Five year report. March December 2013

Transcription

1 Five year report March December 2013

2 2 Introduction Inherited disease within purebred dogs has become headline news in recent years. Strong selection for desired characteristics, and the fact that individual breeds are genetically isolated, means that many breeds of dog have reduced gene pools and lower levels of genetic diversity. An unfortunate consequence of this can be the rapid increase of harmful or damaging diseaseassociated mutations. Inherited conditions observed in some breeds can lead to substantial welfare concerns and, as there are believed to be more than five million purebred dogs in the UK alone, the issue of inherited disease justifies close attention. The Animal Health Trust (AHT), with support from the Kennel Club Charitable Trust and other funding organisations, has been investigating the genetic basis of canine inherited disease for 20 years. Over the last decade huge advances have been made in the field of canine genetics. These advances started with the development of a comprehensive map of the canine genome and culminated in the sequencing of the entire genome in Since then, high density whole-genome marker arrays have been developed, enabling scientists to locate and pinpoint genetic mutations much more easily and quickly than was previously possible. This enables the efficient and effective development of diagnostic tests, which will help future generations of dogs. The Kennel Club Genetics Centre (KCGC) at the AHT, (a collaboration between the Kennel Club and the AHT), was formed in Dr Cathryn Mellersh, an experienced canine geneticist and Dr Sarah Blott, an experienced quantitative geneticist co-lead the KCGC. The aim of the Centre is to help dog breeders reduce or eradicate inherited disease from their breeds, through the development of essential tools, minimising the risk of breeding affected puppies, as well as the design of breeding programmes to improve the overall health and welfare of the breed. This in turn aims to safeguard the long term genetic health of breeds, by preserving genetic diversity. In the first five year funding period, which ended at the end of 2013, the KCGC investigated a number of inherited diseases for their heritability, mode of inheritance, and prevalence within the breed at risk being studied. Whole Genome Scan (WGS) technology was used effectively to identify regions of the genome linked to specific canine inherited diseases. Subsequent fine mapping and sequencing, which included the incorporation of next generation sequencing techniques, were applied to identify the associated mutations. This led to the development of genetic screening tests, to determine affected and carrier dogs, which can be performed with simple mouth swabs. The KCGC also introduced new approaches to aid in dog breeding decisions. One major advance being the development of estimated breeding values (EBVs), to enable whole dog populations to be evaluated for inherited disease, even if individuals haven t been scanned or DNA tested themselves. Consideration of the impact on the health and welfare of dogs, but also the willingness and support of breeders to provide sufficient data and DNA samples for the investigations, have contributed greatly to the success of the KCGC so far. This report highlights the progress and major achievements that have been made by the Centre in the first five year funding period.

3 3 Mutation detection The Canine Genetics team, led by Dr Cathryn Mellersh, liaises closely with dog breeders, owners and veterinarians to identify serious and debilitating clinical disorders that are more prevalent in some breeds than others, and are thus likely to be inherited. The team investigates the genetic basis of a variety of inherited diseases, but has a particular interest in inherited ocular and neurological diseases, both of which are clinical strengths of the AHT. The goal of all of our research projects is to identify the genetic variants associated with these inherited disorders, and develop DNA tests that dog breeders can use to inform their breeding decisions and improve the genetic health of future generations of dogs. The team collects DNA, in the form of buccal cheek swabs, from dogs affected with the various disorders under investigation, as well as from unaffected control dogs of the same breed. Genome wide association studies (GWAS) are used to identify specific regions of the genome associated with the disease being investigated and a variety of state-of-the-art technologies, including next-generation targeted, exome and RNA sequencing techniques are used to pinpoint the precise mutations underlying the disease-risk. Once the causal mutations have been identified DNA tests are developed and made available to the public. DNA samples Since 2009 the canine genetics team has collected and stored DNA samples from 11,000 dogs from 170 different breeds. Nearly one in four of these samples (24%) are from dogs affected with a disorder that is presumed to be inherited. Research success stories When the Kennel Club Genetics Centre (KCGC) was established in 2009 an objective was to undertake five genome-wide association studies per year, with each GWAS being for one disease in one breed. We have met this objective, having undertaken GWASs with DNA samples from 1,461 dogs of 25 different breeds as well as with DNA from 31 crossbred dogs. The conditions under investigation across these 25 breeds have included hereditary cataract, progressive retinal atrophy, geographic retinal dysplasia, ataxia, episodic falling, congenital keratoconjunctivitis sicca, sebaceous adenitis and steroid responsive meningitis. Between 2009 and November 2013 we identified ten unique mutations responsible for inherited disorders that are known to affect 29 different breeds. This brings the total number of mutations identified by the Canine Genetics team to 14. These mutations cause inherited disorders in 30 different breeds, with six of the mutations being found in more than one breed, and six breeds benefitting from more than one DNA test.

