcards
(26 cards)
Why is c.elegans a good model for studying neurodevelopment?
Entire connectome of its 302 neurons has been reconstructed and well-defined
Easily manipulated
What is a cell type?
Cell types are the basic functional units of an organism. They exhibit a broad range of phenotypic properties at multiple levels, making them challenging to define, categorise and understand.
Why study diversity of cell types
Reproducibility, genetic access, discovery, understanding development, understanding evolution, studying disease are all reasons why defining cell types carefully is important.
How can be investigate Neuronal diversity - defining (neuronal) cell types
1.Morphology - detailed anatomical analysis
2.Gene expression - in situ, immunohistochemistry transgenics, RNAseq, scRNA-seq(not everything can be found in the transcriptome, sometimes studying protein function can be just as important)
3.Function - electrical properties, connectomics
Diversity at the molecular level are known as
class-specific gene batteries
Describe two sexes of c.elegans
Males and hermaphrodites (mostly female but can self reproduce without male)
Hermaphrodite )Chr I-V and XX)
*959 somatic cells
*302 neurons (8 sex-specific) & 56 glia
Male cannot reproduce alone so need to find the hermaphrodite
*1031 somatic cells
*387 neurons (93 sex-specific)
*90 glia
What did brenner do to show c elegans is a good model?
From this small worm, they could identify every cell type and its lineages back to investigate neurodevelopment with finer resolution as well as being about to mutate it (genetic analysis)
How many days does it take to create new worms
~3 days at 20 degrees
Where are most neruonal cell bodies located in C.elegans?
Nerve ring - the worms brain.
Most of worms nerves are here
What is promoter analysis
Promoter analysis in C. elegans involves studying the regulatory regions upstream of genes to understand gene expression patterns and how genes are regulated. This is done by using promoter-fusion constructs, where a promoter region is linked to a reporter gene like GFP, to observe where and when the gene is expressed.
Describe genetically amenable screens
Give random point mutations to a hermaphrodite
Forward unbiased genetic screen- unbiased as you do not know which cells will get those random mutations you injected in
Easier with herm because they self reproduce.
Used to create a mutant screen.
C. elegans - full connectome in male vs herm
Herm- 302 neurons
Male - 383 neurons
Describe the specification of dopamine neurons?
conducted promter analysis on all dopaminergic genes
cis-regulatory analysis reveals a dopamine motif found the exact same sequence of DNA on the promoter was important for regulating the specification of dopaminergic neurons - so model 2 is correct.
Model 1
Different TFs regulate different classes of neurons
Model 2
Same TF regulates and gives rise to different classes
Which TF regulates diversity of dopaminergic neurons?
Ast-1
specifically controlling the expression of genes involved in dopamine production. Loss of AST-1 leads to the failure of distinct dopaminergic neuronal subtypes to fully develop.
Which TF regulates diversity of serotonergic neurons?
PET-1
Which TF regulates diversity of Cholinergic neurons? (Kratsios et al,2009)
UNC-3
Initiated and maintained expression of cholinergic fate markers and was sufficient to induce cholinergic fate in other neuron types.
unc-3 is continuously required (heat-shock)
COE (Collier, Olf, EBF)-type transcription factor UNC-3.
What is ast-1 needed for?
Induce and maintain dopaminergic cell fate
Define terminal selector
Defined the gene that is responsible for specifying to a particular neuronla type e.g. ast-1
Terminal selectors can
Auto-regulate so they can turn themselves on and keep themselves on.
What do they mean by heat shock for the TFs
Researchhhh
What does glutamate need to be expressed
No battery- just vGlut to load glutamate into vesicles
What did they find when they did promter analysis for glutamate?
Different bits of the promoter regulate expression in different cells so more modular and follows model 1.
So more than one TF is used to specify glutaminergic neurons.
