INTRODUCTION German shepherd dogs (GSDs) are a popular breed affected by numerous disorders. Few studies have explored genetic variations that influence canine blood metabolite levels. OBJECTIVES To investigate genetic variants affecting the natural metabolite variation in GSDs. METHODS A total of 82 healthy GSDs were genotyped on the Illumina CanineHD Beadchip, assaying 173,650 markers. For each dog, 74 metabolites were measured through liquid and gas chromatography mass spectrometry (LC-MS and GC-MS) and were used as phenotypes for genome-wide association analyses (GWAS). Sliding window and homozygosity analyses were conducted to fine-map regions of interest, and to identify haplotypes and gene dosage effects. RESULTS Summary statistics for 74 metabolites in this population of GSDs are reported. Forty-one metabolites had significant associations at a false discovery rate of 0.05. Two associations were located around genes which encode for enzymes for the relevant metabolites: 4-hydroxyproline was significantly associated to D-amino acid oxidase (DAO), and threonine to L-threonine 3-dehydrogenase (LOC477365). Three of the top ten haplotypes associated to 4-hydroxyproline included at least one SNP on DAO. These haplotypes occurred only in dogs with the highest 15 measurements of 4-hydroxyproline, ranging in frequency from 16.67 to 20%. None of the dogs were homozygous for these haplotypes. The top two haplotypes associated to threonine included SNPs on LOC477365 and were also overrepresented in dogs with the highest 15 measurements of threonine. These haplotypes occurred at a frequency of 90%, with 80% of these dogs homozygous for the haplotypes. In dogs with the lowest 15 measurements of threonine, the haplotypes occurred at a frequency of 26.67% and 0% homozygosity. CONCLUSION DAO and LOC477365 were identified as candidate genes affecting the natural plasma concentration of 4-hydroxyproline and threonine, respectively. Further investigations are needed to validate the effects of the variants on these genes.

中文翻译：

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对德国牧羊犬74种血浆代谢产物的全基因组关联研究显示，两种代谢产物与编码其酶的基因有关。

简介德国牧羊犬（GSD）是受多种疾病影响的流行犬种。很少有研究探索影响犬血液代谢产物水平的遗传变异。目的研究影响GSDs天然代谢产物变异的遗传变异。方法在Illumina CanineHD Beadchip上对82个健康的GSD进行基因分型，共检测173,650个标记。通过液相和气相色谱质谱法（LC-MS和GC-MS）为每只狗测量74种代谢物，并将其用作全基因组关联分析（GWAS）的表型。进行滑动窗口和纯合性分析以精细定位目标区域，并鉴定单倍型和基因剂量效应。结果报告了该GSD人群中74种代谢物的汇总统计数据。41种代谢物具有显着的相关性，错误发现率为0.05。在编码相关代谢物酶的基因周围有两个关联：4-羟基脯氨酸与D-氨基酸氧化酶（DAO）显着相关，苏氨酸与L-苏氨酸3-脱氢酶（LOC477365）显着相关。与4-羟基脯氨酸相关的十大单倍型中的三个包括DAO上的至少一个SNP。这些单倍型仅在4-羟基脯氨酸的15种测量值最高的狗中发生，频率范围为16.67％至20％。对于这些单倍型，没有狗是纯合的。与苏氨酸相关的前两个单倍型包括LOC477365上的SNP，在苏氨酸含量最高的15只狗中也代表过多。这些单倍型的发生频率为90％，这些狗中有80％为单倍型纯合子。在苏氨酸含量最低的15只狗中，单倍型的发生频率为26.67％和0％纯合性。结论DAO和LOC477365被鉴定为分别影响4-羟脯氨酸和苏氨酸的天然血浆浓度的候选基因。需要进一步研究以验证变体对这些基因的影响。