4 4 Mutations identified Mutations have been identified, and DNA tests developed at the AHT, for: 1. Primary lens luxation (PLL) in 17 breeds (Australian Cattle Dog, Chinese Crested Dog, Jack Russell Terrier, Jagd Terrier, Lancashire Heeler, Miniature Bull Terrier, Parson Russell Terrier, Patterdale Terrier, Rat Terrier, Sealyham Terrier, Tenterfield Terrier, Tibetan Terrier, Toy Fox Terrier, Volpino Italiano, Welsh Terrier, Yorkshire Terrier, Wire-haired Fox Terrier). PLL is a painful and potentially blinding condition. In PLL affected dogs the fibres which support the lens within the eye break down or disintegrate, causing the lens to become loose within the eye. If the lens moves to the front of the eye, rapid onset glaucoma and loss of vision can result. Since the launch of the DNA test in October 2009, close to 12,400 dogs of 15 breeds, from 40 different countries, have been tested for the PLL mutation. Of these, 382 have been identified as genetically affected and almost 400 as carriers. 2. Progressive retinal atrophy (PRA) in Golden Retrievers Progressive retinal atrophy (PRA) is a well-recognised inherited condition in many breeds of dog. The condition is characterised by bilateral degeneration of the retina which causes progressive vision loss that culminates in total blindness. There is no treatment for PRA - the most successful way to combat the disease is to identify dogs that carry the mutation and develop informed breeding strategies. In 2010 we developed a DNA test following the identification of the mutation which causes the most common form of PRA among Golden Retrievers in Europe known as GR_PRA1. Since the launch of the DNA test in November 2010, more than 2,600 Golden Retrievers have been tested from 16 different countries. Of these, seven dogs have been identified as affected and 184 as carriers. In 2012 we developed a second DNA test for PRA in the Golden Retriever, based on a different mutation we identified that causes a genetically different form of PRA in this breed. We named this form of the disease GR_PRA2. The two forms of PRA are clinically identical, but are genetically distinct diseases caused by independent mutations. Since the launch of the DNA test in August 2012 we have tested over 2,000 Golden Retrievers for the GR_PRA2 mutation; one affected dog has been identified and 213 carriers.

5 5 3. Progressive retinal atrophy in Tibetan Spaniels and Tibetan Terriers In 2013 our geneticists discovered a mutation that causes a different form of progressive retinal atrophy (PRA) in Tibetan Spaniels and Tibetan Terriers. We are calling this form of the disease PRA3 to distinguish it from other, genetically distinct, forms of PRA that are caused by different mutations, including the rcd4 mutation that is also known to cause PRA in some Tibetan Terriers (described below). Since the launch of the PRA3 DNA test in July 2013 we have tested more than 780 dogs, of which two have been identified as affected with PRA and 47 of which are carriers. 4. Late-onset progressive retinal atrophy (PRA) in Gordon and Irish Setters and Tibetan Terriers Gordon Setters suffer from a late onset form of PRA that doesn t typically affect dogs until they are around eight years of age. Owners report that their affected dogs develop night blindness in the first instance, which is indicative of a rod-cone degeneration, so we have termed this mutation rcd4 (for rod-cone degeneration 4) to distinguish it from other, previously identified, forms of rod cone degeneration. Diane Pearce We have identified the mutation for rcd4, which we believe is the most common form of PRA in the Gordon Setter, but our investigations indicate that there might be another, genetically distinct, rarer form of PRA in this breed. The rcd4 mutation is also present in Irish Setters and Tibetan Terriers. Since the launch of the DNA test in March 2011, we have tested more than 5,100 dogs from 23 different countries for the rcd4 mutation. Of these, 415 dogs have been identified as affected and more than 1,900 as carriers. 5. Curly coat and dry eye (CCDE) syndrome, and episodic falling (EF) in Cavalier King Charles Spaniels Curly coat and dry eye (CCDE) syndrome, known scientifically as congenital keratoconjunctivitis sicca and ichthyosiform dermatosis, affects a dog s eyes and skin. Affected dogs produce no tears making their eyes incredibly sore. Their skin becomes very flaky and dry, particularly around the foot, and this can make standing and walking difficult and painful. This syndrome appears to be a problem unique to Cavalier King Charles Spaniels (CKCS) and most dogs diagnosed with the condition are put to sleep.

