Aus dem Institut für Tierzucht und Vererbungsforschung - Stiftung ...

Review of canine primary cataract
cycle arrest (Fini et al., 1997; Oliver and Gruss, 1997; Ogino and Yasuda, 2000). However,
only in a few cases cataracts are formed at these early stages of development. More and
diverse phenotypes of cataracts occur, if the lens is maturing and mutations affecting the lens
membranes, e.g. aquaporins (Mip), Lim2 or connexins, or the structural proteins of the
cytosol of the lens fiber cells, the crystallins (Graw, 2004). Mutations in crystalline genes are
resulting in proteins with abnormal structure which can result in lens opacity. Mutations are
predicted to disrupt the tertiary structure of the given crystalline, interfering with solution
with associated crystallins (Hejtmancik, 1998). Thus, maintenance of normal structure as well
as normal amounts of various proteins is essential for lens transparency. A noticeable example
for a mutation in crystallins is the Philly mouse, a strain with dominantly inherited cataract
caused by a mutation in the βB2-crystallin and having an internal deletion of four amino acids
(Kador et al., 1980; Chambers and Russell, 1991). In addition, there are several genetically
engineered mouse models with cataract resulting from abnormalities of development (Lang et
al., 1987; Perez-Castro et al., 1993), immunity (Egwuagu et al., 1994; Geiger et al., 1994),
growth (Mahon et al., 1987; Eva et al., 1991; Griep et al., 1993), cytoskeleton (Capetanaki et
al., 1989; Bloemendal et al., 1997) or membrane transport (Dunia et al., 1996). The mouse as
one of the most important model systems in eye development is currently supplemented by
the rapidely increasing number of mutants in the zebrafish (Glass and Dahm, 2004). Table 2
gives an overview over genes known to be associated with primary cataract and their
localization on human, murine and canine chromosomes.
6. Prevalence and inheritance of primary cataract
Cataract is a very common eye condition in the dog, and many different clinical forms are
exhibited in this species. There is a varied aetiology and many cases are of unknown cause
(Barnett, 1985c).
Primary cataracts have been reported to be inherited in several canine breeds including
Leonbergers (Heinrich et al., 2006), Entlebucher Mountain Dogs (Heitmann et al., 2005;
Davidson and Nelms, 1998; Spiess, 1994), Bichon Frise (Gelatt, 2003, 2005), Tibetan Terriers
(Ketteritzsch et al., 2004), Norwegian Buhunds (Bjerkås et al., 1995), Rottweilers (Bjerkås
and Bergsjø, 1991), Chow Chows (Collins et al., 1992), Golden and Labrador Retrievers
(Curtis et al., 1989; Barnett, 1978; Rubin et al., 1974; Gelatt, 1972), German Shepherds
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