Spermatogenesis in house mouse in a Robertsonian polymorphism zone

Area of Science:

• Genetics
• Reproductive Biology
• Evolutionary Biology

Background:

• Robertsonian (Rb) translocations are key in speciation, acting as postzygotic isolation mechanisms.
• Reduced fertility in Rb mice is linked to meiotic non-disjunction, gametogenic impairment, and sex chromosome associations.
• Quantitative histological data on Rb fusions' role in gametogenic impairment are limited.

Purpose of the Study:

• To investigate the impact of Robertsonian fusions on spermatogenesis and germ cell death in mice.
• To understand the role of Rb fusions, in both heterozygous and homozygous states, in gametogenic impairment.
• To assess the relationship between Rb fusions and reduced gene flow in mouse populations.

Main Methods:

• Histological multilevel sampling of spermatogenesis in mice from a Barcelona Rb polymorphism area.
• Analysis of four chromosomal groups: simple heterozygotes, complex heterozygotes, and homozygotes for Rb fusions.
• Evaluation of testicular morphology, seminiferous epithelium cycle stages, and spermatid:spermatocyte ratios.

Main Results:

• Mice with one to three Rb fusions (heterozygous or homozygous) exhibited significantly higher germ cell death (GCD) than control mice.
• Rb fusions, irrespective of their state (heterozygous/homozygous), are associated with increased GCD.
• Increased GCD suggests Rb fusions are a primary factor limiting gene flow between local mouse populations.

Conclusions:

• Robertsonian fusions contribute to reduced fertility and increased germ cell death in mice.
• Both heterozygous and homozygous Rb fusions negatively impact spermatogenesis.
• Rb fusions play a significant role in reproductive isolation and reduced gene flow in natural populations.