Evolution of the Complex Growth Hormone Gene Cluster in Macaques

Area of Science:

• Genomics
• Evolutionary Biology
• Primate Genetics

Background:

• Higher primates exhibit a complex growth hormone (GH) gene locus, unlike other mammals.
• This locus comprises multiple GH-like genes arising from duplication and divergent evolution, expressed in the pituitary and placenta.

Purpose of the Study:

• To investigate the nature and evolution of the GH gene locus in macaques.
• To understand the expansion and ongoing evolutionary processes within this primate genus.

Main Methods:

• Analysis of genomic data from various macaque species, including Macaca fascicularis and Macaca mulatta.
• Examination of GH-like gene expression in the pituitary and placenta of Macaca fascicularis.
• Assessment of sequence change rates and substitution distributions to identify positive selection.

Main Results:

• The macaque GH gene cluster is highly variable, with 11 to 14 GH-like genes found in Macaca fascicularis and gene-number heterozygosity observed in Macaca mulatta.
• GH gene clusters in other macaque species range from 8 to 14 genes, without detected heterozygosity.
• Evidence of positive selection was identified in at least one GH-like gene (GH2), indicating adaptive biological change.

Conclusions:

• The complexity of the GH gene cluster has increased during macaque evolution via gene duplication and divergent evolution.
• These evolutionary processes are ongoing in at least two extant macaque species.
• The adaptive significance of observed changes, potentially related to endocrine function or pathogen response, requires further investigation.