Cattle are central to the lives and diverse cultures of African people. It has played a crucial role in providing valuable protein for billions of households and sources of income and employment for producers and other actors in the livestock value chains. The long-term natural selection of African cattle typically signals signatures in the genome, contributes to high genetic differentiations across breeds. This has enabled them to develop unique adaptive traits to cope with inadequate feed supply, high temperatures, high internal and external parasites, and diseases. However, these unique cattle genetic resources are threatened by indiscriminate cross-breeding, breed replacements with exotic cosmopolitan breeds, and climate change pressures. Although there are no functional genomics studies, recent advancements in genotyping and sequencing technologies have identified and annotated limited functional genes and causal variants associated with unique adaptive and economical traits of African cattle populations. These genome-wide variants serve as candidates for breed improvement and support conservation efforts for endangered cattle breeds against future climate changes. Therefore, this review plans to collate comprehensive information on the identified selection footprints to support genomic studies in African cattle to confirm the validity of the results and provide a framework for further genetic association and QTL fine mapping studies.

【背景】牦牛骨骼肌的生长发育决定其产肉量，进而影响经济收入。因此提高牦牛的产肉性能是发展牦牛产业的重要任务。骨骼肌发育过程受许多基因的调控，包括一些非编码RNA的调控，如miRNA。然而牦牛出生前后骨骼肌中miRNA的转录调控机制并不清楚。【目的】通过小RNA测序挖掘与牦牛骨骼肌生长发育有关的miRNA，并通过C2C12细胞对候选miRNA进行功能研究，为牦牛骨骼肌发育机制解析提供基础。【方法】对出生前后牦牛背最长肌（3个胎牛和3个成年牛）进行miRNA转录本测序，基于（log2 (差异倍数) |>1，P值≤0.05）筛选差异miRNAs，并通过Miranda和TargetScan算法预测差异miRNAs靶基因并求交集，对差异miRNA靶基因进行GO和KEGG富集分析。在C2C12细胞中通过干扰和过表达实验对候选miRNA进行功能分析，通过双荧光素酶实验验证候选miRNA的靶基因。【结果】本研究在胎牛和成年牦牛背最长肌中共鉴定到264个miRNAs。264个差异miRNAs共预测到5183个靶基因。GO和KEGG结果显示，差异miRNA的靶基因主要富集在能量平衡，蛋白激酶结合，ATP结合等GO条目，及一些与肌肉发育有关的信号通路，如MAPK，PI3K-Akt，Hippo等信号通路。其中候选miR-652在胎牛背最长肌中上调表达。通过在C2C12细胞中转染miR-652发现，miR-652可促进C2C12细胞的增殖和分化（P≤0.05），同时抑制C2C12细胞晚期凋亡（P≤0.001）。细胞周期实验结果显示，miR-652可导致C2C12细胞百分比在G1期下降（P≤0.001），S期和G2期上升（P≤0.01）。双荧光素酶实验结果提示ISL1是miR-652的一个靶基因。【结论】牦牛在出生前后骨骼肌中存在大量差异表达的miRNA，表明miRNA参与牦牛骨骼肌发育，miR-652可能通过靶向ISL1基因调控牦牛骨骼肌生长发育。

Endothelial PAS domain protein 1 gene (EPAS1) is a key transcription factor that activates the expression of oxygen-regulated genes. In this study, in order to better understand the effects of EPAS1 gene on hematologic parameters in yak, we firstly quantified the tissue expression patterns for EPAS1 mRNA of yak, identified polymorphism in this gene and evaluated its association with hematologic parameters. Expression of EPAS1 mRNA was detected in all eight tissues (heart, liver, lung, spleen, pancreas, kidney, muscles and ovary). The expressions of EPAS1 in lung and pancreas were extremely higher than other tissues examined. Three novel single nucleotide polymorphisms (SNPs) (g.83052 C>T, g.83065 G>A and g.83067 C>A) within the EPAS1 were identified and genotyped in Pali (PL), Gannan (GN) and Tianzhu White (TZW) yak breeds. Significant higher frequencies of the AA and GA genotypes and A allele of the g.83065 G>A were observed in the PL and GN breeds than that in the TZW breed (P<0.01). Association analysis of the PL breed indicated that the g.83065 G>A polymorphism was significantly associated with hemoglobin (HGB) concentration in yaks (P<0.05). Individuals with genotype AA had significantly higher HGB concentration (P<0.05) than those with genotype GA and GG. All these results will help our further understanding of biological functional of yak EPAS1 gene in responding to hypoxia and also indicate EPAS1 might contribute to the hypoxia adaptation of the yak.