Susana Vaz Nery

Sonic Hedgehog is required for progenitor cell maintenance in telencephalic stem cell niches

To directly test the requirement for hedgehog signaling in the telencephalon from early neurogenesis, we examined conditional null alleles of both the Sonic hedgehog and Smoothened genes. While the removal of Shh signaling in these animals resulted in only minor patterning abnormalities, the number of neural progenitors in both the postnatal subventricular zone and hippocampus was dramatically reduced. In the subventricular zone, this was partially attributable to a marked increase in programmed cell death. Consistent with Hedgehog signaling being required for the maintenance of stem cell niches in the adult brain, progenitors from the subventricular zone of floxed Smo animals formed significantly fewer neurospheres. The loss of hedgehog signaling also resulted in abnormalities in the dentate gyrus and olfactory bulb. Furthermore, stimulation of the hedgehog pathway in the mature brain resulted in elevated proliferation in telencephalic progenitors. These results suggest that hedgehog signaling is required to maintain progenitor cells in the postnatal telencephalon.

The caudal ganglionic eminence is a source of distinct cortical and subcortical cell populations

During development, the mammalian ventral telencephalon is comprised of three major proliferative zones: the medial (MGE), lateral (LGE) and caudal (CGE) ganglionic eminences. Through gene expression studies, in vitro migration assays, genetic mutant analysis and in vivo fate mapping in mice, we found that the CGE is a progenitor region that is distinct from both the MGE and LGE. Notably, CGE cells showed a unique in vivo pattern of migration, and the CGE contributed cells to nuclei distinct from those populated by the MGE and LGE. Moreover, we report that the migratory fate of cells from the CGE is intrinsically determined by embryonic day 13.5 (E13.5). Together, these results provide the first insights into the development and fate of the CGE.

The Temporal and Spatial Origins of Cortical Interneurons Predict Their Physiological Subtype

Interneurons of the cerebral cortex represent a heterogeneous population of cells with important roles in network function. At present, little is known about how these neurons are specified in the developing telencephalon. To explore whether this diversity is established in the early progenitor populations, we conducted in utero fate-mapping of the mouse medial and caudal ganglionic eminences (MGE and CGE, respectively), from which most cortical interneurons arise. Mature interneuron subtypes were assessed by electrophysiological and immunological analysis, as well as by morphological reconstruction. At E13.5, the MGE gives rise to fast-spiking (FS) interneurons, whereas the CGE generates predominantly regular-spiking interneurons (RSNP). Later at E15.5, the CGE produces RSNP classes distinct from those generated from the E13.5 CGE. Thus, we provide evidence that the spatial and temporal origin of interneuron precursors in the developing telencephalic eminences predicts the intrinsic physiological properties of mature interneurons.

Telencephalic cells take a tangent: non-radial migration in the mammalian forebrain

During development of the mammalian telencephalon, cells migrate via diverse pathways to reach their final destinations. In the developing neocortex, projection neurons are generated from cells that migrate radially from the underlying ventricular zone. In contrast, subsets of cells that populate the ventral piriform cortex and olfactory bulb reach these sites by migrating long distances. Additionally, it has been recently established that cells migrate tangentially from the ventral ganglionic eminences to the developing cortex. These tangentially migrating cells are a significant source of cortical interneurons and possibly other cell types such as oligodendrocytes. Here we summarize the known routes of migration in the developing telencephalon, with a particular focus on tangential migration. We also review recent genetic and transplantation studies that have given greater insight into the understanding of these processes and the molecular cues that may guide these migrating cells.

Fibroblast Growth Factor Receptor Signaling Promotes Radial Glial Identity and Interacts with Notch1 Signaling in Telencephalic Progenitors

