# Expression Pattern of the AB1-Gal4 Driver in Drosophila Third-Instar Larvae

## TL;DR

This study examines the expression pattern of the AB1-Gal4 driver in fruit fly larvae, revealing unexpected activity in neurons and eye cells.

## Contribution

The paper provides a detailed characterization of the AB1-Gal4 driver's expression beyond its intended salivary gland target.

## Key findings

- AB1-Gal4 shows activity in Elav-positive neurons of the central nervous system, including motor neurons.
- The driver is also expressed in specific photoreceptor cells within eye discs of third-instar larvae.

## Abstract

Drosophila has provided a highly attractive model system for studying various tissue- and stage-specific processes as well as their pathologies, including a range of human diseases. The existence of a large number of diverse Gal4 drivers to precisely control the expression patterns of UAS transgenes simplifies such studies. However, the choice of driver is always critical, as its possible ectopic expression in non-target cells and tissues can directly impact the results. Therefore, it is very important to thoroughly characterize both the molecular nature and expression pattern of each Gal4 driver line. Here, we aim to fill such gaps regarding the AB1-Gal4 driver, which is typically used to express UAS transgenes in larval salivary glands. In this fly line, the P{GawB} enhancer trap construct encoding the Gal4 protein resides within overlapping evolutionary conserved spastin (spas) and Mitochondrial Rho (Miro) genes. Both these genes are expressed in a number of tissues, including the central nervous system (CNS), and their human orthologs are associated with neurodegenerative diseases. Consistently, we demonstrate that, in third-instar larvae, the expression pattern of AB1-Gal4 is also not restricted to salivary glands. We detect its activity in a subset of Elav-positive neurons in the CNS, including motor neurons, as well as in specific photoreceptor cells in eye discs.