Peer review of: Impaired peroxisomal import in Drosophila oenocytes causes cardiac dysfunction by (2020)

  
 
 

Reviewers' comments: 

 

Reviewer #1 (Remarks to the Author): 

 

The authors have responded appropriately to my comments and have added new relevant data that 
strengthen the manuscript. I believe the manuscript can now be recommended for publication. 

 

 

Reviewer #2 (Remarks to the Author): 

 

The authors have provided a significant amount of new data and explanations to their manuscript. I 
feel that the authors have adequately responded to the reviewers' comments. It is still advisable to 
have the grammar/ word usage checked by a native English speaker as there are problems at a 
number of spots in the text. Nevertheless, their findings are novel and extremely interesting, 
suggesting that non-cardiac peroxisomes play important non-autonomous roles in heart function via 
IL6/UPD3-mediated inter-organ communication, and deserving of publication in Nature 
Communications. 

 

 

Reviewer #3 (Remarks to the Author): 

 

Several issues were well addressed, including a better analysis of the potential involvement of 
peroxisomal metabolic pathways in the observed effects. 

My question why Pex19 knockdown deviates from Pex1, Pex14 and Pex5 was not clarified 
satisfactorily. A potential underlying cause may be that the (partial) knockdown did not result in a 
defect in peroxisomal matrix import. In fact, the authors validate the knockdown of Pex1 and Pex5 
by performing qPCR but do not show data on Pex19. Furthermore, it is possible that even low levels 
of residual PEX19 may support peroxisome biogenesis. Therefore, it is necessary to assess the 
knockdowns by a functional assay and show whether or not import competent peroxisomes have 
been deleted. 

Secondly, I requested to measure ROS levels in the KD oenocytes. These experiments were 
performed but the results are not convincing. The Pex1 and Pex5 knockdown seem to result in 
increased DHE levels. My concern is that it is obvious that in the –RU condition for the Pex19 KD, the 
DHE staining is more intense than in other –RU controls. Why is there a difference? Furthermore, 

this is not reflected in the % DHE values in the graphs. This raises doubts on the reliability of the DHE 
data. Because DHE stains nuclei, it would be better to normalize the DHE to DAPI fluorescence. 

Upon my request, the authors measured ROS levels in Pex1G843D patient fibroblasts. In the text 
they claim that ROS is increased but from the figure it is clear that this does not reach statistical 
significance due to large variability. It is also strange that here another assay to assess ROS levels is 
used (Amplex Red). In the methods it is mentioned that ‘different cell lines’ were analyzed and that 
the experiments were performed in triplicate. It is not clear how many independent lines were used. 

The authors launch the term peroxikine but it should be better determined what this stands for. 

I am sorry that I did not comment on the final sentence in the discussion in my first review. 
However, I want to point out that this is highly speculative. At this point there is no indication that 
the effects of peroxisome deletion in oenocytes/liver on heart function can be translated from the 
fly to human ‘aging diseases’.