# Development and Validation of a Genetically Encoded Method to Trace and Manipulate Neuronal Circuits in Zebrafish - DIVERSITY SUPPLEMENT

> **NIH NIH RF1** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2023 · $177,180

## Abstract

PROJECT SUMMARY
Identifying how neurons are connected to each other in the brain is an important and necessary step towards
understanding how brain activity gives rise to behavior, and how it is perturbed by disease. Currently available
methods have limitations that make it challenging to visualize these brain wiring diagrams. In addition, there is
an urgent need for a method that will make it possible not only to unveil brain connectivity, but also to genetically
modify the functional properties of neurons connected in a circuit. We recently developed a genetic system
named TRACT and showed using Drosophila that it possesses both of these features. However, many complex
brain functions cannot be examined in Drosophila, and understanding them will require the use of vertebrate
animals. The zebrafish has emerged as a useful vertebrate animal model to study complex brain processes due
to its relatively simple yet conserved vertebrate brain, optical transparency, amenability to large-scale behavioral
assays, the emergence of complex behaviors after only 5 days of development, and a growing suite of genetic
tools that allow observation and manipulation of neuronal circuits in behaving animals. However, the usefulness
of zebrafish is constrained by a lack of methods to identify and perturb synaptically connected neurons. In
preliminary studies, we developed a TRACT system that can identify anterograde monosynaptic connections
between neurons in the zebrafish brain. In the parent grant, we propose to further develop TRACT as a tool for
transneuronal tracing in zebrafish by developing additional anatomical tracing modalities, and by establishing
the use of TRACT to genetically manipulate synaptically connected neurons. This diversity supplement
application describes an experimental and conceptual career development plan for a graduate student whose
experimental goals are to (1) determine whether TRACT can function in all neurons in the brain, (2) determine
whether transient expression or electroporation can be used to avoid the need to generate transgenic fish and
thus expedite the use of TRACT for diverse neuronal populations, and (3) use flow cytometry and single cell
RNA sequencing to identify synaptically connected neurons in a comprehensive and high-throughput manner.
This experimental plan directly relates to the parent grant by further developing the TRACT system in zebrafish
in experiments that are separate from, yet synergize with, the experiments described in the parent grant.
Together, the parent grant and diversity supplement have the potential to establish a powerful new technology
for mapping brain circuits that will increase the usefulness of zebrafish as a model system to study vertebrate
neuronal circuit function, to reveal general principles of neuronal circuits that underlie specific behaviors, and to
model complex brain disorders such as autism, Alzheimer’s disease and schizophrenia.

## Key facts

- **NIH application ID:** 10731536
- **Project number:** 3RF1MH130420-01S1
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** CARLOS LOIS
- **Activity code:** RF1 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $177,180
- **Award type:** 3
- **Project period:** 2023-02-01 → 2026-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10731536

## Citation

> US National Institutes of Health, RePORTER application 10731536, Development and Validation of a Genetically Encoded Method to Trace and Manipulate Neuronal Circuits in Zebrafish - DIVERSITY SUPPLEMENT (3RF1MH130420-01S1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10731536. Licensed CC0.

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