A candidate gene approach to identify DNA markers associated with meat quality and production traits: investigation of several cathepsin genes in Italian heavy pigs.
A candidate gene approach to identify DNA markers associated with meat quality and production traits: investigation of several cathepsin genes in Italian heavy pigs.
复制标题
一种识别与肉质和生产性状相关的 DNA 标记的候选基因方法：意大利重型猪中几个组织蛋白酶基因的调查。
DOI：
--
复制
发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Camilla Speroni
中科院分区：
文献类型：
--
作者：
Camilla Speroni
组织蛋白酶代表溶酶体蛋白酶的一个重要家族，在许多（如果不是全部）组织和细胞类型中具有广泛的功能。除了在正常蛋白质周转过程中发挥主要作用外，它们还具有高度特异性的蛋白水解活性，包括免疫反应中的抗原加工以及在肥胖和肿瘤发展中的直接作用。
在猪中，组织蛋白酶参与蛋白水解过程，在肌肉转化为肉类的过程中具有重要作用，因为它们对肉的质地和感官特性有影响，主要是在调味产品中。他们的贡献对于干腌火腿的风味发展至关重要。然而，一些作者已经证明，高组织蛋白酶活性，特别是组织蛋白酶 B，与这些产品的缺陷相关，例如肉过软且游离酪氨酸含量异常、涩味或金属余味以及切割表面形成白色薄膜。
因此，对其遗传变异性的研究不仅有助于识别与这些干腌火腿参数相关的 DNA 标记，而且还有助于识别与意大利重型猪的肉质、产量和胴体性状相关的 DNA 标记。不幸的是，到目前为止，尚未发现组织蛋白酶标记物与肉品质性状之间存在关联，特别是与组织蛋白酶 B 活性之间的关联，这表明除这些基因外，其他基因也会影响肉品质参数。然而，在猪的一些屠体和生产性状中观察到了显着的关联。最近的一项研究表明，位于组织蛋白酶 D (CTSD)、F (CTSF)、H 和 Z 基因中的不同单核苷酸多态性 (SNP) 与意大利大白猪群体的生长、脂肪沉积和生产性状高度相关。
本论文的目的是在其他猪群中证实其中一些结果，并鉴定新的组织蛋白酶标记物，以评估它们对组织蛋白酶活性和其他生产性状的影响。
此外，从前期CTSD基因研究获得的数据出发，我们还分析了位于胰岛素样生长因子2基因（IGF2内含子3-g.3072G>A）的已知多态性。该标记被认为是影响猪肌肉质量和脂肪沉积的数量性状基因座（QTL）的致病突变。由于 IGF2 在图谱上与猪染色体 (SSC) 2 上的 CTSD 非常接近，因此我们想澄清 CTSD 标记的影响是否是由于与 IGF2 内含子 3-g.3072G>A 突变的连锁不平衡所致。
在第一章中，我们报告了这两个 SSC2 基因标记的结果。首先，我们评估了 IGF2 内含子 3-g.3072G>A 多态性在意大利大白品种中的影响，之前没有研究对此标记进行分析。与生产和胴体性状的所有估计育种值均确定了高度显着的关联（P A 突变没有显示出与意大利杜洛克猪的分析性状的任何关联，可能是由于该品种的该多态性位点的变异性较低。在同一杜洛克猪群体中，所有生产和胴体性状的 CTSD 标记均获得显着关联（在 IGF2 纯合的意大利大白猪群体中也证实了 P A 多态性） intron3-g.3072G 等位基因 G (IGF2 intron3-g.3072GG) 和两个所考虑基因的标记之间的单倍型分析综合起来，所有这些数据表明 IGF2 intron3-g.3072G>A 突变并不是影响猪脂肪和肌肉沉积的唯一多态性。
在第二章中，我们报告了组织蛋白酶 L (CTSL) 和组织蛋白酶 S (CTSS) 基因中发现的两个新 SNP 的分析，以及与肉质参数（包括组织蛋白酶 B 活性）和意大利大白猪群体的几个生产性状的关联结果。在 7 个不同的猪品种中评估了这两个标记的等位基因频率。此外，我们使用辐射混合面板将 CTSS 基因绘制在 SSC4 上。对 268 头意大利大白猪进行的几个生产性状的关联研究表明，CTSL 多态性对平均日增重、瘦肉重量和背膘厚度有积极影响（P<0.05）。后面这些性状的结果也通过选择性基因型方法在其他意大利大白猪中得到了证实（P<0.01）。在268头猪组中，CTSS多态性与料重比和平均日增重相关（P<0.05）。相反，在分析的标记物和肉质参数之间没有观察到关联。
最后，我们想要验证组织蛋白酶 L 和 S 标记以及其他先前识别的 SNP（组织蛋白酶 F、组织蛋白酶 Z 及其抑制剂半胱氨酸蛋白酶抑制剂 B）获得的阳性结果是否在意大利杜洛克猪品种中得到证实（第三章）。我们对两组杜洛克猪进行了分析：第一组由 218 头经过性能测试的猪组成，未根据任何表型标准进行选择，第二组由 100 头意大利杜洛克猪组成，其可见肌间脂肪性状极端且分散。在第一组中，CTSL 多态性与瘦肉重量相关（P<0.05），而与平均日增重和背膘厚度也存在暗示性关联（P<0.10）。 CTSL 基因标记的等位基因频率在可见的肌间极端尾部之间也存在正差异。相反，没有观察到其他 DNA 标记对分析性状的积极影响。
总之，与目前的数据以及这些酶的生物学作用相一致，猪 CTSD 和 CTSL 标记：a) 可能对涉及确定猪脂肪和瘦肉含量的生物学机制有直接影响，或 b) 这些标记可能非常接近其他基因中存在的推定功能突变。
这些发现具有重要的实际应用，特别是 CTSD 和 CTSL 突变可应用于意大利大白牛和意大利杜洛克品种的标记辅助选择 (MAS)。标记辅助选择还可以通过添加来自组织蛋白酶 S 基因型的信息来提高效率，但仅限于意大利大白品种。
The cathepsin enzymes represent an important family of lysosomal proteinases with a broad spectrum of functions in many, if not in all, tissues and cell types. In addition to their primary role during the normal protein turnover, they possess highly specific proteolytic activities, including antigen processing in the immune response and a direct role in the development of obesity and tumours.
