Ghrelin and MBOAT4 are lost in Serpentes

Area of Science:

• Evolutionary biology
• Comparative genomics
• Physiological adaptations

Background:

• Metabolic and energetic homeostasis are crucial for organismal survival and adaptation.
• Gene network evolution provides insights into physiological changes in different lineages.
• Ghrelin (GHRL) is a key hormone regulating appetite, food intake, and body weight.

Purpose of the Study:

• To investigate the evolutionary trajectory of the ghrelin (GHRL) hormonal system in reptiles.
• To identify specific reptile lineages where GHRL signaling has been lost.
• To correlate the loss of GHRL with metabolic and physiological adaptations.

Main Methods:

• Genomic analysis of 112 reptile species across Squamata, Testudines, Crocodilia, and Rhynchocephalia.
• Identification of GHRL gene presence/absence and MBOAT4 gene integrity.
• Comparative analysis of gene loss events and physiological traits.

Main Results:

• Independent loss of the GHRL gene was observed in snakes (32 species), chameleons (4 species), and toadhead agamas (2 species).
• The gene for the ghrelin-activating enzyme, MBOAT4, is also eroded in these same lineages.
• The loss of the GHRL/MBOAT4 system correlates with metabolic shifts, including reduced resting energy expenditure.

Conclusions:

• The ghrelin signaling pathway has been independently lost multiple times in reptiles.
• This loss is associated with adaptations for reduced energy expenditure and prolonged fasting capabilities.
• Evolutionary pressures have shaped the energy metabolism and hormonal regulation in these reptile groups.