# Cholinergic signaling modulates intestinal pathophysiology in a Drosophila model of cystic fibrosis

## TL;DR

This study uses fruit flies to model gut issues in cystic fibrosis and finds that boosting cholinergic signaling could help alleviate gastrointestinal symptoms.

## Contribution

The study is the first to show that CFTR loss alters cholinergic signaling and identifies Ace and Fkh as genetic modifiers in CF gut pathogenesis.

## Key findings

- Enterocyte-specific knockdown of Cftr in Drosophila recapitulates CF gut pathologies like reduced motility and nutrient malabsorption.
- Upregulation of acetylcholine esterase (Ace) reduces cholinergic signaling in CF model guts.
- Restoring cholinergic signaling via Ace knockdown rescues CF-associated gut phenotypes.

## Abstract

Cystic fibrosis (CF) is a monogenic genetic disease caused by mutations in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) chloride/bicarbonate channel, which is expressed in certain epithelial cells. Current therapies focus on restoring CFTR function, but many gut-related pathologies persist, highlighting the need for complementary treatments to improve the quality of life of people with CF. In this study, we use Drosophila melanogaster as a model to investigate the gut-specific effects of Cftr loss. We demonstrate that enterocyte specific knockdown of Cftr in flies recapitulates several CF pathologies, including reduced intestinal motility, nutrient malabsorption, and decreased energy stores. Using single-nuclei RNA sequencing (snRNA-seq), we identify significant transcriptional changes in the CF model gut, including the upregulation of acetylcholine esterase (Ace, human AChE), which leads to reduced cholinergic signaling. Cholinergic signaling has been shown to affect CFTR function but this is the first time CFTR loss of function has been shown to alter cholinergic signaling. Functional assays confirm that cholinergic sensitivity is diminished in CF guts. Furthermore, restoring cholinergic signaling via Ace knockdown rescues multiple CF-associated phenotypes. Additionally, we identify the transcription factor Fork head (Fkh), the Drosophila homolog of human FOXA1/FOXA2, which is known to be a positive regulator of Cftr transcription in the intestine, as a positive regulator of Ace expression in CF guts. This study establishes the Drosophila gut as a powerful model to investigate CF pathogenesis, genetic modifiers, and identifies Ace and fkh as genetic modifiers. This work also suggests that enhancing cholinergic signaling may represent a viable therapeutic strategy for gastrointestinal manifestations of CF.

Cystic fibrosis (CF) is a genetic disease that causes complications in multiple organ systems, including the lungs and gastrointestinal tract. While recent therapies have greatly improved life span and respiratory outcomes in people with CF (pwCF), they continue to report significant gastrointestinal symptoms that impact their quality of life. Therefore, there is a need to better understand the progression of CF in the gut and identify gut specific therapeutic targets to improve patient quality of life. In this study we use Drosophila to model gut specific complications of CF and show our model recapitulates many CF clinical presentations. Furthermore, we identify acetylcholine esterase (Ace) as a gene that is increased in our CF model guts and is important for the development of CF pathologies. We additionally perform a screen to identify a transcriptional regulator of Ace, whose genetic manipulation also regulates CF phenotypes. Our findings not only identify a potential target to alleviate GI symptoms in patients with CF, but also validate the Drosophila gut as a robust model for studying CF pathogenesis, genetic modifiers, and screening therapeutics.