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RNA Isolation from Mouse Ocular Lens Epithelium and Fiber Cell Bulk Masses
Published on: October 10, 2025
Inhibition of crystallin expression and induction of apoptosis by lens-specific E1A expression in transgenic mice
Qin Chen1, John D Ash, Phil Branton
1Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Abstract:
Previous studies have shown that the adenovirus E1A oncoprotein can bind to and inactivate the retinoblastoma tumor suppressor protein (pRb) and the transcriptional coactivators CBP/p300. In this study, wild-type E1A12S or two deletion mutants (delN, which binds pRb but not CBP/p300; delCR2, which binds to CBP/p300 but not pRb) were linked to the lens-specific alphaA-crystallin promoter, and used to generate transgenic mice. Lens fiber cells expressing E1A12S or delCR2, both of which bind to CBP/p300, failed to upregulate beta-crystallin and gamma-crystallin expression. In contrast, lens fiber cells expressing delN showed significant expression of beta- and gamma-crystallins. Lens fiber cells expressing delN showed cell cycle entry, marked apoptosis, and evidence for p53 activation, while cells expressing either 12S or delCR2 showed limited apoptosis and no evidence for upregulation of the p53-inducible gene p21. Our results suggest that the transcriptional coactivators CBP and/or p300 are required for the dramatic increases in crystallin expression that accompany terminal differentiation in the lens, and also for activation of p53 in response to inactivation of pRb in the lens.
Insights
Adenovirus E1A oncoprotein
Area of Science:
- Molecular Biology
- Oncology
- Developmental Biology
Background:
- Adenovirus E1A oncoprotein interacts with retinoblastoma tumor suppressor protein (pRb) and transcriptional coactivators CBP/p300.
- The role of these interactions in lens differentiation and tumor suppression is not fully understood.
Purpose of the Study:
- To investigate the function of adenovirus E1A oncoprotein in lens fiber cell differentiation.
- To determine the specific roles of pRb and CBP/p300 in regulating crystallin gene expression and p53 activation during lens development.
Main Methods:
- Generation of transgenic mice expressing wild-type E1A12S or deletion mutants (delN, delCR2) under the control of the alphaA-crystallin promoter.
- Analysis of crystallin expression (beta- and gamma-crystallins), cell cycle entry, apoptosis, and p53/p21 activation in lens fiber cells.
Main Results:
- E1A12S and delCR2 (CBP/p300 binding) inhibited beta- and gamma-crystallin upregulation, with limited apoptosis and no p21 induction.
- delN (pRb binding) promoted beta- and gamma-crystallin expression, cell cycle entry, apoptosis, and p53 activation.
- CBP/p300 binding is essential for crystallin gene upregulation during lens terminal differentiation.
Conclusions:
- Transcriptional coactivators CBP and/or p300 are required for increased crystallin expression during lens terminal differentiation.
- CBP/p300 are also involved in p53 activation in response to pRb inactivation in the lens.
