# The stage-specific regulation of ameloblastin and enamelin by the distinct nuclear factors

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2024 · $502,968

## Abstract

Project Summary/Abstract
Cell identity is largely determined by specific epigenetic landscapes and transcriptional networks. Ameloblast is
the only epithelial cell that can generate calcified tissue during development, where preameloblasts (PABs) first
differentiate to the secretory ameloblasts (SABs) that synthesize and deposit enamel matrix proteins (EMPs) to
scaffold organic matrix, and then to the maturation ameloblasts (MABs) that hydrolyze, endocytose EMPs, and
transport ions to mineralize enamel. To bioengineer enamel, a nonregenerative tissue, we must understand the
transcriptional regulation of ameloblasts that has been limited due to a loss of ameloblasts after the tooth
eruption and a lack of cell line fully recapitulating the characteristics of ameloblasts. Previous fundings allow us
to establish a novel and comprehensive list of genes significant to each developmental stage of ameloblasts
across species and to explore the functions of chromatin organizer SATB1, and enamel matrix modeling
regulators -peptidase KLK4 and the major calcium transporter NCKX4- in the context of ameloblast
differentiation. These efforts resulted in a discovery that SATB1, KLK4, and NCKX4 all contribute to the
transcriptional regulation of ameloblastin (Ambn) and enamelin (Enam), encoding the major EMPs co-
upregulated in SABs and then co-downregulated in MABs. We found that ablation of SATB1, highly expressed
in PABs, repressed Ambn & Enam transcription and H3K27ac level. Our organ culture showed that elevated
histone acetylation upregulated Ambn & Enam. An enhancer and base unpairing region (BUR, selective
SATB1 DNA binding site) have been predicted in the vicinity of Ambn & Enam. These data suggest that
SATB1 organizes chromatin conformation and poises a transcriptional complex to upregulate Ambn & Enam to
advance PABs to SABs. In the case of mice lacking Klk4 and Nckx4—the causative genes for amelogenesis
imperfecta—we found a retention of proline/glutamine (P/G)-rich EMPs resulting from defective hydrolysis.
These Nckx4-/- and Klk4-/- MABs had upregulated Ambn & Enam and downregulated Hif1a. In vitro studies
showed that P/G-rich peptides downregulated Ambn & Enam and upregulated Hif1a. Our RNA-seq analyses
revealed that HIF1A, a transcription factor regulating cell responses to oxidative stress, had a 6-fold
upregulation in MABs vs SABs, reflecting MAB’s robust anti-oxidative capacity to continuously provide energy
for ion transport and protein degradation. These data suggest that retake of P/G-rich peptides upregulate
Hif1a, which in turn downregulate Ambn & Enam. Our in vivo and in vitro studies allow us to hypothesize that
the dynamic expression of Ambn & Enam in the two major functional stages of ameloblasts is coordinately
regulated by distinct factors chromatin organizer SATB1 and transcription factor HIF1A. This hypothesis will be
addressed by specific aim 1: To determine the roles of SATB1 as a pioneer factor in PABs to poise the
enhancer establ...

## Key facts

- **NIH application ID:** 10922871
- **Project number:** 5R01DE027076-07
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Yan Zhang
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $502,968
- **Award type:** 5
- **Project period:** 2023-09-06 → 2027-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10922871

## Citation

> US National Institutes of Health, RePORTER application 10922871, The stage-specific regulation of ameloblastin and enamelin by the distinct nuclear factors (5R01DE027076-07). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10922871. Licensed CC0.

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