Dihydrofolate reductase activity controls neurogenic transitions in the developing neocortex.

One-carbon/folate (1C) metabolism supplies methyl groups required for DNA and histone methylation, and is involved in the maintenance of self-renewal in stem cells. Dihydrofolate reductase (DHFR), a key enzyme in 1C metabolism, is highly expressed in human and mouse neural progenitors at the early stages of neocortical development. Here, we have investigated the role of DHFR in the developing neocortex and report that reducing its activity in human neural organoids and mouse embryonic neocortex accelerates indirect neurogenesis, thereby affecting neuronal composition of the neocortex.

Control of G Phase Duration by CDC25B Modulates the Switch from Direct to Indirect Neurogenesis in the Neocortex.

During development, cortical neurons are produced in a temporally regulated sequence from apical progenitors, directly or indirectly, through the production of intermediate basal progenitors. The balance between these major progenitor types is critical for the production of the proper number and types of neurons, and it is thus important to decipher the cellular and molecular cues controlling this equilibrium. Here we address the role of a cell cycle regulator, the CDC25B phosphatase, in this process.

Heterogeneity in the size of the apical surface of cortical progenitors.

Background: The apical surface (AS) of epithelial cells is highly specialized; it is important for morphogenetic processes that are essential to shape organs and tissues and it plays a role in morphogen and growth factor signaling. Apical progenitors in the mammalian neocortex are pseudoepithelial cells whose apical surface lines the ventricle. Whether changes in their apical surface sizes are important for cortical morphogenesis and/or other aspects of neocortex development has not been thoroughly addressed.

Efnb2 haploinsufficiency induces early gap junction plaque disassembly and endocytosis in the cochlea.

Chromosome 13q deletions encompassing EFNB2, which encodes the transmembrane protein ephrin-B2, are likely to cause syndromic forms of sensorineural hearing loss of unclear origin. Thus, unravelling the pathogenic mechanisms could help to improve therapeutic strategies. In the cochlea, adjacent non-sensory epithelial cells are connected via gap junction channels, the activity of which is critical to maintain cochlear homeostasis.

Targeting androgen signaling in ILC2s protects from IL-33-driven lung inflammation, independently of KLRG1.

Background: Allergic asthma is more severe and frequent in women than in men. In male mice, androgens negatively control group 2 innate lymphoid cell (ILC2) development and function by yet unknown mechanisms.

Objectives: We sought to investigate the impact of androgen on ILC2 homeostasis and IL-33-mediated inflammation in female lungs.

Ephrin-B2 paces neuronal production in the developing neocortex.

Background: During mammalian cerebral cortex development, different types of projection neurons are produced in a precise temporal order and in stereotypical numbers. The mechanisms regulating timely generation of neocortex projection neurons and ensuring production in sufficient numbers of each neuronal identity are only partially understood.

Results: Here, we show that ephrin-B2, a member of the Eph:ephrin cell-to-cell communication pathway, sets the neurogenic tempo in the neocortex.

Cross Talk between One-Carbon Metabolism, Eph Signaling, and Histone Methylation Promotes Neural Stem Cell Differentiation.

Metabolic pathways, once seen as a mere consequence of cell states, have emerged as active players in dictating different cellular events such as proliferation, self-renewal, and differentiation. Several studies have reported a role for folate-dependent one-carbon (1C) metabolism in stem cells; however, its exact mode of action and how it interacts with other cues are largely unknown. Here, we report a link between the Eph:ephrin cell-cell communication pathway and 1C metabolism in controlling neural stem cell differentiation.

Eph/Ephrin Signaling Controls Progenitor Identities In The Ventral Spinal Cord.

Background: In the vertebrate spinal cord, motor neurons (MN) are generated in stereotypical numbers from a pool of dedicated progenitors (pMN) whose number depends on signals that control their specification but also their proliferation and differentiation rates. Although the initial steps of pMN specification have been extensively studied, how pMN numbers are regulated over time is less well characterized.

Results: Here, we show that ephrinB2 and ephrinB3 are differentially expressed in progenitor domains in the ventral spinal cord with several Eph receptors more broadly expressed.

Eph:ephrin-B1 forward signaling controls fasciculation of sensory and motor axons.

Axon fasciculation is one of the processes controlling topographic innervation during embryonic development. While axon guidance steers extending axons in the accurate direction, axon fasciculation allows sets of co-extending axons to grow in tight bundles. The Eph:ephrin family has been involved both in axon guidance and fasciculation, yet it remains unclear how these two distinct types of responses are elicited.

Identification of heat shock factor 1 molecular and cellular targets during embryonic and adult female meiosis.

Heat shock factor 1 (HSF1), while recognized as the major regulator of the heat shock transcriptional response, also exerts important functions during mammalian embryonic development and gametogenesis. In particular, HSF1 is required for oocyte maturation, the adult phase of meiosis preceding fertilization. To identify HSF1 target genes implicated in this process, comparative transcriptomic analyses were performed with wild-type and HSF-deficient oocytes.

Oocyte-targeted deletion reveals that hsp90b1 is needed for the completion of first mitosis in mouse zygotes.

Background: Hsp90b1 is an endoplasmic reticulum (ER) chaperone (also named Grp94, ERp99, gp96,Targ2, Tra-1, Tra1, Hspc4) (MGI:98817) contributing with Hspa5 (also named Grp78, BIP) (MGI:95835) to protein folding in ER compartment. Besides its high protein expression in mouse oocytes, little is known about Hsp90b1 during the transition from oocyte-to-embryo. Because the constitutive knockout of Hsp90b1 is responsible for peri-implantation embryonic lethality, it was not yet known whether Hsp90b1 is a functionally important maternal factor.

Hsp90β1 knockout targeted to male germline: a mouse model for globozoospermia.

