title: SERPINB11 frameshift variant associated with novel hoof specific phenotype in Connemara ponies.
abstract: Horses belong to the order Perissodactyla and bear the majority of their weight on their third toe; therefore, tremendous force is applied to each hoof. An inherited disease characterized by a phenotype restricted to the dorsal hoof wall was identified in the Connemara pony. Hoof wall separation disease (HWSD) manifests clinically as separation of the dorsal hoof wall along the weight-bearing surface of the hoof during the first year of life. Parents of affected ponies appeared clinically normal, suggesting an autosomal recessive mode of inheritance. A case-control allelic genome wide association analysis was performed (ncases = 15, ncontrols = 24). Population stratification (λ = 1.48) was successfully improved by removing outliers (ncontrols = 7) identified on a multidimensional scaling plot. A genome-wide significant association was detected on chromosome 8 (praw = 1.37x10-10, pgenome = 1.92x10-5). A homozygous region identified in affected ponies spanned from 79,936,024-81,676,900 bp and contained a family of 13 annotated SERPINB genes. Whole genome next-generation sequencing at 6x coverage of two cases and two controls revealed 9,758 SNVs and 1,230 indels within the ~1.7-Mb haplotype, of which 17 and 5, respectively, segregated with the disease and were located within or adjacent to genes. Additional genotyping of these 22 putative functional variants in 369 Connemara ponies (ncases = 23, ncontrols = 346) and 169 horses of other breeds revealed segregation of three putative variants adjacent or within four SERPIN genes. Two of the variants were non-coding and one was an insertion within SERPINB11 that introduced a frameshift resulting in a premature stop codon. Evaluation of mRNA levels at the proximal hoof capsule (ncases = 4, ncontrols = 4) revealed that SERPINB11 expression was significantly reduced in affected ponies (p<0.001). Carrier frequency was estimated at 14.8%. This study describes the first genetic variant associated with a hoof wall specific phenotype and suggests a role of SERPINB11 in maintaining hoof wall structure.
authors: Department of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America.
authors: Carrie J
authors: CJ
authors: Finno
authors: Department of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America.
authors: Carlynn
authors: C
authors: Stevens
authors: Department of Animal Science, University of California Davis, Davis, California, United States of America.
authors: Amy
authors: A
authors: Young
authors: Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America.
authors: Verena
authors: V
authors: Affolter
authors: Genome Center Bioinformatics Core, University of California Davis, Davis, California United States of America.
authors: Nikhil A
authors: NA
authors: Joshi
authors: Institute of Veterinary, Animal and Biomedical Sciences (IVABS) Massey University, Palmerston North, New Zealand.
authors: Sheila
authors: S
authors: Ramsay
authors: Department of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America.
authors: Danika L
authors: DL
authors: Bannasch
mesh_terms: D000818:Animals; D016368:Frameshift Mutation; D006724:Hoof and Claw / Q000033:anatomy & histology*; D006736:Horses / Q000235:genetics*; D010641:Phenotype; D011110:Polymorphism, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015843:Serpins / Q000235:genetics* / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D015843:Serpins