The Doublesex-related Dmrta2 safeguards neural progenitor maintenance involving transcriptional regulation of Hes1

The mechanisms that determine whether a neural progenitor cell (NPC) re-enters the cell cycle or exits and differentiates are pivotal for generating cells in correct numbers and diverse types, and hence dictate proper brain development. Combining gain-of-function and loss-of-function approaches in an embryonic stem cell-derived cortical differentiation model, we report that Dmrta2 plays an important role in maintaining NPCs in the cell cycle. Temporally controlled expression of transgenic Dmrta2 in NPCs suppresses differentiation without affecting their neurogenic competence. In contrast, Dmrta2 knockout accelerates the cell cycle exit and differentiation into post-mitotic neurons of NPCs derived from embryonic stem cells and in Emx1-cre conditional mutant mice. Dmrta2 function was linked to the regulation of Hes1 and other proneural genes as demonstrated by genome wide RNAseq and direct binding of Dmrta2 to the Hes1 genomic locus. Moreover, transient Hes1 expression rescues precocious neurogenesis in Dmrta2 knockout NPCs. Our study therefore establishes a novel link between Dmrta2 modulation of Hes1 expression and the maintenance of NPCs during cortical development.

DMRT5, DMRT3, and EMX2 Cooperatively Repress at the Pallium-Subpallium Boundary to Maintain Cortical Identity in Dorsal Telencephalic Progenitors

Specification of dorsoventral regional identity in progenitors of the developing telencephalon is a first pivotal step in the development of the cerebral cortex and basal ganglia. Previously, we demonstrated that the two zinc finger doublesex and mab-3 related (Dmrt) genes, Dmrt5 (Dmrta2) and Dmrt3, which are coexpressed in high caudomedial to low rostrolateral gradients in the cerebral cortical primordium, are separately needed for normal formation of the cortical hem, hippocampus, and caudomedial neocortex. We have now addressed the role of Dmrt3 and Dmrt5 in controlling dorsoventral division of the telencephalon in mice of either sex by comparing the phenotypes of single knock-out (KO) with double KO embryos and by misexpressing Dmrt5 in the ventral telencephalon. We find that DMRT3 and DMRT5 act as critical regulators of progenitor cell dorsoventral identity by repressing ventralizing regulators. Early ventral fate transcriptional regulators expressed in the dorsal lateral ganglionic eminence, such as Gsx2, are upregulated in the dorsal telencephalon of Dmrt3;Dmrt5 double KO embryos and downregulated when ventral telencephalic progenitors express ectopic Dmrt5. Conditional overexpression of Dmrt5 throughout the telencephalon produces gene expression and structural defects that are highly consistent with reduced GSX2 activity. Further, Emx2;Dmrt5 double KO embryos show a phenotype similar to Dmrt3;Dmrt5 double KO embryos, and both DMRT3, DMRT5 and the homeobox transcription factor EMX2 bind to a ventral telencephalon-specific enhancer in the Gsx2 locus. Together, our findings uncover cooperative functions of DMRT3, DMRT5, and EMX2 in dividing dorsal from ventral in the telencephalon. SIGNIFICANCE STATEMENT We identified the DMRT3 and DMRT5 zinc finger transcription factors as novel regulators of dorsoventral patterning in the telencephalon. Our data indicate that they have overlapping functions and compensate for one another. The double, but not the single, knock-out produces a dorsal telencephalon that is ventralized, and olfactory bulb tissue takes over most remaining cortex. Conversely, overexpressing Dmrt5 throughout the telencephalon causes expanded expression of dorsal gene determinants and smaller olfactory bulbs. Furthermore, we show that the homeobox transcription factor EMX2 that is coexpressed with DMRT3 and DMRT5 in cortical progenitors cooperates with them to maintain dorsoventral patterning in the telencephalon. Our study suggests that DMRT3/5 function with EMX2 in positioning the pallial-subpallial boundary by antagonizing the ventral homeobox transcription factor GSX2

Etude du rôle du facteur de transcription Dmrt5 dans le développement du cortex cérébral

Doctorat en sciences, Spécialisation biologie moléculaireinfo:eu-repo/semantics/nonPublishe

The MKK3 module integrates nitrate and light signals to modulate secondary dormancy in Arabidopsis thaliana

