Journal of Heredity Advance Access published online on March 23, 2009
Journal of Heredity, doi:10.1093/jhered/esp010
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MLPH Genotype—Melanin Phenotype Correlation in Dilute Dogs
From the Institute of Genetics, Vetsuisse Faculty, University of Berne, Bremgartenstrasse 109a, 3001 Berne, Switzerland (Haase, Leeb, M. Drögemüller, and C. Drögemüller); the Institute of Animal Breeding and Genetics, University of Veterinary Medicine Hannover, Bünteweg 17p, Hannover, Germany (Philipp); the Institute of Animal Pathology, Vetsuisse Faculty, University of Berne, Länggassstr. 122, Berne, Switzerland (Welle); the Division of Clinical Dermatology, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Berne, Länggassstr. 128, Berne, Switzerland (Rüfenacht and Roosje); the Institute of Veterinary Medicine, University of Göttingen, Burckhardtweg 2, Göttingen, Germany (Scharfenstein, Schütz, and Brenig); the Tierärztliche Spezialisten, Rodigallee 85/Holstenhofweg, Hamburg, Germany (Linek); the Consultant Veterinary Pathology, Bellevue 23, Hamburg, Germany (Mecklenburg); the Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zürich, Winterthurerstr. 268, Zürich, Switzerland (Grest); and the Dermfocus, Vetsuisse Faculty, University of Berne, Berne, Switzerland (Haase, Leeb, C. Drögemüller, Welle, Rüfenacht, and Roosje)
Address correspondence to Prof. Dr. Tosso Leeb, Institute of Genetics, Vetsuisse Faculty, University of Berne, Bremgartenstrasse 109a, 3001 Berne, Switzerland, or e-mail: tosso.leeb{at}itz.unibe.ch.
Coat color dilution in dogs is a specific pigmentation phenotype caused by a defective transport of melanosomes leading to large clumps of pigment. It is inherited as a Mendelian autosomal recessive trait and may be accompanied by hair loss, the so-called color dilution alopecia (CDA), or black hair follicular dysplasia (BHFD). We previously identified the noncoding c.-22G>A transition in the melanophilin gene (MLPH) as a candidate causative mutation for the dilute phenotype. We have now extended our study and genotyped 935 dogs from 20 breeds segregating for dilute coat color. The dilute-associated A allele segregates in many different breeds suggesting an old mutation event. We also investigated skin biopsies of dogs suspected of having either CDA or BHFD, and our data clearly indicate that the dilute mutation is required but not sufficient to develop clinical signs of the disease. The risk to develop CDA/BHFD seems to be breed specific. Interestingly, 22 out of 29 dogs with clinical signs of CDA/BHFD have clumped melanin in the epidermis, the follicular epithelium, and the hair shafts, whereas in dilute dogs without clinical disease, clumped melanin is only found in the follicular epithelium and the hair shafts but not in the epidermis.
Key Words: black hair follicular dysplasia • coat color • color dilution alopecia • dog • melanophilin
Corresponding Editor: Francis Gailbert
Received November 20, 2008
Revised January 26, 2009
Accepted February 25, 2009