Fourth Postnatal Week Research Articles

Testis-Specific Gene C7orf61 Is Involved in Mouse Sperm-Egg Fusion.

Chromosome 7 open reading frame 61 (C7orf 61) was a testis-specific gene, and may be involved in the process of spermatogenesis. This study aimed to investigate the expression of C7orf61 in the testis and determine its role in spermatogenesis. Reverse transcription-quantitative polymerase chain reaction, Western blot and immunofluorescence were performed to evaluate the expression characteristics of C7orf61 in mice and humans. In vitro fertilization assay was used to determine the role of the C7ORF61 protein in sperm-egg fusion. The results demonstrated that C7orf61 was a testis-specific gene; the C7ofr61 mRNA expression level sharply increased in the fourth postnatal week and gradually increased until the adult stage. The C7ORF61 protein was located throughout the subacrosomal area and close to the nucleus in both mouse and human sperm. The incubation with the C7ORF61 antibody significantly decreased the fertilization rate of mouse eggs. The present findings suggested that the C7ORF61 protein might be involved in sperm-egg fusion, and could serve as a useful target for contraceptives. However, further research is still needed to know the detailed molecularmechanismofitsrole.

Influence of chronic hypoxia on the hypoxic ventilatory response of juvenile and adult rats

Chronic hypoxia (CH) from birth attenuates the acute hypoxic ventilatory response (HVR) in rats and other mammals, but CH is often reported to augment the HVR in adult mammals. To test the hypothesis that this transition – from blunting to augmenting the HVR – occurs in the third or fourth postnatal week in rats, juvenile and adult rats were exposed to normobaric CH (12% O2) for 7 days and the HVR was assessed by whole-body plethysmography. No transition was observed, however, and the acute HVR was reduced by 61 – 85% across all ages studied. The failure to observe an augmented HVR in adult rats could not be explained by the substrain of Sprague Dawley rats used, the duration of the CH exposure, the order in which test gases were presented, the level of hypoxia used for CH and to assess the HVR, or the effects of CH on the metabolic response to hypoxia and the hypercapnic ventilatory response. A literature survey revealed several distinct patterns of ventilatory acclimatization to hypoxia (VAH) in adult rats, with most studies (77%) revealing a decrease or no change in the acute HVR after CH. In conclusion, the effects of CH on respiratory control are qualitatively similar across age groups, at least within the populations of Sprague Dawley rats used in the present study, and there does not appear to be one “typical” pattern for VAH in adult rats.

Postnatal Maturation of Membrane Potential Dynamics during in Vivo Hippocampal Ripples.

Sharp-wave ripples (SWRs) are transient high-frequency oscillations of local field potentials (LFPs) in the hippocampus and play a critical role in memory consolidation. During SWRs, CA1 pyramidal cells exhibit rapid spike sequences that often replay the sequential activity that occurred during behavior. This temporally organized firing activity gradually emerges during 2 weeks after the eye opening; however, it remains unclear how the organized spikes during SWRs mature at the intracellular membrane potential (Vm) level. Here, we recorded Vm of CA1 pyramidal cells simultaneously with hippocampal LFPs from anesthetized immature mice of either sex after the developmental emergence of SWRs. On postnatal days 16 and 17, Vm dynamics around SWRs were premature, characterized by prolonged depolarizations without either pre- or post-SWR hyperpolarizations. The biphasic hyperpolarizations, features typical of adult SWR-relevant Vm, formed by approximately postnatal day 30. This Vm maturation was associated with an increase in SWR-associated inhibitory inputs to pyramidal cells. Thus, the development of SWR-relevant inhibition restricts the temporal windows for spikes of pyramidal cells and allows CA1 pyramidal cells to organize their spike sequences during SWRs.SIGNIFICANCE STATEMENT Sharp-wave ripples (SWRs) are prominent hippocampal oscillations and play a critical role in memory consolidation. During SWRs, hippocampal neurons synchronously emit spikes with organized temporal patterns. This temporal structure of spikes during SWRs develops during the third and fourth postnatal weeks, but the underlying mechanisms are not well understood. Here, we recorded in vivo membrane potentials from hippocampal neurons in premature mice and suggest that the maturation of SWR-associated inhibition enables hippocampal neurons to produce precisely controlled spike times during SWRs.

