# Coordination of Growth and Form in the Embryonic Salivary Gland and Trachea

> **NIH NIH R56** · JOHNS HOPKINS UNIVERSITY · 2021 · $549,088

## Abstract

Organs must be the right size and shape to fulfill their roles in the animal. Although size is
intimately linked to organ function, we know almost nothing about how size control is coupled to
organ differentiation during embryonic development. In the proposed work, we focus on how
developmental growth and differentiation are coordinated in the Drosophila embryo, an ideal
system for revealing the underlying molecular and cellular mechanisms. We have discovered
that the nuclear protein Ribbon (Rib) is required for growth and morphogenesis of two distinct
organs in the Drosophila embryo and that Rib promotes growth by two different mechanisms in
the two tissues. In rib mutants, both salivary gland and tracheal cells are only ~50% the size of
WT, and both organs have additional morphological defects. In the salivary gland, Rib binds
genes encoding most of the >80 ribosomal protein genes, suggesting that Rib promotes growth
in this tissue by increasing the translational capacity of its large secretory cells. In the trachea,
Rib binds components of the Tor growth control pathway and other growth genes. We propose
the model that Rib couples Tor signaling to FGF signaling to coordinate growth and directional
migration in response to both developmental and physiological cues. In this proposal, we test
these ideas and we ask how Rib independently regulates morphogenetic factors, specifically
those that function at the apical cell surface to control tube elongation. We begin by testing the
idea that Rib upregulates ribosomal protein gene expression in the salivary gland to increase
translation in these professional secretory cells and we test the model that the small cell size
observed in the salivary glands of rib mutants is a ribosome deficiency problem. We then test
the model that Rib coordinates growth in the trachea by linking the FGF and Tor signaling
pathways to build a system that links growth to migratory cues. We also explore the role of other
candidate growth regulators. We determine if a candidate Rib target that is bound by Rib in both
the SG and trachea also regulates growth and we determine if Rib affects levels of protein
translation. Finally, we ask how Rib coordinates growth and morphogenesis by identifying the
co-activators relevant to each process and by characterizing the functions of a subset of target
genes linked to cell shape change.

## Key facts

- **NIH application ID:** 10453482
- **Project number:** 1R56DE029450-01A1
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** Deborah J Andrew
- **Activity code:** R56 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $549,088
- **Award type:** 1
- **Project period:** 2021-08-05 → 2022-11-04

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10453482

## Citation

> US National Institutes of Health, RePORTER application 10453482, Coordination of Growth and Form in the Embryonic Salivary Gland and Trachea (1R56DE029450-01A1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10453482. Licensed CC0.

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