Effect of heat stress on HSP70 gene expression pattern in different vital organs of Malabari goats

Exploring Epigenetic and Genetic Modulation in Animal Responses to Thermal Stress

There is increasing evidence indicating that global temperatures are rising significantly, a phenomenon commonly referred to as 'global warming', which in turn is believed to be causing drastic changes to the global climate. Global warming (GW) directly impacts animal health, reproduction, production, and welfare, presenting several challenges to livestock enterprises. Thermal stress (TS) is one of the key consequences of GW, and all animal species, including livestock, have diverse physiological, epigenetic and genetic mechanisms to respond to TS. As a result, TS can significantly affect an animals' health, immune responsiveness, metabolic pathways etc. which can also influence the productivity, performance, and welfare of animals. Moreover, prolonged exposure to TS can lead to transgenerational and intergenerational changes that are mediated by epigenetic changes. For example, in several animal species, the effects of TS are encoded epigenetically during the animals' growth or productive stage, and these epigenetic changes can be transmitted intergenerationally. Such epigenetic changes can affect animal productivity by changing the phenotype so that it aligns with its ancestors' environment, irrespective of its immediate environment. Furthermore, epigenetic and genetic changes can also help protect cells from the adverse effects of TS by modulating the transcriptional status of heat-responsive genes in animals. This review focuses on the genetic and epigenetic modulation and regulation that occurs in TS conditions via HSPs, histone alterations and DNA methylation.

Transcription pattern of key molecular chaperones in heat shocked caprine cardiac fibroblasts

The present study was attempted to unveil the impact of heat stress on transcription pattern of major heat shock response genes in caprine cardiac fibroblasts. Cardiac tissues (n = 6) were collected and primary cardiac cell culture was done. Cultured cardiac fibroblasts were kept in an atmosphere of 5% CO2 and 95% air at 38.5 °C. Cardiac cells achieved 70-75% confluence after 72 hours of incubation. Heat stress was induced on confluent cardiac fibroblasts at 42 °C for 0 (control), 20, 60, 100 and 200 min. Quantitative RT-PCR for β2m (internal control), HSP60, HSP70, HSP90, and HSP110 was done and their transcription pattern was assessed by Pfaffl method. HSP60, HSP90, and HSP110 transcription did not differ at 20 min, up-regulated (p < 0.05) from 60 to 200 min and registered highest at 200 min of heat exposure. HSP70 transcription was gradually escalated (p < 0.05) time dependently from 20 to 200 min and reached zenith at 200 min of heat exposure. Differential induction in transcription of key molecular chaperones at various durations of heat exposure might reduce cardiac fibroblasts apoptosis and thus could maintain cardiac tissue function during heat stress.

Novel Insights to Assess Climate Resilience in Goats Using a Holistic Approach of Skin-Based Advanced NGS Technologies

A novel study was conducted to elucidate heat-stress responses on a number of hair- and skin-based traits in two indigenous goat breeds using a holistic approach that considered a number of phenotypic and genomic variables. The two goat breeds, Kanni Aadu and Kodi Aadu, were subjected to a simulated heat-stress study using the climate chambers. Four groups consisting of six goats each (KAC, Kaani Aadu control; KAH, Kanni Aadu heat stress; KOC, Kodi Aadu control; and KOH, Kodi Aadu heat stress) were considered for the study. The impact of heat stress on caprine skin tissue along with a comparative assessment of the thermal resilience of the two goat breeds was assessed. The variables considered were hair characteristics, hair cortisol, hair follicle quantitative PCR (qPCR), sweating (sweating rate and active sweat gland measurement), skin histometry, skin-surface infrared thermography (IRT), skin 16S rRNA V3-V4 metagenomics, skin transcriptomics, and skin bisulfite sequencing. Heat stress significantly influenced the hair fiber characteristics (fiber length) and hair follicle qPCR profile (Heat-shock protein 70 (HSP70), HSP90, and HSP110). Significantly higher sweating rate, activated sweat gland number, skin epithelium, and sweat gland number (histometry) were observed in heat stressed goats. The skin microbiota was also observed to be significantly altered due to heat stress, with a relatively higher alteration being noticed in Kanni Aadu goats than in Kodi Aadi goats. Furthermore, the transcriptomics and epigenetics analysis also pointed towards the significant impact of heat stress at the cellular and molecular levels in caprine skin tissue. The higher proportion of differentially expressed genes (DEGs) along with higher differentially methylated regions (DMRs) in Kanni Aadu goats due to heat stress when compared to Kodi Aadu goats pointed towards the better resilience of the latter breed. A number of established skin, adaptation, and immune-response genes were also observed to be significantly expressed/methylated. Additionally, the influence of heat stress at the genomic level was also predicted to result in significant functional alterations. This novel study thereby highlights the impact of heat stress on the caprine skin tissue and also the difference in thermal resilience exhibited by the two indigenous goat breeds, with Kodi Aadu goats being more resilient.

