Meslin Camille, Desert Colette, Callebaut Isabelle, Djari Anis, Klopp Christophe, Pitel Frédérique, Leroux Sophie, Martin Pascal, Froment Pascal, Guilbert Edith, Gondret Florence, Lagarrigue Sandrine, Monget Philippe
UMR85 Physiologie de la Reproduction et des Comportements, INRA, Nouzilly, France UMR7247, CNRS, Nouzilly, France Université François Rabelais de Tours, France Institut Français du Cheval et de l'Equitation, Nouzilly, France.
INRA, UMR1348 Physiologie, Environnement et Génétique pour l'Animal et les Systèmes d'élevage, Saint-Gilles, France Agrocampus-Ouest, UMR1348, Rennes, France.
Genome Biol Evol. 2015 Apr 24;7(5):1332-48. doi: 10.1093/gbe/evv072.
Free fatty acid receptors (FFAR) belong to a family of five G-protein coupled receptors that are involved in the regulation of lipid metabolism, so that their loss of function increases the risk of obesity. The aim of this study was to determine the expansion of genes encoding paralogs of FFAR2 in the chicken, considered as a model organism for developmental biology and biomedical research. By estimating the gene copy number using quantitative polymerase chain reaction, genomic DNA resequencing, and RNA sequencing data, we showed the existence of 23 ± 1.5 genes encoding FFAR2 paralogs in the chicken genome. The FFAR2 paralogs shared an identity from 87.2% up to 99%. Extensive gene conversion was responsible for this high degree of sequence similarities between these genes, and this concerned especially the four amino acids known to be critical for ligand binding. Moreover, elevated nonsynonymous/synonymous substitution ratios on some amino acids within or in close-vicinity of the ligand-binding groove suggest that positive selection may have reduced the effective rate of gene conversion in this region, thus contributing to diversify the function of some FFAR2 paralogs. All the FFAR2 paralogs were located on a microchromosome in a same linkage group. FFAR2 genes were expressed in different tissues and cells such as spleen, peripheral blood mononuclear cells, abdominal adipose tissue, intestine, and lung, with the highest rate of expression in testis. Further investigations are needed to determine whether these chicken-specific events along evolution are the consequence of domestication and may play a role in regulating lipid metabolism in this species.
游离脂肪酸受体（FFAR）属于一个由五个G蛋白偶联受体组成的家族，它们参与脂质代谢的调节，因此其功能丧失会增加肥胖风险。本研究的目的是确定鸡中编码FFAR2旁系同源物的基因的扩增情况，鸡被视为发育生物学和生物医学研究的模式生物。通过使用定量聚合酶链反应、基因组DNA重测序和RNA测序数据估计基因拷贝数，我们发现在鸡基因组中存在23±1.5个编码FFAR2旁系同源物的基因。FFAR2旁系同源物的序列同一性在87.2%至99%之间。广泛的基因转换导致了这些基因之间高度的序列相似性，尤其是涉及到已知对配体结合至关重要的四个氨基酸。此外，配体结合凹槽内或其附近某些氨基酸上较高的非同义/同义替换率表明，正选择可能降低了该区域基因转换的有效率，从而有助于使一些FFAR2旁系同源物的功能多样化。所有的FFAR2旁系同源物都位于同一个连锁群的一条微染色体上。FFAR2基因在不同的组织和细胞中表达，如脾脏、外周血单核细胞、腹部脂肪组织、肠道和肺，在睾丸中的表达率最高。需要进一步研究来确定这些鸡在进化过程中特有的事件是否是驯化的结果，以及是否可能在调节该物种的脂质代谢中发挥作用。
