Hypothalamus and Control of Sleep Flashcards
What are the stages of sleep explained by neuroscience?
- Two stable states that switch due to ‘build-up’ of ‘sleep pressure’
- When you sleep this pressure dissipates
- Poorly understood
What is the difference between sleep and wake in terms of antagonising neurons?
- Wake-promoting neurons activated by dissipating sleep pressure and promote transition to wakefulness
- Sleep-promoting neurons activated by increasing sleep pressure and promote transition to sleep
How have we proved these neurons do the role we claim?
You can stimulate them neurons via stimulating a lively mouse’s sleep neuron and it will fall asleep immediately
Are the sleep neurons a network or localised?
- Form a network
- Wake-promoting neurons found in various areas such as lateral hypothalamus and tuberal mammillary nucleus
What do each of these different neurons secrete?
Wake-up Function = Lateral hypothalamus neurons secreting hypocretin
Wake up Function = Tuberomammillary neurons secreting histidine
What does lesioning/dysfunction of the TMN or lateral hypothalamus cause?
Narcolepsy
How many people does narcolepsy affect and what is it?
- Effects 1 in 2000 - 1 in 20,000
- Chronic sleep disorder which causes daytime napping
What do you find in the brain of someones who had/has narcolepsy?
- Significant reduction in hypocretin neurons
Who wrote the paper regarding regulation of hypocretin neuron specification by Lhx9?
Liu et al, 2015
What is Lhx9?
- a TF necessary to specify Hypocretin neurons
How did this paper solve the question: Can we identify what progenitor cell type gives rise to a hypocretin neuron?
- Moment when the cell is differentiating from a progenitor to a neuron where it will express an important marker along with hypocretin
- Make a transgenic fish whereyou fuse hypocretin promoter upstream of GFP
- Where expressed, if you shine light the cells will glow red
- Take the brain + dissociate the cells
- Put them down a FACS machine which separates fluorescing from non fluorescing
- Look at all of the mRNA and look at what is expressed in high levels
- Lhx9 expressed in high levels in hypocretin fluorescent cells
How are the transitioning cells arranged in the transition from progenitor to neuron?
Earliest progenitor closest to midline
Middle is a little further away
Differentiated cell is the furthest away
What experiment was done to see if Lhx9 is SUFFICIENT?
-KO and GOF
- Overexpression in ectopic location via heat shock should mean you see hypocretin +ve cells ectopically expressed
- Shows lhx9 can specify hypocretin neurons but doesnt show its required
- KO via CRISPR/CAS9 you can see no hpcrt
Is Lhx9 influencing downstream signals or is it directly binding and upregulating transcription of hpcrt neurons?
- Mutate binding site upstream of hypocretin and ask whether Lhx9 is no longer able to activate the transcription of hypocretin
- That is what they found, implying hypocretin directly binds and regulates
Are there any narcoleptic cures?
- No cures, but drugs to help with symptoms
- They all have lots of side effects
How can cell replacement therapy using induced pluripotent stem cells be used as potential narcoleptic therapies?
Step 1:
- Take differentiated cell and add 4 key TFs that reverse programming, so it behaves like a stem cell
- Gives an induced pluripotent stem cell
- Culture iPS in a dish/lab
Step 2:
- Apply the key TFs in a dish to make it differentiate in to the desired cell
What is this cell replacement therapy technique mainly being used for now?
- Disease models, understanding how they work and what could make them die (narcolepsy)
- Can we figure out small molecules that rescue them/make them more stable