6 6 Episodic falling is a neurological condition, induced by exercise, excitement or frustration, in which muscle tone increases. During an episode an affected dog is unable to relax its muscles, becomes rigid and often falls over. Affected dogs usually start to demonstrate clinical signs before one year of age, with most cases having their first episode aged four to seven months. We identified the mutation for EF at the same time as we found the mutation for CCDE (above), and a DNA test has been developed that screens for both mutations simultaneously. Since the launch of the DNA test in April 2011, we have tested over 6,500 CKCS from 15 different countries for both mutations. Of these, 203 dogs have been identified as affected with EF, five as affected with CCDE and more than 1,800 dogs as carriers of either EF or CCDE. 6. Late onset ataxia in the Parson Russell Terrier Late onset ataxia (LOA) in the Parson Russell Terrier (PRT) is a disease of incoordination of gait and lack of balance. The onset age for the disease is usually between six months and one year of age, when owners may start to notice that their dog is showing changes in gait pattern, (often weaving of the hind limbs), and some difficulty balancing. The disease is progressive and affected dogs become increasingly uncoordinated with difficulty balancing, which makes moving around and everyday tasks such as going up and down stairs difficult. There is no treatment or cure for LOA and affected dogs are often euthanized, typically around two years after onset, on humane grounds, as their quality of life diminishes. We undertook extensive investigations of LOA in the PRT and successfully identified the mutation responsible for the disease. In November 2012 we developed a DNA test, based on this mutation, and since that time we have tested more than 1,500 PRTs, of which 20 are affected and 230 are carriers. 7. Neonatal cerebellum cortical degeneration in the Beagle Neonatal cerebellar cortical degeneration (NCCD) is a hereditary disease that can affect Beagle puppies. Affected puppies start showing clinical signs around three weeks of age. They are slower and less coordinated than their littermates, fall more often and are unable to regulate a normal gait. This disease has minimal progression, but currently there is no cure. The clinical signs are due to damage in their cerebellum, which is the part of the nervous system that controls the movement and the equilibrium. Vigor Beagles In 2012, together with the AHT s own veterinary neurologists, a novel technique was used to identify the mutation for NCCD in the Beagle and make a DNA test available. Since the launch of the test over 250 Beagles have been tested, of which 14 are carriers.

