# Impact of Floating-Harbor syndrome mutations on chromatin remodeling by the SRCAP complex

> **NIH NIH R03** · UNIV OF MASSACHUSETTS MED SCH WORCESTER · 2020 · $83,750

## Abstract

The long-term goal of our research is to investigate the molecular mechanisms by which epigenetic
alterations of chromatin structure promote human developmental disorders and diseases such as Floating-
Harbor syndrome (FHS). It was recently found that mutations of the SRCAP (SNF2-related CBP activator
protein) gene cause FHS, which is a rare dominant disorder characterized by proportionate short stature with
dysmorphic facial features, delayed osseous maturation, and delayed speech development. However, the
molecular bases underlying the disease remain to be elucidated. SRCAP is a member of the SNF2 family of
ATP-dependent chromatin remodeling enzymes, and forms a 12-subunit, large protein complex. All of SRCAP
mutations in FHS patients are heterozygous truncating alleles, tightly clustered within the final 33th and 34th
exons, suggesting that the C-terminal domain of SRCAP is crucial for the SRCAP function. Importantly, it was
reported that individuals carrying a deletion of a chromosomal region containing the SRCAP gene have no
reported phenotype, suggesting that SRCAP deletion is haplosufficient. The SRCAP complex is required for
the incorporation of histone variant H2A.Z into nucleosomes. H2A.Z is deposited within promoter-proximal
nucleosomes, and plays essential roles in transcription, genome stability, and proper stem cell differentiation.
The overall objective of this proposed research is to characterize the SRCAP complex, and determine how
SRCAP mutations alter epigenetic chromatin structure and function, thus resulting in FHS. Our overall
strategy in this proposal is to exploit a powerful combination of biochemical, biophysical, and genomics
techniques to dissect the molecular mechanisms by which the SRCAP complex regulates H2A.Z deposition
and the truncated SRCAP causes FHS. In Aim 1, we will dissect the mechanism of H2A.Z deposition by the
SRCAP complex. The molecular mechanism by which the SRCAP complex catalyzes H2A.Z deposition is
largely unknown, mainly due to the limited protein availability, as SRCAP forms a large multi-protein complex.
To address this, we have successfully reconstituted the whole SRCAP complex from individual, recombinant
subunits using the Multibac baculovirus expression system. We will define the detailed biochemical properties,
especially histone exchange activity, of the SRCAP complex. We will employ various chromatin remodeling
assays including FRET-based assays. Furthermore, we will investigate the function of SRCAP in mouse
embryonic stem cells (ESCs), since H2A.Z is necessary for ESC differentiation. We will perform genomics
analyses to dissect how SRCAP regulates the epigenetic landscape of H2A.Z during ESC differentiation. In
Aim 2, we will define the effects of Floating-Harbor syndrome mutations on the SRCAP complex. Although all
SRCAP mutations in FHS patients are heterozygous truncating alleles, it remains unclear how the truncated
SRCAP produces a dominant negative effect. To define the effects of...

## Key facts

- **NIH application ID:** 9975861
- **Project number:** 5R03HD095088-02
- **Recipient organization:** UNIV OF MASSACHUSETTS MED SCH WORCESTER
- **Principal Investigator:** Shinya Watanabe
- **Activity code:** R03 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $83,750
- **Award type:** 5
- **Project period:** 2019-07-11 → 2021-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9975861

## Citation

> US National Institutes of Health, RePORTER application 9975861, Impact of Floating-Harbor syndrome mutations on chromatin remodeling by the SRCAP complex (5R03HD095088-02). Retrieved via AI Analytics 2026-05-29 from https://api.ai-analytics.org/grant/nih/9975861. Licensed CC0.

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