MrSnappy Posted March 8, 2007 Report Share Posted March 8, 2007 I found this on the BC Museum section. I don't understand genetics so I don't understand the article. http://www.akcchf.org/news/index.cfm?article_id=138 Quote Link to comment Share on other sites More sharing options...
collies4me Posted March 8, 2007 Report Share Posted March 8, 2007 I found this on the BC Museum section. I don't understand genetics so I don't understand the article. http://www.akcchf.org/news/index.cfm?article_id=138 Im more neuroscience than genetics, but I think the article is just stating to the fact that the merles gene is closely related to the genes responsible for occular and cochlear deficits in dogs, it seems to have some decent correlations that might hold some empirical value to studying both expressions. Quote Link to comment Share on other sites More sharing options...
laurie etc Posted March 8, 2007 Report Share Posted March 8, 2007 I don't think its a very well written (or understandable article)... I think they fail to mention that it is Homozygous Merles (double merles) that can suffer from occular and auditory problems, not Heterozygous (regular merles with one normal parent and one merle parent). I'm pretty sure that this is not "news", but maybe in some other breeds like dachshunds, great danes, shelties and aussies, where the merle (or harlequin or dappled) color is more prevelent - determining whether an animal is homozygous is more of an issue - or whether an animal is a "cryptic merle". (?) And it would make sense that IF there is a similar gene in humans that causes deafness, you might want to know before "breeding". (hmmm....Are we talking genetic selection for humans here ?) Laurie Quote Link to comment Share on other sites More sharing options...
Rosanne Posted March 8, 2007 Report Share Posted March 8, 2007 Interesting - it does state that merles heterozygous OR homozygous suffer from ocular and auditor issues. . . I'd never heard that before, and like Laurie, I own one (her eyes and ears were fine) . . . I thougth the genetic testing is needed mostly in dogs with coats where you can't quite tell if it's merle or not; such as sable-merle shelties, dark blue merles that may only have a couple small dapples. . . stuff like that. Puzzling. . . . oh well. Honestly I think I've met more uni-, and bi-laterally deaf dogs who showed NO outward coloring differences, than I have those that do. Quote Link to comment Share on other sites More sharing options...
SoloRiver Posted March 9, 2007 Report Share Posted March 9, 2007 I'm not sure why there needs to be a test for merle, since even if a particular dog is "cryptic" knowledge about that dog's parents should solve the mystery quite easily. The article says that the specific gene for merle has been identified (as in the locus, or where exactly it is in the genome). They managed to locate the gene by using a genetic marker that is in linkage disequilibrium with (meaning it is significantly associated with, because of close physical proximity) a region that corresponds to the region in the human genome that contains the SILV gene, which is a pigmentation gene that had previously been identified. So, merle is governed by SILV, which is known to be associated with pigmentation in mammals. According to another article (see below), normal merle coloration is also associated with increased likelihood of hearing defects. The authors don't differentiate between heterozygous and homozygous merle in the body of the article, but the discussion about homozygous merles on p. 1360 (Associations with Phenotype) indicates that they understand this difference and suggests that the merle dogs in the study were normal merles, or heterozygous. Article here: http://www.bordercolliesociety.com/BC_Info.../bcdeafness.pdf (will download pdf) Prevalence of Unilateral and Bilateral Deafness in Border Collies and Association with Phenotype J Vet Intern Med 2006;20:1355–1362 Simon Platt, Julia Freeman, Alberta di Stefani, Lara Wieczorek, and William Henley Background: Congenital sensorineural deafness (CSD) occurs in Border Collies, but its prevalence and inheritance are unknown. This study estimated the prevalence of CSD in Border Collies and investigated its association with phenotypic attributes linked to the merle gene, including coat pigmentation and iris color. Hypothesis: Deafness in Border Collies is associated with pigmentation patterns linked to the merle gene. Animals: A total of 2597 Border Collies from the United Kingdom. Methods: A retrospective study of Border Collies tested, during 1994–2002, by using brainstem auditory evoked responses. Associations between deafness and phenotypic attributes were assessed by using generalized logistic regression. Results: The prevalence of CSD in puppies was estimated as 2.8%. The corresponding rates of unilateral and bilateral CSD were 2.3 and 0.5%, respectively. Adjustment for clustering of hearing status by litter reduced the overall prevalence estimate to 1.6%. There was no association between CSD and sex (P 5 .2). Deaf Border Collies had higher rates of merle coat pigmentation, blue iris pigment, and excess white on the head than normal hearing Border Collies (all P , .001). The odds of deafness were increased by a factor of 14 for Border Collies with deaf dams, relative to the odds for dogs with normal dams (P 5 .007), after adjustment for phenotypic attributes. Conclusions and Clinical Importance: Associations between CSD and pigmentation patterns linked to the merle gene were demonstrated for Border Collies. Evidence for an inherited component to CSD in Border Collies supports selective breeding from only tested and normal parents to reduce the prevalence of this disease. Key words: Brainstem auditory evoked response; Congenital deafness; Hearing; Merle; Neurophysiology. Quote Link to comment Share on other sites More sharing options...
laurie etc Posted March 9, 2007 Report Share Posted March 9, 2007 ...Hypothesis: Deafness in Border Collies is associated with pigmentation patterns linked to the merle gene. Animals: A total of 2597 Border Collies from the United Kingdom. Methods: A retrospective study of Border Collies tested, during 1994–2002, by using brainstem auditory evoked responses. Associations between deafness and phenotypic attributes were assessed by using generalized logistic regression. ...Results: The prevalence of CSD in puppies was estimated as 2.8%. The corresponding rates of unilateral and bilateral CSD were 2.3 and 0.5%, respectively. Adjustment for clustering of hearing status by litter reduced the overall prevalence estimate to 1.6%. There was no association between CSD and sex (P 5 .2). Deaf Border Collies had higher rates of merle coat pigmentation, blue iris pigment, and excess white on the head than normal hearing Border Collies (all P , .001). I read through that study earlier, but what bothers me about it is that the study lumped merle, blue eyes and excessive white on the head into the same category for the results. I'm under the impression that the three traits are not necessarily related (my merle is non-white factored, with two brown eyes, very little white on her head, and hears just fine (BAER tested twice). My daughter's merle is a uni. He is highly white factored (from 2 white factored parents) and has 2 blue eyes. What made him a uni... the coat color, the white, the eye color, or the combination? His full brother is merle with one partial blue eye and has normal hearing. Like Rosanne, I've met more non-merle Uni's than merle Uni's; although currently in the agility world, it's sometimes hard to find a Border Collie who doesn't "go back to" a merle somewhere in the pedigree. Laurie Quote Link to comment Share on other sites More sharing options...
Pipedream Farm Posted March 9, 2007 Report Share Posted March 9, 2007 I've wondered if the authors were trying to lump together easily identifiable markings associated with pink pigmentation on the face. Often, but not always, dogs with these markings will be associated with excess pink (lack of pigmentation) around the nose and eyes. This is from the linked paper. It has been proposed that the association ofcongenital deafness with coat color is related to the 3 different recessive alleles of the S locus.23 This locus affects the distribution patterns of pigmented and nonpigmented areas of the body; other genes determine the actual color of the pigmented areas.23 Mark Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.