Maturation of nucleus accumbens synaptic transmission signals a critical period for the rescue of social deficits in a mouse model of autism spectrum disorder

Social behavior emerges early in development, a time marked by the onset of neurodevelopmental disorders featuring social deficits, including autism spectrum disorder (ASD). Although social deficits are at the core of the clinical diagnosis of ASD, very little is known about their neural correlates at the time of clinical onset. The nucleus accumbens (NAc), a brain region extensively implicated in social behavior, undergoes synaptic, cellular and molecular alterations in early life, and is particularly affected in ASD mouse models. To explore a link between the maturation of the NAc and neurodevelopmental deficits in social behavior, we compared spontaneous synaptic transmission in NAc shell medium spiny neurons (MSNs) between the highly social C57BL/6J and the idiopathic ASD mouse model BTBR T+Itpr3tf/J at postnatal day (P) 4, P6, P8, P12, P15, P21 and P30. BTBR NAc MSNs display increased spontaneous excitatory transmission during the first postnatal week, and increased inhibition across the first, second and fourth postnatal weeks, suggesting accelerated maturation of excitatory and inhibitory synaptic inputs compared to C57BL/6J mice. BTBR mice also show increased optically evoked medial prefrontal cortex-NAc paired pulse ratios at P15 and P30. These early changes in synaptic transmission are consistent with a potential critical period, which could maximize the efficacy of rescue interventions. To test this, we treated BTBR mice in either early life (P4-P8) or adulthood (P60-P64) with the mTORC1 antagonist rapamycin, a well-established intervention for ASD-like behavior. Rapamycin treatment rescued social interaction deficits in BTBR mice when injected in infancy, but did not affect social interaction in adulthood.

A shift in the mechanisms controlling hippocampal engram formation during brain maturation

The ability to form precise, episodic memories develops with age, with young children only able to form gist-like memories that lack precision. The cellular and molecular events in the developing hippocampus that underlie the emergence of precise, episodic-like memory are unclear. In mice, the absence of a competitive neuronal engram allocation process in the immature hippocampus precluded the formation of sparse engrams and precise memories until the fourth postnatal week, when inhibitory circuits in the hippocampus mature. This age-dependent shift in precision of episodic-like memories involved the functional maturation of parvalbumin-expressing interneurons in subfield CA1 through assembly of extracellular perineuronal nets, which is necessary and sufficient for the onset of competitive neuronal allocation, sparse engram formation, and memory precision.

Developmental changes in brain activity of heterozygous Scn1a knockout rats.

Dravet syndrome (DS) is an infantile-onset developmental and epileptic encephalopathy characterized by an age-dependent evolution of drug-resistant seizures and poor developmental outcomes. Functional impairment of gamma-aminobutyric acid (GABA)ergic interneurons due to loss-of-function mutation of SCN1A is currently considered the main pathogenesis. In this study, to better understand the age-dependent changes in the pathogenesis of DS, we characterized the activity of different brain regions in Scn1a knockout rats at each developmental stage. We established an Scn1a knockout rat model and examined brain activity from postnatal day (P) 15 to 38 using a manganese-enhanced magnetic resonance imaging technique (MEMRI). Scn1a heterozygous knockout (Scn1a +/-) rats showed a reduced expression of voltage-gated sodium channel alpha subunit 1 protein in the brain and heat-induced seizures. Neural activity was significantly higher in widespread brain regions of Scn1a +/- rats than in wild-type rats from P19 to P22, but this difference did not persist thereafter. Bumetanide, a Na+-K+-2Cl- cotransporter 1 inhibitor, mitigated hyperactivity to the wild-type level, although no change was observed in the fourth postnatal week. Bumetanide also increased heat-induced seizure thresholds of Scn1a +/- rats at P21. In Scn1a +/- rats, neural activity in widespread brain regions increased during the third postnatal week, corresponding to approximately 6 months of age in humans, when seizures most commonly develop in DS. In addition to impairment of GABAergic interneurons, the effects of bumetanide suggest a possible contribution of immature type A gamma-aminobutyric acid receptor signaling to transient hyperactivity and seizure susceptibility during the early stage of DS. This hypothesis should be addressed in the future. MEMRI is a potential technique for visualizing changes in basal brain activity in developmental and epileptic encephalopathies.

