# Re-assessment of the subcellular localization of Bazooka/Par-3 in Drosophila: no evidence for localization to the nucleus and the neuromuscular junction

## TL;DR

This study finds that Bazooka/Par-3 does not localize to the nucleus or neuromuscular junction in Drosophila, contradicting previous reports.

## Contribution

The study systematically re-evaluates and refutes prior claims about Baz's localization to the nucleus and neuromuscular junction.

## Key findings

- Baz does not localize to the nucleus in Drosophila tissues.
- Baz is not localized to the neuromuscular junction.
- Multiple experimental approaches confirmed the absence of Baz at these sites.

## Abstract

Bazooka/Par-3 (Baz) is an evolutionarily conserved scaffold protein that functions as a master regulator for the establishment and maintenance of cell polarity in many different cell types. In the vast majority of published research papers Baz has been reported to localize at the cell cortex and at intercellular junctions. However, there have also been several reports showing localization and function of Baz at additional subcellular sites, in particular the nuclear envelope and the neuromuscular junction. In this study we have re-assessed the localization of Baz to these subcellular sites in a systematic manner. We used antibodies raised in different host animals against different epitopes of Baz for confocal imaging of Drosophila tissues. We tested the specificity of these antisera by mosaic analysis with null mutant baz alleles and tissue-specific RNAi against baz. In addition, we used a GFP-tagged gene trap line for Baz and a bacterial artificial chromosome (BAC) expressing GFP-tagged Baz under control of its endogenous promoter in a baz mutant background to compare the subcellular localization of the GFP-Baz fusion proteins to the staining with anti-Baz antisera. Together, these experiments did not provide evidence for specific localization of Baz to the nucleus or the neuromuscular junction.

Summary: The authors found that Bazooka/Par-3 does not localize to the nucleus or the neuromuscular junction, questioning earlier findings reporting a function of Baz at these subcellular sites.