Dynamic evolution of great ape Y chromosomes

Area of Science:

• Genomics
• Evolutionary Biology
• Primatology

Background:

• The mammalian Y chromosome is crucial for male traits but is poorly understood due to its complex structure.
• Great ape Y chromosomes present an evolutionary puzzle, with gene content similarities not aligning with known ancestry.
• Understanding Y chromosome evolution is vital for studying species dispersal, especially in endangered primates.

Purpose of the Study:

• To investigate the evolutionary dynamics of Y chromosomes across all extant great ape genera.
• To resolve the apparent paradox of Y chromosome gene content similarity in great apes.
• To explore the impact of factors like sperm competition on Y chromosome evolution.

Main Methods:

• Assembly of bonobo and orangutan Y chromosomes using short and long sequencing reads.
• Alignment of newly generated Y chromosome assemblies with existing human, chimpanzee, and gorilla data.
• Analysis of sequence data, gene content, substitution rates, and chromatin interactions (Hi-C).

Main Results:

• The genus Pan (chimpanzee, bonobo) shows accelerated substitution rates and high gene death rates, linked to sperm competition.
• Great ape common ancestor likely had multicopy sequences similar to human/chimpanzee palindromes, with species-specific additions.
• Increased chromatin contacts within and between palindromic regions suggest mechanisms for gene conversion and rearrangement.

Conclusions:

• Great ape Y chromosome evolution is highly dynamic, characterized by species-specific amplifications and rearrangements.
• Sperm competition appears to be a significant driver of Y chromosome evolution in the genus Pan.
• This study provides insights into primate Y chromosome evolution and aids conservation efforts for endangered great apes.