Relationship between early nutrition and deep gray matter and lateral ventricular volumes of preterm infants at term-equivalent age

BackgroundThe survival of preterm infants has improved over the last decade, but impaired brain development leading to poor neurological outcomes is still a major comorbidity associated with prematurity. The aim of this study was to evaluate the effect of nutrition on neurodevelopment in preterm infants and identify markers for improved outcomes.MethodsTotally 67 premature infants with a gestational age of 24–34 weeks and a birth weight of 450–2085 g were included. Clinical parameters and documented diet were collected from medical records. The nutritional analysis comprised the protein, fat, carbohydrate, and energy intake during different time spans. Brain development was assessed by determining deep gray matter (DGM; basal ganglia and thalamus) and lateral ventricular (LV) volumes as measured on cerebral magnetic resonance imaging scans obtained at term-equivalent age (TEA), and potential associations between nutrition and brain volumetrics were detected by regression analysis.ResultsWe observed a negative correlation between mean daily protein intake in the third postnatal week and MRI-measured DGM volume at TEA (P = 0.007). In contrast, head circumference at a corrected age of 35 weeks gestation (P < 0.001) and mean daily fat intake in the fourth postnatal week (P = 0.004) were positively correlated with DGM volume. Moreover, mean daily carbohydrate intake in the first postnatal week (P = 0.010) and intraventricular hemorrhage (P = 0.003) were revealed as independent predictors of LV volume.ConclusionThe study emphasizes the importance of nutrition for brain development following preterm birth.

Adenosine and Astrocytes Determine the Developmental Dynamics of Spike Timing-Dependent Plasticity in the Somatosensory Cortex.

During development, critical periods of synaptic plasticity facilitate the reordering and refinement of neural connections, allowing the definitive synaptic circuits responsible for correct adult physiology to be established. The L4-L2/3 synapses in the somatosensory cortex (S1) exhibit a presynaptic form of spike timing-dependent long-term depression (t-LTD) that probably fulfills a role in synaptic refinement. This t-LTD persists until the fourth postnatal week in mice, disappearing thereafter. When we investigated the mechanisms underlying this maturation-related loss of t-LTD in either sex mouse slices, we found that it could be completely recovered by antagonizing adenosine type 1 receptors. By contrast, an agonist of A1R impeded the induction of t-LTD at P13-27. Furthermore, we found that the adenosine that mediated the loss of t-LTD at the end of the fourth week of development is most probably supplied by astrocytes. At more mature stages (P38-60), we found that the protocol used to induce t-LTD provokes t-LTP. We characterized the mechanisms underlying the induction of this form of LTP, and we found it to be expressed presynaptically, as witnessed by paired-pulse and coefficient of variation analysis. In addition, this form of presynaptic t-LTP requires the activation of NMDARs and mGlu1Rs, and the entry of Ca2+ into the postsynaptic neuron through L-type voltage-dependent Ca2+ channels. Nitric oxide is also required for t-LTP as a messenger in the postsynaptic neuron as are the adenosine and glutamate that are released in association with astrocyte signaling. These results provide direct evidence of the mechanisms that close the window of plasticity associated with t-LTD and that drive the switch in synaptic transmission from t-LTD to t-LTP at L4-L2/3 synapses, in which astrocytes play a central role.SIGNIFICANCE STATEMENT During development, critical periods of plasticity facilitate the reordering and refining of neural connections, allowing correct adult physiology to be established. The L4-L2/3 synapses in the somatosensory cortex exhibit a presynaptic form plasticity (LTD) that probably fulfills a role in synaptic refinement. It is present until the fourth postnatal week in mice, disappearing thereafter. The mechanisms that are responsible for this loss of plasticity are not clear. We describe here these mechanisms and those involved in the switch from LTD to LTP observed as the brain matures. Defining these events responsible for closing (and opening) plasticity windows may be important for brain repair, sensorial recovery, the treatment of neurodevelopmental disorders, and for educational policy.