Seed dormancy corresponds to a reversible blockage of germination. Primary dormancy is established during seed maturation while secondary dormancy is set up on the dispersed seed, following an exposure to unfavourable factors. Both dormancies are relieved in response to environmental factors, such as light, nitrate and coldness. QTL analyses for preharvest sprouting identified MKK3 kinase in cereals as a player in dormancy control. Here, we showed that MKK3 also plays a role in secondary dormancy in Arabidopsis within a signalling module composed of MAP3K13/14/19/20, MKK3 and clade-C MAPKs. Seeds impaired in this module acquired heat-induced secondary dormancy more rapidly than WT seeds and this dormancy is less sensitive to nitrate, a signal able to release dormancy. We also demonstrated that MPK7 was strongly activated in the seed during dormancy release, especially in response to light and nitrate. This activation was greatly reduced in map3k13/14/19/20 and mkk3 mutants. Finally, we showed that the module was not regulated, and apparently did not regulate, the genes controlling ABA/GA hormone balance, one of the crucial mechanisms of seed dormancy control. Overall, our work identified a whole new MAPK module controlling seed germination and enlarged the panel of functions of the MKK3-related modules in plants

The homeobox leucine zipper gene Homez plays a role in Xenopus laevis neurogenesis.

The Homez gene encodes a protein with three atypical homeodomains and two leucine zipper motifs of unknown function. Here we show that during neurula stages, Xenopus Homez is broadly expressed throughout the neural plate, the strongest expression being detected in the domains where primary neurons arise. At later stages, Homez is maintained throughout the central nervous system in differentiating progenitors. In accordance with this expression, Homez is positively regulated by neural inducers and by Ngnr1 and negatively by Notch signaling. Interference with Homez function in embryos by injection of an antisense morpholino oligonucleotide results in the specific disruption of the expression of late neuronal markers, without affecting the expression of earlier neuronal and early neurectodermal markers. Consistent with this finding, Homez inhibition also interferes with the expression of late neuronal markers in Ngnr1 overexpressing animal cap explants and in Notch inhibited embryos. In gain of function experiments, Homez inhibits the expression of late neuronal markers but has no effect on earlier ones. These data suggest a role for Homez in neuronal development downstream of proneural/neurogenic genes.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Dmrt5 is controlled by negative autoregulation and has autonomous effects on hippocampus development and neocortex arealization

Patterning of the cerebral hemispheres and arealization of the neocortex depends initially on interplay between morphogens secreted by organizing centers and transcription factors expressed in gradients across the cortical primordium. One of these, Dmrt5/Dmrta2, a zinc finger doublesex and mab-3 related (Dmrt) gene, is expressed in mouse cortical progenitors in a high caudomedial to low rostrolateral gradient. Dmrt5 is required for the development of the caudomedial part of the cerebral cortex but its mode of action remains unclear. In Dmrt5 null mice, the caudomedial cortical organizing center, the Wnt-and Bmp rich cortical hem, is greatly reduced, implying that hem formation relies on DMRT5 activity, and that loss of Dmrt5 affects caudomedial cortex via decreased hem signalling. In a positive feedback loop however, WNT signalling upregulates Dmrt5 expression, suggesting a downstream patterning role for DMRT5. Here we investigated the latter role by inactivating Dmrt5 conditionally in dorsal telencephalon progenitors, and by generating conditional Dmrt5 gain-of-function transgenic mice. In each mouse line, WNT and BMP signaling at the hem appeared largely unaffected. In these conditional mutants, the hemispheres were however smaller than in controls, and the hippocampus and primary visual area (V1) of the neocortex were sharply reduced. No such defects were observed in Dmrt5 hem specific ablated mice. While heterozygous Dmrt5 null mice show a similar reduction of V1 area, opposite changes are observed when Dmrt5 was overexpressed from midgestation onwards. In each mouse line, expression levels of the cortical patterning genes Emx2, Lhx2, and Pax6 were altered. Dmrt5 expression itself was perturbed revealing that it is controlled by negative feedback autoregulation. Together, our findings reveal that DMRT5 levels are tightly controlled and have autonomous effects on hippocampal development and neocortical arealization.info:eu-repo/semantics/inPres

Dmrt5, a novel neurogenic factor, reciprocally regulates Lhx2 to control the neuron-glia cell fate switch in the developing hippocampus

Regulation of the neuron-glia cell-fate switch is a critical step in the development of the CNS. Previously, we demonstrated that Lhx2 is a necessary and sufficient regulator of this process in the mouse hippocampal primordium, such that Lhx2 overexpression promotes neurogenesis and suppresses gliogenesis, whereas loss of Lhx2 has the opposite effect.Wetested a series of transcription factors for their ability to mimic Lhx2 overexpression and suppress baseline gliogenesis, and also to compensate for loss of Lhx2 and suppress the resulting enhanced level of gliogenesis in the hippocampus. Here, we demonstrate a novel function of Dmrt5/Dmrta2 as a neurogenic factor in the developing hippocampus. We show that Dmrt5, as well as known neurogenic factors Neurog2 and Pax6, can each not only mimic Lhx2 overexpression, but also can compensate for loss of Lhx2 to different extents. We further uncover a reciprocal regulatory relationship between Dmrt5 and Lhx2, such that each can compensate for loss of the other. Dmrt5 and Lhx2 also have opposing regulatory control on Pax6 and Neurog2, indicating a complex bidirectionally regulated network that controls the neuron-glia cell-fate switch. Finally, we confirm that Lhx2 binds a highly conserved putative enhancer of Dmrt5, suggesting an evolutionarily conserved regulatory relationship between these factors. Our findings uncover a complex network that involves Lhx2, Dmrt5, Neurog2, and Pax6, and that ensures the appropriate amount and timing of neurogenesis and gliogenesis in the developing hippocampus.Significance Statement Weidentify Dmrt5 as a novel regulator of the neuronglia cell-fate switch in the developing hippocampus.Wedemonstrate Dmrt5 to be neurogenic, and reciprocally regulated by Lhx2: loss of either factor promotes gliogenesis; overexpression of either factor suppresses gliogenesis and promotes neurogenesis; each can substitute for loss of the other. Furthermore, each factor has opposing effects on established neurogenic genes Neurog2 and Pax6. Dmrt5 is known to suppress their expression, and we show that Lhx2 is required to maintain it. Our study reveals a complex regulatory network with bidirectional control of a fundamental feature of CNS development, the control of the production of neurons versus astroglia in the developing hippocampus.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

DMRT5 together with DMRT3 directly controls hippocampus development and neocortical area map formation

Mice that are constitutively null for the zinc finger doublesex and mab-3 related (Dmrt) gene, Dmrt5/Dmrta2, show a variety of patterning abnormalities in the cerebral cortex, including the loss of the cortical hem, a powerful cortical signaling center. In conditional Dmrt5 gain of function and loss of function mouse models, we generated bidirectional changes in the neocortical area map without affecting the hem. Analysis indicated that DMRT5, independent of the hem, directs the rostral-to-caudal pattern of the neocortical area map. Thus, DMRT5 joins a small number of transcription factors shown to control directly area size and position in the neocortex. Dmrt5 deletion after hem formation also reduced hippocampal size and shifted the position of the neocortical/paleocortical boundary. Dmrt3, like Dmrt5, is expressed in a gradient across the cortical primordium. Mice lacking Dmrt3 show cortical patterning defects akin to but milder than those in Dmrt5 mutants, perhaps in part because Dmrt5 expression increases in the absence of Dmrt3 DMRT5 upregulates Dmrt3 expression and negatively regulates its own expression, which may stabilize the level of DMRT5. Together, our findings indicate that finely tuned levels of DMRT5, together with DMRT3, regulate patterning of the cerebral cortex

The Doublesex Homolog Dmrt5 is Required for the Development of the Caudomedial Cerebral Cortex in Mammals.

Regional patterning of the cerebral cortex is initiated by morphogens secreted by patterning centers that establish graded expression of transcription factors within cortical progenitors. Here, we show that Dmrt5 is expressed in cortical progenitors in a high-caudomedial to low-rostrolateral gradient. In its absence, the cortex is strongly reduced and exhibits severe abnormalities, including agenesis of the hippocampus and choroid plexus and defects in commissural and thalamocortical tracts. Loss of Dmrt5 results in decreased Wnt and Bmp in one of the major telencephalic patterning centers, the dorsomedial telencephalon, and in a reduction of Cajal-Retzius cells. Expression of the dorsal midline signaling center-dependent transcription factors is downregulated, including Emx2, which promotes caudomedial fates, while the rostral determinant Pax6, which is inhibited by midline signals, is upregulated. Consistently, Dmrt5(-/-) brains exhibit patterning defects with a dramatic reduction of the caudomedial cortex. Dmrt5 is increased upon the activation of Wnt signaling and downregulated in Gli3(xt/xt) mutants. We conclude that Dmrt5 is a novel Wnt-dependent transcription factor required for early cortical development and that it may regulate initial cortical patterning by promoting dorsal midline signaling center formation and thereby helping to establish the graded expression of the other transcription regulators of cortical identity.JOURNAL ARTICLESCOPUS: ar.jinfo:eu-repo/semantics/publishe