The Notch and fibroblast growth factor (FGF) pathways both regulate cell fate specification during mammalian neural development. We have shown previously that Notch1 activation in the murine forebrain promotes radial glial identity. This result, together with recent evidence that radial glia can be progenitors, suggested that Notch1 signaling might promote progenitor and radial glial character simultaneously. Consistent with this idea, we found that in addition to promoting radial glial character in vivo, activated Notch1 (ActN1) increased the frequency of embryonic day 14.5 (E14.5) ganglionic eminence (GE) progenitors that grew into neurospheres in FGF2. Constitutive activation of C-promoter binding factor (CBF1), a Notch pathway effector, also increased neurosphere frequency in FGF2, suggesting that the effect of Notch1 on FGF responsiveness is mediated by CBF1. The observation that ActN1 promoted FGF responsiveness in telencephalic progenitors prompted us to examine the effect of FGF pathway activation in vivo. We focused on FGFR2 because it is expressed in radial glia in the GEs where ActN1 increases FGF2 neurosphere frequency, but not in the septum where it does not. Like ActN1, activated FGFR2 (ActFGFR2) promoted radial glial character in vivo. However, unlike ActN1, ActFGFR2 did not enhance neurosphere frequency at E14.5. Additional analysis demonstrated that, unexpectedly, neither ActFGFR2 nor ActFGFR1 could replace the need for ligand in promoting neurosphere proliferation. This study suggests that telencephalic progenitors with radial glial morphology are maintained by interactions between the Notch and FGF pathways, and that the mechanisms by which FGF signaling promotes radial glial character in vivo and progenitor proliferation in vitro can be uncoupled.

Cell Migration along the Lateral Cortical Stream to the Developing Basal Telencephalic Limbic System

During embryogenesis, the lateral cortical stream (LCS) emerges from the corticostriatal border (CSB), the boundary between the developing cerebral cortex and striatum. The LCS is comprised of a mix of pallial- and subpallial-derived neural progenitor cells that migrate to the developing structures of the basal telencephalon, most notably the piriform cortex and amygdala. Using a combination of in vitro and in vivo approaches, we analyzed the timing, composition, migratory modes, origin, and requirement of the homeodomain-containing transcription factor Gsh2 (genomic screened homeobox 2) in the development of this prominent migratory stream. We reveal that Pax6 (paired box gene 6)-positive pallial-derived and Dlx2 (distal-less homeobox 2)-positive subpallial-derived subpopulations of LCS cells are generated in distinct temporal windows during embryogenesis. Furthermore, our data indicate the CSB border not only is comprised of separate populations of pallial- and subpallial-derived progenitors that contribute to the LCS but also a subpopulation of cells coexpressing Pax6 and Dlx2. Moreover, despite migrating along a route outlined by a cascade of radial glia, the Dlx2-positive population appears to migrate primarily in an apparent chain-like manner, with LCS migratory cells being generated locally at the CSB with little contribution from other subpallial structures such as the medial, lateral, or caudal ganglionic eminences. We further demonstrate that the generation of the LCS is dependent on the homeodomain-containing gene Gsh2, revealing a novel requirement for Gsh2 in telencephalic development.

ON THE ROLE OF THE GENERAL TRANSCRIPTION FACTOR SP1 IN THE ACTIVATION AND REPRESSION OF DIVERSE MAMMALIAN OXIDATIVE PHOSPHORYLATION GENES

To gain insight into the role of the general transcription factor,Sp1, in the expression of nuclear genes involved in mitochondrial biogenesis,we investigated Sp1 activation of the adenine nucleotide translocator 2,cytochrome c1, F1-ATPase β subunit, and themitochondria transcription factor (mtTFA) promoters transfected intoDrosophila cell lines. The numbers and organization of GC elementsvary in the four promoters, but the magnitude of activation by coexpressedhuman Sp1 was similar. A feature common to the four promoters is the presenceof multiple, proximal Sp1-activating elements that account for 50% ormore of the transcription activation by Sp1. The distribution and function ofindividual distal Sp1 elements is less defined and appear to be morepromoter-specific. Finally, data from transfected Drosophila cellsprovide the first direct proof for the involvement of Sp1 in the negativeregulation of the ANT2 promoter and as a possible participant in repressionof the β-subunit promoter. The role of Sp1 in both the positive andnegative regulation of OXPHOS promoters is unique.