Early and Bi-hemispheric seizure onset in a rat glioblastoma Multiforme model

GBM is the most life-threatening neurological disease with annual incidence of ∼ 5 cases per 100,000 people and a median survival of less than 15 months. Seizures are the first clinical symptoms in 40%-45% of patients with GBM and its epileptogenic mechanisms are poorly understood, largely due to the challenge to develop a clinically-relevant animal model and the unknown latent period. In this study, we used continuous video-EEG monitoring to detect the earliest interictal and ictal events in a CRISPR- IUE GBM rat model that shares pathological and clinical features with those observed in human patients. To our best knowledge, we showed for the first time that interictal epileptiform discharges emerged during early postnatal weeks and the first ictal event occurred during the fourth postnatal week. We also showed GBM animals showed independent bi-hemispheric epileptogenic events, suggesting a widespread circuitry dysregulation. Together, our work identified the temporal- and spatial frame of epileptogenic network in a highly clinically-relevant GBM animal model, paving ways for mechanistic studies at molecular, cellular and circuitry levels.

Extensive Structural Remodeling of the Axonal Arbors of Parvalbumin Basket Cells during Development in Mouse Neocortex.

Parvalbumin-containing (PV+) basket cells are specialized cortical interneurons that regulate the activity of local neuronal circuits with high temporal precision and reliability. To understand how the PV+ interneuron connectivity underlying these functional properties is established during development, we used array tomography to map pairs of synaptically connected PV+ interneurons and postsynaptic neurons from the neocortex of mice of both sexes. We focused on the axon-myelin unit of the PV+ interneuron and quantified the number of synapses onto the postsynaptic neuron, length of connecting axonal paths, and their myelination at different time points between 2 weeks and 7 months of age. We find that myelination of the proximal axon occurs very rapidly during the third and, to a lesser extent, fourth postnatal weeks. The number of synaptic contacts made by the PV+ interneuron on its postsynaptic partner meanwhile is significantly reduced to about one-third by the end of the first postnatal month. The number of autapses, the synapses that PV+ interneurons form on themselves, however, remains constant throughout the examined period. Axon reorganizations continue beyond postnatal month 2, with the postsynaptic targets of PV+ interneurons gradually shifting to more proximal locations, and the length of axonal paths and their myelin becoming conspicuously uniform per connection. These continued microcircuit refinements likely provide the structural substrate for the robust inhibitory effects and fine temporal precision of adult PV+ basket cells.SIGNIFICANCE STATEMENT The axon of adult parvalbumin-containing (PV+) interneurons is highly specialized for fast and reliable neurotransmission. It is myelinated and forms synapses mostly onto the cell bodies and proximal dendrites of postsynaptic neurons for maximal impact. In this study, we follow the development of the PV+ interneuron axon, its myelination and synapse formation, revealing a rapid sequence of axonal reorganization, myelination of the PV+ interneuron proximal axon, and pruning of almost two-thirds of the synapses in an individual connection. This is followed by a prolonged period of axon refinement and additional myelination leading to a remarkable precision of connections in the adult mouse cortex, consistent with the temporal precision and fidelity of PV+ interneuron action.

Sensitive timing of undifferentiation in oligodendrocyte progenitor cells and their enhanced maturation in primary visual cortex of binocularly enucleated mice.

