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title: JC 2021
disqus: hackmd
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> Documentation [name=MrDr.Staffan]
###### tags: `jc`

# JC 2021

### Table of Contents
1. [Lee *et al.*, Astrocytes phagocytose synapses. Laura Morcom](https://hackmd.io/@sholmqvist/r1cPVgsoH/%2F3UTdFl91Q-KB3sbqYkb4QQ#Laura-Morcom-Astrocytes-phagocytose-adult-hippocampal-synapses-for-circuit-homeostasis)

2. [Wang *et al.*, Astrocyte secreted IL-33 effect on synapses. Katherine Ridley.](https://hackmd.io/@sholmqvist/r1cPVgsoH/%2F3UTdFl91Q-KB3sbqYkb4QQ#Wang-et-al-Astrocyte-secreted-IL-33-effect-on-synapses-Katherine-Ridley)
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# Lee *et al.*, Astrocytes phagocytose adult hippocampal synapses for circuit homeostasis.Laura Morcom.
https://www.nature.com/articles/s41586-020-03060-3

**Astrocytes & microglia engulfed synapses.**

#### 1. **Uptake of dye-labled fusion contructs excitatory and inhibitory pre-/post synapses**

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#### 2. **Uptake into endosomes and then lost their EGFP fluorescence in low pH of lysosomes.**
- EGFP stop fluorece at low pH.
:arrow_right: mCherry signal alone indicates fusion protein in a low pH lysosome.


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#### 3. **Showed that in enriched environments astrocytes mainly pruned pre+post-excitatory synapses.**

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#### 4. **This mechanism being dependt on astrocytic Megf10 expression (previously reported.)**
- **cKO Megf10 :arrow_right: less Punctae** in astrocytes. (Syn-cherry & PSD95-cherry)
- AAV. Aldh1l1-creERT2:Megf10fl/fl mice

[Megf10 is a receptor for C1q - binding phosphatidylserine in membrane of apoptotic cells]


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#### 5. **Electrophys** (that we might or might not have had the knowledge to interpret in a meaningful way) & **behaviour Novel object Recognition**.

- inhibiting astroctyte engulfment :arrow_right: dont learn to distingish the new object.**
- cKO:Megf10 :arrow_right:Decrease in ExPSP in Megf10 mice.
- cKO:Megf10 :arrow_right: did not explore the new object more than the old.


### discussed issues.
- counting samples per animal instead of animals as n:s.
- presented experiments not replicating their own data.
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**Notes**
[Megf10 cooperates with ABCA1 (cholesterol efflux) SH.anm.)]

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# Wang et al., Astrocyte secreted IL-33 effect on synapses. Katherine Ridley.
https://pubmed.ncbi.nlm.nih.gov/33443211/

Last week we talked about astrocytes engulfment of synapses. Dependent on Megf10. This week we discuss astrocyte in synapse formation.

* astrocytes are important regulators of synaptic transmission and plasticity, it is largely unclear how they interact with neurons to regulate synaptic plasticity at the circuit level.

* neuronal activity blockade selectively increases the expression and secretion of IL-33 (interleukin-33)


* activation of neuronal IL-33 receptor complex and synaptic recruitment of the scaffold protein PSD-95

* tetrodotoxin in hippocampal slices
* inhibition of by optogenetic manipulation
:arrow_right: increases IL-33 expression in CA1 astrocytes

* IL-33 administration in vivo promotes the formation of functional excitatory synapses


* blockade of IL-33 and its receptor signaling in vivo by intracerebroventricular administration of its decoy receptor inhibits homeostatic synaptic plasticity
:arrow_right: inhibit memory formation in mice.

* cKO of IL-33 in astrocytes impair synapse function


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**Technnical**
In conditioned media experiments. Where cultures where treated with media from cells exposed to TTX. They separate away the TTX by spinning.

**Comments.**
IL33 is not a traditional inflammatory interleukin. (**Katherine**)

Interleukin-33 acts as a pro-inflammatory cytokine. (**G.lam**)

Il33 expression also increased in other cells (e.g. oligos) but only secreted by Astrocytes. (**Laura**)

They do not discuss the mechanism of how IL33 inhibit neuronal activity. (**Ginez**)

The paper does not discuss what the mechanism for IL33 secretion is (**Chao**).
[Botox](https://go.drugbank.com/drugs/DB00042). This would have blocked the neurotransmitter vesicle release, (TTX used in the study blocks voltage gated sodium channels VGCS Nav:s preventing neuronal depolarization) (**JohnS**).

[Confirmed that TTX the poison from blow fish is specific to VGSCs](https://pubchem.ncbi.nlm.nih.gov/compound/11174599#section=BioAssay-Results&fullscreen=true). (**Staffan**)

Co-localisation of pre & post synaptic proteins (e.g. PSD-95 and Vglut1) is on its own not enough evidence to convince there is more connectivity. (**JohnS**)

**In the meta-commentary, participant input:**
* It is important that people attending are getting something useful out of JC.

* Dont take for granted that you are the only one in the room, not understanding something! speak up if you want something explained!

* What is the significance of this paper/topic to our labs?!