Know Your Organoid
The authors generated human ___ organoids, abbreviated hCerOs, capable of replicating the fetal cerebellum's cellular diversity.
cerebellar
These glutamatergic neurons, derived from the rhombic lip, make up the most abundant cell type in the cerebellum and are marked by BARHL1 and ATOH1.
Granule cells (GCs) / Granule cell progenitors (GCPs)
To image spontaneous neuronal activity inside intact organoids, researchers used live ___ microscopy after infecting organoids with AAV8-GCaMP6f.
Two-photon microscopy
True or false: prior to this study, functional Purkinje cell maturation had been achieved in all-human culture systems without the need for mouse glia or granule cells.
False — previous studies required co-culture with mouse glia and/or granule cells. This paper was the first to achieve Purkinje cell functional maturation in an all-human system.
The human brain can power a light bulb of up to how many watts?
25
True or false: the commonly used FGF2 + insulin patterning strategy was found to be sufficient for generating pure cerebellar cell types in this study.
False — FGF2 + insulin produced significant forebrain contamination. The authors developed an improved protocol using dual SMAD inhibition, CHIR, and FGF8b.
Match the marker to the cell type:
SKOR2 → ?,
MEIS2 → ?,
SOX14 → ?,
EOMES → ?
SKOR2 → Purkinje cells;
MEIS2 → inhibitory cerebellar nuclei (iCN);
SOX14 → molecular layer interneurons (MLI);
EOMES → unipolar brush cells (UBC)
In the calcium imaging experiments, tetrodotoxin (TTX) was applied to organoids. What was the purpose of this, and what did the result demonstrate?
TTX blocks voltage-gated sodium channels, silencing action potentials. Its suppression of calcium signals confirmed the activity observed was genuine neuronal firing, not artifactual.
In patch-clamp recordings, ___ % of recorded PCP2/L7+ neurons showed spontaneous, TTX-sensitive action potentials, with an average frequency of 14.63 Hz.
42.10%
Your spinal cord stops growing at age __.
4
Which signaling pathway activator was added on Day 4 to specify the midbrain-hindbrain boundary?
FGF8b — added at Day 4 to suppress midbrain fate and recreate the isthmic organizing center.
True or false: the human rhombic lip contains a subventricular zone (RLsvz) that is shared with other vertebrates, making it a conserved feature of cerebellar development.
False — the RLsvz is a human-specific feature not found in other vertebrates. Its generation in hCerOs was a first for any in vitro system.
SDF1a was added to hCerOs to induce laminar layering. At what concentration and for how long?
a) 50 ng/mL for 2 weeks
b) 100 ng/mL for 1 month
c) 300 ng/mL for 7 days
d) 200 ng/mL for 3 months
b) 100 ng/mL for 1 month (days 30–60). The authors note that 300 ng/mL for 7 days, used in prior work, actually produced a reversed organization.
Patch-clamp recordings revealed an Ih current in hCerO Purkinje cells. What is Ih, and why is its presence significant for validating the identity of these neurons?
Ih is a hyperpolarization-activated inward cation current carried by HCN channels. It is a hallmark electrophysiological property of mature Purkinje cells in vivo, so its detection confirms the neurons have reached a physiologically authentic state.
How many distinct scents can a brain recognize?
50,000
What was the highest scaled correlation brain region for 2-month-old hCerOs when mapped onto the BrainSpan transcriptomic dataset, compared against PCW 12–24 samples?
The cerebellum (CB) — confirmed via VoxHunt analysis.
In vivo, ___ cells act as a scaffold for granule cell migration into proper orientation. They were identified in hCerOs by markers including PTPRZ1, GFAP, and HOPX.
Bergmann glia
Put these protocol stages in the correct order:
(A) Transfer to bioreactor/10cm dish;
(B) Add FGF8b at Day 4;
(C) Aggregate iPSCs in V-bottom plates with dual SMAD inhibitors;
(D) Add BDNF after Day 60.
C → B → A → D. iPSC aggregation with SMAD inhibitors first, FGF8b at Day 4, transfer to dishes at Day 16, BDNF supplemented from Day 60 onward.
Calbindin imaging of 6-month-old hCerO Purkinje cells showed morphology comparable to human fetal Purkinje cells at PCW 22–28. What does this suggest about the developmental trajectory of hCerOs?
It suggests hCerOs follow a similar developmental timeline in vitro as seen in vivo, maturing at a pace roughly mirroring human fetal development rather than accelerating or diverging significantly.
The pathologist who performed Einstein’s autopsy kept the brain in a ___ in his basement for 40 years.
Jar, Tupperware
Why was it important that hCerOs could be generated reproducibly across multiple hiPSC lines, including PGP1, 11a, D2, and H9?
Reproducibility across lines demonstrates the protocol captures an intrinsic cerebellar developmental program rather than a cell-line-specific artifact, increasing confidence in the model's general validity.
The VZ produces GABAergic neurons while the rhombic lip produces glutamatergic neurons. Name two specific cell types from each zone mentioned in the paper.
VZ (GABAergic): Purkinje cells, molecular layer interneurons (MLIs), inhibitory cerebellar nuclei (iCNs).
RL (glutamatergic): granule cells (GCs), unipolar brush cells (UBCs), excitatory cerebellar nuclei (eCNs).
The L7/PCP2 promoter was used to drive eOPN3 expression specifically in Purkinje cells. When LED light silenced these cells, broader organoid calcium activity went up. What does this tell us?
It demonstrates that Purkinje cells are actively integrated into the hCerO network and exert inhibitory control over other neurons. Their silence disinhibited the network, confirming functional GABAergic connectivity.
A student writes: 'Purkinje cells in hCerOs were identified solely by CALB1 expression and showed induced-only firing at rest, with an average resting membrane potential of −70 mV.' Identify two errors.
Error 1: Purkinje cells were identified using multiple markers (PCP2, DAB1, RORA, FOXP2, CALB1) — CALB1 alone is insufficient.
Error 2: The average RMP was −53.88 mV, not −70 mV, and 42% of cells showed spontaneous (not only induced) firing.
sphenopalatine ganglioneuralgia