Sensory experience modulates proliferation, differentiation, and migration of oligodendrocyte progenitor cells (OPCs). In the mouse primary visual cortex (V1), visual deprivation-dependent modulation of OPCs has not been demonstrated. Here, we demonstrate that undifferentiated OPCs developmentally peaked around postnatal day (P) 25, and binocular enucleation (BE) from the time of eye opening (P14-15) elevated symmetrically-divided undifferentiated OPCs in a reversible G0/G1 state even more at the bottom lamina of the cortex by reducing maturing oligodendrocyte (OL) lineage cells. Experiments using the sonic hedgehog (Shh) signaling inhibitor cyclopamine in vivo suggested that Shh signaling pathway was involved in the BE-induced undifferentiation process. The undifferentiated OPCs then differentiated within 5 days, independent of the experience, becoming mostly quiescent cells in control mice, while altering the mode of sister cell symmetry and forming quiescent as well as maturing cells in the enucleated mice. At P50, BE increased mature OLs via symmetric and asymmetric modes of cell segregation, resulting in more populated mature OLs at the bottom layer of the cortex. These data suggest that fourth postnatal week, corresponding to the early critical period of ocular dominance plasticity, is a developmentally sensitive period for OPC state changes. Overall, the visual loss promoted undifferentiation at the early period, but later increased the formation of mature OLs via a change in the mode of cell type symmetry at the bottom layer of mouse V1.

Visual deprivation induces transient upregulation of oligodendrocyte progenitor cells in the subcortical white matter of mouse visual cortex.

Sensory experience influences proliferation and differentiation of oligodendrocyte progenitor cells (OPCs). Enhanced sensorimotor experience promoted the lineage progression of OPCs and myelination in the gray matter and white matter (WM) of sensorimotor cortex. In the visual cortex, reduced experience reportedly delayed the maturation of myelination in the gray matter, but whether and how such experience alters the subcortical WM is unclear. Here we investigated if binocular enucleation from the onset of eye opening (i.e., P15) affects the cell state of OPCs in mouse primary visual cortex (V1). Proliferative cells in the WM declined nearly half over 3 days from postnatal day (P) 25. A 3-day BrdU-labeling showed gradual decline in proliferation rates from P19 to P28. Binocular enucleation resulted in an increase in the cycling state of the OPCs that were proliferated from P22 to P25 but not before or after this period. This increase in proliferative OPCs was not associated with lineage progression toward differentiated oligodendrocytes. Proliferative OPCs arose mostly due to symmetric cell division but also asymmetric formation of proliferative and quiescent OPCs. By P30, almost all the proliferated cells exited the cell cycle. Maturing oligodendrocytes among the proliferated cells increased at this age, but most of them disappeared over 25 days. The cell density of the maturing oligodendrocytes was unaffected by binocular enucleation, however. These data suggest that binocular enucleation transiently elevates proliferative OPCs in the subcortical WM of V1 during a specific period of the fourth postnatal week without subsequently affecting the number of maturing oligodendrocytes several days later.

Defining the latent period of epileptogenesis and epileptogenic zone in a focal cortical dysplasia type II (FCDII) rat model.

SummaryObjectivesFocal cortical dysplasia type II (FCDII) is one of the most common underlying pathologies in patients with drug‐resistant epilepsy. However, mechanistic understanding of FCDII fails to keep pace with genetic discoveries, primarily due to the significant challenge in developing a clinically relevant animal model. Conceptually and clinically important questions, such as the unknown latent period of epileptogenesis and the controversial epileptogenic zone, remain unknown in all experimental FCDII animal models, making it even more challenging to investigate the underlying epileptogenic mechanisms.MethodsIn this study, we used continuous video‐electroencephalography (EEG) monitoring to detect the earliest interictal and ictal events in a clustered regularly interspaced short palindromic repeats (CRISPR)‐in utero electroporation (IUE) FCDII rat model that shares genetic, pathological, and electroclinical signatures with those observed in humans. We then took advantage of in vivo local field potential (LFP) recordings to localize the epileptogenic zone in these animals.ResultsTo the best of our knowledge, we showed for the first time that epileptiform discharges emerged during the third postnatal week, and that the first seizure occurred as early as during the fourth postnatal week. We also showed that both interictal and ictal discharges are localized within the dysplastic cortex, concordant with human clinical data.SignificanceTogether, our work identified the temporal and spatial frame of epileptogenesis in a highly clinically relevant FCDII animal model, paving the way for mechanistic studies at molecular, cellular, and circuitry levels.

