高原绵羊β_3-肾上腺素受体基因(ADRB3)变异与适应性进化分析

为了探讨ADRB3基因变异及其与高原绵羊适应性进化关系,研究以‘甘肃高山细毛羊’‘藏绵羊’及‘滩羊’3个绵羊品种为观测对象,采用PCR-SSCP方法检测ADRB3基因部分内含子序列的遗传多态性,同时基于DA遗传距离用NJ法进行系统聚类分析,明确3个绵羊品种与不同物种群体间的遗传进化关系.结果表明:3个绵羊品种共检测到5种等位基因(A,B,C,D和E),构成了7种基因型(AA,AD,BD,BE,CC,CD和DD),存在6个突变位点(T/C,C/T,A/G/C,T/C,A/C和T/C),‘滩羊’中未检测到等位基因A和基因型AA与AD,优势等位基因与基因型在不同群体间各不相同;聚类结果显示,不同物种总体上分为2大类,其中绵羊、山羊和家牛等聚为一支,且‘藏绵羊’与‘甘肃高山细毛羊’之间的遗传距离最小,‘滩羊’次之;而大猩猩、人和小家鼠聚为一支.研究发现,ADRB3基因在3个绵羊群体中存在丰富的多态性,且存在群体间差异.ADRB3基因多态性丰富的绵羊品种在高海拔地区适应性能力较强,ADRB3基因可能在绵羊适应性进化中具有一定功能.     

An insertion/deletion variant of a thymine base in exon 2 of the porcine beta 3‐adrenergic receptor gene associated with loin eye muscle area

An insertion/deletion variant of a thymine base (T5 and T6) in exon 2 of porcine beta 3‐adrenergic receptor (ADRB3) gene has been described. In the current study, we made an association study between the ADRB3 polymorphisms and production traits in 735 Duroc pigs. The allele frequencies for the T5 and T6 alleles in our study population were 0.433 and 0.567, respectively. Any associations between ADRB3 genotype and average daily weight gain during test period, or backfat thickness and intramuscular fat content were not detected in either sex. However the size of the loin eye muscle area (EMA) was significantly associated with ADRB3 genotypes in gilts. T6‐homozygous gilts had a higher mean of EMA (40.6 ± 0.6 cm²) than T5‐homozygous (38.1 ± 0.4 cm², P = 0.002) and heterozygous (38.8 ± 0.3 cm², P = 0.034) gilts. This association was not detected in males. In addition, a multiple traits animal model best linear unbiased predictor (BLUP) analysis revealed that the T6‐homozygous genotype had positive effects on breeding value of EMA. Accordingly, we suggest that ADRB3 polymorphism has the potential to be an important genetic marker for prediction of EMA in Duroc pigs.     

绵羊β3肾上腺素能受体蛋白结构和分子进化分析

β3肾上腺素能受体(ADRB3)是G蛋白耦联受体超家族的成员之一,主要作用于脂肪组织,参与调节脂肪分解和能量代谢。本文基于NCBI上已经发表的14个物种的ADRB3基因mRNA和蛋白质序列,利用网络信息资源和生物学软件,对绵羊等14个物种进行分子进化分析,为进一步研究其表达调控奠定基础。结果表明:该蛋白包含1段50个氨基酸组成的信号肽,是一种具有7个跨膜区结构的不稳定的疏水性膜蛋白。二级结构由α螺旋(23.95%)、β延伸链(20.49%)和无规则卷曲(55.56%)构成;分子进化分析结果显示,14个物种被分成2支,绵羊、山羊、牛、猪、马、狗、猫、豚鼠、大鼠、小鼠、猕猴、黑猩猩和人聚为一支,虹鳟鱼单独为一支,该聚类结果和公认的动物分类及进化关系吻合;非同义替换率与同义替换率的比值ω为3.756,说明ADRB3基因发生了正向选择,即受自然选择的作用较大。     

The novel polymorphism of the beta 3-adrenergic receptor gene and its distribution in domestic pigs and wild boars in Asia

The beta 3‐adrenergic receptor (ADRB3) is a G protein‐coupled receptor that is involved in regulating energy homeostasis. We have studied DNA sequences of porcine ADRB3 to find candidate genetic polymorphisms for economically important growth and performance traits in pigs. Five novel haplotypes derived from the three In/dels and 44 SNPs were identified among domestic pigs and wild boars. Three of them encode non‐synonymous amino acid sequences by five missense polymorphisms and a frameshift by a thymine insertion. The amino acid polymorphic sites were distributed as follows: one substitution was in extracellular loop 1, three substitutions were in intracellular loop3 and one substitution and the deletion of two amino acids were at the carboxyl‐terminal. There was no polymorphism in the transmembrane domains. In addition, we surveyed the allelic frequency of the thymine insertion that cause frameshift in South‐east Asian local pigs, including some commercial breeds and wild boars. This thymine insertion was distributed widely in the domestic pigs and wild boars. The frequencies of this allele were relatively low in Western improved breeds, while they were very common in Asian breeds and wild boars in Asia. This result indicates that this insertion originally occurred in ancient Asian wild boars and then circulated among Asian domestic pigs. This allele also spread over Western breeds, probably through the introgression of Asian pigs into European stocks during the 18th and 19th centuries.     

Nucleotide sequence polymorphisms of beta1‐, beta2‐, and beta3‐adrenergic receptor genes on Jinhua,Meishan, Duroc and Landrace pigs

The full amino acid coding sequences of adrenergic receptor genes beta1, beta2, and beta3 (ADRB1, ADRB2, and ADRB3)were determined for Jinhua, Meishan, Duroc and Landrace pigs. Non‐synonymous substitution of Arg458Pro was found in the porcine ADRB1 gene, resulting in a 469 amino acid sequence. Continuous substitutions of Asn29Asp and Glu30Gln were found in the porcine ADRB2 gene, resulting in a 418 amino acid sequence. Additionally, a Lys30 polymorphism of the ADRB2 gene was found in the Jinhua pigs. There were three non‐synonymous substitutions of Asn24Thr, Arg264Gln and Asn398Asp on the porcine ADRB3 gene. A thymine insertion in the ADRB3 gene, resulting in a protein with two fewer amino acids, was found in the Jinhua and Meishan pigs. To assess the effect of ADRB polymorphisms on porcine subcutaneous fat layer thickness, we calculated the genetic frequency of the variants in fatty and lean groups, each consisting of 24 pigs that were crossbreds of Duroc and Jinhua pigs. The effect of the ADRB3 gene polymorphism was not evaluated, because there was insufficient variation on the ADRB3 gene in the examined groups. Although Fisher's exact test showed no significant difference in the frequency of ADRB1 and ADBR2 variants between the two groups, the Arg458 variant of ADRB1 was higher (P = 0.11) in the lean group, and pigs in that group had a thinner fat layer than did those with the Pro458 variant. These results imply a possibility of ADRB1 polymorphism as a minor factor in porcine fat layer thickness. The Asp29 variant of ADRB2 was higher in the lean group (P = 0.11), and the Glu30 variant was higher in the fatty group (P = 0.15), but the Asp29 variant was found only in the Chinese pigs. Thus, the effect of ADRB2 polymorphisms was not clear in this study.