Insulin initiation of lens fiber differentiation in culture: Elongation of embryonic lens epithelial cells

The Shumiya cataract rat (SCR) is a model for hereditary cataract. Two-thirds of these rats develop lens opacity within 10-11 weeks. Onset of cataract is attributed to the synergetic effect of lanosterol synthase (Lss) and farnesyl-diphosphate farnesyltransferase 1 (Fdft1) mutant alleles that lead to cholesterol deficiency in the lenses, which in turn adversely affects lens biology including the growth and differentiation of lens epithelial cells (LECs). Nevertheless, the molecular events and changes in gene expression associated with the onset of lens opacity in SCR are poorly understood. In the present study, a microarray-based approach was employed to analyze comparative gene expression changes in LECs isolated from the precataractous and cataractous stages of lenses of 5-week-old SCRs. The changes in gene expression observed in microarray results in the LECs were further validated using real-time reverse transcribed quantitative PCR (RT-qPCR) in 5-, 8-, and 10-week-old SCRs. A mild posterior and cortical opacity was observed in 5-week-old rats. Expressions of approximately 100 genes, including the major intrinsic protein of the lens fiber (Mip and Aquaporin 0), deoxyribonuclease II beta (Dnase2B), heat shock protein B1 (HspB1), and crystallin γ (γCry) B, C, and F, were found to be significantly downregulated (0.07-0.5-fold) in rat LECs derived from cataract lenses compared to that in noncataractous lenses (control). Thus, our study was aimed at identifying the gene expression patterns during cataract formation in SCRs, which may be responsible for cataractogenesis in SCR. We proposed that cataracts in SCR are associated with reduced expression of these lens genes that have been reported to be related with lens fiber differentiation. Our findings may have wider implications in understanding the effect of cholesterol deficiency and the role of cholesterol-lowering therapeutics on cataractogenesis.

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A Role for Caspases in Lens Fiber Differentiation

The Journal of Cell Biology ◽

10.1083/jcb.140.1.153 ◽

1998 ◽

Vol 140 (1) ◽

pp. 153-158 ◽

Cited By ~ 189

Author(s):

Yasuki Ishizaki ◽

Michael D. Jacobson ◽

Martin C. Raff

Keyword(s):

Epithelial Cells ◽

Cysteine Proteases ◽

Lens Epithelial Cells ◽

Lens Fiber ◽

Caspase Family ◽

Vitro Model ◽

Normal Differentiation ◽

Enzymatic Machinery

There is increasing evidence that programmed cell death (PCD) depends on a novel family of intracellular cysteine proteases, called caspases, that includes the Ced-3 protease in the nematode Caenorhabditis elegans and the interleukin-1β–converting enzyme (ICE)-like proteases in mammals. Some developing cells, including lens epithelial cells, erythroblasts, and keratinocytes, lose their nucleus and other organelles when they terminally differentiate, but it is not known whether the enzymatic machinery of PCD is involved in any of these normal differentiation events. We show here that at least one CPP32 (caspase-3)-like member of the caspase family becomes activated when rodent lens epithelial cells terminally differentiate into anucleate lens fibers in vivo, and that a peptide inhibitor of these proteases blocks the denucleation process in an in vitro model of lens fiber differentiation. These findings suggest that at least part of the machinery of PCD is involved in lens fiber differentiation.

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The Notch Signaling Pathway Controls the Size of the Ocular Lens by Directly Suppressing p57Kip2 Expression

Molecular and Cellular Biology ◽

10.1128/mcb.00780-07 ◽

2007 ◽

Vol 27 (20) ◽

pp. 7236-7247 ◽

Cited By ~ 58

Author(s):

Junling Jia ◽

Min Lin ◽

Lingna Zhang ◽

J. Philippe York ◽

Pumin Zhang

Keyword(s):

Epithelial Cells ◽

Notch Signaling ◽

Signaling Pathway ◽

Cell Cycle Control ◽

Notch Signaling Pathway ◽

Lens Epithelial Cells ◽

Lens Fiber ◽

Ocular Lens ◽

Fiber Cells ◽

Proliferation And Differentiation

ABSTRACT The size of an organ must be tightly controlled so that it fits within an organism. The mammalian lens is a relatively simple organ composed of terminally differentiated, amitotic lens fiber cells capped on the anterior surface by a layer of immature, mitotic epithelial cells. The proliferation of lens epithelial cells fuels the growth of the lens, thus controling the size of the lens. We report that the Notch signaling pathway defines the boundary between proliferation and differentiation in the developing lens. The loss of Notch signaling results in the loss of epithelial cells to differentiation and a much smaller lens. We found that the Notch effector Herp2 is expressed in lens epithelium and directly suppresses p57 Kip2 expression, providing a molecular link between Notch signaling and the cell cycle control machinery during lens development.

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Changes in phosphatidylinositol metabolism during differentiation of lens epithelial cells into lens fiber cells in the embryonic chick.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)86028-3 ◽

1980 ◽

Vol 255 (4) ◽

pp. 1296-1300 ◽

Cited By ~ 1

Author(s):

P.S. Zelenka

Keyword(s):

Epithelial Cells ◽

Lens Epithelial Cells ◽

Embryonic Chick ◽

Lens Fiber ◽

Fiber Cells ◽

Phosphatidylinositol Metabolism

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Developmental analysis of the eye lens obsolescence (Elo) gene in the mouse: cell proliferation and Elo gene expression in the aggregation chimera

Development ◽

10.1242/dev.113.4.1293 ◽

1991 ◽

Vol 113 (4) ◽

pp. 1293-1304 ◽

Cited By ~ 1

Author(s):

A. Yoshiki ◽

M. Hanazono ◽

S. Oda ◽

N. Wakasugi ◽

T. Sakakura ◽

...