The Impact of Gut Microbiome on Metabolic Disorders During Catch-Up Growth in Small-for-Gestational-Age.

ObjectiveCatch-up growth (CUG) in small for gestational age (SGA) leads to increased risk of metabolic syndrome and cardiovascular diseases in adults. It remains unclear if microbiota could play an important role in CUG-SGA independent of genetic or nutritional factors. The present study explored the role of gut microbiota in, and its association with, metabolic disorders during CUG-SGA.MethodsAn SGA rat model was established by restricting food intake during pregnancy, and the rats were divided into catch-up growth (CUG-SGA) and non-catch-up growth (NCUG-SGA) groups based on body weight and length at the fourth postnatal week. High-throughput sequencing of 16S rRNA was conducted to detect the diversity and composition of the gut microbiota. Fecal short-chain fatty acids (SCFAs) were detected by gas chromatography-mass spectrometry. Transcriptome sequencing of liver tissue was performed and verified using real-time PCR. Concentrations of insulin and total cholesterol were determined using enzyme-linked immunosorbent assay.ResultsThe composition of gut microbiota in CUG-SGA rats differed from that of NCUG-SGA rats, with reduced abundance of Lactobacillus in the CUG-SGA group. The decrease in Lactobacillus was significantly associated with increased body weight and upregulated insulin and total cholesterol levels. Five SCFAs and two branched chain fatty acids were significantly higher in the CUG-SGA group than in the NCUG-SGA group. Additionally, SCFAs were positively associated with clinical indices such as weight, body mass index, insulin, and total cholesterol. Transcriptomic data revealed that insulin-like growth factor-2 expression was significantly decreased in CUG-SGA rats and was associated with a decrease in Lactobacillus bacteria.Conclusion Lactobacillus and SCFAs were associated with the metabolic disorders during CUG in SGA. Gut microbiome may play a certain role on metabolic disorders during catch-up growth in small-for-gestational-age.

Gamma activity accelerates during prefrontal development.

Gamma oscillations are a prominent activity pattern in the cerebral cortex. While gamma rhythms have been extensively studied in the adult prefrontal cortex in the context of cognitive (dys)functions, little is known about their development. We addressed this issue by using extracellular recordings and optogenetic stimulations in mice across postnatal development. We show that fast rhythmic activity in the prefrontal cortex becomes prominent during the second postnatal week. While initially at about 15 Hz, fast oscillatory activity progressively accelerates with age and stabilizes within gamma frequency range (30-80 Hz) during the fourth postnatal week. Activation of layer 2/3 pyramidal neurons drives fast oscillations throughout development, yet the acceleration of their frequency follows similar temporal dynamics as the maturation of fast-spiking interneurons. These findings uncover the development of prefrontal gamma activity and provide a framework to examine the origin of abnormal gamma activity in neurodevelopmental disorders.

Investigation of the Relationship Between Maternal Attachment and Breastfeeding Self-Efficacy and Affecting Factors in Turkish Sample

PurposeThis research aimed to investigate the factors affecting the perception of mothers about breastfeeding self-efficacy and their maternal attachment between the fourth and eighth postnatal weeks and their relation. Design and methodsThis research, which is descriptive, was conducted on 351 postpartum women between December 2017–2018. The study used the Mother Descriptive Information Form, Maternal Attachment Inventory (MAI), and the Short Form of the Breastfeeding Self-Efficacy Scale (BSES-SF). ResultsIt was found that, mothers' mean scores on the BSES-SF and MAI were affected by their educational level, the status of regular health checkups during the last pregnancy, the number of visits for health checkups during the last pregnancy, the place where they held their babies, the status of breastfeeding previous babies, prenatal breastfeeding training, the status of finding their own breast milk sufficient, the time when they first breastfed the baby, the first food the baby received, the status of being willing to breastfeed, the status of having fatigue due to breastfeeding, the planned duration of breastfeeding, the status of using additional infant formula, and the status of having a close relative or friend also breastfeeding. It was also determined that there was a low positive relationship between breastfeeding self-efficacy and maternal attachment. ConclusionsThe level of breastfeeding self-efficacy and maternal attachment status of mothers should be determined in the postpartum period, and health personnel should intervene on alterable factors that adversely affect breastfeeding self-efficacy and attachment status, especially in mothers at risk.

