Oligodendrocyte precursor cells sculpt the visual system by regulating axonal remodeling

A collaboration from the lab is out!

Did you ever wonder what all the oligodendrocyte precursors in the brain are up to when they don’t make myelin? They fine-tune circuits! Funded by @ERC_Research & @DFG_public. Congrats to Yan Xiao and Laura Hoodless in Czopka_Lab, and Luigi Petrucco from our lab! Check their full work here!

Many regions in the zebrafish larvae brain are not myelinated, but they contain many oligodendrocyte precursor cells (OPCs). We know that some of those precursors stay around until adulthood. What are those cells doing? Could they have some other unknown function?

We investigated this by looking at the optic tectum. In zebrafish larvae, this region shows no signs of myelination but contains many OPCs.

Labelling of larval zebrafish optic tectum at 5 and 14 days post fertilization (dpf), showing OPCs (green) and myelin (magenta).

Early (2 days post-fertilization) genetic and chemogenetic depletions of OPCs show an interesting phenotype: retinal ganglion cells projections from the tectum make aberrant arborization outside the tectum!

Ectopic RGCs form additional branches extending outside the tectum when OPCs are ablated compared to the non-ablated control.

Late (7 dpf) depletions (chemogenetic/laser ablations) also affected axonal remodeling, with a decrease in the number of eliminated neurites. Indeed, time-lapses reveal that many axonal retractions happened after an interaction with an OPC process.

Movie showing the interactions between RGC axons (magenta) and OPC processes (green).

Since the ability to remove axon branches is crucial in the development of a functional circuit, we asked whether removing OPCs could have an effect on visual performance.

By imaging neurons in the optic tectum, we observed that after OPC ablations their visual responses had decreased amplitudes, with a lower signal-to-noise ratio!

Average fluorescent response of tectal neurons when OPCs are ablated (green) and in non-ablated controls (black).

Moreover, after ablation, the larvae were performing worse at an optomotor assay that probed their visual acuity, and were worse at capturing paramecia.

Non-ablated controls (black) captured more paramecia (reduced % paramecia remaining) than OPC ablated larvae (green).

We conclude that OPCs can have another fundamental role, independent from the production of myelin: they can assist the process of pruning and plastic remodeling of axons, essential in the development of a working nervous system.
If you want to know more, check out the paper and share it on Twitter!

Oligodendrocyte precursor cells sculpt the visual system by regulating axonal remodeling
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