7 7 8. Cerebellar ataxia in the Italian Spinone Cerebellar ataxia (CA) in the Italian Spinone is a serious neurological disease. In affected dogs the cerebellum, which is the part of the brain responsible for the co-ordination of motor movement in the body, becomes diseased. Affected dogs are born normal, but clinical signs, which include the development of an unsteady gait, loss of co-ordination and poor balance usually appear within the first weeks or months of life. The disease is progressive; symptoms worsen during the first year of the dog s life such that most dogs are euthanased before they are one year old. There is no treatment for the disease, which has an autosomal recessive mode of inheritance. In 2008 we identified the region of the genome that contained the CA mutation and developed a linkage-based DNA test for the disease which we estimated gave an accurate result for between 95% and 98% of dogs tested. Since its launch we have tested 574 Spinone, of which 35 were carriers. The test has been used by Spinone breeders to effectively eliminate the condition from the breed in the UK and, as far as we are aware, no affected dogs have been born since the test was launched. Recently we identified the precise mutation responsible for CA in the Italian Spinone and a manuscript is currently being prepared for publication. Additional DNA tests offered by the Animal Health Trust Apart from the DNA tests based on the 14 mutations identified by geneticists from the KCGC, the AHT offers DNA tests for 12 additional inherited disorders to around 20 additional breeds. The AHT s DNA testing facility tests around 12,000 dogs each year. (Overall, canine samples submitted for DNA testing in 2013 were up 11% on numbers for 2012.) A full list of the canine DNA tests we offer can be found on our website ( DNA testing statistics The AHT DNA testing facility has tested over 38,000 dogs for the 10 mutations that we have identified between , and over 67,000 dogs for all 14 mutations that the genetics team have identified. More than 14,000 of the dogs tested have been found to be carriers of at least one diseaseassociated mutation; as all the mutations are recessive a DNA test is the only way to reliably identify carriers prior to breeding, and the carrier status of most of these dogs would therefore have been indiscernible before the development of these DNA tests. PhD success story Four of the mutations identified are responsible for genetically distinct forms of progressive retinal atrophy, (an incurable disease that leads to total blindness). The four mutations, which segregate in the Golden Retriever (two mutations), the Gordon and Irish Setter, the Tibetan Spaniel and the Tibetan Terrier (two mutations) were identified by Louise Downs and the work formed the basis of her PhD thesis, which she successfully defended in October The KCGC is thus enabling research that both improves the genetic health of future generations of purebred dogs, but also contributes to the training of future generations of scientists.

8 8 DNA testing at Animal Health Trust ( ) The tables below list the number of DNA tests performed during the period , indicating those tests for which the causative mutation was identified by the Kennel Club Genetics Centre (Table 1) and those for which the causal mutation was identified by the Canine Genetics research group at the AHT, prior to the establishment of the Kennel Club Genetics Centre (Table 2). Table 1 Disorder Abbreviation Breed(s) Number of Tests Performed Progressive retinal atrophy GR_PRA1 Golden Retriever 2,655 Progressive retinal atrophy GR_PRA2 Golden Retriever 2,023 Progressive retinal atrophy RCD4 Gordon and Irish Setters, Tibetan Terriers Progressive retinal atrophy PRA3 Tibetan Spaniels and Tibetan Terriers 781 5,130 Episodic falling EF Cavalier King Charles Spaniel 6,573 Curly coat dry eye syndrome CCDE Cavalier King Charles Spaniel 6,573 Neonatal cerebellar cortical degeneration NCCD Beagle 258 Late onset ataxia LOA Parson Russell Terrier 1,526 Primary lens luxation PLL Various breeds 12,368 Cerebellar ataxia CA Italian Spinone ,461 Table 2 Disorder Abbreviation Breed(s) Hereditary cataract HC Staffordshire Bull Terriers, French Bulldogs, Boston Terriers Number of Tests Performed 8,234 Hereditary cataract HC Australian Shepherds 3,322 Cone-rod dytrophy CORD1 Miniature Longhaired Dachshunds and English Springer Spaniels 8,619 L-2-Hydroxyglutaric aciduria L-2-HGA Staffordshire Bull Terriers 8,463 28,638

