The research progress of farm animal genomics based on sequencing technologies.

Various farm animal breeds have been domesticated and bred for thousands years, and they provide adequate animal-derived proteins to meet the human nutrition requirement. Although quantitative genetics was applied in animal breeding, which launched a technological revolution in the past century, a number of complex traits remain difficult to be selected based on pedigree derived breeding, due to complicated animal genetics and development mechanisms. Farm animal's genetic potential hasn't yet to be fully exploited. The concept and technology from the Human Genome Project have greatly promoted farm animal genomic researches. It is possible to fine map the causal variations at the whole genome level and then exploit their biological functions, thus providing the theoretical basis for molecular designed breeding. In this review, we summarize the genomics research progress of main farm animals during the past decade, including pigs, cattle, yaks, goats, sheep, chickens, ducks and geese. We focus on the reference genome sequencing and follow-up population-level genomic studies based on high throughput resequencing technologies, and meanwhile envision the future work of farm animal genomics.

The fear gene stathmin alleles generated heterosis on feed efficiency parameters in Peking ducks.

Stathmin is an inhibitor of microtubule formation, as highly expressed in the lateral nucleus (LA) of the amygdala as well as in the thalamic and cortical structures that send information to the LA about the learned and innate fear. So we assume that STMN1 genetic variation may also affect the physical activity so as to influence the Residual Feed Intake (RFI) of duck. The Single Nucleotide Polymorphisms (SNPs) in duck Stathmin gene were screened by sequencing and genotyped by restriction endonuclease Msp I, EcoR I, Xho I, Taq I, EcoR II. A total of five SNPs (c.187 -15G > A, c.187 -110T > C, c.379 -95G > A, c.379 -318C > T, c.426 C > T) were detected in duck STMN1 gene. The c.187 -15G > A is near the 3' splice site of intron 2, which has a putative effect on the STMN1 pre-mRNA secondary structures. The c.187 -15G > A genotypes had significant effect on RFI of Peking drakes (P < 0.01). Individuals with heterozygous genotypes were more productive than that with homozygous genotypes, which suggested a molecular heterosis in c.187 -15 alleles on RFI. The current study is the first step to confirm the relationship between STMN1 gene polymorphisms and RFI. Supplemental material is available for this article. Go to the publisher's online edition of Animal Biotechnology for a figure of linkage disequilibrium between SNPs and table about frequencies of haploype.

Riboflavin (Vitamin B2) Deficiency Induces Apoptosis Mediated by Endoplasmic Reticulum Stress and the CHOP Pathway in HepG2 Cells.

Riboflavin is an essential micronutrient and a precursor of flavin mononucleotide and flavin adenine dinucleotide for maintaining cell homeostasis. Riboflavin deficiency (RD) induces cell apoptosis. Endoplasmic reticulum (ER) stress is considered to induce apoptosis, and C/EBP homologous protein (CHOP) is a key pathway involved in this process. However, whether RD-induced apoptosis is mediated by ER stress and the CHOP pathway remains unclear and needs further investigation. Therefore, the current study presents the effect of RD on ER stress and apoptosis in the human hepatoma cell line (HepG2). Firstly, cells were cultured in a RD medium (4.55 nM riboflavin) and a control (CON) medium (1005 nM riboflavin). We conducted an observation of cell microstructure characterization and determining apoptosis. Subsequently, 4-phenyl butyric acid (4-PBA), an ER stress inhibitor, was used in HepG2 cells to investigate the role of ER stress in RD-induced apoptosis. Finally, CHOP siRNA was transfected into HepG2 cells to validate whether RD triggered ER stress-mediated apoptosis by the CHOP pathway. The results show that RD inhibited cell proliferation and caused ER stress, as well as increased the expression of ER stress markers (CHOP, 78 kDa glucose-regulated protein, activating transcription factor 6) (p < 0.05). Furthermore, RD increased the cell apoptosis rate, enhanced the expression of proapoptotic markers (B-cell lymphoma 2-associated X, Caspase 3), and decreased the expression of the antiapoptotic marker (B-cell lymphoma 2) (p < 0.05). The 4-PBA treatment and CHOP knockdown markedly alleviated RD-induced cell apoptosis. These results demonstrate that RD induces cell apoptosis by triggering ER stress and the CHOP pathway.

Three chromosome-level duck genome assemblies provide insights into genomic variation during domestication.

Domestic ducks are raised for meat, eggs and feather down, and almost all varieties are descended from the Mallard (Anas platyrhynchos). Here, we report chromosome-level high-quality genome assemblies for meat and laying duck breeds, and the Mallard. Our new genomic databases contain annotations for thousands of new protein-coding genes and recover a major percentage of the presumed "missing genes" in birds. We obtain the entire genomic sequences for the C-type lectin (CTL) family members that regulate eggshell biomineralization. Our population and comparative genomics analyses provide more than 36 million sequence variants between duck populations. Furthermore, a mutant cell line allows confirmation of the predicted anti-adipogenic function of NR2F2 in the duck, and uncovered mutations specific to Pekin duck that potentially affect adipose deposition. Our study provides insights into avian evolution and the genetics of oviparity, and will be a rich resource for the future genetic improvement of commercial traits in the duck.

Relationship between Residual Feed Intake and Production Traits in a Population of F2 Ducks.

Improving feed efficiency is important for decreasing feed cost in poultry production, because feed account for approximately 70% of the total production costs. The selection of feed efficiency may affect other important economic traits. Therefore, the objectives of this present study was to evaluate the relationships of the residual feed intake (RFI) with live body weight, carcass weight, carcass composition, and size of small intestines in a population of F2 Pekin ducks. Nine-hundred and eighty F2 ducks were derived from a cross between 40 Pekin ducks and 10 Mallard ducks. The results showed no significant correlation of RFI with live body weight and eviscerated carcass weight. RFI had negative effects on breast meat weight and gizzard weight. A positive correlation of RFI with abdominal fat weight, skin weight, and jejunum length was detected. Our results indicated that the selection of RFI could improve the feed efficiency of ducks without affecting their carcass compositions.

Gene expression profiling in Pekin duck embryonic breast muscle.

Lean-type Pekin duck is a breed gained through long-term selection and great effort has been exerted to understand the mechanisms underlying increased muscle yields. However, the genes involved in Pekin duck embryonic breast muscle development have not been explored to date. In this study, we investigated gene expression profiles in Pekin Duck embryonic breast muscle at hatched day 13 (E13), E19, and E27 using RNA-seq. In total, we produced 519,312,178 raw reads resulting in 497,348,158 high-quality reads after filtering. The mapping, distribution of reads along annotated genes, and consistency across replicates demonstrates the high quality of the RNA-seq data used in this study, allowing us to continue with the downstream analysis. Significantly fewer differentially expressed genes (DEGs) were identified between E13 and E19 (203 DEGs) compared to E27 and E19 (2,797 DEGs). Many DEGs highly expressed in E19 are involved in metabolic processes and cell division. KEGG analysis showed many pathways associated with fat development were significantly enriched for DEGs highly expressed in E27. These results provide a basis for the further investigation of the mechanisms involved in Pekin duck embryonic breast muscle development.