Cellular resolution maps of X chromosome inactivation: implications for neural development, function, and disease

Area of Science:

• Genetics and Epigenetics
• Neuroscience
• Mammalian Biology

Background:

• Female eutherian mammals utilize X chromosome inactivation (XCI) to epigenetically regulate gene expression from approximately 4% of the genome.
• Understanding the spatial distribution of XCI is crucial for comprehending cellular function and organismal development.

Purpose of the Study:

• To quantitatively map the topography of XCI at single-cell resolution in defined cell types.
• To investigate the spatial scales of XCI mosaicism and its implications for central nervous system (CNS) function.

Main Methods:

• Generation of female mice with X-linked, Cre-activated fluorescent reporters (GFP and tdTomato) on separate X chromosomes.
• Utilizing Cre-driver lines to activate reporters in specific cell types.
• Quantitative mapping of XCI mosaicism in CNS cell types and retinal vasculature.

Main Results:

• Defined the topographies of XCI mosaicism for multiple CNS cell types.
• Observed fluctuations in XCI mosaicism across a wide range of spatial scales, from neighboring cells to left-right body sides.
• Characterized XCI patterns in retinal vascular dysfunction in a Norrie disease model.

Conclusions:

• XCI plays a significant role in generating female-specific, stochastic diversity.
• The spatial scales of XCI variation are predicted to impact CNS function within and between individuals.
• This research provides a high-resolution map of XCI topography, essential for understanding its functional consequences.