9 9 Quantitative Genetics Research carried out by the Quantitative Genetics team aims to develop effective methods of genetic evaluation for complex diseases, as management of these diseases poses the greatest challenge to dog breeders. Of the 489 currently known genetic diseases in dogs, 72% are believed to be complex ( The Quantitative Genetics team also aims to develop breeding strategies for canine populations that will maintain long-term health by managing rates of inbreeding, while reducing the prevalence of existing disease; and to encourage the implementation of state-of-the-art breeding techniques in dog breeding by developing Internet-based tools for breeders. Development of Mate Select The Quantitative Genetics team worked with Kennel Club IT developers to implement the algorithm for calculating inbreeding coefficients for all KC registered dogs, and for prospective matings. Phase one of Mate Select, launched in May 2011, enables breeders to: access a dog s individual inbreeding coefficient access the average inbreeding coefficient for any breed recognized by the KC perform hypothetical matings and predict the inbreeding coefficients of the puppies. This service now attracts more than 23,000 searches per month (statistic measured in 2012). We are now creating technologies that will underpin the second and third phases of Mate Select. This includes developing statistical models, so EBVs for conditions such as hip and elbow dysplasia can be calculated. We are also researching the impact of optimum contributions (OCs) when applied to dog breeds. By using OCs we will be able to understand the impact that using any particular dog will have on the future diversity of a breed. Going forward, once all three tools are operational, we will continue to carry out the routine calculation of EBVs and OCs ensuring the data breeders are accessing is as accurate and up-todate as possible. We also hope that through our continued research we will be able to develop new features for the program, ensuring that Mate Select remains an innovative and cuttingedge development in dog breeding.

10 10 Estimated breeding values (EBVs) Complex diseases, such as hip dysplasia and epilepsy, are believed to be caused by a combination of genetic and environmental effects. Pedigree information and population-wide data on disease, such as that collected for the BVA/KC health screening schemes, are analysed using advanced statistical techniques to calculate the extent to which a disease is genetic (its heritability), and this information is used to determine EBVs. EBVs are an objective numerical assessment of the genetic status of an individual dog, with environmental effects removed. By using EBVs breeders can distinguish between dogs of high and low genetic risk when selecting parents. The research required to establish heritabilities for hip and elbow dysplasia and to develop appropriate statistical models for EBVs has been carried out. The results have been published in six peer-reviewed papers. EBVs for hip score in 15 breeds and elbow score in five breeds have been developed. The breeds are: Labrador Retriever, Golden Retriever, German Shepherd Dog, Rottweiler, Border Collie, Flat Coat Retriever, Bernese Mountain Dog, Newfoundland, Siberian Husky, Bearded Collie, English Setter, Gordon Setter, Akita, Tibetan Terrier, Rhodesian Ridgeback. These breeds encompass more than 80,000 KC registrations per year, so that EBVs will initially be available for about 33% of all KC registered dogs. An informative display has been developed for EBVs in Mate Select. For example, the accuracy of the EBV is reflected graphically using a feathered bar to represent the probability density around the EBV (Figure 1). This will ensure that breeders take account of both the EBV and its accuracy in the comparison of dogs.

11 11 Figure 1: Example of graphical display of EBVs in Mate Select. The results for two different dogs are shown, showing both their hip and elbow score EBVs. The EBV is shown as a circle on a coloured bar, the shading around the circle indicates the accuracy of the EBV. The breed average is represented by the vertical line in the middle of the bar. EBVs which are lower risk than average fall in the green area and those at higher risk than average in the red area. Dog A. Score EBV Accuracy Elbow % Higher Risk Breed Average Lower Risk Hip % Higher Risk Breed Average Lower Risk Dog B. Score EBV Accuracy Elbow % Higher Risk Breed Average Lower Risk Hip 1/0 = % Higher Risk Breed Average Lower Risk The main benefits of introducing EBV to UK dog breeding have been described by Lewis et al. (2013). The possibility of international collaboration to generate EBV relevant across international populations has also been investigated. Fikse et al. (2013) have demonstrated the fulfilment of two important pre-requisites for international collaboration to be of benefit: 1) there has been substantial migration of dogs between the UK and other countries in at least four breeds studied (Labrador Retriever, Golden Retriever, Flat Coat Retriever and Bearded Collie) and 2) EBV for hip dysplasia in the UK and Europe are strongly and favourably correlated, despite differences in screening methods. Heritability analyses were carried out for syringomyelia and mitral valve disease (MVD) in the Cavalier King Charles Spaniel. The production of routine EBVs for these conditions requires suitable screening and data collection procedures to be in place. A new KC/BVA scheme for syringomyelia, open to all breeds, has been launched.

