Expression of the gene for main intrinsic polypeptide (MIP): separate spatial distributions of MIP and beta-crystallin gene transcripts in rat lens development.

Yancey, S B; Koh, Kyung Mi; Chung, Jeeyun; Revel, Jean‐Paul

doi:10.1083/jcb.106.3.705

Cited by 50 publications

(20 citation statements)

References 46 publications

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“…There is a report on the expression of AQP0 transcript at E11.5; the investigators used mouse embryonic head total RNA and performed RT-PCR (Zhou et al, 2002). Another report states that AQP0 protein expression begins at E12.5, in rat embryonic lens (Yancey et al, 1988). Based upon these two studies, Zhou et al (2002) speculated that AQP0 transcripts might have been produced a day before the protein was actually synthesized.…”

Section: Discussionmentioning

confidence: 99%

Functional expression of aquaporins in embryonic, postnatal, and adult mouse lenses

Varadaraj

Kumari

Mathias

2007

Developmental Dynamics

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Aquaporin 0 (AQP0) and AQP1 are expressed in the lens, each in a different cell type, and their functional roles are not thoroughly understood. Our previous study showed that these two AQPs function as water transporters. In order to further understand the functional significance of these two different aquaporins in the lens, we investigated their initiation and continued expression. AQP0 transcript and protein were first detected at embryonic stage (E) 11.25 in the differentiating primary fiber cells of the developing lens; its synthesis continued through the adult stage in the secondary fiber cells. Low levels of AQP1 expression were first seen in lens anterior epithelial cells at E17.5; following postnatal day (P) 6.5, the expression gradually progressed towards the equatorial epithelial cells. In the postnatal lens, the increase in membrane water permeability of epithelial cells and lens transparency coincides with the increase in AQP1 expression. AQP1 expression reaches its peak at P30 and continues through the adult stage both in the anterior and equatorial epithelial cells. The enhancement in AQP1 expression concomitant with the increase in the size of the lens suggests the progression in the establishment of the lens microcirculatory system. In vitro and in vivo studies show that both aquaporins share at least one important function, which is water transport in the lens microcirculatory system. However, the temporal expression of these two AQPs suggests an apparently unique role/s in lens development and transparency. To our knowledge, this is the first report on the expression patterns of AQP0 and AQP1 during lens development and differentiation and their relation to lens transparency. Developmental Dynamics 236:1319 -1328, 2007.

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Section: Discussionmentioning

confidence: 99%

Functional expression of aquaporins in embryonic, postnatal, and adult mouse lenses

Varadaraj

Kumari

Mathias

2007

Developmental Dynamics

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“…β-crystallin and aquaporin-0 (also known as Major Intrinsic Protein or MIP26) are expressed and accumulate in fiber cells exclusively and therefore serve as useful markers for fiber differentiation (Yancey et al, 1988). Lens explants were incubated in unsupplemented medium, FGF/control medium or FGF/Wnt CM for 5 days.…”

Section: Wnts Stimulate Cultured Lens Epithelial Cells To Form Lens Fmentioning

confidence: 99%

Wnt signaling enhances FGF2-triggered lens fiber cell differentiation

Lyu

Joo

2004

Development

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Wnt signaling is implicated in many developmental processes, including cell fate changes. Several members of the Wnt family, as well as other molecules involved in Wnt signaling, including Frizzled receptors, LDL-related protein co-receptors, members of the Dishevelled and Dickkopf families, are known to be expressed in the lens during embryonic or postembryonic development. However, the function of Wnt signaling in lens fiber differentiation remains unknown. Here, we show that GSK-3β kinase is inactivated and that β-catenin accumulates during the early stages of lens fiber cell differentiation. In an explant culture system, Wnt conditioned medium (CM) induced the accumulation of β-crystallin, a marker of fiber cell differentiation, without changing cell shape. In contrast, epithelial cells stimulated with Wnt after priming with FGF elongated, accumulated β-crystallin, aquaporin-0, p57kip2, and altered their expression of cadherins. Treatment with lithium, which stabilizes β-catenin, induced the accumulation of β-crystallin, but explants treated with lithium after FGF priming did not elongate as they did after Wnt application. These results show that Wnts promote the morphological aspects of fiber cell differentiation in a process that requires FGF signaling, but is independent of β-catenin. Wnt signaling may play an important role in lens epithelial-tofiber differentiation.

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“…The MIP gene is specifically expressed in lens fiber cells, which arise by differentiation of the lens epithelium (2). MIP may play an important role in maintaining lens transparency by reducing the interfiber space, as suggested by its ability to function as a weak water channel (3,4) and possibly as an adhesion molecule (5).…”

Section: Introductionmentioning

confidence: 99%

Overlapping Sp1 and AP2 binding sites in a promoter element of the lens-specific MIP gene

Ohtaka-Maruyama

Wang

et al. 1998

Nucleic Acids Research

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The MIP gene, the founder of the MIP family of channel proteins, is specifically expressed in fiber cells of the ocular lens and expression is regulated temporally and spatially during development. We previously found that a DNA fragment containing 253 bp of 5′-flanking sequence and 42 bp of exon 1 of the human MIP gene contains regulatory elements responsible for lensspecific expression of the MIP gene. In this report we have analyzed the function of overlapping Sp1 and AP2 binding sites present in the MIP promoter. Using DNase I footprinting analysis we found that purified Sp1 and AP2 transcription factors interact with several domains of the human MIP promoter sequence -253/+42. Furthermore, addition of purified Sp1 to Drosophila nuclear extracts activates in vitro transcription from the MIP promoter -253/+42. This promoter activity is competed by oligonucleotides containing domains footprinted with Sp1. Using promoter-reporter gene (CAT) constructs we found that the sequence -39/-70 contains a cis regulatory element essential for promoter activity in transient assays in lens cells. EMSA analysis showed that lens nuclear extracts contain factors that bind to the MIP 5′-flanking sequence containing overlapping Sp1 and AP2 binding domains at positions -37/-65. Supershift experiments with lens nuclear extracts indicated that Sp3 is also able to interact with this regulatory element, suggesting that Sp1 and Sp3 may be involved in regulation of transcription of the MIP gene in the lens.

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Expression of the gene for main intrinsic polypeptide (MIP): separate spatial distributions of MIP and beta-crystallin gene transcripts in rat lens development.

Cited by 50 publications

References 46 publications

Functional expression of aquaporins in embryonic, postnatal, and adult mouse lenses

Functional expression of aquaporins in embryonic, postnatal, and adult mouse lenses

Wnt signaling enhances FGF2-triggered lens fiber cell differentiation

Overlapping Sp1 and AP2 binding sites in a promoter element of the lens-specific MIP gene

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