Analyse der molekularen Funktion des Zinkfinger-Transkriptionsfaktors Sp8 während der Embryonalentwicklung des Vorderhirns und des Olfaktorischen Systems der Maus

The zinc-finger transcription factor Sp8 is expressed in the developing nervous system, limbs and the tail bud. Analysis of Sp8 knockout mice revealed severe truncations of the limbs and tail, while at the midbrain-hindbrain boundary (MHB) a defect of A/P patterning occurred. To gain more insights into the role of Sp8 in the developing telencephalon and to overcome exencephaly, we analyzed Foxg1-Cre-mediated conditional Sp8 mutants. We present evidence that, in the absence of Sp8, the D/V patterning at the medial telencephalic wall is perturbed. Sp8 is essential for maintenance of ventral cell identity in the septum and medial ganglionic eminence. This is probably mediated through a positive regulatory interaction with Fgf8 in the medial wall, and Nkx2.1 in the rostral MGE anlage. Additionally, due to the modulation of the graded expression territories of Emx2 and Pax6 in pallial progenitors, a caudalization of primary cortical areas occurs. Our study indicates that Sp8 function is required to prevent pallial progenitors from apoptosis, and to control the molecular specification of subsets of cortical layer neurons. This is consistent with an essential role for Sp8 in the patterning of the developing forebrain along the A/P and D/V axes. Furthermore, our findings support the idea of a direct interaction between Sp8 and Emx2 proteins. In addition our analysis supports preliminary evidence for an important role of Sp8 during development of the olfactory bulbs and olfactory epithelium.Der Zinkfinger-Transkriptionsfaktor Sp8 ist im sich entwickelnden Nervensystem, in den Gliedern und in der Schwanzknospe expremiert. Die Analyse von Sp8-Knockout-Mäusen deckte starke Verstümmelungen der Glieder und der Schwanzknospe auf und zeigte, daß an der Mittelhirn-Hinterhirngrenze (MHB) die anterior-posterior Musterbildung gestört ist. Um weitere Einblicke in die Rolle von Sp8 im sich entwickelnden Vorderhirn zu gewinnen und um die Exenzephalie von Sp8-Knockout-Mäusen zu überwinden, generierte ich, durch die Kreuzung gefloxter Sp8-Mäuse mit Foxg1-Cre-transgenen Mäusen, konditionelle Sp8-Mutanten. Diese Studie zeigt, daß die dorsal-ventral Musterbildung der kortikalen Mittellinie in konditionellen Mutanten gestört ist. Sp8 ist für die Aufrechterhaltung ventraler Identität von Vorläuferzellenin der kortikalen Mittellinie und der medialen Basalganglien verantwortlich. Dieses wird vermutlich durch einen positiven regulatorischen Mechanismus zwischen Sp8 und Fgf8 in der Mittellinie, sowie zwischen Sp8 und Nkx2.1 in den rostralen Basalganglien vermittelt. Zusätzlich sind in Mutanten die normalen Expressionsgradiente von Emx2 und von Pax6 in kortikalen Vorläuferzellen dereguliert, was schließlich zur Kaudalisierung primärer kortikaler Areale führt. Diese Studie zeigt ferner, daß normale Funktion von Sp8 nötig ist, um die Apoptose von Vorläuferzellen im Vorderhirn zu kontrollieren, und die molekulare Spezifikation spezifischer kortikaler Schichtneurone zu steuern. Diese Ergebnisse stehen mit einer wesentlichen Rolle von Sp8 während der Musterbildung des sich entwickelnden Vordergirns entlang der anterior-posterior-, sowie der dorsal-ventral Achse überein. Außerdem stützen die vorliegenden Untersuchungen ein Modell der direkten Interaktion zwischen Sp8- und Emx2 Proteinen während dieser Prozesse. Zusätzlich bietet diese Studie erste Hinweise für eine wichtige Rolle von Sp8 während der Entwicklung der Riechkolben und des olfaktorischen Epithels

Genetic interplay between the transcription factors Sp8 and Emx2 in the patterning of the forebrain

