Biology subjects

Flossmann, T.

Publications and source records attributed to Flossmann, T..

3 recordsLinked to original sources

bioRxiv2025

The chloride cotransporter NKCC1 regulates self-renewal of hippocampal neural stem cells via the transcription factor Sox11

The GABAergic-mediated depolarization plays a key role in controlling stem cell fate and neurogenesis within the dentate gyrus of the hippocampal formation. This depolarization effect is highly dependent on the balance between the chloride co-transporters NKCC1 and KCC2. It is not known how changes in NKCC1 modulate the fate of Nestin-positive stem cells (NSCs) in the hippocampus during adult neurogenesis. In our study, we demonstrate that a knockout of Nkcc1 in NSCs increase their proliferation by symmetric self-renewal and expand the stem cell pool. Using single-cell RNA sequencing, we identified Sox11 as a key transcription factor that is significantly downregulated following Nkcc1 knockout. In agreement with this finding, we found that Sox11 knockout enhances proliferation and self-renewal of NSCs, which is also marked by an increase in symmetric stem cell division. Based on these findings, we propose that altering Nkcc1 expression in NSCs shifts their fate from neurogenesis towards self-renewal via Sox11 regulation. Furthermore, we observed that NKCC1 levels decline in NSCs during aging, which correlates with a further increase in self-renewal. Our data strongly suggest that the age-related decline in NKCC1 levels promote symmetric division and self-renewal contributing to the age-dependent decrease in neurogenesis. NKCC1 via Sox11 is a key regulator of NSCs fate decision, critically balancing self-renewal and neuronal differentiation in the adult hippocampus. HighlightsNKCC1 is a key factor in regulating the Nestin-positive neural stem cell symmetric self-renewal. Sox11 is a downstream effector of NKCC1 in Nestin-positive stem cells and is involved in expansion of the stem cell pool. Aging reduces NKCC1 expression in Nestin-positive stem cells and increases their self-renewal. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=170 HEIGHT=200 SRC="FIGDIR/small/662334v1_ufig1.gif" ALT="Figure 1000"> View larger version (38K): org.highwire.dtl.DTLVardef@1babdcforg.highwire.dtl.DTLVardef@1038bfborg.highwire.dtl.DTLVardef@1db105corg.highwire.dtl.DTLVardef@10f2cde_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Chemogenetic silencing reveals presynaptic Gi/o protein-mediated inhibition of synchronized activity in the developing hippocampus in vivo

The development of neuronal circuits is an activity-dependent process. Research aimed at deciphering the learning rules governing these developmental refinements is increasingly utilizing a class of chemogenetic tools that employ Gi/o protein signaling (Gi-DREADDs) for neuronal silencing. However, their mechanisms of action and inhibitory efficacy in immature neurons with incompletely developed Gi/o signaling are poorly understood. Here, we analyze the impact of Gi/o signaling on cellular and network excitability in the neonatal hippocampus by expressing the Gi-DREADD hM4Di in telencephalic glutamatergic neurons of neonatal mice of both sexes. Using acousto-optic two-photon Ca2+ imaging, we report that activation of hM4Di leads to a complete arrest of spontaneous synchronized activity in CA1 in vitro. Electrophysiological analyses demonstrate that hM4Di-mediated silencing is not accounted for by changes in intrinsic excitability of CA1 pyramidal cells (PCs). Instead, activation of hM4Di robustly restrains synaptic glutamate release by the first postnatal week, effectively reducing recurrent excitation in CA1. In vivo, inhibition through hM4Di potently suppresses early sharp waves (eSPWs) and discontinuous oscillatory network activity in CA1 of head-fixed mice before eye opening. In summary, hM4Di dampens glutamatergic neurotransmission through a presynaptic mechanism sufficient to terminate spontaneous synchronized activity in the neonatal CA1. Our findings have implications for designing and interpreting experiments utilizing Gi-DREADDs in immature neurons and further point to a potential role of Gi/o-dependent endogenous neuromodulators in activity-dependent hippocampal development. Significance StatementRecent advances in understanding how early activity shapes developing brain circuits increasingly rely on Gi/o-dependent inhibitory chemogenetic tools (Gi-DREADDs). However, their single-cellular mechanisms and efficacy in neurons with immature Gi/o signaling are elusive. To close this gap, we analyzed the impact of the Gi-DREADD hM4Di in the neonatal murine hippocampus. We report that hM4Di does not mediate hyperpolarization or shunting but rather acts as a potent presynaptic silencer of glutamatergic neurotransmission in CA1 pyramidal cells. Presynaptic inhibition of excitation suffices to arrest spontaneous synchronized network activity in vitro and in vivo. Our findings provide novel insights into the generative mechanisms of spontaneous synchronized activity and bear relevance for applying chemogenetic silencing at early stages of brain development.

neuroscience↗

bioRxiv2020

Intraneuronal chloride accumulation via NKCC1 is not essential for hippocampal network development in vivo

NKCC1 is the primary transporter mediating chloride uptake in immature principal neurons, but its role in the development of in vivo network dynamics and cognitive abilities remains unknown. Here, we address the function of NKCC1 in developing mice using electrophysiological, optical and behavioral approaches. We report that NKCC1 deletion from telencephalic glutamatergic neurons decreases in-vitro excitatory GABA actions and impairs neuronal synchrony in neonatal hippocampal brain slices. In vivo, it has a minor impact on correlated spontaneous activity in the hippocampus and does not affect network activity in the intact visual cortex. Moreover, long-term effects of the developmental NKCC1 deletion on synaptic maturation, network dynamics and behavioral performance are subtle. Our data reveal a neural network function of depolarizing GABA in the hippocampus in vivo, but challenge the hypothesis that NKCC1 is essential for major aspects of hippocampal development.

neuroscience↗