This is a journal club presentation on the manuscript by Owen et al, published in May 2021 in the journal Developmental cell. It describes how the myelinoids were derived from the iPSCs and can be considered as model to study myelin biology.

1. Journal club to present manuscript “iPSC-
derived myelinoids to study myelin biology of
humans”
Authors: Owen G. James, Bhuvaneish T. Selvaraj, Dario
Magnani, ..., Charles ffrench-Constant, David A. Lyons,
Siddharthan Chandran; Developmental Cell; May 2021
Journal club presenter: Dr. Leena Shingavi

2. CNS and PNS myelination

3. Myelin sheath subdomains

4. Introduction
• The formation and maintenance of myelin in the CNS of
humans is a dynamic life-long process
• Normal myelinated axon functions, namely efficient nerve
conduction, metabolic support to the axon and adaptive
myelination requires both normal myelin wrapping and
myelination or myelinated axon organization
• Its disruption across the life course is associated with
neurodevelopmental, psychiatric, and degenerative disorders

5. Graphical abstract

6. Introduction
• Recent human models of oligodendrogenesis demonstrate
oligodendrocyte differentiation in 3D spheroids containing
neurons and astrocytes
• In vitro systems with mature myelinated axons have focused on
generating myelinating oligodendrocytes using forebrain-
patterned cultures
• In-utero, the emergence of ventral spinal cord-derived
oligodendrocytes is earlier and the maturation of the
myelinated axons is much faster than the forebrain-derived
oligodendrocytes

7. Aim
• To establish an iPSC-derived spinal cord patterned model of
myelin formation to investigate myelin development, disease,
pharmacological interventions and adaptive myelination in
human context

8. Materials and methods
• 1. Culture of human iPSCs: 3 hPSCs (males) lines were obtained
and validated using chromosomal analysis, pluripotency and
absence of plasmid integration. iPSC lines for Nfasc155-/-
clone1, female and Nfasc155-/- clone 2, female were
generated by Cedars-Sinai
• 2. Generation of iPSC myelinoids: (3 phases)
• 3. Dissociated myelinoid cultures: to supplement with 3nM of
tetanus neurotoxin (TeNT)

9. Materials and methods
• 4. Immunostaining of whole-mounted myelinoids
• 5. Cryopreservation and immunostaining
• 6. Image acquistion by confocal microscopy
• 7. Transmission Electron microscopy: toluidine blue staining for
compact myelin
• 8. PCR amplification of Nfasc155: to confirm the presence of
homozygous Nfasc155 mutation in patient-derived iPSCs
• 9. qRT-PCR: of rostrocaudal axis genes to characterise the regional
identity and cellular composition of the myelinoids

10. Materials and methods
• Image analysis by confocal microscopy
• Automated analysis using MetaXpress software: for unbiased
3D quatification of global myelin volume and axonal density

11. Results: Generation and characterisation of
iPSC myelinoids

12. Results: Temporal development of myelin
formation

13. Results: Temporal development of myelin
formation

14. Results: Temporal development of myelin
formation

15. Results: Structural organisation of myelinated
axons and myelin-compaction
These myelinating organoids are thus referred to as myelinoids

16. Results:Nfasc155-/- patient-derived myelinoids recapitulate
disease pathology of disordered myelinated axon organisation
Thus, iPSC myelinoids can be used to model disorders of myelinated axon organisation

17. Results: Myelinoids predictably respond to
pharmacological cues at both individual
cell level and whole-myelinoid levels

18. Results: Myelinoids predictably respond to
pharmacological cues at both individual cell
level and whole-myelinoid levels
The myelinating profile of individual oligodendrocytes can be modulated pharmacologically.
Also demostrates widespread effects of human myelination can be assessed using the myelinoid
model

19. Results: TeNT supresses human
myelination
Reduced vesicular release supresses myelin development, providing an opportunity to
study human adaptive myelination

20. Conclusions
• Spinal cord patterned myelinoids recapitulates compact myelin
formation and myelinated axon organisation; allowing the study of
nodal assembly and disruption in health and disease
• Patient-derived myelinoids demonstrated in the key pathology of
Nfasc155 deficiency, namely impaired paranode (PNJ) formation
• Investigations into the long term impact of Nfasc deficiency or other
mutations on nodal domain stability and axonal health may be well
served using iPSC myelinoids

21. Conclusions
• Inhibition of synaptic vesicle release secondary to TeNT
resulted in preferential myelin targeting, a reduction in
internodes per oligodendrocyte and a reduction in global
myelin volume and sheaths per cell
• The study established iPSC-derived myelinoids as a tractable
and quantifiable platform for evaluation of human myelin
biology in a tissue-level context

22. Limitations of the study
• Inferences made on myelin development in this model may not be
generalizable due to the spinal cord identity of myelinoid cultures.; limiting
their use in studying myelin development in the context of certain
neurological conditions
• The extended time frame over which myelination occurs in this system can
be challenging to optimize the dosing of small molecules/treatments that
influence myelin development or neuronal activity
• A common limitation of organoid models is that they lack the full
complement and diversity of cell types found in vivo, e.g. microglia are
absent in these organoids and yet play critical roles in neurodevelopment

23. Thank you