Keyword(s):

Cell Proliferation ◽

Epithelial Cells ◽

Cell Number ◽

S Phase ◽

Lens Epithelium ◽

Posterior Region ◽

Lens Epithelial Cells ◽

Eye Lens ◽

Lens Fiber ◽

Fiber Cells

This study investigates the primary effect of the eye lens obsolescence (Elo) gene of the mouse. Morphological features of the Elo lens were defined as follows: (1) deficient elongation of lens fiber cells, (2) morphological abnormality of nuclei of lens fiber cells, (3) lack of eosinophilic granules in the central fiber cells and (4) rupture of lens capsule in the posterior region. We have immunohistologically examined, by means of an in vivo BrdU incorporation system, whether or not the Elo gene regulates cell proliferation during lens development. The lens fiber cells were morphologically abnormal in day 13 embryonic Elo lens. However, there were no significant differences in morphology or cell proliferation between normal and Elo lens epithelium until day 14 of gestation. After day 15, the total cell number in the Elo lens epithelium was significantly less than that in the normal, but the total numbers of S-phase cells in the two genotypes were not significantly different. The ratio of the total S-phase cell number to the total number of lens epithelial cells may be affected by the developmental stage, but not directly by the genotype. The genotype, however, may be having a direct influence at later ages because malformation of Elo lens fiber cells must cause reduction of the total number of lens epithelial cells in older embryos. Although, at 30 days old, Elo lens cells were externally extruded through the ruptured capsule into the vitreous cavity, BrdU-labelled lens epithelial cells were detectable. To investigate whether the Elo lens phenotype is determined by its own genotype or by its cellular environment, we produced aggregation chimeras between C3H-Elo/+(C/C) and BALB/c(c/c). Most lenses of BALB/c dominant chimeras were oval in shape without the ruptured lens capsule. However, they were opaque in the center and slightly smaller in size than normal. The lenses of C3H-Elo/+ dominant chimeras were morphologically similar to the Elo lens. Although normal nuclei were regularly arranged in the anterior region, Elo-type nuclei were located in the posterior region. Immunohistological staining by using anti-C3H strain-specific antibody demonstrated that the lens fiber cells with abnormal nuclei were derived only from C3H-Elo/+, not from BALB/c. These observations suggest that the primary effect of the Elo gene in the developing lens may be specific to the fiber cell differentiation rather than to the cell proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

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The major polypeptide (MIP) of lens fiber junctions and its synthesis in cultured differentiating lens epithelial cells

Biophysics of Structure and Mechanism ◽

10.1007/bf00539107 ◽

1982 ◽

Vol 9 (2) ◽

pp. 95-101 ◽

Cited By ~ 3

Author(s):

H. Rink

Keyword(s):

Epithelial Cells ◽

Lens Epithelial Cells ◽

Lens Fiber

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Dual Roles for Pax-6: a Transcriptional Repressor of Lens Fiber Cell-Specific β-Crystallin Genes

Molecular and Cellular Biology ◽

10.1128/mcb.18.9.5579 ◽

1998 ◽

Vol 18 (9) ◽

pp. 5579-5586 ◽

Cited By ~ 72

Author(s):

Melinda K. Duncan ◽

John I. Haynes ◽

Ales Cvekl ◽

Joram Piatigorsky

Keyword(s):

Epithelial Cells ◽

Promoter Activity ◽

Direct Interaction ◽

Promoter Sequence ◽

Full Length ◽

Lens Epithelial Cells ◽

Lens Fiber ◽

High Concentration ◽

Mobility Shift ◽

Lens Fiber Cell

ABSTRACT It has been demonstrated previously that Pax-6, a paired domain (PD)/homeodomain (HD) transcription factor critical for eye development, contributes to the activation of the αB-, αA-, δ1-, and ζ-crystallin genes in the lens. Here we have examined the possibility that the inverse relationship between the expression of Pax-6 and β-crystallin genes within the developing chicken lens reflects a negative regulatory role of Pax-6. Cotransfection of a plasmid containing the βB1-crystallin promoter fused to the chloramphenicol acetyltransferase reporter gene and a plasmid containing the full-length mouse Pax-6 coding sequences into primary embryonic chicken lens epithelial cells or fibroblasts repressed the activity of this promoter by as much as 90%. Pax-6 constructs lacking the C-terminal activation domain repressed βB1-crystallin promoter activity as effectively as the full-length protein, but the PD alone or Pax-6 (5a), a splice variant with an altered PD affecting its DNA binding specificity, did not. DNase footprinting analysis revealed that truncated Pax-6 (PD+HD) binds to three regions (−183 to −152, −120 to −48, and −30 to +1) of the βB1-crystallin promoter. Earlier experiments showed that the βB1-crystallin promoter sequence from −120 to −48 contains a cis element (PL2 at −90 to −76) that stimulates the activity of a heterologous promoter in lens cells but not in fibroblasts. In the present study, we show by electrophoretic mobility shift assay and cotransfection that Pax-6 binds to PL2 and represses its ability to activate promoter activity; moreover, mutation of PL2 eliminated binding by Pax-6. Taken together, our data indicate that Pax-6 (via its PD and HD) represses the βB1-crystallin promoter by direct interaction with the PL2 element. We thus suggest that the relatively high concentration of Pax-6 contributes to the absence of βB1-crystallin gene expression in lens epithelial cells and that diminishing amounts of Pax-6 in lens fiber cells during development allow activation of this gene.

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