Molecular epidemiological study of germline APC variant associated with hereditary gastrointestinal polyposis in dogs: current frequency in Jack Russell Terriers in Japan and breed distribution

Abstract

Background Cases of gastrointestinal (GI) neoplastic polyps in Jack Russell Terriers (JRTs) have increased in Japan since the late 2000s. We recently demonstrated that JRTs with GI polyps heterozygously harbor an identical germline variant in the adenomatous polyposis coli (APC) gene, c.[462_463delinsTT]; therefore, this is an autosomal dominant hereditary disease. We conducted a molecular epidemiological study to explore the current frequency of the APC variant in JRTs in Japan and the breed distribution of this disease. Results Peripheral blood samples from 792 JRTs were collected at 93 veterinary hospitals in Japan in 2020. Using an established polymerase chain reaction-restriction fragment length polymorphism assay, the germline APC variant was detected in 15 JRTs, with an overall frequency of 1.89%. The frequency was not significantly different for sex, age, and coat type criteria. Notably, the variant carriers had a current or previous history of GI neoplastic polyps, providing further evidence of the association of the germline APC variant with GI polyposis. Pedigree analysis of carrier dogs revealed that the germline APC variant was no longer confined to a few specific families but was widely spread among JRTs in Japan. Furthermore, some ancestors of the carriers were from Australia or New Zealand, suggesting the possible presence of carriers in countries other than Japan. Next, we retrospectively investigated the germline APC variant status of dogs with GI epithelial tumors using genomic DNA samples extracted from archived pathological specimens (28 purebred dogs of 14 breeds and four mixed-breed dog), as well as those stored in a canine genome bank (38 dogs of 18 breeds and a mixed-breed dogs). In total, 66 purebred dogs of 25 breeds, including another four JRTs, and five mixed-breed dogs were examined. While three variant carriers were found in JRTs, the germline APC variant was not detected in any of the other breeds. Conclusion The current frequency of the germline APC variant was approximately 2% in JRTs in Japan and the frequency remained roughly flat during the last 15 years. In addition, hereditary GI polyposis associated with the variant was virtually specific to JRTs.

Clinical and Pathological Diagnosis of Hereditary Gastrointestinal Polyposis in Jack Russell Terriers

“…According to data compiled by the Japan Kennel Club (JKC) [ 8 ], JRTs have maintained a certain level of popularity in Japan over the last two decades, and nearly 3500 JRTs were registered in the JKC in 2021, ranking 16th among all purebred dogs. In our prior epidemiological survey conducted in 2020, the frequency of germline APC variants in Japan was determined to be 1.89% in a screening of approximately 800 JRTs [ 10 ]. Taken together, a certain number of JRTs with germline APC variants are still present today in Japan, and veterinary clinicians and pathologists would have the opportunity to examine patients and their GI lesions for some time in the future.…”

“…Taken together, a certain number of JRTs with germline APC variants are still present today in Japan, and veterinary clinicians and pathologists would have the opportunity to examine patients and their GI lesions for some time in the future. Moreover, judging from the fact that there were many JRTs introduced from overseas in the ancestors of the JRTs with the APC variant found in Japan [ 10 ] and that JRTs are also popular breeds outside Japan, it is likely that veterinarians in other countries could encounter JRTs with hereditary GI polyposis. It has previously been reported that JRTs with hereditary GI cancers have a significantly longer survival time than sporadic cases but were at a higher risk for disease recurrence [ 2 ].…”

“…In the present study, our aim was to collect as much information as possible, and therefore all available histopathological samples of the hereditary GI tumors in JRTs were retrospectively examined. Some of the present cases overlapped with dogs examined in our previous studies ( Supplementary Table S2 ) [ 2 , 10 ] and most cases from the clinical study (n = 11) were included. The present study included 133 GI epithelial tumors, including 54 gastric, 9 duodenal or jejunoileal, and 70 colorectal tumors, which were surgically or endoscopically resected from 37 JRTs diagnosed with hereditary GI polyposis between 2008 and 2022.…”

“…All JRTs examined in the clinical and pathological studies tested positive for the germline APC variant c.[462_463delinsTT]. The APC genotypes were determined via polymerase chain reaction (PCR)-direct sequencing as previously described [ 2 , 10 , 11 ]. Genomic DNA was extracted from EDTA-anticoagulated peripheral blood samples using the Wizard Genomic DNA Purification Kit (Promega, Madison, WI, USA), the DNeasy Blood & Tissue Kit (QIAGEN, Venlo, Netherlands), or from normal tissues on formalin-fixed paraffin-embedded (FFPE) sections using the QIAamp DNA FFPE Tissue Kit (QIAGEN).…”

“…Although JRTs are a popular dog breed in many countries, there has been no report of JRTs with hereditary GI polyposis in any country other than Japan. However, when examining pedigree certificates of JRTs with hereditary GI polyposis found in Japan, many had ancestors introduced from overseas, mainly from Australia [ 10 ], indicating the possibility of the presence of JRTs with the germline APC variant in other countries. Therefore, awareness of this novel hereditary disease must be raised among veterinary clinicians and pathologists worldwide, and the information necessary for an appropriate diagnosis should be provided.…”