Clock Genes Expression in Peripheral Leukocytes and Plasma Melatonin Daily Rhythm in Horses.

The research article investigates the expression of clock genes in peripheral leukocytes in horses. The study found that these clock genes, which regulate daily physiological and behavioral rhythms, display daily cycles in their expression, which are correlated with the oscillations of the hormone melatonin.

Methodology

• The study involved 10 Italian Saddle gelding horses aged between 9 to 11 years and weighing approximately 475 Kg.
• These horses were housed individually, under natural photoperiod and environmental temperature conditions.
• Blood samples were collected from the horses at intervals of 4 hours over a period of 48 hours. This was achieved by cannulation of the left jugular furrow of each horse, allowing for the collection of blood samples into heparinized tubes and PAX gene Blood RNA Tubes.

Data Collection and Analysis

• The blood samples collected in the heparinized tubes were used to assess the concentration of the hormone melatonin by means of a radioimmunoassay. Melatonin is commonly measured in studies of circadian rhythms as its concentration in the blood follows a daily cycle, increasing during the night and decreasing during the day.
• The blood samples taken into the PAX gene Blood RNA Tubes allowed for genomic research and specifically, were used to assess the expression of the so-called ‘clock genes’ (Bmal1, Cry 1, Per 1, Per 2, and Per 3) through a real-time RT-quantitative polymerase chain reaction (RTqPCR).
• All tested genes – except for Clock – were found to have daily rhythmicity in their expression in the peripheral blood of horses. This suggests that these genes are part of the ‘molecular clock’ that drives the daily rhythms in physiology and behavior in horses.

Observations and Conclusions

• There was a well-established daily rhythm in the concentration of melatonin in the horses’ blood, with the concentration peaking during the night (acrophase) at approximately half past nine in the evening on both days.
• The expression of two clock genes, Bmal1 and Per 2, was found to correlate with the daily rhythm of melatonin concentration. Notably, the peak of the daily cycle in the expression of these genes (their acrophase) occurred about 3 hours earlier than the acrophase of melatonin concentration.
• This research supports the idea that a cyclic transcription of clock genes is present in the peripheral leukocytes (a type of white blood cell) in horses. However, more research is needed to understand the full implications of these findings for horse health and wellbeing, and to investigate why the expression of the Clock gene does not display daily rhythmicity.