Neonatal Hypoxia–Ischemia Causes Functional Circuit Changes in Subplate Neurons

Abstract Neonatal hypoxia–ischemia (HI) in the preterm human results in damage to subcortical developing white matter and cognitive impairments. Subplate neurons (SPNs) are among the first-born cortical neurons and are necessary for normal cerebral development. While moderate or severe HI at P1 in rats leads to SPN loss, it is unclear if HI, esp. forms not associated with overt cell loss lead to altered SPN circuits. Thus, we used two HI models with different severities in P1 rats. Cauterization of the common carotid artery (CCA) causes a largely transient and thus milder ischemia (HI-Caut) while CCA ligation causes more severe ischemia (HI-Lig). While HI-Lig caused subplate damage, HI-Caut did not cause overt histological damage on the light microscopic level. We used laser-scanning photostimulation (LSPS) in acute thalamocortical slices of auditory cortex during P5–10 to study the functional connectivity of SPNs. Both HI categories resulted in hyperconnectivity of excitatory and inhibitory circuits to SPNs. Thus, alterations on the circuit level are present in the absence of cell loss. Our results show that SPN circuits are uniquely susceptible to HI. Given the key developmental role of SPNs, our results suggest that altered SPN circuits might underlie the abnormal development of cortical function after HI.

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Unbiased Quantification of Subplate Neuron Loss following Neonatal Hypoxia-Ischemia in a Rat Model

Developmental Neuroscience ◽

10.1159/000460815 ◽

2017 ◽

Vol 39 (1-4) ◽

pp. 171-181 ◽

Cited By ~ 8

Author(s):

Alexandra Mikhailova ◽

Naveena Sunkara ◽

Patrick S. McQuillen

Keyword(s):

Brain Injury ◽

Lower Layer ◽

Cell Number ◽

Cortical Layer ◽

Rodent Model ◽

Cortical Layers ◽

Cortical Injury ◽

Neonatal Hypoxia ◽

Subplate Neurons ◽

Hypoxia Ischemia

Background: Cellular targets of neonatal hypoxia-ischemia (HI) include both oligodendrocyte and neuronal lineages with differences in the patterns of vulnerable cells depending upon the developmental stage at which the injury occurs. Injury to the developing white matter is a characteristic feature of human preterm brain injury. Data are accumulating, however, for neuronal injury in the developing cerebral cortex. In the most widely used rodent model of preterm HI brain injury, conflicting data have been reported regarding the sensitivity of subplate neurons to early neonatal HI, with some reports of selective vulnerability and others that find no increased loss of subplate neurons in comparison with other cortical layers. Methods used to identify subplate neurons and quantify their numbers vary across studies. Objective: To use recently developed cortical layer-specific markers quantified with definitive stereologic methods to determine the magnitude and specificity of subplate neuron cell loss following neonatal HI in a rodent model. Methods: Postnatal day 2 (P2) rats underwent right common carotid artery coagulation followed by 2-3 h of hypoxia (5.6% oxygen). Categorically moderately injured brains were stained with subplate and cortical layer III-V markers (Complexin3 and Foxp1, respectively) at P8 and P21 (Foxp1 only). An Optical Fractionator was used to quantify subplate and middle/lower cortical neuronal numbers and these were compared across groups (naive control, hypoxia hemisphere, and HI hemisphere). Results: Following HI at P2 in rats, the total Complexin3-expressing subplate neuron number decreases significantly in the HI hemisphere compared with naive controls or hypoxia alone (HI vs. control 26,747 ± 7,952 vs. 35,468 ± 8,029, p = 0.04; HI vs. hypoxia, 26,747 ± 7,952 vs. 40,439 ± 7,363, p = 0.003). In contrast, the total Foxp1-expressing layer III-V cell number did not differ across the 3 conditions at P8 (HI vs. control 1,195,085 ± 436,609 vs. 1,234,640 ± 178,540, p = 0.19; HI vs. hypoxia, 1,195,085 ± 436,609 vs. 1,289,195 ± 468,941, p = 0.35) and at P21 (HI vs. control 1,265,190 ± 48,089 vs. 1,195,632 ± 26,912, p = 0.19; HI vs. hypoxia, 1,265,190 ± 48,089 vs. 1,309,563 ± 41,669, p = 0.49). Conclusions: There is significant biological variability inherent in both the subplate neuron cell number and the pattern and severity of cortical injury following HI at P2 in rats. Despite this variability, the subplate neuron cell number is lower following P2 HI in animals with mild or moderate cortical injury, whereas the middle-to-lower-layer cortical neuronal number is unchanged. In more severe cases, neurons are lost from the lower cortical layers, suggesting a relative vulnerability of subplate neurons.