12 12 Inbreeding and population analyses Inbreeding is one of the risk factors for inherited disease in purebred dogs. It is important to understand how the population structure of breeds may be contributing to an increased rate of inbreeding. Analysis of the population structure and rate of inbreeding for all 211 Kennel Club recognised breeds is currently underway. Population analyses have been completed for 132 breeds. There are a further 49 breeds with more than 100 total registrations and mean number of registrations per year of at least 20, for which analyses will be attempted. The mean effective population size, calculated for 127 breeds, was 93 with a minimum of 14 (Cesky Terrier) and a maximum of 1,673 (Australian Shepherd). Five breeds had a declining rate of inbreeding meaning the effective population size is increasing. Figure 2 shows the distribution of breed effective population sizes. Approximately 40% of the breeds analysed have effective population sizes below 50, which is the minimum size recommended in order to manage the effects of inbreeding and maintain a viable population. Figure 2: frequency distribution (histogram) and cumulative distribution of effective population sizes in the sample of 127 breeds.

13 13 Summary The Kennel Club Genetics Centre at the AHT has made outstanding progress since its launch in The initial vision of combining the resources and expertise of the Kennel Club and the Animal Health Trust to create one centre of excellence, aimed at promoting the health and welfare of dogs both individuals and whole breeds has proven extremely successful. There is still much to achieve, therefore it is tremendous news that the Kennel Club Charitable Trust have provided a further five years of funding to continue this important work. We will continue to take full advantage of new and developing technologies to discover more mutations, in the hope that they will lead to the development of further DNA screening tests that breeders can use to control, or even eliminate, painful and devastating diseases. We will also continue to advance the tools available to dog breeders, particularly for dealing with the risk of complex diseases. This will include expanding the range of complex diseases for which EBVs are available, and researching new methods for calculating genetic risk. We will also be testing breeding strategies aimed at improving canine health, and diminishing the impact of inherited disease, using computer modelling. Through publications, articles and seminars we will continue to update dog owners and breeders on progress, as well as advise them on available tests and appropriate breeding strategies, aimed at minimising disease risk specifically for their breeds. We are committed to helping dog breeders in the UK, and across the world, to produce happy and healthy puppies. We are confident that breeders will continue to make the most of the scientific developments that we are generating, to ensure we are all able to achieve this important goal. Acknowledgements We would like to thank all the breed clubs, societies, individuals and veterinary surgeons - both at the AHT and at other practices - who have helped fund and contribute to our progress and achievements. Without your support, information and samples, we would not have been able to produce the DNA tests and diagnostic tools that we have developed over the last five years. On many of the individual projects, within the KCGC at the AHT, we have collaborated with scientists and veterinary professionals working elsewhere. These include: Dr David Sargan (Cambridge University), Dr David Gould (Davies Veterinary Specialists), Professor John Woolliams (The Roslin Institute and the Royal Dick School of Veterinary Medicine), Professor Jacques Penderis (University of Glasgow School of Veterinary Medicine) and Professor Brian Kinghorn (University of New England, Armidale, Australia). We are grateful for additional funding from The WALTHAM Foundation, the PetPlan Charitable Trust, and the LUPA project (

