MHC class I molecules are present both pre- and postsynaptically in the visual cortex during postnatal development...

Area of Science:

• Neuroscience
• Immunology
• Developmental Biology

Background:

• Immune molecules, including Major Histocompatibility Complex class I (MHCI), are increasingly recognized for their roles in brain development, function, and plasticity.
• MHCI proteins are expressed in the central nervous system and influence visual pathway refinement and are implicated in neurodevelopmental disorders like schizophrenia and autism.
• Understanding how MHCI molecules regulate cortical connections requires detailed knowledge of their spatial and temporal distribution during development.

Purpose of the Study:

• To investigate the spatial and temporal distribution of MHCI proteins in the developing rat visual cortex.
• To determine the subcellular localization of MHCI proteins at different developmental stages.

Main Methods:

• Utilized a pan-specific antibody for MHCI variants in biochemical and immunohistochemical analyses.
• Employed pre- and postembedding immunogold electron microscopy (EM) to examine protein localization at the synapse.

Main Results:

• MHCI proteins are expressed in the rat visual cortex across all examined ages, from synaptogenesis through adulthood.
• MHCI protein abundance peaked during early postnatal development, decreasing in later stages of plasticity and adulthood.
• Electron microscopy revealed MHCI proteins localized to both presynaptic and postsynaptic compartments, often within the postsynaptic density and near synaptic vesicles.

Conclusions:

• MHCI proteins are present throughout the visual cortex during key developmental periods and adulthood.
• Contrary to previous assumptions, MHCI molecules are found on both sides of the synapse.
• These findings propose a novel model where MHCI molecules regulate mammalian visual cortex connectivity pre- and postsynaptically across development.