To study the role of Hsp90β1, an endoplasmic chaperone, we have built a conditional knockout by crossing Hsp90β1(flox/flox) with the Vasa-Cre transgenic line. Spermatozoa deficient in Hsp90β1 could not naturally fertilize oocytes and exhibited large and globular heads with abnormal intermediate pieces, a phenotype reminiscent of human globozoospermia.

Nuclear profiles of H3 histones trimethylated on Lys27 in bovine (Bos taurus) embryos obtained after in vitro fertilization or somatic cell nuclear transfer.

Histone H3 trimethylation on lysine 27 is one of the histone modifications associated with chromatin of silenced regions. H3K27me3 labeling is initially asymmetrical between pronuclei in mammalian embryos, and then it is remodeled during early development. However, in mouse embryos obtained after somatic cell nuclear transfer (SCNT), H3K27me3 histones inherited from the somatic female cell and associated with X chromosome inactivation have been reported to escape remodeling.

Lack of maternal Heat Shock Factor 1 results in multiple cellular and developmental defects, including mitochondrial damage and altered redox homeostasis, and leads to reduced survival of mammalian oocytes and embryos.

Heat Shock Factor 1 (HSF1) is a transcription factor whose loss of function results in the inability of Hsf1(-/-) females to produce viable embryos, as a consequence of early developmental arrest. We previously demonstrated that maternal HSF1 is required in oocytes to regulate expression of chaperones, in particular Hsp90alpha, and is essential for the progression of meiotic maturation. In the present work, we used comparative morphological and biochemical analytic approaches to better understand how Hsf1(-/-) oocytes undergo irreversible cell death.

Syntheses of difluorinated carbasugar phosphates from trifluoroethanol.

Difluorinated cyclohexene diols (prepared from trifluoroethanol) can be elaborated to racemic analogues of phosphorylated sugars via regioselective protection and phosphorylation of the exposed C-1 hydroxyl group. Cis-diol protection was achieved using stannylene methodology, though the regioselectivity depended on the orientation of the methyl group at C-5. UpJohn dihydroxylation is effective with the phosphotriester in place and global deprotection to the tetrol monophosphates is efficient.

Dynamics of constitutive heterochromatin: two contrasted kinetics of genome restructuring in early cloned bovine embryos.

Efficient reprograming of the donor cell genome in nuclear transfer (NT) embryos is linked to the ability of the embryos to sustain full-term development. As the nuclear architecture has recently emerged as a key factor in the regulation of gene expression, we questioned whether early bovine embryos obtained from transfer of cultured fibroblasts into enucleated oocytes would adopt an embryo-like nuclear organization. We studied the dynamics of constitutive heterochromatin in the stages prior to embryonic genome activation by distribution analysis of heterochromatin protein CBX1 (HP1), centromeric proteins CENPA and CENPB, and histone H3 three-methylated at lysine 9.

An appraisal of oxoketene cycloaddition methodology for the synthesis of 2,6-dideoxysugars and fluorinated 2,6-dideoxysugars.

The cycloaddition reaction of acylketenes with vinyl ethers affords an extremely direct route to 2,6-dideoxysugars and their methyl ethers. The lithium enolate of commercial 2,6,6-trimethyldioxinone 3 was fluorinated in good yield to afford fluorinated dioxinone 8. An illustrative range of fluorinated 2,6-dideoxysugar derivatives was prepared via the acetyl ketene-vinyl ether cycloadduct.

Genome restructuring in mouse embryos during reprogramming and early development.

Although a growing number of studies investigates functional genome organization in somatic cell nuclei, it is largely unknown how mammalian genome organization is established during embryogenesis. To address this question, we investigated chromo center formation and the peculiar arrangements of chromosome domains in early mouse embryos. At the one-cell stage, we observed characteristic arrangements of chromosomes and chromo center components.

A potentially divergent and rapid route to analogues of deoxycyclitols, pentopyranoses, 6-deoxyhexoses, and hexoses.

Direct precursors to analogues of pentopyranoses, 6-deoxyhexoses, and hexoses, in which a CF(2) center replaces the pyranose oxygen, have been synthesized rapidly from trifluoroethanol. A simple scaleable allylation reaction delivers ethers which undergo dehydrofluorination/metalation, followed by addition to either acrolein or cinnamaldehyde, to afford allylic alcohols. Fluorine-assisted [3,3]-rearrangement followed by reduction with sodium borohydride delivers diols, which undergo RCM smoothly to afford cyclohexene diols.

A stereodivergent asymmetric approach to difluorinated aldonic acids.

A (bromodifluoromethyl)alkyne has been deployed in a stereoselective route to difluorinated aldonic acid analogues, in which a Sharpless asymmetric dihydroxylation reaction and diastereoisomer separation set the stage for phenyl group oxidation.

Synthesis of 4,4-difluoroglycosides using ring-closing metathesis.

4-Deoxy-4,4-difluoro-glycosides have been synthesised for the first time via a direct sequence involving ring-closing metathesis and indium-mediated difluoroallylation with 1-bromo-1,1-difluoropropene in water. Two protecting group strategies were explored, one to allow protection of the primary C-6 hydroxyl group throughout the sequence, while the second was intended to allow deprotection after RCM and before dihydroxylation. The benzyl ether could be used in the first role, and pivaloyl is effective in the second.

Enantioselective synthesis of BMS-204352 (MaxiPost) using N-fluoroammonium salts of cinchona alkaloids (F-CA-BF4).

The enantioselective synthesis of a potent Maxi-K potassium channel opener (BMS-204352) mediated by N-fluoroammonium salts of cinchona alkaloids is described. Two synthetic pathways were evaluated. An ee as high as 88% was achieved (>99% after a single recrystallisation).