Intermediate progenitors (IPs) amplify the production of pyramidal neurons, but their role in selective genesis of cortical layers or neuronal subtypes remains unclear. Using genetic lineage tracing ...in mice, we find that IPs destined to produce upper cortical layers first appear early in corticogenesis, by embryonic day 11.5. During later corticogenesis, IP laminar fates are progressively limited to upper layers. We examined the role of Tbr2, an IP-specific transcription factor, in laminar fate regulation using Tbr2 conditional mutant mice. Upon Tbr2 inactivation, fewer neurons were produced by immediate differentiation and laminar fates were shifted upward. Genesis of subventricular mitoses was, however, not reduced in the context of a Tbr2-null cortex. Instead, neuronal and laminar differentiation were disrupted and delayed. Our findings indicate that upper-layer genesis depends on IPs from many stages of corticogenesis and that Tbr2 regulates the tempo of laminar fate implementation for all cortical layers.
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•Intermediate progenitors (IPs) generate all types of cortical projection neurons•A subset of early IPs produces upper-layer neurons•Projection neuron laminar fates are dysregulated in the Tbr2-deficient cortex•Tbr2 is mainly necessary for differentiation, not genesis, of IPs
The role of intermediate progenitors (IPs) in corticogenesis has been unclear. Mihalas et al. show that early IP cohorts produce lower- and upper-layer neurons and that Tbr2 is required to regulate differentiation, not genesis, of IPs.
Areas and layers of the cerebral cortex are specified by genetic programs that are initiated in progenitor cells and then, implemented in postmitotic neurons. Here, we report that Tbr1, a ...transcription factor expressed in postmitotic projection neurons, exerts positive and negative control over both regional (areal) and laminar identity. Tbr1 null mice exhibited profound defects of frontal cortex and layer 6 differentiation, as indicated by down-regulation of gene-expression markers such as Bcl6 and Cdh9. Conversely, genes that implement caudal cortex and layer 5 identity, such as Bhlhb5 and Fezf2, were up-regulated in Tbr1 mutants. Tbr1 implements frontal identity in part by direct promoter binding and activation of Auts2, a frontal cortex gene implicated in autism. Tbr1 regulates laminar identity in part by downstream activation or maintenance of Sox5, an important transcription factor controlling neuronal migration and corticofugal axon projections. Similar to Sox5 mutants, Tbr1 mutants exhibit ectopic axon projections to the hypothalamus and cerebral peduncle. Together, our findings show that Tbr1 coordinately regulates regional and laminar identity of postmitotic cortical neurons.
The cortical area map is initially patterned by transcription factor (TF) gradients in the neocortical primordium, which define a “protomap” in the embryonic ventricular zone (VZ). However, ...mechanisms that propagate regional identity from VZ progenitors to cortical plate (CP) neurons are unknown. Here we show that the VZ, subventricular zone (SVZ), and CP contain distinct molecular maps of regional identity, reflecting different gene expression gradients in radial glia progenitors, intermediate progenitors, and projection neurons, respectively. The “intermediate map” in the SVZ is modulated by Eomes (also known as Tbr2), a T-box TF. Eomes inactivation caused rostrocaudal shifts in SVZ and CP gene expression, with loss of corticospinal axons and gain of corticotectal projections. These findings suggest that cortical areas and connections are shaped by sequential maps of regional identity, propagated by the Pax6 → Eomes → Tbr1 TF cascade. In humans, PAX6 , EOMES , and TBR1 have been linked to intellectual disability and autism.