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Transient coupling between subplate and subgranular layers to L1 neurons before and during the critical period

10.1101/2020.05.05.077784 ◽

2020 ◽

Author(s):

Xiangying Meng ◽

Yanqing Xu ◽

Joseph P. Y. Kao ◽

Patrick O. Kanold

Keyword(s):

Similar Pattern ◽

Critical Period ◽

Laser Scanning ◽

Primary Auditory Cortex ◽

Excitatory Input ◽

Cortical Layer ◽

Cortical Circuits ◽

Inhibitory Circuits ◽

Sensory Activity ◽

Laser Scanning Photostimulation

AbstractCortical layer 1 (L1) contains a diverse population of interneurons which can modulate processing in superficial cortical layers but the intracortical sources of synaptic input to these neurons and how these inputs change over development is unknown. We here investigated the changing intracortical connectivity to L1 in primary auditory cortex (A1) in slices of mouse A1 across development using laser-scanning photostimulation. Before P10 L1 cells receive most excitatory input from within L1, L2/3, L4 and L5/6 as well as the subplate. Excitatory inputs from all layers increase and peak during P10-P16, the peak of the critical period. Inhibitory inputs followed a similar pattern. Functional circuit diversity in L1 emerges after P16. In adult, L1 neurons receive ascending inputs from superficial L2/3 and subgranular L5/6, but only few inputs from L4. A subtype of L1 neurons, NDNF+ neurons, follow a similar pattern, suggesting that transient hyperconnectivity is a universal feature of developing cortical circuits. Our results demonstrate that deep excitatory and superficial inhibitory circuits are tightly linked in early development and might provide a functional scaffold for the layers in between. These results suggest that early thalamic driven spontaneous and sensory activity in subplate can be relayed to L1 from the earliest ages on, that the critical period is characterized by high transient columnar hyperconnectivity, and that in particular circuits originating in L5/6 and subplate might play a key role.

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Non-canonical role for Lpar1-EGFP subplate neurons in early postnatal somatosensory cortex

10.1101/2020.05.12.088450 ◽

2020 ◽

Author(s):

Filippo Ghezzi ◽

Andre Marques-Smith ◽

Paul Anastasiades ◽

Daniel Lyngholm ◽

Cristiana Vagnoni ◽

...

Keyword(s):

Somatosensory Cortex ◽

Laser Scanning ◽

Columnar Structure ◽

Neuronal Population ◽

Early Postnatal Development ◽

Thalamic Input ◽

Subplate Neurons ◽

Caged Glutamate ◽

Laser Scanning Photostimulation ◽

Local Input

ABSTRACTSubplate neurons (SPNs) are a transient neuronal population shown to play a key role in nascent sensory processing relaying thalamic information to the developing cerebral cortex. However there is little understanding of how heterogeneity within this population relates to emergent function. To address this question we employed optical and electrophysiological technologies to investigate the synaptic connectivity of SPNs defined by expression of the Lpar1-EGFP transgene through the first postnatal week in primary whisker somatosensory cortex (S1BF) in mouse. Our data identify that the Lpar1-EGFP SPNs represent two morphological subtypes: (1) transient, fusiform SPNs with axons largely restricted to the subplate zone; (2) pyramidal SPNs with axon collaterals that traverse the overlying cortex to extend through the marginal zone. Laser scanning photostimulation of caged glutamate was used to determine columnar glutamatergic and GABAergic input onto both of these SPN subtypes. These experiments revealed that the former receive translaminar input from more superficial cortical layers up until the emergence of the whisker barrels (~postnatal (P)5). In contrast, pyramidal SPNs only receive local input from the adjacent subplate network at early ages but then at later ages can acquire varied input from the overlying cortex. Combined electrical stimulation of the ventral posterior nucleus of the thalamus and optogenetic activation of thalamic afferents in thalamocortical slice preparations revealed that Lpar1-EGFP SPNs only receive sparse thalamic innervation during early postnatal development. Taken together, these data reveal two components of the postnatal network that interpret sparse thalamic input to direct the emergent columnar structure of neonatal somatosensory cortex.

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Selective Vulnerability of Subplate Neurons after Early Neonatal Hypoxia-Ischemia

Journal of Neuroscience ◽

10.1523/jneurosci.23-08-03308.2003 ◽

2003 ◽

Vol 23 (8) ◽

pp. 3308-3315 ◽

Cited By ~ 233

Author(s):

Patrick S. McQuillen ◽

R. Ann Sheldon ◽

Carla J. Shatz ◽

Donna M. Ferriero

Keyword(s):

Selective Vulnerability ◽

Neonatal Hypoxia ◽

Subplate Neurons ◽

Hypoxia Ischemia

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Doublecortin in the Cerebrospinal Fluid Is a Candidate Biomarker of Neurogenesis after Neonatal Hypoxia Ischemia Brain Injury in Rats

Journal of Neurological Surgery Part A Central European Neurosurgery ◽

10.1055/s-0035-1564547 ◽

2015 ◽

Vol 76 (S 01) ◽

Author(s):

C. Bregere ◽

U. Fisch ◽

S. Lieb ◽

M. Sailer ◽

L. Chicha ◽

...

