The major neural stem cell population in the developing cerebral cortex is composed of the radial glial cells, which generate glial cells and neurons. The mechanisms that modulate the maintenance of the radial glia (RG) stem cell phenotype, or its differentiation, are not yet completely understood. We previously demonstrated that the transforming growth factor-β1 (TGF-β1) promotes RG differentiation into astrocytes in vitro (Glia 2007; 55:1023-33) through activation of multiple canonical and non-canonical signaling pathways (Dev Neurosci 2012; 34:68-81). However, it remains unknown if TGF-β1 acts in RG-astrocyte differentiation in vivo. Here, we addressed the astrogliogenesis induced by TGF-β1 by using the intraventricular in utero injection in vivo approach. We show that injection of TGF-β1 in the lateral ventricles of E14,5 mice embryos resulted in RG fibers disorganization and premature gliogenesis, evidenced by appearance of GFAP positive cells in the cortical wall. These events were followed by decreased numbers of neurons in the cortical plate (CP). Together, we also described that TGF-β1 actions are region-dependent, once RG cells from dorsal region of the cerebral cortex demonstrated to be more responsive to this cytokine compared with RG from lateral cortex either in vitro as well as in vivo. Our work demonstrated that TGF-β1 is a critical cytokine that regulates RG fate decision and differentiation into astrocytes in vitro and in vivo. We also suggest that RG cells are heterogeneous population that acts as distinct targets of TGF-β1 during cerebral cortex development.

plate motion is consistent with the direction of anisotropy, but would not explain the regional contrasts. Instead, the anisotropy appears to be related to Archean structure and tectonic history.

The major neural stem cell population in the developing cerebral cortex is the radial glia cells, which generate neurons and glial cells. The mechanisms that modulate the maintenance of the radial glia stem cell phenotype, or its differentiation, are not completely elucidated. We previously demonstrated that transforming growth factor-β₁ (TGF-β₁) promotes radial glia differentiation into astrocytes in vitro [Glia 2007;55:1023–1033]. Here we investigated the intracellular signaling pathways involved in the TGF-β₁-induced radial glia fate commitment. We demonstrate that the mechanisms underlying the TGF-β₁ effect on radial glia cell differentiation or progenitor potential maintenance diverge. Whereas radial glia differentiation into astrocytes is mediated by the activation of the MAPK signaling pathway, neurogenesis is modulated by different levels of PI3K and SMAD2/3 activity. Our work demonstrates that radial glia cells are a heterogeneous population and a potential target of TGF-β₁, and suggests that its effect on radial glia fate commitment is mediated by the recruitment of a complex multipathway mechanism that controls astrocyte and neuronal generation in the developing cerebral cortex.

Neuroangiogenesis in the developing central nervous system is controlled by interactions between endothelial cells (ECs) and radial glia (RG) neural stem cells, although RG-derived molecules implicated in these events are not fully known. Here, we investigated the role of RG-secreted TGF-β1, in angiogenesis in the developing cerebral cortex. By isolation of murine microcapillary brain endothelial cells (MBECs), we demonstrate that conditioned medium from RG cultures (RG-CM) promoted MBEC migration and formation of vessel-like structures in vitro, in a TGF-β1-dependent manner. These events were followed by endothelial regulation of GPR124 and BAI-1 gene expression by RG-CM. Proteome profile of RG-CM identified angiogenesis-related molecules IGFBP2/3, osteopontin, endostatin, SDF1, fractalkine, TIMP1/4, Ang-1, pentraxin3, and Cyr61, some of them modulated by TGF-β1 induction. In vivo gain and loss of function assays targeting RG cells demonstrates a specific TGF-β1-dependent control of blood vessels branching in the cerebral cortex. Together, our results point to TGF-β1 signaling pathway as a potential mediator of the RG-EC interactions and shed light to the key role of RG in paving the brain vascular network.