Epigenetic factors (EFs) regulate multiple aspects of cerebral cortex development, including proliferation, differentiation, laminar fate, and regional identity. The same neurodevelopmental processes ...are also regulated by transcription factors (TFs), notably the Pax6→ Tbr2→ Tbr1 cascade expressed sequentially in radial glial progenitors (RGPs), intermediate progenitors, and postmitotic projection neurons, respectively. Here, we studied the EF landscape and its regulation in embryonic mouse neocortex. Microarray and
hybridization assays revealed that many EF genes are expressed in specific cortical cell types, such as intermediate progenitors, or in rostrocaudal gradients. Furthermore, many EF genes are directly bound and transcriptionally regulated by Pax6, Tbr2, or Tbr1, as determined by chromatin immunoprecipitation-sequencing and gene expression analysis of TF mutant cortices. Our analysis demonstrated that Pax6, Tbr2, and Tbr1 form a direct feedforward genetic cascade, with direct feedback repression. Results also revealed that each TF regulates multiple EF genes that control DNA methylation, histone marks, chromatin remodeling, and non-coding RNA. For example, Tbr1 activates
and
to promote the formation of non-canonical Polycomb repressive complex 1 (PRC1). Also, Pax6, Tbr2, and Tbr1 collectively drive massive changes in the subunit isoform composition of BAF chromatin remodeling complexes during differentiation: for example, a novel switch from
(Baf40c) to
(Baf40a), the latter directly activated by Tbr2. Of 11 subunits predominantly in neuronal BAF, 7 were transcriptionally activated by Pax6, Tbr2, or Tbr1. Using EFs, Pax6→ Tbr2→ Tbr1 effect persistent changes of gene expression in cell lineages, to propagate features such as regional and laminar identity from progenitors to neurons.
Previous studies demonstrated specific expression of transcription factor Tbr2 in unipolar brush cells (UBCs) of the cerebellum during development and adulthood. To further study UBCs and the role of ...Tbr2 in their development we examined UBC morphology in transgenic mouse lines (reporter and lineage tracer) and also examined the effects of Tbr2 deficiency in
(MGI:
) conditional knock-out (cKO) mice. In
reporter and lineage tracer cerebellum, UBCs exhibited more complex morphologies than previously reported including multiple dendrites, bifurcating dendrites, and up to four dendritic brushes. We propose that "dendritic brush cells" (DBCs) may be a more apt nomenclature. In
cKO cerebellum, mature UBCs were completely absent. Migration of UBC precursors from rhombic lip to cerebellar cortex and other nuclei was impaired in
cKO mice. Our results indicate that UBC migration and differentiation are sensitive to Tbr2 deficiency. To investigate whether UBCs develop similarly in humans as in rodents, we studied Tbr2 expression in mid-gestational human cerebellum. Remarkably, Tbr2
UBC precursors migrate along the same pathways in humans as in rodent cerebellum and disperse to create the same "fountain-like" appearance characteristic of UBCs exiting the rhombic lip.
The Breit frame provides a natural frame to analyze lepton–proton scattering events. In this reference frame, the parton model hard interactions between a quark and an exchanged boson defines the ...coordinate system such that the struck quark is back-scattered along the virtual photon momentum direction. In Quantum Chromodynamics (QCD), higher order perturbative or non-perturbative effects can change this picture drastically. As Bjorken-
x
decreases below one half, a rather peculiar event signature is predicted with increasing probability, where no radiation is present in one of the two Breit-frame hemispheres and all emissions are to be found in the other hemisphere. At higher orders in
α
s
or in the presence of soft QCD effects, predictions of the rate of these events are far from trivial, and that motivates measurements with real data. We report on the first observation of the empty current hemisphere events in electron–proton collisions at the HERA collider using data recorded with the H1 detector at a center-of-mass energy of 319 GeV. The fraction of inclusive neutral-current DIS events with an empty hemisphere is found to be
0.0112
±
3.9
%
stat
±
4.5
%
syst
±
1.6
%
mod
in the selected kinematic region of
150
<
Q
2
<
1500
GeV
2
and inelasticity
0.14
<
y
<
0.7
. The data sample corresponds to an integrated luminosity of 351.1 pb
-
1
, sufficient to enable differential cross section measurements of these events. The results show an enhanced discriminating power at lower Bjorken-
x
among different Monte Carlo event generator predictions.
For application in broiler production, we developed a multispecies (MSPB) and a chicken-specific (CSPB) probiotic preparation in fluid form. The MSPB contained different probiotic species of human ...origin, whereas the CSPB consisted of 7 Lactobacillus species isolated from the digestive tract of chickens. In a field trial with broilers, MSPB treatment resulted in a slight increase (by 1.84%) in broiler productivity based on an index taking into account daily weight gain, feed efficiency, and mortality. The CSPB treatment reduced mortality in 2 subsequent field trials and raised productivity by 2.94 and 8.70%. In a controlled trial with broilers showing a high index of productivity, probiotic treatment further raised productivity by 3.72%. Based on the present 4 studies in combination with 9 studies published earlier, it is suggested that with higher productivity rates of the broilers the effect of probiotics becomes smaller.
