Laminar and subcellular heterogeneity of GLAST and GLT-1 immunoreactivity in the developing postnatal mouse hippocampus.
Astrocytes express two sodium-coupled transporters, glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1), which are essential for the maintenance of low extracellular glutamate levels. We performed a comparative analysis of the laminar and subcellular expression profile of GLAST and GLT-1 in the developing postnatal mouse hippocampus by using immunohistochemistry and western blotting and employing high-resolution fluorescence microscopy. Astrocytes were identified by costaining with glial fibrillary acidic protein (GFAP) or S100β. In CA1, the density of GFAP-positive cells and GFAP expression rose during the first 2 weeks after birth, paralleled by a steady increase in GLAST immunoreactivity and protein content. Upregulation of GLT-1 was completed only at postnatal days (P) P20-25 and was thus delayed by about 10 days. GLAST staining was highest along the stratum pyramidale and was especially prominent in astrocytes at P3-5. GLAST immunoreactivity indicated no preferential localization to a specific cellular compartment. GLT-1 exhibited a laminar expression pattern from P10-15 on, with the highest immunoreactivity in the stratum lacunosum-moleculare. At the cellular level, GLT-1 immunoreactivity did not entirely cover astrocyte somata and exhibited clusters at processes. In neonatal and juvenile animals, discrete clusters of GLT-1 were also detected at perivascular endfeet. From these results, we conclude there is a remarkable subcellular heterogeneity of GLAST and GLT-1 expression in the developing hippocampus. The clustering of GLT-1 at astrocyte endfeet indicates that it might serve a specialized functional role at the blood-brain barrier during formation of the hippocampal network.
Institute of Neurobiology, Heinrich Heine University Duesseldorf, 40225, Duesseldorf, Germany.
Alexandra E
AE
Schreiner
Simone
S
Durry
Tomomi
T
Aida
Martin C
MC
Stock
Ulrich
U
Rüther
Kohichi
K
Tanaka
Christine R
CR
Rose
Karl W
KW
Kafitz
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D015153:Blotting, Western; D027341:Excitatory Amino Acid Transporter 1 / Q000378:metabolism*; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism*; D005260:Female; D005904:Glial Fibrillary Acidic Protein; D006624:Hippocampus / Q000254:growth & development* / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D015854:Up-Regulation
D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; C493396:Slc1a2 protein, mouse; C493393:Slc1a3 protein, mouse; C528900:glial fibrillary astrocytic protein, mouse
EAAT; GFAP, S100β; astrocyte; perivascular endfeet