Growth hormone and prolactin--molecular and functional evolution.

Area of Science:

• Evolutionary biology
• Molecular endocrinology
• Comparative genomics

Background:

• Growth hormone, prolactin, somatolactin, and placental lactogen form a hormone family with shared tertiary structures.
• These hormones interact with single transmembrane-domain receptors, part of the cytokine receptor superfamily utilizing the Jak-Stat pathway.

Purpose of the Study:

• To investigate the evolutionary history and functional divergence of growth hormone and prolactin families.
• To understand the co-evolution of these hormones and their receptors.

Main Methods:

• Comparative analysis of hormone and receptor gene sequences across vertebrate species.
• Phylogenetic analysis to infer evolutionary relationships and rates of change.

Main Results:

• Hormones and receptors likely arose from early vertebrate gene duplication events.
• Mammalian growth hormone and prolactin exhibit variable evolutionary rates, with accelerated episodes in specific lineages.
• Placental lactogen evolved independently multiple times from prolactin or growth hormone.
• Receptor evolution rates partially correlate with ligand changes, but functional adaptations may involve regulatory elements more than protein structure.

Conclusions:

• The growth hormone/prolactin family demonstrates complex evolutionary patterns driven by gene duplication and divergence.
• While conserved functions like growth hormone's role in postnatal growth persist, prolactin exhibits diverse, species-specific roles.
• Functional evolution is not always tightly correlated with molecular evolution, suggesting significant roles for regulatory changes.