AKAP6 orchestrates the nuclear envelope microtubule-organizing center by linking golgi and nucleus via AKAP9

Acceptance summary:

While the composition and assembly of the centrosomal MTOC is still not fully understood, even less is known about non-centrosomal MTOCs. In this study Vergarajauregui et al. identify AKAP6 as a crucial assembly factor for the MTOC at the nuclear envelope in muscle cells and osteoclasts, by recruiting centrosomal proteins. Moreover, in cooperation with AKAP9, AKAP6 tethers the Golgi to the nuclear periphery, which also functions as MTOC in these cells.

Decision letter after peer review:

Thank you for submitting your article "AKAP6 orchestrates the nuclear envelope microtubule organizing center by linking Golgi and nucleus via AKAP9" for consideration by eLife. Your article has been reviewed by three peer reviewers, including Jens Lüders as the Reviewing Editor and Reviewer #1, and the evaluation has been overseen by Suzanne Pfeffer as the Senior Editor.

The reviewers have discussed the reviews with one another and the Reviewing Editor has drafted this decision to help you prepare a revised submission.

As the editors have judged that your manuscript is of interest, but as described below that additional experiments are required before it is published, we would like to draw your attention to changes in our revision policy that we have made in response to COVID-19 (https://elifesciences.org/articles/57162). First, because many researchers have temporarily lost access to the labs, we will give authors as much time as they need to submit revised manuscripts. We are also offering, if you choose, to post the manuscript to bioRxiv (if it is not already there) along with this decision letter and a formal designation that the manuscript is "in revision at eLife". Please let us know if you would like to pursue this option. (If your work is more suitable for medRxiv, you will need to post the preprint yourself, as the mechanisms for us to do so are still in development.)

Summary:

This study unveils the mechanisms of non-centrosomal microtubule organization from perinuclear sites in specialized vertebrate cell types, identifying AKAP6 as a key adapter molecule that recruits microtubule nucleation complexes. It is further shown that both nuclear envelope and Golgi-associated protein complexes contribute to perinuclear microtubule organizing activity.

Overall all three reviewers agreed that this is an important contribution and that the data is of high quality and well-presented. There are two major points that we would like you to address.

Essential revisions:

1) The authors performed an AKAP6 rescue experiment and checked whether Pcnt and AKAP9 could still localise to the nuclear envelope. Instead of measuring the fluorescent intensity of Pcnt and AKAP9, as they had done in Figure 1C, they quantified the percentage of cells with a "positive" nuclear signal (Figure 1—figure supplement 2F, H). This may hide a potential incomplete rescue (perhaps the signal is reduced). We ask the authors to redo this analysis as before with fluorescence intensity measurements.

2) In Figure 7, we suggest that you demonstrate that AKAP6/nesprin-1α are sufficient for the re-localization of endogenous centrosome proteins, instead of performing their assays with overexpressed forms of pericentrin. This would make the main argument of the manuscript much stronger.