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Updated: May 9, 2026
Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates
Published on: January 30, 2014
Adaptive phenotype of microglial cells during the normal postnatal development of the somatosensory "Barrel" cortex
Isabelle Arnoux1, Maki Hoshiko, Léo Mandavy
1Inserm, U603, Paris, France; CNRS UMR, 8154, Paris, France; Paris Descartes University, Paris, France.
Abstract:
Accumulative evidence indicates that microglial cells influence the normal development of central nervous system (CNS) synapses. Yet, the functional properties of microglia in relation with synapse development remain unclear. We recently showed that in layer 4 of the whisker-related barrel field of the mouse somatosensory cortex, microglial cells are recruited only after postnatal day (P)5 in the center of the barrels where thalamo-cortical synapses are concentrated and begin their maturation. In the present study, we analyzed the phenotype of microglia during this developmental process. We show that between P5 and P7 microglial cells acquire a more ramified morphology with a smaller soma, they express classical markers of microglia (Iba1, CD11b, and CD68) but never markers of activation (Mac-2 and MHCII) and rarely the proliferation marker Ki67. Electrophysiological recordings in acute cortical slices showed that at P5 a proportion of layer 4 microglia transiently express voltage-dependant potassium currents of the delayed rectifier family, mostly mediated by Kv1.3 subunits, which are usually expressed by activated microglia under pathological conditions. This proportion of cells with rectifying properties doubles between P5 and P6, in concomitance with the beginning of microglia invasion of the barrel centers. Finally, analysis of the responses mediated by purinergic receptors indicated that a higher percentage of rectifying microglia expressed functional P2Y6 and P2Y12 receptors, as compared with nonrectifying cells, whereas all cells expressed functional P2X7 receptors. Our results indicate that during normal cortical development distinct microglia properties mature differentially, some of them being exquisitely influenced by the local environment of the maturating neuronal network.
Insights
Microglia in the developing mouse cortex exhibit unique functional properties, including transient potassium currents and purinergic receptor expression, influencing synapse maturation. These distinct microglial characteristics are shaped by their local environment during neural development.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- Microglial cells are crucial for central nervous system (CNS) synapse development.
- The precise functional roles of microglia in synapse maturation remain largely undefined.
- Microglia are recruited to layer 4 of the mouse somatosensory cortex after postnatal day 5 (P5) to support synapse maturation.
Purpose of the Study:
- To investigate the phenotypic and functional properties of microglia during early postnatal cortical development.
- To understand how microglial characteristics change in relation to the maturation of thalamo-cortical synapses.
- To identify specific molecular and electrical properties of microglia during this critical developmental window.
Main Methods:
- Analysis of microglial morphology and expression of key markers (Iba1, CD11b, CD68, Mac-2, MHCII, Ki67) in postnatal day 5-7 (P5-P7) mouse cortex.
- Electrophysiological recordings in acute cortical slices to assess microglial ion channel activity, specifically delayed rectifier potassium currents (Kv1.3).
- Investigation of purinergic receptor (P2Y6, P2Y12, P2X7) function in microglia using electrophysiology and response analysis.
Main Results:
- Between P5 and P7, microglia adopted a more ramified morphology and expressed standard microglial markers without activation markers.
- A subset of layer 4 microglia transiently expressed voltage-dependent potassium currents (Kv1.3) starting at P5, with this proportion doubling by P6.
- Rectifying microglia showed higher expression of functional P2Y6 and P2Y12 receptors compared to non-rectifying cells, while all expressed P2X7 receptors.
Conclusions:
- Microglial cells display distinct, differentially maturing properties during normal cortical development.
- The expression of Kv1.3 potassium currents and specific purinergic receptors in microglia is influenced by the local microenvironment of the developing neuronal network.
- These findings highlight a dynamic role for microglia in shaping neural circuit maturation through environment-dependent functional specialization.