Application of a Multiplex Quantitative PCR to Assess Prevalence and Intensity Of Intestinal Parasite Infections in a Controlled Clinical Trial

Background Accurate quantitative assessment of infection with soil transmitted helminths and protozoa is key to the interpretation of epidemiologic studies of these parasites, as well as for monitoring large scale treatment efficacy and effectiveness studies. As morbidity and transmission of helminth infections are directly related to both the prevalence and intensity of infection, there is particular need for improved techniques for assessment of infection intensity for both purposes. The current study aimed to evaluate two multiplex PCR assays to determine prevalence and intensity of intestinal parasite infections, and compare them to standard microscopy. Methodology/Principal Findings Faecal samples were collected from a total of 680 people, originating from rural communities in Timor-Leste (467 samples) and Cambodia (213 samples). DNA was extracted from stool samples and subject to two multiplex real-time PCR reactions the first targeting: Necator americanus, Ancylostoma spp., Ascaris spp., and Trichuris trichiura; and the second Entamoeba histolytica, Cryptosporidium spp., Giardia. duodenalis, and Strongyloides stercoralis. Samples were also subject to sodium nitrate flotation for identification and quantification of STH eggs, and zinc sulphate centrifugal flotation for detection of protozoan parasites. Higher parasite prevalence was detected by multiplex PCR (hookworms 2.9 times higher, Ascaris 1.2, Giardia 1.6, along with superior polyparasitism detection with this effect magnified as the number of parasites present increased (one: 40.2% vs. 38.1%, two: 30.9% vs. 12.9%, three: 7.6% vs. 0.4%, four: 0.4% vs. 0%). Although, all STH positive samples were low intensity infections by microscopy as defined by WHO guidelines the DNA-load detected by multiplex PCR suggested higher intensity infections. Conclusions/Significance Multiplex PCR, in addition to superior sensitivity, enabled more accurate determination of infection intensity for Ascaris, hookworms and Giardia compared to microscopy, especially in samples exhibiting polyparasitism. The superior performance of multiplex PCR to detect polyparasitism and more accurately determine infection intensity suggests that it is a more appropriate technique for use in epidemiologic studies and for monitoring large-scale intervention trials.

Notch signaling coordinates the patterning of striatal compartments.

Numerous lines of evidence suggest that Notch signaling plays a pivotal role in controlling the production of neurons from progenitor cells. However, most experiments have relied on gain-of-function approaches because perturbation of Notch signaling results in death prior to the onset of neurogenesis. Here, we examine the requirement for Notch signaling in the development of the striatum through the analysis of different single and compound Notch1 conditional and Notch3 null mutants. We find that normal development of the striatum depends on the presence of appropriate Notch signals in progenitors during a critical window of embryonic development. Early removal of Notch1 prior to neurogenesis alters early-born patch neurons but not late-born matrix neurons in the striatum. We further show that the late-born striatal neurons in these mutants are spared as a result of functional compensation by Notch3. Notably, however, the removal of Notch signaling subsequent to cells leaving the germinal zone has no obvious effect on striatal organization and patterning. These results indicate that Notch signaling is required in neural progenitor cells to control cell fate in the striatum, but is dispensable during subsequent phases of neuronal migration and differentiation.

Closing the praziquantel treatment gap: new steps in epidemiological monitoring and control of schistosomiasis in African infants and preschool-aged children

SUMMARY Where very young children come into contact with water containing schistosome cercariae, infections occur and schistosomiasis can be found. In high transmission environments, where mothers daily bathe their children with environmentally drawn water, many infants and preschool-aged children have schistosomiasis. This ‘new’ burden, inclusive of co-infections with Schistosoma haematobium and Schistosoma mansoni, is being formally explored as infected children are not presently targeted to receive praziquantel (PZQ) within current preventive chemotherapy campaigns. Thus an important PZQ treatment gap exists whereby infected children might wait up to 4–5 years before receiving first treatment in school. International treatment guidelines, set within national treatment platforms, are presently being modified to provide earlier access to medication(s). Although detailed pharmacokinetic studies are needed, to facilitate pragmatic dosing in the field, an extended ‘dose pole’ has been devised and epidemiological monitoring has shown that administration of PZQ (40 mg/kg), in either crushed tablet or liquid suspension, is both safe and effective in this younger age-class; drug efficacy, however, against S. mansoni appears to diminish after repeated rounds of treatment. Thus use of PZQ should be combined with appropriate health education/water hygiene improvements for both child and mother to bring forth a more enduring solution.