Untersuchungen zu familiären und rassespezifischen ...

5 Elimination of SILV as a candidate for congenital
sensorineural deafness in Dalmatian dogs
Source/description: Canine congenital sensorineural deafness (CCSD) has been
described in many dog breeds with the highest incidence in Dalmatian dogs. 1-3 A
relationship between deafness and blue iris color has been identified for Dalmatian
dogs in several studies. 3-5 Blue eyes are also typical for merle dogs. The merle coat
pattern with patches of diluted pigment intermingled with normal coat colour is almost
expressed in dogs heterozygous for merle (Mm), whereas dogs homozygous for
merle (MM) are predominantly white. Dogs homozygous for merle, also known as
double merles exhibit deafness caused by anomalies of the inner ears and a wide
range of ocular malformations. Ophthalmologic anomalies include microphthalmia,
microcoria, colobomas and in some cases rudimentary lenses and ectasia of
episcleral vessels. 6 The canine merle locus has been localized to CFA10. A 253 bp
SINE insertion (g.7255_7256ins253 (GenBank NC_006592.2)) at the intron 10/exon
11 boundary of the silver homolog (mouse) (GeneID: 481102, NC_006592.2) gene is
associated with the merle phenotype in several dog breeds like Australian shepherd,
Border Collie, Cardigan Welsh Corgi, Collie, Dachshund, Great Dane and Shetland
sheepdog. 7 Most of the nonmerle Shetland sheepdogs and Great Danes did not
harbour the SILV SINE insert, merle dogs of several breeds were heterozygous for
the SILV SINE insert and two double merle Shetland sheepdogs and one double
merle Great Dane were homozygous for the SILV SINE insert. 7 A disease phenotype
was not reported for these three double merle dogs 7 and thus, it remains unclear
whether the SILV SINE insert may be involved in an impaired function of the auditory
and ophthalmologic systems. Dalmatian dogs are not considered to have the merle
phenotype rather than the unique coat pattern is caused by extreme-white spotting
(s w s w ), flecking (ff) and ticking (TT) alleles. 8
SILV (OMIM no. 155550, NC_000012) encodes the type I integral membrane
proteins PMEL17 and GP100 of 668 and 661 amino acids (aa), respectively, that are