<p>Abstract</p> <p>Background</p> <p>The forebrain consists of multiple structures necessary to achieve elaborate functions. Proper patterning is, therefore, a prerequisite for the generation of optimal functional areas. Only a few factors have been shown to control the genetic networks that establish early forebrain patterning.</p> <p>Results and conclusion</p> <p>Using conditional inactivation, we show that the transcription factor Sp8 has an essential role in the molecular and functional patterning of the developing telencephalon along the anteroposterior axis by modulating the expression gradients of <it>Emx2 </it>and <it>Pax6</it>. Moreover, Sp8 is essential for the maintenance of ventral cell identity in the septum and medial ganglionic eminence (MGE). This is probably mediated through a positive regulatory interaction with Fgf8 in the medial wall, and Nkx2.1 in the rostral MGE anlage, and independent of SHH and WNT signaling. Furthermore, <it>Sp8 </it>is required during corticogenesis to sustain a normal progenitor pool, and to control preplate splitting, as well as the specification of cellular diversity within distinct cortical layers.</p

Pax7 is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to Pax3 during superior collicular development

<p>Abstract</p> <p>Background</p> <p><it>Pax7 </it>encodes a transcription factor well-established as an important determinant of mesencephalic identity and superior collicular development. <it>Pax7 </it>mutant mice, however, present with no obvious morphological impairments to the superior colliculus. This finding is paradoxical and has been attributed to functional redundancy afforded by its paralogue <it>Pax3</it>. Here we utilise <it>Pax7 </it>mutant mice to investigate the precise role of this important developmental regulator during superior collicular development and neuronal specification/differentiation. We also assess its spatiotemporal relationship with <it>Pax3 </it>during embryonic development.</p> <p>Results</p> <p>Analysis of the superior colliculus of <it>Pax7 </it>mutant and wildtype mice at a variety of developmental timepoints revealed that whilst correct initial specification is maintained, a subpopulation of dorsal mesencephalic neurons is lost at early postnatal stages. Moreover, a comparative analysis of embryonic <it>Pax3 </it>and <it>Pax7 </it>expression profiles indicate that <it>Pax3 </it>expression overlaps extensively with that of <it>Pax7 </it>initially, but their expression domains increasingly diverge as development progresses, coinciding spatiotemporally with neuronal differentiation and maturation of the tissue. Furthermore, <it>Pax3 </it>expression is perturbed within the CNS of embryonic <it>Pax7 </it>mutant mice.</p> <p>Conclusion</p> <p>In summary, these results demonstrate that during superior collicular development, <it>Pax7 </it>is required to maintain a subpopulation of dorsal, mesencephalic neurons and partially regulates, spatiotemporally, <it>Pax3 </it>expression within the CNS. The differential nature of <it>Pax7 </it>and <it>Pax3 </it>with respect to neuronal differentiation may have implications for future stem cell therapies aimed at exploiting their developmental capabilities.</p

Is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to during superior collicular development-5

Rol indicating expression in astrocytes of the myelencephalon. GFAP+ processes extend from cells located at the pial surface, however the dorsal half of the superior colliculus in mice, like that of wildtype, is not populated by GFAP+ cells. Therefore, cell fate switching and/or transdifferentiation towards the astrocytic lineage does not account for the reduction in Pax7cells dorsally. Immunohistochemical detection of Pax6 (e, f, [inset from e]) and Engrailed (En-1) (g, h [inset from g]) was utilised to examine mesencephalic boundary formation, which appear morphologically unaffected in mutant mice. Abbrev. , cerebral cortex; , interpeduncular fossa;, mesencephalon; , pretectum; , rhombencephalic isthmus. Scale bar: a-d,f,h 100 μm; e,g 500 μm.<p><b>Copyright information:</b></p><p>Taken from "is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to during superior collicular development"</p><p>http://www.biomedcentral.com/1471-213X/8/62</p><p>BMC Developmental Biology 2008;8():62-62.</p><p>Published online 30 May 2008</p><p>PMCID:PMC2430198.</p><p></p

Is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to during superior collicular development-2

L) and unique (ventral [E11]/dorsal [E13]) expression patterns (a). We propose that cells generated at E13 show reduced capacity for long term maintenance in mutant mice (b), generating a phenotype whereby a superficial region is absent of Pax7cells, and the region immediately ventral to this exhibits a reduction in the number of Pax7cells (refer Fig 2e). Abbrev. , cerebral cortex; , inferior colliculus.<p><b>Copyright information:</b></p><p>Taken from "is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to during superior collicular development"</p><p>http://www.biomedcentral.com/1471-213X/8/62</p><p>BMC Developmental Biology 2008;8():62-62.</p><p>Published online 30 May 2008</p><p>PMCID:PMC2430198.</p><p></p

Is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to during superior collicular development-1

Nerated at E11 populate the SS and SP, whereas cells generated at E13 intersect these regions to populate the SI, with a subsequent migration of a subpopulation upwards to the SS by E17. Thus, the SS consists of two different populations of cells, with the most recently generated cells residing in the more superficial regions. Adapted from [14]. Abbrev. , strata ; , ; , . "Cells Migrated" column relates to the developmental timepoint when the cells have migrated to their final destination.<p><b>Copyright information:</b></p><p>Taken from "is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to during superior collicular development"</p><p>http://www.biomedcentral.com/1471-213X/8/62</p><p>BMC Developmental Biology 2008;8():62-62.</p><p>Published online 30 May 2008</p><p>PMCID:PMC2430198.</p><p></p

Is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to during superior collicular development-3

W levels of expression compared to other regions (such as developing upper strata or ventricular zone, respectively) showing darker staining. Abbrev. , cerebral cortex; , cerebellum; , cerebellar primordium; , choroid plexus; , diencephalon; , myelencephalon; , pons; , prosencephalon; , pretectum; , subthalamus; , superior colliculus; , tectum (mesencephalon); , 3ventricle; , 4ventricle. Illustrations are not to scale.<p><b>Copyright information:</b></p><p>Taken from "is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to during superior collicular development"</p><p>http://www.biomedcentral.com/1471-213X/8/62</p><p>BMC Developmental Biology 2008;8():62-62.</p><p>Published online 30 May 2008</p><p>PMCID:PMC2430198.</p><p></p

Establishment of human iPSC-based models for the study and targeting of glioma initiating cells

International audienceGlioma tumour-initiating cells (GTICs) can originate upon the ă transformation of neural progenitor cells (NPCs). Studies on GTICs have ă focused on primary tumours from which GTICs could be isolated and the ă use of human embryonic material. Recently, the somatic genomic landscape ă of human gliomas has been reported. RTK (receptor tyrosine kinase) and ă p53 signalling were found dysregulated in similar to 90% and 86% of ă all primary tumours analysed, respectively. Here we report on the use of ă human-induced pluripotent stem cells (hiPSCs) for modelling ă gliomagenesis. Dysregulation of RTK and p53 signalling in hiPSC-derived ă NPCs (iNPCs) recapitulates GTIC properties in vitro. In vivo ă transplantation of transformed iNPCs leads to highly aggressive tumours ă containing undifferentiated stem cells and their differentiated ă derivatives. Metabolic modulation compromises GTIC viability. Last, ă screening of 101 anti-cancer compounds identifies three molecules ă specifically targeting transformed iNPCs and primary GTICs. Together, ă our results highlight the potential of hiPSCs for studying human ă tumourigenesis

Urocortin3 mediates somatostatin-dependent negative feedback control of insulin secretion.

The peptide hormone urocortin3 (Ucn3) is abundantly expressed by mature beta cells, yet its physiological role is unknown. Here we demonstrate that Ucn3 is stored and co-released with insulin and potentiates glucose-stimulated somatostatin secretion via cognate receptors on delta cells. Further, we found that islets lacking endogenous Ucn3 have fewer delta cells, reduced somatostatin content, impaired somatostatin secretion, and exaggerated insulin release, and that these defects are rectified by treatment with synthetic Ucn3 in vitro. Our observations indicate that the paracrine actions of Ucn3 activate a negative feedback loop that promotes somatostatin release to ensure the timely reduction of insulin secretion upon normalization of plasma glucose. Moreover, Ucn3 is markedly depleted from beta cells in mouse and macaque models of diabetes and in human diabetic islets. This suggests that Ucn3 is a key contributor to stable glycemic control, whose reduction during diabetes aggravates glycemic volatility and contributes to the pathophysiology of this disease