In pigs, the involvement of cathepsin enzymes in proteolytic processes have important effects during the conversion of muscle to meat, due to their influence on meat texture and sensory characteristics, mainly in seasoned products. Their contribution is fundamental in flavour development of dry-curing hams. However, several authors have demonstrated that high cathepsin activity, in particular of cathepsin B, is correlated to defects of these products, such as an excessive meat softness together with abnormal free tyrosine content, astringent or metallic aftertastes and formation of a white film on the cut surface.
Thus, investigation of their genetic variability could be useful to identify DNA markers associated with these dry cured hams parameters, but also with meat quality, production and carcass traits in Italian heavy pigs. Unfortunately, no association has been found between cathepsin markers and meat quality traits so far, in particular with cathepsin B activity, suggesting that other genes, besides these, affect meat quality parameters. Nevertheless, significant associations were observed with several carcass and production traits in pigs. A recent study has demonstrated that different single nucleotide polymorphisms (SNPs) localized in cathepsin D (CTSD), F (CTSF), H and Z genes were highly associated with growth, fat deposition and production traits in an Italian Large White pig population.
The aim of this thesis was to confirm some of these results in other pig populations and identify new cathepsin markers in order to evaluate their effects on cathepsin activity and other production traits.
Furthermore, starting from the data obtained in previous studies on CTSD gene, we also analyzed the known polymorphism located in the insulin-like growth factor 2 gene (IGF2 intron3-g.3072G>A). This marker is considered the causative mutation for the quantitative trait loci (QTL) affecting muscle mass and fat deposition in pigs. Since IGF2 maps very close to CTSD on porcine chromosome (SSC) 2, we wanted to clarify if the effects of the CTSD marker were due to linkage disequilibrium with the IGF2 intron3-g.3072G>A mutation or not.
In the first chapter, we reported the results from these two SSC2 gene markers. First of all, we evaluated the effects of the IGF2 intron3-g.3072G>A polymorphism in the Italian Large White breed, for which no previous studies have analysed this marker. Highly significant associations were identified with all estimated breeding values for production and carcass traits (P A mutation did not show any associations with the analyzed traits in the Italian Duroc pigs, probably due to the low level of variability at this polymorphic site for this breed. In the same Duroc pig population, significant associations were obtained for the CTSD marker for all production and carcass traits (P A polymorphism were also confirmed in a group of Italian Large White pigs homozygous for the IGF2 intron3-g.3072G allele G (IGF2 intron3-g.3072GG) and by haplotype analysis between the markers of the two considered genes. Taken together, all these data indicated that the IGF2 intron3-g.3072G>A mutation is not the only polymorphism affecting fatness and muscle deposition in pigs.
In the second chapter, we reported the analysis of two new SNPs identified in cathepsin L (CTSL) and cathepsin S (CTSS) genes and the association results with meat quality parameters (including cathepsin B activity) and several production traits in an Italian Large White pig population. Allele frequencies of these two markers were evaluated in 7 different pig breeds. Furthermore, we mapped using a radiation hybrid panel the CTSS gene on SSC4. Association studies with several production traits, carried out in 268 Italian Large White pigs, indicated positive effects of the CTSL polymorphism on average daily gain, weight of lean cuts and backfat thickness (P<0.05). The results for these latter traits were also confirmed using a selective genotype approach in other Italian Large White pigs (P<0.01). In the 268 pig group, the CTSS polymorphism was associated with feed:gain ratio and average daily gain (P<0.05). Instead, no association was observed between the analysed markers and meat quality parameters.
Finally, we wanted to verify if the positive results obtained for the cathepsin L and S markers and for other previous identified SNPs (cathepsin F, cathepsin Z and their inhibitor cystatin B) were confirmed in the Italian Duroc pig breed (third chapter). We analysed them in two groups of Duroc pigs: the first group was made of 218 performance-tested pigs not selected by any phenotypic criteria, the second group was made of 100 Italian Duroc pigs extreme and divergent for visible intermuscular fat trait. In the first group, the CTSL polymorphism was associated with weight of lean cuts (P<0.05), while suggestive associations were obtained for average daily gain and backfat thickness (P<0.10). Allele frequencies of the CTSL gene marker also differed positively among the visible intermuscular extreme tails. Instead, no positive effects were observed for the other DNA markers on the analysed traits.
In conclusion, in agreement with the present data and for the biological role of these enzymes, the porcine CTSD and CTSL markers: a) may have a direct effect in the biological mechanisms involved in determining fat and lean meat content in pigs, or b) these markers could be very close to the putative functional mutation(s) present in other genes.
These findings have important practical applications, in particular the CTSD and CTSL mutations could be applied in a marker assisted selection (MAS) both in the Italian Large White and Italian Duroc breeds. Marker assisted selection could also increase in efficiency by adding information from the cathepsin S genotype, but only in the Italian Large White breed.