The Ocular Lens Epithelium

An adult lens contains two easily discernible, morphologically distinct compartments, the epithelium and the fiber-cell mass. The fiber-cell mass provides the lens with its functional phenotype, transparency. Metabolically, in comparison to the fiber cells the epithelium is the more active compartment of the ocular lens. For the purposes of this review we will only discuss the surface epithelium that covers the anterior face of the adult ocular lens. This single layer of cells, in addition to acting as a metabolic engine that sustains the physiological health of this tissue, also works as a source of stem cells, providing precursor cells, which through molecular and morphological differentiation give rise to fiber cells. Morphological simplicity, defined developmental history and easy access to the experimenter make this epithelium a choice starting material for investigations that seek to address universal questions of cell growth, development, epithelial function, cancer and aging. There are two important aspects of the lens epithelium that make it highly relevant to the modern biologist. Firstly, there are no known clinically recognizable cancers of the ocular lens. Considering that most of the known malignancies are epithelial in origin this observation is more than an academic curiosity. The lack of vasculature in the lens may explain the absence of tumors in this tissue, but this provides only a teleological basis to a very important question for which the answers must reside in the molecular make-up and physiology of the lens epithelial cells. Secondly, lens epithelium as a morphological entity in the human lens is first recognizable in the 5th–6th week of gestation. It stays in this morphological state as the anterior epithelium of the lens for the rest of the life, making it an attractive paradigm for the study of the effects of aging on epithelial function. What follows is a brief overview of the present status and lacunae in our understanding of the biology of the lens epithelium.

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Intercellular communication between epithelial and fiber cells of the eye lens

Journal of Cell Science ◽

10.1242/jcs.107.4.799 ◽

1994 ◽

Vol 107 (4) ◽

pp. 799-811 ◽

Cited By ~ 2

Author(s):

S. Bassnett ◽

J.R. Kuszak ◽

L. Reinisch ◽

H.G. Brown ◽

D.C. Beebe

Keyword(s):

Gap Junctions ◽

Gap Junction ◽

Freeze Fracture ◽

Cell Types ◽

Lens Epithelium ◽

Fiber Cell ◽

Fracture Plane ◽

Metabolic Cooperation ◽

Fiber Cells ◽

Resistance Pathway

Results of electrical, dye-coupling and morphological studies have previously suggested that gap junctions mediate communication between the anterior epithelium of the lens and the underlying lens fiber cells. This connection is believed to permit ‘metabolic cooperation’ between these dissimilar cell types and may be of particular importance to the fiber cells, which are thought incapable of autonomous ionic homeostasis. We reinvestigated the nature of the connection between epithelial and fiber cells of the embryonic chicken lens using fluorescence confocal microscopy and freeze-fracture analysis. In contrast to earlier studies, our data provided no support for gap-junction-mediated transport from the lens epithelium to the fibers. Fluorescent dyes loaded biochemically into the lens epithelium were retained there for more than one hour. There was a decrease in epithelial fluorescence over this period, but this was not accompanied by an increase in fiber cell fluorescence. Diffusional modeling suggested that these data were inconsistent with the presence of extensive epithelium-fiber cell coupling, even if the observed decrease in epithelial fluorescence was attributed exclusively to the diffusion of dye into the fiber mass via gap junctions. Furthermore, the rate of loss of fluorescence from isolated epithelia was indistinguishable from that measured in whole lenses, suggesting that decreased epithelial fluorescence resulted from photobleaching and leakage of dye rather than diffusion, via gap junctions, into the fibers. Analysis of freeze-fracture replicas of plasma membranes at the epithelial-fiber cell interface failed to reveal evidence of gap-junction plaques, although evidence of endocytosis was abundant. These studies were done under conditions where the location of the fracture plane was unambiguous and where gap junctions could be observed in the lateral membranes of neighboring epithelial and fiber cells. Paradoxically, tracer molecules injected into the fiber mass were able to pass into the epithelium via a pathway that was not blocked by incubation at 4 degrees C or by treatment with octanol and which excluded large (approximately 10 kDa) molecular mass tracers. Together with previous measurements of electrical coupling between fiber cells and epithelial cells, these data indicate the presence of a low-resistance pathway connecting these cell types that is not mediated by classical gap junctions.

