Postnatal development of the molecular complex underlying astrocyte polarization

Area of Science:

• Neuroscience
• Cell Biology
• Developmental Biology

Background:

• Astrocytes are polarized cells vital for brain function, with specialized endfeet interacting with microvessels and synapses.
• Loss of astrocyte polarization is linked to neurological diseases like epilepsy, Alzheimer's, and stroke.
• The mechanisms driving astrocyte polarization in vivo remain largely unknown.

Purpose of the Study:

• To investigate the developmental profile of the endfoot-basal lamina junctional complex (EBJC) in the mouse brain.
• To understand the temporal sequence of EBJC component assembly during postnatal development.
• To identify potential roles of extracellular matrix (ECM) in establishing astrocyte polarization.

Main Methods:

• Light microscopic and high-resolution immunogold cytochemistry.
• Quantitative reverse transcription PCR (RT-PCR).
• Western blotting and quantitative immunoblot analyses.

Main Results:

• The EBJC is established after the first postnatal week.
• Extracellular matrix proteins, laminin and agrin, are expressed earlier, peaking at postnatal day 7 (P7).
• Aquaporin-4 (AQP4), α-syntrophin, and Kir4.1 expression increase towards adulthood, following ECM component appearance.

Conclusions:

• The extracellular matrix plays an instructive role in establishing astrocyte polarization during postnatal development.
• Distinct ontogenic profiles of EBJC members suggest a sequential assembly process.
• Understanding EBJC development is crucial for exploring its involvement in neurological diseases.