Effect of Early-Onset Preeclampsia on Offspring's Blood Pressure during the First Month of Life

To explore the effect of early-onset preeclampsia on the blood pressure of offspring during the first month of life. This prospective case-control study included 106 neonates of mothers with early-onset preeclampsia (developing at <34weeks of gestation) and 106 infants of normotensive mothers, matched 1-to-1 for sex and gestational age. Serial blood pressure measurements were obtained on admission, daily for the first postnatal week, and then weekly up to the fourth week of life. There were no differences in blood pressure values on admission and the first day of life between cases and controls. Conversely, infants exposed to preeclampsia had significantly higher systolic (SBP), diastolic (DBP), and mean blood pressure (MBP) on the subsequent days up to the fourth postnatal week (P<.001-.033). Multiple regression analyses with adjustment for sex, gestational age, antenatal corticosteroid use, and maternal antihypertensive medication use confirmed the foregoing findings (P<.001-.048). Repeated-measures ANOVA also identified preeclampsia as a significant determinant of trends in SBP, DBP, and MBP during the first month of life (F=16.2, P<.001; F=16.4, P<.001; and F=17.7, P<.001, respectively). Infants of mothers with early-onset preeclampsia have elevated blood pressure values throughout the neonatal period compared with infants born to normotensive mothers.

P75 Neurotrophin Receptor Activation Regulates the Timing of the Maturation of Cortical Parvalbumin Interneuron Connectivity and Promotes Juvenile-like Plasticity in Adult Visual Cortex.

By virtue of their extensive axonal arborization and perisomatic synaptic targeting, cortical inhibitory parvalbumin (PV) cells strongly regulate principal cell output and plasticity and modulate experience-dependent refinement of cortical circuits during development. An interesting aspect of PV cell connectivity is its prolonged maturation time course, which is completed only by end of adolescence. The p75 neurotrophin receptor (p75NTR) regulates numerous cellular functions; however, its role on cortical circuit development and plasticity remains elusive, mainly because localizing p75NTR expression with cellular and temporal resolution has been challenging. By using RNAscope and a modified version of the proximity ligation assay, we found that p75NTR expression in PV cells decreases between the second and fourth postnatal week, at a time when PV cell synapse numbers increase dramatically. Conditional knockout of p75NTR in single PV neurons in vitro and in PV cell networks in vivo causes precocious formation of PV cell perisomatic innervation and perineural nets around PV cell somata, therefore suggesting that p75NTR expression modulates the timing of maturation of PV cell connectivity in the adolescent cortex. Remarkably, we found that PV cells still express p75NTR in adult mouse cortex of both sexes and that its activation is sufficient to destabilize PV cell connectivity and to restore cortical plasticity following monocular deprivation in vivo Together, our results show that p75NTR activation dynamically regulates PV cell connectivity, and represent a novel tool to foster brain plasticity in adults.SIGNIFICANCE STATEMENT In the cortex, inhibitory, GABA-releasing neurons control the output and plasticity of excitatory neurons. Within this diverse group, parvalbumin-expressing (PV) cells form the larger inhibitory system. PV cell connectivity develops slowly, reaching maturity only at the end of adolescence; however, the mechanisms controlling the timing of its maturation are not well understood. We discovered that the expression of the neurotrophin receptor p75NTR in PV cells inhibits the maturation of their connectivity in a cell-autonomous fashion, both in vitro and in vivo, and that p75NTR activation in adult PV cells promotes their remodeling and restores cortical plasticity. These results reveal a new p75NTR function in the regulation of the time course of PV cell maturation and in limiting cortical plasticity.

