SilentX: Unraveling the Rise and Fall of Meiotic Sex Chromosome Inactivation in Insects.

Objetivo

Sex chromosomes evolve from ordinary autosomes, often degenerating in the absence of recombination. This degeneration triggers the evolution of regulatory mechanisms such as dosage compensation in somatic cells and meiotic sex chromosome inactivation (MSCI) in germ cells. While dosage compensation has been extensively studied, MSCI, an epigenetic silencing of sex chromosomes during meiosis, remains poorly understood, despite its likely major role in sex chromosome evolution. MSCI has evolved multiple times across animals, but is remarkably variable in insects: some lineages retain classical MSCI, others have lost it entirely, and still others show modified or transient forms.
SilentX will exploit this diversity to uncover the origins, mechanisms, and evolutionary consequences of MSCI. Using a phylogenetically broad screen of 15 insect orders, we will map MSCI presence, dynamics, and chromatin signatures, integrating these data with X chromosome histories inferred from high-quality genomes. We will test competing hypotheses for MSCI evolution: whether it is an ancient, conserved genome-surveillance program, an adaptation to protect unpaired chromosomes, a defense against selfish genetic elements, or a resolution to sexual conflict, and identify contexts driving its loss.
Mechanistic dissection will focus on stick insects, which show strong MSCI phenotypes, conserved “ancient” X chromosome content, and experimental tractability. By combining comparative cytology, single-nucleus transcriptomics, chromatin profiling, and functional genomics, we will identify molecular players and reconstruct the sequence of events leading to X inactivation.
SilentX will generate the first comprehensive, evolutionary framework for MSCI, reveal how its loss reshapes sex chromosome content and regulation, and open new avenues for targeted, species-specific control of insect pests.