Related Experiment Video
Updated: Aug 7, 2026
15:02
Preparation and Culture of Rat Lens Epithelial Explants for Studying Terminal Differentiation
Published on: September 22, 2009
Nuclear degeneration in the developing lens and its regulation by TNFalpha
1Department of Physiology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada.
Experimental Eye Research
|June 17, 1998
Summary
This study shows that tumor necrosis factor-alpha (TNFα) and its receptors play a role in programmed nuclear degeneration during lens cell differentiation. The TUNEL assay effectively labels these degenerating nuclei in lens fiber cells.
Area of Science:
- Ophthalmology
- Cell Biology
- Molecular Biology
Background:
- Programmed cell death, or apoptosis, involves nuclear fragmentation.
- Lens fiber cells undergo nuclear degeneration during differentiation.
- The role of specific signaling factors in lens cell nuclear degeneration is not fully understood.
Purpose of the Study:
- To investigate the role of tumor necrosis factor-alpha (TNFα) and its receptors in the programmed degeneration of lens fiber cell nuclei.
- To evaluate the utility of the terminal deoxynucleotidyl transferase (TdT)-mediated biotin-dUTP nick end labelling (TUNEL) assay for identifying degenerating nuclei in differentiating lens cells.
- To determine if TNFα signaling influences nuclear degeneration in lens epithelial cell cultures.
Main Methods:
- Utilized the TUNEL assay to detect DNA fragmentation in degenerating lens fiber cell nuclei.
- Induced differentiation of lens epithelial cells into lens fiber-like cells (lentoids) using insulin.
- Employed immunofluorescence and confocal microscopy to visualize TNFα, TNFR1, and TNFR2 distribution in chick embryo lenses and cultured lens cells.
- Administered TNFα and agonistic/neutralizing antibodies against TNFα receptors to cultured lens cells to assess effects on nuclear degeneration.
Main Results:
- The TUNEL assay effectively labeled degenerating nuclei in both in vivo lens fiber cells and in vitro lentoid cells.
- TNFα, TNFR1, and TNFR2 immunoreactivity were detected in various parts of the chick embryo lens and in cultured lens cells.
- Exogenous TNFα and agonistic antibodies to TNFR1/TNFR2 significantly increased the number of TUNEL-positive nuclei.
- A neutralizing antibody to TNFα significantly reduced the number of TUNEL-positive nuclei.
Conclusions:
- TUNEL is a reliable method for labeling degenerating lens fiber nuclei during differentiation.
- TNFα-like factors and their receptors are implicated in the nuclear degeneration of lens fiber cells.
- Nuclear degeneration in lens fiber cells may be analogous to apoptosis but uncoupled from plasma membrane events.
Related Concept Videos
01:45Regulation of Nuclear Protein Sorting
Nuclear protein sorting regulates nucleus composition and gene expression, crucial for determining the fate of a eukaryotic cell. Hence, the entry and exit of molecules across the nuclear envelope is a tightly controlled process. Nuclear protein sorting can be inhibited by one of the following ways: 1) masking cargo signal sequences, 2) modifying the nuclear receptor's affinity for cargo, 3) controlling the nuclear pore size, 4) retaining the cargo during its transit to the cytosol or the...
02:26NF-κB-dependent Signaling Pathway
The transcription factor NF-κB was discovered in 1986 in the lab of Nobel laureate Professor David Baltimore, for its interaction with the immunoglobulin light chain enhancer in B-cells. After more than three decades of study, it is now evident that NF-κB regulates the expression of over 100 genes. Most of these genes play an essential role in the innate and adaptive immune responses as well as the inflammatory responses of animals.
NF-κB-dependent Signaling Mechanism
The heterodimer of NF-κB...
NF-κB-dependent Signaling Mechanism
The heterodimer of NF-κB...
01:15Receptor Downregulation in MVBs
Multivesicular bodies (MVBs) are mature endosomes that sort ubiquitinated proteins and then fuse with lysosomes to degrade the sorted proteins. Epidermal growth factor (EGF) and its receptor (EGFR) form a complex that can be internalized through endocytosis, sorted into an MVB, and later degraded.
The EGFR can initiate signaling pathways that lead to cell proliferation, migration, and differentiation. Overexpression of EGFR stimulates cells to proliferate. Excessive EGFR activation may...
The EGFR can initiate signaling pathways that lead to cell proliferation, migration, and differentiation. Overexpression of EGFR stimulates cells to proliferate. Excessive EGFR activation may...
01:24Regulation of Angiogenesis and Blood Supply
Rapidly dividing tumors, embryos, and wounded tissues require more oxygen than usual, lowering the oxygen concentration in the blood. At low oxygen or hypoxic conditions, an oxygen-sensitive transcription factor called the hypoxia-inducible factor 1 or HIF1 is activated. HIF1 is a dimeric protein of alpha (ɑ) and beta (β) subunits. Under optimal oxygen conditions, HIF1β is present in the nucleus while HIF1ɑ remains in the cytosol. HIF1ɑ is hydroxylated by prolyl hydroxylase and factor...
01:16TGF - β Signaling Pathway
The TGF-β signaling pathway regulates cell growth, differentiation, adhesion, motility, and development. TGF-β ligands that induce TGF-β signaling are synthesized in their latent form. Several proteases or cell surface receptors such as integrins act upon the latent form, releasing the active ligand. There are three types of mammalian TGF-βs: (TGF-β1, TGF-β2, and TGF-β3) that bind as homodimers or heterodimers to TGF-β receptors. The TGF-β receptors are of three kinds RI, RII, and RIII. The RI...