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Data Independent Acquisition Mass Spectrometry of the Human Lens Enhances Spatiotemporal Measurement of Fiber Cell Aging

10.1101/2021.05.13.444062 ◽

2021 ◽

Author(s):

Lee S Cantrell ◽

Kevin L Schey

Keyword(s):

Dynamic Range ◽

High Dynamic Range ◽

Fiber Cell ◽

Human Lens ◽

Cell Aging ◽

Fiber Cells ◽

Data Independent Acquisition ◽

Age Related ◽

Cell Age ◽

Independent Analysis

The ocular lens proteome undergoes post-translational and progressive degradation as fiber cells age. The oldest fiber cells and the proteins therein are present at birth and are retained through death. Transparency of the lens is maintained in part by the high abundance crystallin family proteins (up to 300 mg/mL), which establishes a high dynamic range of protein abundance. As a result, previous Data Dependent Analysis (DDA) measurements of the lens proteome are less equipped to identify the lowest abundance proteins. In an attempt to probe more deeply into the lens proteome, we measured the insoluble lens proteome of an 18-year-old human with DDA and newer Data Independent Analysis (DIA) methods. By applying library free DIA search methods, 4,564 protein groups, 48,474 peptides and 5,577 deamidation sites were detected: significantly outperforming the quantity of identifications in using DDA and Pan-Human DIA library searches. Finally, by segmenting the lens into multiple fiber cell-age related regions, we uncovered cell-age resolved changes in proteome composition and putative function.

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Initial Healing Response of the Ocular Lens Following Eye Injury

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100050159 ◽

1974 ◽

Vol 32 ◽

pp. 28-30

Author(s):

N.J. Unakar ◽

C. Bullock ◽

J.R. Reddan ◽

A. Weinsieder

Keyword(s):

Cell Cycle ◽

Lens Epithelium ◽

Eye Injury ◽

Lens Fiber ◽

Anterior Pole ◽

Ocular Lens ◽

Fiber Cells ◽

Outer Capsule ◽

External Stimuli ◽

Lens Surface

Lens epithelium is diposed on the anterior lens surface as a monolayer sandwiched between an outer capsule and the inner lens fiber cells. The epithelical cells of the anterior pole, held in an extended G1 phase of the cell cycle, rarely divide. However, these cells can be coerced to re-enter the cell cycle by a variety of external stimuli: injury, explanation, and chemical injury.

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Genome-wide identification and expression analysis of the GhIQD gene family in upland cotton (Gossypium hirsutum L.)

Journal of Cotton Research ◽

10.1186/s42397-021-00079-3 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Lingling DOU ◽

Limin LV ◽

Yangyang KANG ◽

Ruijie TIAN ◽

Deqing HUANG ◽

...

Keyword(s):

Gossypium Hirsutum ◽

Gene Family ◽

Segmental Duplication ◽

Gene Expression Pattern ◽

Cell Development ◽

Fiber Cell ◽

Fiber Cells ◽

Genome Wide ◽

Duplication Events ◽

Signaling Receptors

Abstract Background Calmodulin (CaM) is one of the most important Ca2+ signaling receptors because it regulates diverse physiological and biochemical reactions in plants. CaM functions by interacting with CaM-binding proteins (CaMBPs) to modulate Ca2+ signaling. IQ domain (IQD) proteins are plant-specific CaMBPs that bind to CaM by their specific CaM binding sites. Results In this study, we identified 102 GhIQD genes in the Gossypium hirsutum L. genome. The GhIQD gene family was classified into four clusters (I, II, III, and IV), and we then mapped the GhIQD genes to the G. hirsutum L. chromosomes. Moreover, we found that 100 of the 102 GhIQD genes resulted from segmental duplication events, indicating that segmental duplication is the main force driving GhIQD gene expansion. Gene expression pattern analysis showed that a total of 89 GhIQD genes expressed in the elongation stage and second cell wall biosynthesis stage of the fiber cells, suggesting that GhIQD genes may contribute to fiber cell development in cotton. In addition, we found that 20 selected GhIQD genes were highly expressed in various tissues. Exogenous application of MeJA significantly enhanced the expression levels of GhIQD genes. Conclusions Our study shows that GhIQD genes are involved in fiber cell development in cotton and are also widely induced by MeJA. Thw results provide bases to systematically characterize the evolution and biological functions of GhIQD genes, as well as clues to breed better cotton varieties in the future.

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