Genetic studies of heat stress regulation in goat during hot climatic condition

Various direct and indirect environmental constraints have an impact on livestock performance. The physiological parameters, such as rectal temperature, heart rate, and respiratory rate, are the primary indicators of thermal stress. Under a stressed environment temperature humidity index (THI) had established as a vital measurement to identify the thermal stress in livestock. THI in association with climatic variations can define the environmental effect as stressful or comfortable for livestock. Goats are small ruminants that adapt to a wide range of ecological variations due to their anatomical and physiological characteristics. However, the productivity of animals declines at the individual level during thermal stress. Stress tolerance can be determined through genetic studies associated with at the cellular level using physiological as well as molecular approaches. Information on genetic association with thermal stress in goats is scanty, this severely affects their survival and hence productivity of livestock. The ever-increasing demand for food across the globe needs deciphering novel molecular markers as well as stress indicators that play a vital role in livestock improvement. This review represents an analysis of current knowledge of phenotypic differences during thermal stress and signifies the importance of physiological responses and their association at the cellular level in goats. The regulation of vital genes associated with thermal stress such as Aquaporins (AQP 0, 1, 2, 4, 5, 6, 8), aquaglyceroporins (AQP3, 7, 9, and 10) and super-aquaporins (AQP 11, 12); BAX inhibitors such as PERK (PKR like ER kinase), IRE 1(inositol-requiring-1); Redox regulating genes such as NOX; Transport of Na+ and K+ such as ATPase (ATP1A1) and several heat shock proteins have been implicated in heat-stress related adaptations have been elucidated. As these changes have a significant impact on production performance as well as on livestock productivity. Such efforts may help in the development of molecular markers and will assist the breeders to develop heat-tolerant goats with improved productivity.

Hyper-transcription of heat shock factors and heat shock proteins safeguard caprine cardiac cells against heat stress

The present study was undertaken to document the transcriptional abundance of heat shock factors and heat shock proteins and their role in survivability of caprine cardiac cells during heat stress. Cardiac tissues were collected from different goats (n = 6) and primary cardiac cell culture was done in an atmosphere of 5% CO₂ and 95% air at 38.5 °C. Cardiac cells accomplished 70-75% confluence after 72 h of incubation. Confluent cardiac cells were exposed to heat stress at 42 °C for 0 (control), 20, 60, 100 and 200 min. Quantitative RT-PCR for β2m (internal control), heat shock factors (HSF1, HSF2, HSF4, HSF5), heat shock proteins (HSP10, HSP40), and Caspase-3 was done and their transcriptional abundance was assessed by Pfaffl method. Transcriptional abundance of HSF1, HSF2, and HSF4 did not change at 20 min, increased (P < 0.05) from 60 to 200 min and reached zenith at 200 min of heat exposure. However, transcriptional abundance of HSF5 was gradually escalated (P < 0.05) from 20 to 200 min and registered highest at 200 min of heat exposure. Transcriptional abundance of HSP10 and HSP40 followed an similar pattern like that of HSF5. Transcriptional abundance of Caspase-3 was significantly down-regulated at 200 min of heat exposure. It could be speculated that over-expression of HSFs and HSPs might have reduced Caspase-3 expression at 200 min of heat exposure suggesting their involvement in cardiac cells survival under heat stress. Moreover, hyper-expression of HSFs and HSPs could maintain the integrity and endurance of cardiac tissues of goats under heat stress.

Genetic profiling of HSP70 gene in local Iraqi goats

Animals display numerous physiological and behavioral responses that reduce the effects of heat stress. Moreover, genetic variance is strongly associated with responses to heat stress, including variants of heat shock proteins (HSPs) that are necessary for thermoregulation and stress resistance. Herein, we performed the molecular profiling of the HSP70 gene, and its polymorphism was demonstrated as a possible factor in the stress tolerance of local Iraqi goats. A number of different mutations were found owing to seven main polymorphisms. Results indicated the occurrence of silent and missense mutations in sequences obtained for Iraqi local goats. Genetic diversity was observed in the HSP70 gene of Iraqi local goats on the basis of phylogenetic-tree analysis as some mutations occurred once whereas others occurred multiple times. The polymorphisms LC616787, LC616788, and LC616791 were combined with the reference gene in the same branch, whereas polymorphisms (LC616785 and LC616786) and (LC616789 and LC616790) met in different branches, respectively. Moreover, all studied proteins had mismatches in their three-dimensional structures. Therefore, the presence of specific genetic differences within the HSP70 gene in Iraqi goats can increase the possibility of selecting animals more suitable to various levels of stress.

Prediction models, assessment methodologies and biotechnological tools to quantify heat stress response in ruminant livestock

Livestock industries have an important role in ensuring global food security. This review discusses the importance of quantifying the heat stress response of ruminants, with an emphasis on identifying thermo-tolerant breeds. There are numerous heat stress prediction models that have attempted to quantify the response of ruminant livestock to hot climatic conditions. This review highlights the importance of investigating prediction models beyond the temperature-humidity index (THI). Furthermore, this review highlights the importance of incorporating other climatic variables when developing prediction indices to ensure the accurate prediction of heat stress in ruminants. Prediction models, particularly the heat load index (HLI) were developed to overcome the limitations of the THI by incorporating ambient temperature (AT), relative humidity (RH), solar radiation (SR) and wind speed (WS). Furthermore refinements to existing prediction models have been undertaken to account for the interactions between climatic variables and physiological traits of livestock. Specifically, studies have investigated the relationships between coat characteristics, respiration rate (RR), body temperature (BT), sweating rate, vasodilation, body weight (BW), body condition score (BCS), fatness and feed intake with climatic conditions. While advancements in prediction models have been occurring, there has also been substantial advancement in the methodologies used to quantify animal responses to heat stress. The most recent development in this field is the application of radio frequency identification (RFID) technology to record animal behaviour and various physiological responses. Rumen temperature measurements using rumen boluses and skin temperature recording using infrared thermography (IRT) are making inroads to redefine the quantification of the heat stress response of ruminants. Further, this review describes several advanced biotechnological tools that can be used to identify climate resilient breeds of ruminant livestock.