Keyword(s):

Cerebrospinal Fluid ◽

Brain Injury ◽

Neonatal Hypoxia ◽

Hypoxia Ischemia

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Brain damage caused by neonatal hypoxia-ischemia and the effects of hypothermia in severe combined immunodeficient (SCID) mice

Experimental Neurology ◽

10.1016/j.expneurol.2020.113577 ◽

2021 ◽

Vol 337 ◽

pp. 113577

Author(s):

Yuko Ogawa ◽

Emi Tanaka ◽

Yoshiaki Sato ◽

Masahiro Tsuji

Keyword(s):

Brain Damage ◽

Scid Mice ◽

Neonatal Hypoxia ◽

Hypoxia Ischemia

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Altered network properties in C9ORF72 repeat expansion cortical neurons are due to synaptic dysfunction

Molecular Neurodegeneration ◽

10.1186/s13024-021-00433-8 ◽

2021 ◽

Vol 16 (1) ◽

Author(s):

Emma M. Perkins ◽

Karen Burr ◽

Poulomi Banerjee ◽

Arpan R. Mehta ◽

Owen Dando ◽

...

Keyword(s):

Synaptic Plasticity ◽

Synaptic Vesicle ◽

Cortical Neurons ◽

Electrode Array ◽

Repeat Expansion ◽

Cortical Network ◽

Synaptic Function ◽

Network Activity ◽

Cortical Function ◽

Network Function

Abstract Background Physiological disturbances in cortical network excitability and plasticity are established and widespread in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) patients, including those harbouring the C9ORF72 repeat expansion (C9ORF72RE) mutation – the most common genetic impairment causal to ALS and FTD. Noting that perturbations in cortical function are evidenced pre-symptomatically, and that the cortex is associated with widespread pathology, cortical dysfunction is thought to be an early driver of neurodegenerative disease progression. However, our understanding of how altered network function manifests at the cellular and molecular level is not clear. Methods To address this we have generated cortical neurons from patient-derived iPSCs harbouring C9ORF72RE mutations, as well as from their isogenic expansion-corrected controls. We have established a model of network activity in these neurons using multi-electrode array electrophysiology. We have then mechanistically examined the physiological processes underpinning network dysfunction using a combination of patch-clamp electrophysiology, immunocytochemistry, pharmacology and transcriptomic profiling. Results We find that C9ORF72RE causes elevated network burst activity, associated with enhanced synaptic input, yet lower burst duration, attributable to impaired pre-synaptic vesicle dynamics. We also show that the C9ORF72RE is associated with impaired synaptic plasticity. Moreover, RNA-seq analysis revealed dysregulated molecular pathways impacting on synaptic function. All molecular, cellular and network deficits are rescued by CRISPR/Cas9 correction of C9ORF72RE. Our study provides a mechanistic view of the early dysregulated processes that underpin cortical network dysfunction in ALS-FTD. Conclusion These findings suggest synaptic pathophysiology is widespread in ALS-FTD and has an early and fundamental role in driving altered network function that is thought to contribute to neurodegenerative processes in these patients. The overall importance is the identification of previously unidentified defects in pre and postsynaptic compartments affecting synaptic plasticity, synaptic vesicle stores, and network propagation, which directly impact upon cortical function.

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Aberrant development of excitatory circuits to inhibitory neurons in the primary visual cortex after neonatal binocular enucleation

Scientific Reports ◽

10.1038/s41598-021-82679-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Rongkang Deng ◽

Joseph P. Y. Kao ◽

Patrick O. Kanold

Keyword(s):

Visual Cortex ◽

Nmda Receptors ◽

Laser Scanning ◽

Inhibitory Neurons ◽

Gabaergic Interneurons ◽

Cortical Circuits ◽

Retinal Input ◽

Layer 4 ◽

Ampa And Nmda Receptors ◽

Laser Scanning Photostimulation

AbstractThe development of GABAergic interneurons is important for the functional maturation of cortical circuits. After migrating into the cortex, GABAergic interneurons start to receive glutamatergic connections from cortical excitatory neurons and thus gradually become integrated into cortical circuits. These glutamatergic connections are mediated by glutamate receptors including AMPA and NMDA receptors and the ratio of AMPA to NMDA receptors decreases during development. Since previous studies have shown that retinal input can regulate the early development of connections along the visual pathway, we investigated if the maturation of glutamatergic inputs to GABAergic interneurons in the visual cortex requires retinal input. We mapped the spatial pattern of glutamatergic connections to layer 4 (L4) GABAergic interneurons in mouse visual cortex at around postnatal day (P) 16 by laser-scanning photostimulation and investigated the effect of binocular enucleations at P1/P2 on these patterns. Gad2-positive interneurons in enucleated animals showed an increased fraction of AMPAR-mediated input from L2/3 and a decreased fraction of input from L5/6. Parvalbumin-expressing (PV) interneurons showed similar changes in relative connectivity. NMDAR-only input was largely unchanged by enucleation. Our results show that retinal input sculpts the integration of interneurons into V1 circuits and suggest that the development of AMPAR- and NMDAR-only connections might be regulated differently.

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