NKCC1 knockdown decreases neuron production through GABA(A)-regulated neural progenitor proliferation and delays dendrite development

• Published in: The Journal of neuroscience Vol. 32; no. 39; pp. 13630 - 13638
• Main Authors: Young, Stephanie Z, Taylor, M Morgan, Wu, Sharon, Ikeda-Matsuo, Yuri, Kubera, Cathryn, Bordey, Angélique
• Format: Journal Article
• Language: English
• Published: United States 26-09-2012
• Subjects: Age Factors; Analysis of Variance; Animals; Animals, Newborn; Calcium - metabolism; Cell Count; Cell Differentiation - drug effects; Cell Differentiation - physiology; Cell Proliferation - drug effects; Cells, Cultured; Cerebral Ventricles - cytology; Cerebral Ventricles - growth & development; Dendrites - drug effects; Dendrites - physiology; Egtazic Acid - analogs & derivatives; Egtazic Acid - metabolism; Electroporation; Female; GABA Modulators - pharmacology; GABA-A Receptor Agonists - pharmacology; Green Fluorescent Proteins - genetics; In Vitro Techniques; Ki-67 Antigen - metabolism; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Male; Mice; Muscimol - pharmacology; Neural Stem Cells; Neurons - cytology; Neurons - drug effects; Neurons - physiology; Olfactory Bulb - cytology; Patch-Clamp Techniques; Pentobarbital - pharmacology; Receptors, GABA-A - metabolism; Red Fluorescent Protein; RNA, Small Interfering - genetics; RNA, Small Interfering - metabolism; Sodium-Potassium-Chloride Symporters - deficiency; Solute Carrier Family 12, Member 2; SOXB1 Transcription Factors - metabolism; Transfection
• DOI: 10.1523/JNEUROSCI.2864-12.2012
• EISSN: 1529-2401
• ISSN: 0270-6474

Signaling through GABA(A) receptors controls neural progenitor cell (NPC) development in vitro and is altered in schizophrenic and autistic individuals. However, the in vivo function of GABA(A) signaling on neural stem cell proliferation, and ultimately neurogenesis, remains unknown. To examine GABA(A) function in vivo, we electroporated plasmids encoding short-hairpin (sh) RNA against the Na-K-2Cl cotransporter NKCC1 (shNKCC1) in NPCs of the neonatal subventricular zone in mice to reduce GABA(A)-induced depolarization. Reduced GABA(A) depolarization identified by a loss of GABA(A)-induced calcium responses in most electroporated NPCs led to a 70% decrease in the number of proliferative Ki67(+) NPCs and a 60% reduction in newborn neuron density. Premature loss of GABA(A) depolarization in newborn neurons resulted in truncated dendritic arborization at the time of synaptic integration. However, by 6 weeks the dendritic tree had partially recovered and displayed a small, albeit significant, decrease in dendritic complexity but not total dendritic length. To further examine GABA(A) function on NPCs, we treated animals with a GABA(A) allosteric agonist, pentobarbital. Enhancement of GABA(A) activity in NPCs increased the number of proliferative NPCs by 60%. Combining shNKCC1 and pentobarbital prevented the shNKCC1 and the pentobarbital effects on NPC proliferation, suggesting that these manipulations affected NPCs through GABA(A) receptors. Thus, dysregulation in GABA(A) depolarizing activity delayed dendritic development and reduced NPC proliferation resulting in decreased neuronal density.