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Regulation of eye development by transcription control of CCCTC binding factor (CTCF)
1Division of Molecular Medicine, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California-Los Angeles, Torrance, California 90502-2006, USA.
Abstract:
CCCTC binding factor (CTCF), a transcriptional regulator, plays important roles in epigenetics and development. In the present study, we report that overexpression of CTCF in transgenic mice during embryonic development suppresses Pax6 gene expression. This effect causes defects in ocular development that result in microophthalmia. In eye-derived cells transfected with a tetracycline turn-on CTCF system, up-regulation of CTCF expression significantly suppressed Pax6 expression. In contrast, the knockdown of CTCF mRNA resulted in the down-regulation of CTCF protein expression, which in turn enhanced the Pax6 expression. CTCF controls Pax6 transcription by interacting with a repressor element located in the 5'-flanking region upstream of the Pax6 P0 promoter. This interaction suppressed Pax6 gene transcription by blocking the effect of an ectoderm enhancer located 3.5 kb upstream from the P0 promoter. We also found an 80-bp sequence in a region -1.2 kbp upstream from the P0 promoter that contained multiple CTCF binding sites and interacted with nuclear proteins obtained from eye-derived cells forming electrophoretic mobility shift assay complexes with CTCF. We conclude that a novel function of CTCF is to regulate Pax6 transcription by binding to the repressor element, which in turn blocks the effect of the ectoderm enhancer resulting in the inhibition of P0 promoter activity.
Insights
CCCTC binding factor (CTCF) regulates Pax6 gene expression, impacting ocular development. Overexpression of CTCF suppresses Pax6, causing microphthalmia, while CTCF knockdown enhances Pax6 expression.
Area of Science:
- Epigenetics
- Developmental Biology
- Gene Regulation
Background:
- CCCTC binding factor (CTCF) is a crucial transcriptional regulator involved in epigenetics and embryonic development.
- Pax6 gene expression is vital for normal ocular development.
Purpose of the Study:
- To investigate the role of CTCF in regulating Pax6 gene expression during embryonic development.
- To elucidate the mechanism by which CTCF influences ocular development through Pax6.
Main Methods:
- Utilized transgenic mice with CTCF overexpression during embryonic development.
- Employed a tetracycline-inducible CTCF system in eye-derived cells for controlled expression studies.
- Performed mRNA knockdown of CTCF and analyzed protein expression levels.
- Investigated CTCF interaction with regulatory elements of the Pax6 gene promoter using electrophoretic mobility shift assays.
Main Results:
- Overexpression of CTCF in transgenic mice suppressed Pax6 gene expression, leading to microphthalmia.
- In eye-derived cells, CTCF up-regulation suppressed Pax6 expression, while CTCF knockdown enhanced it.
- CTCF binds to a repressor element in the 5'-flanking region of the Pax6 P0 promoter.
- This binding inhibits Pax6 transcription by blocking an ectoderm enhancer's activity.
Conclusions:
- CTCF functions as a novel regulator of Pax6 transcription.
- CTCF-mediated repression of Pax6 contributes to the regulation of ocular development.
- CTCF binding to a specific repressor element is key to inhibiting Pax6 P0 promoter activity.