β‐Methyltryptophans (β‐mTrp) are precursors in the biosynthesis of bioactive natural products and are used in the synthesis of peptidomimetic‐based therapeutics. Currently β‐mTrp is produced by inefficient multistep synthetic methods. Here we demonstrate how an engineered variant of tryptophan synthase from Salmonella (StTrpS) can catalyse the efficient condensation of l‐threonine and various indoles to generate β‐mTrp and derivatives in a single step. Although l‐serine is the natural substrate for TrpS, targeted mutagenesis of the StTrpS active site provided a variant (βL166V) that can better accommodate l‐Thr as a substrate. The condensation of l‐Thr and indole proceeds with retention of configuration at both α‐ and β‐positions to give (2S,3S)‐β‐mTrp. The integration of StTrpS (βL166V) with l‐amino acid oxidase, halogenase enzymes and palladium chemocatalysts provides access to further d‐configured and regioselectively halogenated or arylated β‐mTrp derivatives.

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12The terminal step in the biosynthesis of non-ribosomal peptides is the hydrolytic release, and 13 frequently, macrocyclization of an aminoacyl-S-thioester by an embedded thioesterase. The 14 surugamide biosynthetic pathway is composed of two NRPS assembly lines where one produces 15 surugamide A, which is a cyclic octapeptide, and the other produces surugamide F, a linear 16 decapeptide. The terminal module of each system lacks an embedded thioesterase, which led us to 17 question how the peptides are released from the assembly line (and cyclized in the case of surugamide 18 A). We characterized a cyclase belonging to the -lactamase superfamily (SurE) in vivo and 19 established that it is a trans-acting release factor for both compounds and verified this functionality 20 in vitro with a thioester mimic of linear surugamide A. Using bioinformatics, we estimate that ~11% 21 of filamentous Actinobacteria harbor an NRPS system lacking an embedded thioesterase and instead 22 employ a trans-acting cyclase. This study expands the paradigmatic understanding of how non-23 ribosomal peptides are released from the terminal PCP and adds a new dimension to the synthetic 24 biology toolkit. 25 Non-ribosomal peptides (NRPs) are a large family of structurally complex and diverse natural 26 products, often with biologically and therapeutically relevant activities. They are synthesized by large 27 multifunctional enzymes called non-ribosomal peptide synthetases (NRPSs), which are organised 28 into relatively independently functioning modules that work in an assembly line-like manner until the 29 final polypeptide structure is generated. 1 During biosynthesis, the growing peptide chain remains 30 covalently linked to the 4´-phosphopantetheinyl cofactor of the peptidyl carrier protein (PCP) 31 domains. The terminal module usually possesses a C-terminal thioesterase (TE) domain, which off-32 loads the polypeptide intermediate from the PCP on to a conserved serine residue whereby either a 33 hydrolytic or macrocylization reaction occurs to produce the mature peptide. 2 34 Surugamide A (1) and associated minor products B-E (2-5) are cyclic octapeptides initially 35 identified from Streptomyces sp. JAMM992 as inhibitors of cathepsin B, which also possess 36 antibacterial activity. 3,4 Identification of the surugamide (sur) biosynthetic gene cluster (BGC) from 37this organism revealed the presence of four NRPS genes (surABCD), which encoded 18 biosynthetic 38 modules (Figure 1, Scheme 1). The eight modules encoded by SurAD were consistent with the 39 biosynthesis of 1-5, whereas the remaining 10 modules encoded by SurBC were shown to direct the 40 biosynthesis of an unrelated linear decapeptide named, surugamide F (7), which is structurally similar 41 to gramicidin A. 5 S. albus J1074 was recently shown to produce surugamides, including an unusual 42 derivative named acyl-surugamide A (6), which has antifungal bioactivity. 6,7 We identified the same 43 BGC in a related strain, S. albus S4 8 and verified that it produced the major produ...

3-Amino-substituted saturated nitrogen heterocycles are an important subclass of b-diamines,a ppearing in an umber of clinical agents. Herein, we reportaunified approach to theseproducts based upon the regioselective photoredox-mediated hydroaminationo fe necarbamates. The amine coupling partner can encompass diverse amine types under as ingle set of reactionc onditions, including primary alkyl amines,a mmonia,a ryl and heteroaryl amines, and NÀHh eterocycles. The method enables the synthesis of aw ide range of pharmaceutically relevant building blocks.