# Small molecule regulation of endogenous transcription factors for circuit-specific neuromodulation

> **NIH NIH RF1** · STANFORD UNIVERSITY · 2021 · $1,261,798

## Abstract

PROJECT SUMMARY
Methods for regulating cellular processes within distinct populations of neurons are needed to elucidate
relationships between molecular mechanisms, circuits, and behavior; and to develop cell type- or circuit-
selective treatments for neurological disorders. We propose a novel, non-genetic, small molecule method—
transcription factor-chemically induced proximity (TF-CiP)—that harnesses the cell type- and circuit-specificity
of endogenous transcription factors to regulate gene expression in subsets of neurons. TF-CiP utilizes a
bifunctional small molecule to heterodimerize an “anchor” transcription factor, which naturally binds to a target
gene, with a “hijacked” transcription factor, which enhances or represses transcription of the target gene. Cell
specificity is determined from the intersection of expression of each transcription factor. TF-CiP can
theoretically be adapted for any organism and because transcription factors are well conserved, it is possible
that the same TF-CiP small molecule can be used to modulate neuronal processes across animal species. We
will develop TF-CiP to regulate the expression of the rate-limiting enzyme for brain serotonin synthesis, TPH2,
as a means to tune serotonin levels in subsets of serotonergic neurons. Although the population of central
serotonergic neurons is relatively small, these neurons send projections throughout the brain and serve
important roles in regulating mood, anxiety, sleep, and social behavior. Achieving circuit-specificity for a
serotonin-modulatory small molecule would be an improvement over current therapies, which can have
undesirable side-effects due to indiscriminate targeting of serotonin signaling in the central and peripheral
nervous systems. TPH2 transcription is regulated by stress, sex hormones, and several transcription factors.
We leverage this knowledge along with single-cell RNA-sequencing and projection mapping data in
serotonergic neurons as a resource for candidate TF-CiP transcription factors. In Aim 1, we will screen for
transcription factors that regulate TPH2 transcription cooperatively upon chemically-induced heterodimerization
of their FRB and FKBP tags. This screen will employ a Tph2-Venus reporter and orthophthalaldehyde-
mediated serotonin visualization as readouts in serotonergic cells. In Aim 2, we will work with structural
biologists and chemists to synthesize bifunctional TF-CiP molecules for TPH2 transcriptional regulation. This
will involve virtual binding screens of over 8 million small molecules, binding validation using surface plasmon
resonance and isothermal titration calorimetry, small molecule functionalization, and chemical linkage of two
transcription factor-binding molecules. In Aim 3, TF-CiP molecules will be screened for cytotoxicity, selectivity,
and efficacy at regulating TPH2 transcription and serotonin synthesis in cells. In Aim 4, we will test TF-CiP
molecules for efficacy and selectivity in vivo using murine social behavio...

## Key facts

- **NIH application ID:** 10260250
- **Project number:** 1RF1MH126720-01
- **Recipient organization:** STANFORD UNIVERSITY
- **Principal Investigator:** Gerald R. Crabtree
- **Activity code:** RF1 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $1,261,798
- **Award type:** 1
- **Project period:** 2021-09-15 → 2024-09-14

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10260250

## Citation

> US National Institutes of Health, RePORTER application 10260250, Small molecule regulation of endogenous transcription factors for circuit-specific neuromodulation (1RF1MH126720-01). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10260250. Licensed CC0.

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