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.

The growth and development of skeletal muscle also determine the meat production of yak, ultimately affecting the economic benefits.  Hence, improving growth performance is a top priority in the yak industry.  Skeletal muscle development is a complex process involving the regulation of several genes, including microRNAs (miRNAs).  However, the transcription of miRNAs in yak skeletal muscle during prenatal to postnatal stages is unknown.  We used small RNA sequencing (small RNA-Seq) to determine the global miRNAs of longissimus dorsi muscle from yak (the samples were collected from three fetuses and three adults).  Totally 264 differently expressed miRNAs (|log₂(fold change)|>1 and P-value≤0.05) were detected between the two groups.  Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that differently expressed miRNAs-targeted genes participated in pathways associated with muscle development, such as MAPK, PI3K-Akt, and Hippo signaling pathways, etc.  MiR-652, which was up-regulated in the fetal group, was transfected into C2C12 myoblasts to examine its role.  miR-652 promoted (P≤0.05) proliferation and differentiation, but inhibited (P≤0.001) apoptosis at early period.  Furthermore, miR-652 reduced (P≤0.001) the proportion of C2C12 myoblasts in the G1 phase while increasing (P≤0.01) the proportion of cells in the S and G2 phases.  Dual-luciferase reporter assays indicated that ISL1 served as a target of miR-652.  In general, these findings expand our understanding of yak skeletal muscle miRNAs, and suggested that miR-652 probably regulated myogenesis by regulating ISL1.

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.