Sequence and expression analysis of cardiac ryanodine receptor 2 in broilers that died from sudden death syndrome

Heart-specific expression of the green fluorescent protein gene in avian embryos by administration of recombinant adenovirus type-5 vector into the embryonic blood vessel

Genetic modification in vivo could provide direct functions of genes that could potentially contribute to diverse areas of research including genetics, developmental biology, and physiology. It has been reported that genes of interest could be introduced via recombinant adenovirus type 5 (Ad5) in poultry. Successful gene delivery to mammal fetuses in utero promises substantial progress in clinical and developmental biology, but it is limited because of difficulties in injecting specific sites and invasiveness. On the other hand, developing avian embryos are easily accessible by making a window on the eggshell. Therefore, the objective of this study is to determine permissive embryonic stages for gene transfer into specific avian tissue/organs by injection of Ad5 containing the green fluorescent protein (GFP) gene into blood vessels. At 2 d of post-injection, a strong GFP signal was predominantly identified in the heart of chicken embryos injected at Hamilton-Hamburger (HH) 14, 15, 16 and17 stages with the percentages (44%, 53%, 25%, and 14%, respectively) of GFP positive embryos. In quail embryos, the injection at the HH 15 resulted in heart-specific expression of GFP. Western blot analysis revealed that GFP was exclusively expressed in the avian hearts. These results suggest that the GFP gene is specifically delivered to the avian embryonic hearts when Ad5 is injected through the blood vessel at HH 14-17. This adenoviral transduction of genes of interest in avian embryonic hearts can provide new models for understanding functions of genetic factors on embryonic heart development and unravel genetic etiology of congenital heart diseases.

Heritability of sudden cardiac death in Thoroughbred racehorses

BACKGROUND

Sudden cardiac death (SCD) is an important cause of exercise-associated fatalities in Thoroughbred racehorses. Equine deaths share similarities with fatalities in human athletes that result from inherited cardiac disease. Whilst genetic causes have been postulated in horses, these have not been confirmed and heritability of SCD has not previously been estimated in Thoroughbred racehorses.

OBJECTIVES

To determine the heritability of SCD in a sample population of Thoroughbred racehorses.

STUDY DESIGN

Retrospective case-control study.

METHODS

Steward and post-mortem reports of Thoroughbred racehorses in Australia between 2007 and 2020 were reviewed to identify horses with SCD. Control horses were randomly selected from races in which SCD occurred or from races on the date of the case fatality. A five-generation integrated pedigree chart was collected for each horse. Estimates of heritability were obtained using an animal model in the ASReml-R program with variance components estimated assuming SCD was normally distributed, and on the logit transformed scale. Inbreeding coefficients were calculated and the risk of producing SCD-affected progeny was calculated for stallions that sired ≥5 individuals in the case-control population.

RESULTS

Ninety-three horses with SCD and 465 control horses were identified. Heritability on the underlying scale was 0.15 ± 0.09 (logit animal) and 0.24 ± 0.12 (normal animal). Inbreeding coefficients were not significantly different between groups. Of the 16 first generation sires that appeared ≥5 times in the case-control data set, two sires more frequently produced affected progeny (OR 7.95-10.41).

MAIN LIMITATIONS

Challenges in definitively confirming SCD may lead to misclassification of some cases. Some control horses may have not been exposed to environmental influences of SCD. Case numbers are low and the studied population may not represent the entire Thoroughbred genetic pool.

CONCLUSION

The heritability of SCD in this population was relatively low. However, individual stallions appear more likely to produce affected progeny. Further studies are required to understand the genetic and environmental influences that contribute to disease expression.

A new haplotype-resolved turkey genome to enable turkey genetics and genomics research

BACKGROUND

The domesticated turkey (Meleagris gallopavo) is a species of significant agricultural importance and is the second largest contributor, behind broiler chickens, to world poultry meat production. The previous genome is of draft quality and partly based on the chicken (Gallus gallus) genome. A high-quality reference genome of M. gallopavo is essential for turkey genomics and genetics research and the breeding industry.

RESULTS

By adopting the trio-binning approach, we were able to assemble a high-quality chromosome-level F1 assembly and 2 parental haplotype assemblies, leveraging long-read technologies and genome-wide chromatin interaction data (Hi-C). From a total of 40 chromosomes (2n = 80), we captured 35 chromosomes in a single scaffold, showing much improved genome completeness and continuity compared to the old assembly build. The 3 assemblies are of higher quality than the previous draft quality assembly and comparable to the chicken assemblies (GRCg7) shown by the largest contig N50 (26.6 Mb) and comparable BUSCO gene set completeness scores (96-97%). Comparative analyses confirm a previously identified large inversion of around 19 Mbp on the Z chromosome not found in other Galliformes. Structural variation between the parent haplotypes was identified, which poses potential new target genes for breeding.

CONCLUSIONS

We contribute a new high-quality turkey genome at the chromosome level, benefiting turkey genetics and other avian genomics research as well as the turkey breeding industry.

Sudden death syndrome in broiler chickens: a review on the etiology and prevention of the syndrome

Sudden death syndrome (SDS) is a condition in which apparently healthy broiler chickens die suddenly. There are short convulsions and frantic wing-beating prior to death, and the weight of internal organs is the same as in healthy chickens. The exact etiology of SDS is unknown. Heart problems have been implicated as a potential cause of the disease in broiler chickens. Despite considerable research, effective methods of prevention are still being sought. Furthermore, the prophylactic measures often make production less profitable (reduced body weight gain resulting from restricted feeding) and prolong the growth period. It is necessary to continue research on SDS, in particular on stimulation of the cardiovascular system to reduce the susceptibility of broilers to sudden death syndrome under intensive production systems.

Research-Relevant Background Lesions and Conditions in Common Avian and Aquatic Species

Non-mammalian vertebrates including birds, fish, and amphibians have a long history of contributing to ground-breaking scientific discoveries. Because these species offer several experimental advantages over higher vertebrates and share extensive anatomic and genetic homology with their mammalian counterparts, they remain popular animal models in a variety of fields such as developmental biology, physiology, toxicology, drug discovery, immunology, toxicology, and infectious disease. As with all animal models, familiarity with the anatomy, physiology, and spontaneous diseases of these species is necessary for ensuring animal welfare, as well as accurate interpretation and reporting of study findings. Working with avian and aquatic species can be especially challenging in this respect due to their rich diversity and array of unique adaptations. Here, we provide an overview of the research-relevant anatomic features, non-infectious conditions, and infectious diseases that impact research colonies of birds and aquatic animals, including fish and Xenopus species.