Differential Effects of the Absence of Nkx2-3 and MAdCAM-1 on the Distribution of Intestinal Type 3 Innate Lymphoid Cells and Postnatal SILT Formation in Mice.

Seeding of leukocytes to developing lymphoid tissues in embryonic and early postnatal age and to the mucosa throughout adulthood depends on the interaction between endothelial MAdCAM-1 addressin and its cognate ligand α4β7 integrin. Nkx2-3 as a transcriptional regulator of MAdCAM-1 controls vascular patterning in visceral lymphoid tissues in mice, and has been identified as a susceptibility factor for inflammatory bowel diseases in humans, associated with lymphoid neogenesis in the inflamed intestines. The role of Nkx2-3 in the organogenesis of the solitary intestinal lymphoid tissues (SILTs) involving type 3 innate lymphoid cells (ILC3) is still unknown. Here we investigated the effect of Nkx2-3 on the postnatal distribution of intestinal ILC3s and the development of SILTs, comparing these to mice lacking MAdCAM-1, but preserving Nkx2-3. At 1 week of age small intestines (SI) contained significantly higher number of ILC3s relative to the colon, with a substantial reduction in MAdCAM-1−/− mice compared to C57BL/6 controls. One week later SI ILC3 number decreased in all genotypes, the number of colonic ILC3 of both Nkx2-3-deficient and Nkx2-3-heterozygous mice significantly increased. On the fourth postnatal week a further reduction of SI ILC3s was observed in both Nkx2-3-deficient and Nkx2-3-heterozygous mice, while in the colon the number of ILC3s showed a significant reduction in all genotypes. At 1 week of age only sporadic SILT components were present in all genotypes. By the second week mice deficient for either Nkx2-3 or MAdCAM-1 showed absence of SILT maturation compared to their relevant controls, lacking mature isolated lymphoid follicles (ILF). By the fourth week both Nkx2-3-deficient and Nkx2-3-heterozygous mice showed a similar distribution of ILFs relative to cryptopatches (CP), whereas in MAdCAM-1−/− mice CPs and immature ILFs were present, mature ILFs were scarce. Our data demonstrate that the complete absence of MAdCAM-1 partially impairs intestinal seeding of ILC3s and causes partial blockade of SILT maturation, without affecting peripheral lymph node development. In contrast, the inactivation of Nkx2-3 permits postnatal seeding, and its blocking effect on SILT maturation prevails at later stage, thus other adhesion molecules may compensate for the intestinal homing of ILC3s in the absence of MAdCAM-1.

A databank for intracellular electrophysiological mapping of the adult somatosensory cortex.

BackgroundNeurons in the supragranular layers of the somatosensory cortex integrate sensory (bottom-up) and cognitive/perceptual (top-down) information as they orchestrate communication across cortical columns. It has been inferred, based on intracellular recordings from juvenile animals, that supragranular neurons are electrically mature by the fourth postnatal week. However, the dynamics of the neuronal integration in adulthood is largely unknown. Electrophysiological characterization of the active properties of these neurons throughout adulthood will help to address the biophysical and computational principles of the neuronal integration.FindingsHere, we provide a database of whole-cell intracellular recordings from 315 neurons located in the supragranular layers (L2/3) of the primary somatosensory cortex in adult mice (9–45 weeks old) from both sexes (females, N = 195; males, N = 120). Data include 361 somatic current-clamp (CC) and 476 voltage-clamp (VC) experiments, recorded using a step-and-hold protocol (CC, N = 257; VC, N = 46), frozen noise injections (CC, N = 104) and triangular voltage sweeps (VC, 10 (N = 132), 50 (N = 146) and 100 ms (N = 152)), from regular spiking (N = 169) and fast-spiking neurons (N = 66).ConclusionsThe data can be used to systematically study the properties of somatic integration and the principles of action potential generation across sexes and across electrically characterized neuronal classes in adulthood. Understanding the principles of the somatic transformation of postsynaptic potentials into action potentials will shed light onto the computational principles of intracellular information transfer in single neurons and information processing in neuronal networks, helping to recreate neuronal functions in artificial systems.