14 14 Published papers The research undertaken by the KCGC has resulted in the following publications, with an additional manuscript in press and two more in preparation: Forman, O. P., De Risio, L. & Mellersh, C. S. (2013) Missense Mutation in CAPN1 Is Associated with Spinocerebellar Ataxia in the Parson Russell Terrier Dog Breed. PLoS ONE, 8, e Sanchez-Molano E, Woolliams JA, Blott SC, Wiener P. (2013) Assessing the impact of genomic selection against hip dysplasia in the Labrador retriever. Journal of Animal Breeding and Genetics, Oct 18. E-pub ahead of print. Lewis TW, Blott SC, Woolliams JA. (2013) Comparative analyses of genetic trends and prospects for selection against hip and elbow dysplasia in 15 UK dog breeds. BMC Genet. Mar 2; 14: 16. Highly accessed: 1,585 views. Fikse WF, Malm S, Lewis TW. (2013) Opportunities for international collaboration in dog breeding from the sharing of pedigree and health data. Vet J. 197: Forman, O. P., Penderis, J., Hartley, C., Hayward, L. J., Ricketts, S. L. & Mellersh, C. S. (2012) Parallel Mapping and Simultaneous Sequencing Reveals Deletions in BCAN and FAM83H Associated with Discrete Inherited Disorders in a Domestic Dog Breed. PLoS Genetics, 8, e Miyadera, K., Kato, K., Boursnell, M., Mellersh, C. S. & Sargan, D. R. (2012) Genome-wide association study in RPGRIP1 (-/-) dogs identifies a modifier locus that determines the onset of retinal degeneration. Mammalian Genome, 23, Mellersh, C. (2012) DNA testing and domestic dogs. Mamm Genome, 23, Forman, O. P., De Risio, L., Stewart, J., Mellersh, C. S. & Beltran, E. (2012) Genome-wide mrna sequencing of a single canine cerebellar cortical degeneration case leads to the identification of a disease associated SPTBN2 mutation. BMC Genetics, 13, 55. Downs, L. M., Bell, J. S., Freeman, J., Hartley, C., Hayward, L. J. & Mellersh, C. S. (2012) Lateonset progressive retinal atrophy in the Gordon and Irish Setter breeds is associated with a frameshift mutation in C2orf71. Animal Genetics. Downs, L. M., Wallin-Hakansson, B., Boursnell, M., Marklund, S., Hedhammar, A., Truve, K., Hubinette, L., Lindblad-Toh, K., Bergstrom, T. & Mellersh, C. S. (2011) A Frameshift Mutation in Golden Retriever Dogs with Progressive Retinal Atrophy Endorses SLC4A3 as a Candidate Gene for Human Retinal Degenerations. PLoS ONE, 6, e Mellersh, C. (2011) DNA testing man's best friend. Veterinary Record, 168, Gould, D., Pettitt, L., Mclaughlin, B., Holmes, N., Forman, O., Thomas, A., Ahonen, S., Lohi, H., O'leary, C., Sargan, D. & Mellersh, C. (2011) ADAMTS17 mutation associated with primary lens luxation is widespread among breeds. Veterinary Ophthalmology, 14, 1-7. Woolliams JA, Lewis TW, Blott SC. (2011) Canine hip and elbow dysplasia in UK Labrador retrievers. Vet J. 189: Review.

15 15 Lewis TW, Ilska JJ, Blott SC, Woolliams JA. (2011) Genetic evaluation of elbow scores and the relationship with hip scores in UK Labrador retrievers. Vet J. 189: Farias, F. H., Johnson, G. S., Taylor, J. F., Giuliano, E., Katz, M. L., Sanders, D. N., Schnabel, R. D., Mckay, S. D., Khan, S., Gharahkhani, P., O'leary, C. A., Pettitt, L., Forman, O. P., Boursnell, M., Mclaughlin, B., Ahonen, S., Lohi, H., Hernandez-Merino, E., Gould, D. J., Sargan, D. & Mellersh, C. S. (2010) An ADAMTS17 Splice Donor Site Mutation in Dogs with Primary Lens Luxation. Investigative Ophthalmology and Visual Science, 51, Lewis TW, Woolliams JA, Blott SC.(2010) Optimisation of breeding strategies to reduce the prevalence of inherited disease in pedigree dogs. Animal Welfare. 2010; 19(S): Lewis TW, Woolliams JA, Blott SC. (2010) Genetic evaluation of the nine component features of hip score in UK Labrador Retrievers. PLoS One 5(10): e ,208 views, 8 citations. Lewis TW, Blott SC, Woolliams JA. (2010) Genetic evaluation of hip score in UK Labrador Retrievers. PLoS One 5(10): e12797, 3,037 views, 13 citations. Lewis T, Swift S, Woolliams JA, Blott S. (2010) Heritability of premature mitral valve disease in Cavalier King Charles spaniels. Vet J. 188: Lewis T, Rusbridge C, Knowler P, Blott S, Woolliams JA. (2010) Heritability of syringomyelia in Cavalier King Charles spaniels. Vet J. 183: AHT registered charity no: