Zebrafish Models of Autosomal Recessive Ataxias

Round 1

Reviewer 1 Report

The paper by Quelle-Regaldie A, et al., entitled “Zebrafish models of Autosomal Dominant Ataxias”, presents an updated, complete and very interesting review regarding the impact of Zebrafish models on the study of dominant ataxias, a group of neurodegenerative diseases that displays clinical, genetic, and neuropathological heterogeneity. Hallmarks of this family of disorders include gait ataxia and poor coordination of hands, speech, and eye movements.  

The review discuss the Zebrafish models for spinocerebellar ataxias (SCA2, SCA3, SCA6/episodic ataxia 2, SCA7, SCA13, SCA14, SCA17 and SCA37) and other ataxias (sensory dominant ataxia 1, episodic ataxia 1 and episodic ataxia). The references considered for this update were obtained from the zfin database (https://zfin.org/) and the PubMed database (https://pubmed.ncbi.nlm.nih.gov/.  

The authors claim that in view there is no effective treatments for dominant ataxias, Zebrafish models have been very useful to characterize these neuronal disorders, due to its small size, external fertilization, optic transparency of the embryos and larvae, its conserved vertebrate genetics, and the facility to perform genetic edition.  

The author were clearly successful in showing how Zebrafish models have contributed to the study of ataxias by defining genetic function, behavior, and candidate drugs for treatments. They emphasized not only in the advantages of these models but also in their limitations. They describe the strategies for generation of Zebrafish models, which includes loss of function models (achieved by knock down with antisense morpholinos), stable knocks out (achieved using mutagens) and the recently developed models using gene editing through CRISPR/Cas9 techniques. Within limitations of the models, they mentioned the difficulty to generate gain- of-function models, because knock in methods are poor effective in zebrafish.  

The review offers a description of each ataxia, including clinical characterization, the genetic origin (with emphasis in CAG repeats expansion), protein function, and the molecular pathways altered, including also causes of neurotoxicity (protein aggregation, ARN toxicity, altered calcium homeostasis, impaired proteostasis, mitochondrial stress and autophagy). 

Finally, the review shows the conclusions and future development of Zebrafish models for ataxias using CRISPR/Cas9 technology. They highlighted that most of the studies in zebrafish were performed with morpholinos, which can cause off target effects, being necessary to validate them with a control morpholino or mRNA rescue.  

 

What is the main question addressed by the research?  

 

The Manuscript offers an updated review of the impact of Zebrafish models on the study of dominant ataxias. It covers Zebrafish models for spinocerebellar ataxias (SCA2, SCA3, SCA6/episodic ataxia 2, SCA7, SCA13, SCA14, SCA17 and SCA37) and other ataxias (sensory dominant ataxia 1, episodic ataxia 1 and episodic ataxia). The review offers a description of each ataxia, including clinical characterization, genetic origin, protein function, and the altered molecular pathways. The authors emphasize not only in the advantages of these models but also in their limitations. 

 

Is it relevant and interesting? 

 

The topic is very interesting and relevant because the generation of Zebrafish models have aided in defining genetic function, behavior, and candidate drugs for treatments. Such models are very useful because of the lack of effective treatments for dominant ataxias.  

How original is the topic? What does it add to the subject area compared
with other published material? 

 

The review is original and make a critical discussion of the benefits and limitation of Zebrafish models for the study of ataxias. The authors use their own point of view but based on previously reported references.  

Is the paper well written? Is the text clear and easy to read? 

 

The manuscript is well written and is easily followed.  

 

Are the conclusions consistent with the evidence and arguments
presented? Do they address the main question posed?

The conclusions of the use of Zebrafish models for the study of ataxias and the perspectives of such animal models were properly defined.  

In my opinion it deserves publishing in Cells presented  

Author Response

We would like to thank the editor and reviewer 1 for the comments

Reviewer 2 Report

The authors in this review titled “Zebrafish Models of Autosomal Recessive Ataxias” give a good account of the genetic bases of ataxia disease and describe the different models of zebrafish (either knock-down or knockout) that unraveled some molecular aspects of Ataxia associated pathologies. The review mainly focuses on summarizing the described phenotypes of the available zebrafish models.

 

The review reads generally well, is of potential interest to a broad audience. It is organized in a logical way, however, it would be beneficial if the English would be checked.

I have a few comments and suggestions that I hope could help in clarifying some misunderstandings and enhance the manuscript.

• Even though the authors did a great job assembling all available information into tables, I would suggest that the authors would try to add some figures, e.g. assembling genes into groups based on their function or signaling pathways or phenotypic trait. It would be much easier for the reader to recapitulate some information through a figure.
• Think that all the tables outlining tools would benefit from a bit of colour, maybe grouping diseases into different colours
• Line 41 based on
• Line 62 to help unravel
• Line 73 such as
• Line 74 to 77 This sentence is slightly confusing, would it be possible to clarify it?
• Line 104 as well as would be and
• Line 127-128 What are exactly the phenotypes that have been rescued following p53 mutation?
• Line 136 SPG39 is not clear, to define
• Line 156 Increase in
• Line 160 morphants would be morphant cells
• Line 237 by zebrafish E is not clear, it is also better if authors would introduce the link between vitamin E and ttpa
• Line 392 Rapamycin
• Line 492 did not reveal
• Line 655 than would be that
• Line 671 to define RNF1 and OTUD4
• Line 729 no would be not
• Line 797 define WWOX
• Line 807 with would be to
• Line 811 define NPC
• Line 832 As would be since
• Line 856-857 The sentence is not clear
• Line 897 lost would be loss
• Line 912 in would be on
• Line 913 on would be in
• Line 914 define AH1
• Line 931 define cep290
• Line 938 define all the mentioned genes in this case
• Line 954 no would be not
• Line 959 survival rate
• Line 961 define rars2
• Line 966 define SLC25A46
• Line 981 a word is missing: mitochondria from… were
• Line 1007 not would be non
• Line 1011 not would be non
• In the “Conclusions” paragraph, genes that were not described before should be defined here.
• Line 1016 studied should be study
• Line 1016 remarking would be highlighting
• Line 1021 caused would be cause
• Line 1026 add do not always
• There are some typos in the excel file, to be checked and corrected.
• It is very important to make sure that every disease and gene’s acronym is well defined throughout the text.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I would like to thank the authors for their effort, just two minor issues before acceptance:

1- Line 924 first "lost" to keep, second “lost” would be “loss” so that would read: …the larvae lost their ability to swim until higher doses caused a complete loss.

2- Is it possible to color code the table in the text like the one in the Supplementary.

 

Author Response

We would like to thank the reviewer 2 for her/his efforts in correcting the manuscript. We have followed all the reviewer’s suggestions.