Genetics, Vol. 161, 1633-1640, August 2002, Copyright © 2002

Ethylnitrosourea-Induced Base Pair Substitution Affects Splicing of the Mouse {gamma}E-Crystallin Encoding Gene Leading to the Expression of a Hybrid Protein and to a Cataract

Jochen Grawa, Angelika Neuhäuser-Klausa, Jana Löstera, Norman Kloppa, and Jack Favora
a GSF-National Research Center for Environment and Health, Institute of Mammalian Genetics, D-85764 Neuherberg, Germany

Corresponding author: Jochen Graw, Institute of Mammalian Genetics, D-85764 Neuherberg, Germany., graw{at}gsf.de (E-mail)

Communicating editor: C. KOZAK

A novel ENU-induced mutation in the mouse leading to a nuclear and cortical opacity of the eye lens (ENU418) was mapped to proximal chromosome 1 by a genome-wide mapping approach. It suggests that the cluster of {gamma}-crystallin encoding genes (Cryg) and the ßA2-crystallin encoding gene Cryba2 are excellent candidate genes. An A -> G exchange in the middle of intron 1 of the Cryge gene was found as the only alteration cosegregating with the cataractous phenotype. The mutation was confirmed by the presence of a novel restriction site for ApaI in the corresponding genomic DNA fragment. The mutation represses splicing of intron 1; the additional 92 bp in the corresponding cDNA leads to a frameshift and the expression of a novel hybrid protein containing 3 amino acids of the {gamma}E-crystallin at the N terminus, but 153 novel amino acids. The CrygeENU418 protein has a calculated molecular mass of ~15.6 kD and an alkaline isoelectric point (pH 10.1) and is predicted to have two hydrophobic domains. Western blot analysis using a polyclonal antibody against the hydrophilic C-terminal part of the CrygeENU418-specific protein demonstrated its stable expression in the cataractous lenses; it was not found in the wild types. Histological analysis of the cataractous lenses indicated that the expression of the new protein disrupts the cellular structure of the eye lens.




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