The growth of the human lens is linear from age 10 to 90. Thus, lens epithelial cells divide and differentiate into lens fibers at a constant rate during adulthood. Any defects that arise during fiber formation will remain in the lens. We postulate that the unusual growth properties of the lens contribute to cataract formation, a disease that usually occurs later in life. If the growth rate of the lens could be reduced, the onset of cataracts might be delayed and fewer cataracts would reach clinical significance. To test these hypotheses we must be able to control the growth of the lens. However, the factor responsible for the growth of the lens in vivo has not been identified. We have recently identified a lens growth activity in chicken embryo serum. Several well-characterized growth factors did not replace this activity. We will use three approaches to describe and characterize this activity, including: purification by microbore liquid chromatography, the assay of new, purified growth factors as they become available and the identification of all tyrosine kinase growth factor receptors on lens epithelial cells, using PCR and limited DNA sequencing. These studies will identify, for the first time, a factor that controls lens growth in vivo. This laboratory has previously shown that lens fiber cell elongation is driven by an increase in cell volume. Increased cell volume is initially caused by potassium accumulation and the accompanying influx of water. A candidate for the potassium channel that controls this process has recently been identified. In collaboration with Dr. James Rae, we will test whether this is the channel that is regulated during fiber formation. If it is, we will identify the factors that control its activity. Our recent data suggest that high levels of cyclic AMP increase potassium efflux and prevent fiber cell elongation. We will measure cAMP levels, then examine the effects of cAMP agonists and antagonists on ion channels with patch clamp methods. If a regulated lens potassium channel is identified, it will be cloned and its mRNA expressed in Xenopus oocytes, where more extensive studies of channel regulation will be possible. We showed that lens fiber formation in chicken embryos is caused by exposure of lens epithelial cells to IGF-1 in the vitreous humor. In collaboration with two other labs, we recently identified binding proteins for IGF-1 in chicken vitreous humor. The kinds and amounts of these proteins were different in serum and vitreous humor. We will describe the distribution of IGF binding proteins and their mRNAs in embryonic eyes. Vitreous humor will be depleted of IGF binding proteins to test whether these molecules augment or suppress IGF activity. We will also determine the distribution of IGF-1 mRNA in the eye by in situ hybridization and the polymerase chain reaction. Recent studies led us to question the widely-held view that lens epithelial cells must be directly coupled to underlying lens fibers. To resolve this issue, we will use confocal microscopy to examine the pathways by which small molecules enter the extracellular spaces of the lens, measure the rate of transfer of small molecules between epithelial cells and fibers and determine how the lens epithelium maintains the ionic composition of the fibers.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY004853-11
Application #
2159167
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1983-12-01
Project End
1995-11-30
Budget Start
1993-12-01
Budget End
1994-11-30
Support Year
11
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Henry M. Jackson Fdn for the Adv Mil/Med
Department
Type
DUNS #
City
Rockville
State
MD
Country
United States
Zip Code
20817
Oltean, Alina; Huang, Jie; Beebe, David C et al. (2016) Tissue growth constrained by extracellular matrix drives invagination during optic cup morphogenesis. Biomech Model Mechanobiol 15:1405-1421
Huang, Jie; Liu, Ying; Filas, Benjamen et al. (2015) Negative and positive auto-regulation of BMP expression in early eye development. Dev Biol 407:256-64
Huang, Jie; Liu, Ying; Oltean, Alina et al. (2015) Bmp4 from the optic vesicle specifies murine retina formation. Dev Biol 402:119-26
Chen, Ziyan; Huang, Jie; Liu, Ying et al. (2014) FGF signaling activates a Sox9-Sox10 pathway for the formation and branching morphogenesis of mouse ocular glands. Development 141:2691-701
Wolf, Louise; Harrison, Wilbur; Huang, Jie et al. (2013) Histone posttranslational modifications and cell fate determination: lens induction requires the lysine acetyltransferases CBP and p300. Nucleic Acids Res 41:10199-214
Li, Qi; Yan, Hong; Ding, Tian-Bing et al. (2013) Oxidative responses induced by pharmacologic vitreolysis and/or long-term hyperoxia treatment in rat lenses. Curr Eye Res 38:639-48
Xie, Qing; Yang, Ying; Huang, Jie et al. (2013) Pax6 interactions with chromatin and identification of its novel direct target genes in lens and forebrain. PLoS One 8:e54507
Almony, Arghavan; Holekamp, Nancy M; Bai, Fang et al. (2012) Small-gauge vitrectomy does not protect against nuclear sclerotic cataract. Retina 32:499-505
Wiley, Luke A; Rajagopal, Ramya; Dattilo, Lisa K et al. (2011) The tumor suppressor gene Trp53 protects the mouse lens against posterior subcapsular cataracts and the BMP receptor Acvr1 acts as a tumor suppressor in the lens. Dis Model Mech 4:484-95
Huang, Jie; Rajagopal, Ramya; Liu, Ying et al. (2011) The mechanism of lens placode formation: a case of matrix-mediated morphogenesis. Dev Biol 355:32-42

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