Mutations of two genes that encode gap junction proteins that are expressed in the lens (CX46 and CX50) are among the most frequent genetic causes of congenital cataracts. Our previous studies of a variety of cataract-associated connexin mutants (predominantly through expression in Xenopus oocytes or transfected mammalian cell lines) have shown that most of these connexin mutants are not functional (and sometimes act as dominant negative inhibitors of their wild type counterparts). Moreover, many of these mutants exhibit one of two types of abnormal cellular behaviors: (1) they accumulate in cytoplasmic inclusions and appear to be resistant to degradation or (2) they do not traffic properly to the plasma membrane and localize within the secretory pathway. We hypothesize that lens cells expressing mutant connexins that form cytoplasmic inclusions or are retained within the secretory pathway will exhibit unique abnormalities due to abnormal interactions (or lack of interactions) of the connexin mutants with lens-specific proteins causing their retention, altered abundance, or decreased function. Experiments are proposed to study representative members of each class of connexin mutants in lens cells (of chicken embryos, stably transfected lens epithelial cell lines, or lenses of mice carrying connexin mutations). A repertoire of microscopy, cell biological and biochemical approaches will be used to address two central questions: " What are the fates of the mutant connexins in the lens? " What are the consequences of expression of the mutant connexins upon other lens components? The data obtained from these studies are likely to have broad implications towards understanding cataract formation in general, since similar cellular abnormalities (formation of inclusions and retention in the biosynthetic pathway) have also been observed for many other cataract-associated mutant proteins.

Public Health Relevance

Cataracts are the major cause of blindness worldwide and are a major cause of visual impairment in the United States. Mutations of two genes that encode gap junction proteins (CX46 and CX50) that are expressed in the lens are among the most frequent genetic causes of congenital cataracts. Studies are proposed to elucidate the cellular and biochemical basis of cataracts due to these mutant connexins.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY008368-23
Application #
8485610
Study Section
Special Emphasis Panel (ZRG1-ETTN-E (02))
Program Officer
Araj, Houmam H
Project Start
1990-01-01
Project End
2015-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
23
Fiscal Year
2013
Total Cost
$387,945
Indirect Cost
$139,262
Name
University of Chicago
Department
Pediatrics
Type
Schools of Medicine
DUNS #
005421136
City
Chicago
State
IL
Country
United States
Zip Code
60637
Falk, Matthias M; Kells, Rachael M; Berthoud, Viviana M (2014) Degradation of connexins and gap junctions. FEBS Lett 588:1221-9
Berthoud, Viviana M; Minogue, Peter J; Yu, Helena et al. (2014) Connexin46fs380 causes progressive cataracts. Invest Ophthalmol Vis Sci 55:6639-48
Berthoud, Viviana M; Minogue, Peter J; Osmolak, Patricia et al. (2014) Roles and regulation of lens epithelial cell connexins. FEBS Lett 588:1297-303
Senthil Kumar, G; Kyle, John W; Minogue, Peter J et al. (2013) An MIP/AQP0 mutation with impaired trafficking and function underlies an autosomal dominant congenital lamellar cataract. Exp Eye Res 110:136-41
Minogue, Peter J; Beyer, Eric C; Berthoud, Viviana M (2013) A connexin50 mutant, CX50fs, that causes cataracts is unstable, but is rescued by a proteasomal inhibitor. J Biol Chem 288:20427-34
Berthoud, Viviana M; Minogue, Peter J; Yu, Helena et al. (2013) Connexin50D47A decreases levels of fiber cell connexins and impairs lens fiber cell differentiation. Invest Ophthalmol Vis Sci 54:7614-22
Tong, Jun-Jie; Minogue, Peter J; Guo, Wenji et al. (2011) Different consequences of cataract-associated mutations at adjacent positions in the first extracellular boundary of connexin50. Am J Physiol Cell Physiol 300:C1055-64
Martinez, Agustin D; Maripillan, Jaime; Acuna, Rodrigo et al. (2011) Different domains are critical for oligomerization compatibility of different connexins. Biochem J 436:35-43
Berthoud, Viviana M; Beyer, Eric C (2009) Oxidative stress, lens gap junctions, and cataracts. Antioxid Redox Signal 11:339-53
Lichtenstein, Alexandra; Gaietta, Guido M; Deerinck, Thomas J et al. (2009) The cytoplasmic accumulations of the cataract-associated mutant, Connexin50P88S, are long-lived and form in the endoplasmic reticulum. Exp Eye Res 88:600-9

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