Peer-reviewed by 3 reviewers with median rating of 16/20. Review process was triple-blinded.
Round 1 (16/20)
Conceptual advance and Impact8
Overall, I think the technical quality of the manuscript is very solid. I only have minor suggestions about including an example of KDEL-GFP change upon FLIP in AP and BP, to contrast with the observation in Sec61a-GFP, in order to demonstrate a clear presence of ER membrane diffusion barrier in AP and BP.
In terms of conceptual advance, I think the profiling of developmental change of diffusion barriers in AP and BP is an incremental update of the atuhors' previous work. It may be worth expanding the discussion a bit on the temporal significance of diffusion barrier change in each progenitor population.
I suggest that the authors show snapshots of FLIP-induced fluorescence changes of KDEL-GFP in apical and basal progenitors over time, just like what was shown in Panel B.
Conceptual advance and Impact7
The work is technically sound and I endorse its publication in Science Matters Selected.
RGs give rise to astrocytes, oligodendrocyte and ependymal cells. There are better rerferences to that than in vitro work only.
At this point, I don't think that the data allow authors to make any statement about the role of ER barrier in asymmetric cell division. They discuss this limitation at the end of the manuscript, but I think that the abstract should also tune down this interpretation.
Conceptual advance and Impact6
The authors present interesting data about the presence of a diffusion barrier in the ER of NPCs. Based on their data, the barrier differs in APs and BPs during the course of neurogenesis. As mentioned in discussion, it would be interesting to understand if the barrier's strength correlate with the symmetry/asymmetry of division and cell fate specification. On a more general note: considering how the neurogenesis field is developing, the focus on trafficking events/organelles dynamics in NPCs is very timely and appreciated.
- the authors wrote "...that the strength of the ER barrier is increased in APs compared to BPs."
Since BPs derive from APs, and not the opposite, it would be more appropriate to re-phrase so that the sentence reads as follows:
"...that the strength of the ER barrier is decreased in BPs compared to APs."
Results & Discussion
- In the final sentence of Results and Discussion, the authors mentioned self renewal differences between APs and BPs. The authors should comment/elaborate on polarity features differences as well, as they have the potential to be correlated with the presence of a diffusion barrier.
- It is not clear how the polarity barrier is oriented relative to the plane of division and to the apical plasma membrane (in case of APs). The authors should clarify/address that.