Faster-X adaptive protein evolution in house mice

Area of Science:

• Evolutionary genetics
• Genomics
• Speciation research

Background:

• The X chromosome's significant role in reproductive isolation and speciation is a long-standing question.
• The faster-X hypothesis posits higher adaptive evolution rates for X-linked genes due to recessive mutations.

Purpose of the Study:

• To compare adaptive evolution rates between autosomal and X-linked genes.
• To investigate the influence of tissue-specific gene expression on adaptive evolution.
• To explore the role of meiotic sex chromosome inactivation (MSCI) in X-linked adaptive evolution.

Main Methods:

• Analysis of genome-wide nucleotide polymorphism data in Mus musculus castaneus.
• Comparison of nucleotide divergence with Mus famulus and Rattus norvegicus.
• Assessment of adaptive evolution rates for autosomal and X-linked protein-coding genes.

Main Results:

• X-linked loci exhibit significantly faster adaptive evolution compared to autosomal loci.
• Genes with expression in male-specific tissues show a pronounced faster-X effect.
• X-linked genes escaping MSCI during spermatogenesis display rapid adaptive evolution.

Conclusions:

• Faster-X adaptive evolution is supported, potentially driven by recessive mutations or X chromosome gene content affecting male function.
• Findings provide insights into the X chromosome's substantial impact on speciation processes.