It has become increasingly clear that desertification can only be tackled through a multi-disciplinary approach that not only involves scientists but also stakeholders. In the DESIRE project such an ...approach was taken. As a first step, a conceptual framework was developed in which the factors and processes that may lead to land degradation and desertification were described. Many of these factors do not work independently, but can reinforce or weaken one another, and to illustrate these relationships sustainable management and policy feedback loops were included. This conceptual framework can be applied globally, but can also be made site-specific to take into account that each study site has a unique combination of bio-physical, socio-economic and political conditions. Once the conceptual framework was defined, a methodological framework was developed in which the methodological steps taken in the DESIRE approach were listed and their logic and sequence were explained. The last step was to develop a concrete working plan to put the project into action, involving stakeholders throughout the process. This series of steps, in full or in part, offers explicit guidance for other organizations or projects that aim to reduce land degradation and desertification.
P/Q-type voltage-gated calcium channels (Ca(v)2.1) play critical presynaptic and postsynaptic roles throughout the nervous system and have been implicated in a variety of neurological disorders. Here ...we report that mice with a genetic ablation of the Ca(v)2.1 pore-forming α(1A) subunit (α(1A)⁻/⁻) encoded by CACNA1a (Jun et al., 1999) suffer during postnatal development from increasing breathing disturbances that lead ultimately to death. Breathing abnormalities include decreased minute ventilation and a specific loss of sighs, which was associated with lung atelectasis. Similar respiratory alterations were preserved in the isolated in vitro brainstem slice preparation containing the pre-Bötzinger complex. The loss of Ca(v)2.1 was associated with an alteration in the functional dependency on N-type calcium channels (Ca(v)2.2). Blocking N-type calcium channels with conotoxin GVIA had only minor effects on respiratory activity in slices from control (CT) littermates, but abolished respiratory activity in all slices from α(1A)⁻/⁻ mice. The amplitude of evoked EPSPs was smaller in inspiratory neurons from α(1A)⁻/⁻ mice compared with CTs. Conotoxin GVIA abolished all EPSPs in inspiratory neurons from α(1A)⁻/⁻ mice, while the EPSP amplitude was reduced by only 30% in CT mice. Moreover, neuromodulation was significantly altered as muscarine abolished respiratory network activity in α(1A)⁻/⁻ mice but not in CT mice. We conclude that excitatory synaptic transmission dependent on N-type and P/Q-type calcium channels is required for stable breathing and sighing. In the absence of P/Q-type calcium channels, breathing, sighing, and neuromodulation are severely compromised, leading to early mortality.
Increasing wildfire frequency in the Mediterranean Basin could affect future plant-soil–water-dynamics. The capacity of soils to retain water is a key parameter affecting plant post-fire ...regeneration. Yet, few research has looked at how different soil properties related to water retention is affected by increasing wildfire frequency. This study aimed at understanding the relationship between wildfire frequency, soil–water-related properties and the dynamics of surface water in soils. To this, after a 2012-summer wildfire in Portugal, three sets of three replicate maritime pine stands with contrasted wildfire frequency were selected (0
vs.
1
vs
. 4 fires since 1975). At each of the nine study sites, three re-sprouter shrubs and neighbouring bare soil were chosen (54 microsites). There, soil cover, soil–water retention curves and surface (0–5 cm) soil–water-related properties (texture, bulk density, organic matter content, soil moisture, soil surface water repellency) were monitored for one year. Furthermore, records of post-fire soil moisture dynamics were analysed continuously using 72 probes installed at 2.5 and 7.5 cm depth. The hillslopes affected by 1 fire showed higher plant recovery than the 4 fires hillslopes. During the dry season, the threshold for water stress was reached 17 days sooner in the 4 fires hillslopes, and also 10 days sooner on bare microsites. Periods of plant water stress were longer and bare soil patches size bigger. The increase in wildfire frequency promoted high soil organic matter contents but less available water content, stressing the importance of soil organic matter quality characterization in water-related properties.
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