Human Glial Progenitor Cells Effectively Remyelinate the Demyelinated Adult Brain

Neonatally transplanted human glial progenitor cells (hGPCs) can myelinate the brains of myelin-deficient shiverer mice, rescuing their phenotype and survival. Yet, it has been unclear whether implanted hGPCs are similarly able to remyelinate the diffusely demyelinated adult CNS. We, therefore, ask if hGPCs could remyelinate both congenitally hypomyelinated adult shiverers and normal adult mice after cuprizone demyelination. In adult shiverers, hGPCs broadly disperse and differentiate as myelinating oligodendrocytes after subcortical injection, improving both host callosal conduction and ambulation. Implanted hGPCs similarly remyelinate denuded axons after cuprizone demyelination, whether delivered before or after demyelination. RNA sequencing (RNA-seq) of hGPCs back from cuprizone-demyelinated brains reveals their transcriptional activation of oligodendrocyte differentiation programs, while distinguishing them from hGPCs not previously exposed to demyelination. These data indicate the ability of transplanted hGPCs to disperse throughout the adult CNS, to broadly myelinate regions of dysmyelination, and also to be recruited as myelinogenic oligodendrocytes later in life, upon demyelination-associated demand

Genome-wide association study identifies a variant in HDAC9 associated with large vessel ischemic stroke

Genetic factors have been implicated in stroke risk but few replicated associations have been reported. We conducted a genome-wide association study (GWAS) in ischemic stroke and its subtypes in 3,548 cases and 5,972 controls, all of European ancestry. Replication of potential signals was performed in 5,859 cases and 6,281 controls. We replicated reported associations between variants close to PITX2 and ZFHX3 with cardioembolic stroke, and a 9p21 locus with large vessel stroke. We identified a novel association for a SNP within the histone deacetylase 9(HDAC9) gene on chromosome 7p21.1 which was associated with large vessel stroke including additional replication in a further 735 cases and 28583 controls (rs11984041, combined P = 1.87×10−11, OR=1.42 (95% CI) 1.28-1.57). All four loci exhibit evidence for heterogeneity of effect across the stroke subtypes, with some, and possibly all, affecting risk for only one subtype. This suggests differing genetic architectures for different stroke subtypes

Development of the Nodes of Ranvier in Wild Type and Dysmyelinated Mice

Advised by Steven A. Goldman, M.D., PhD., Department of Neurology, University of Rochester

Reversible Inhibition/Activation of Olefin Metathesis: A Kinetic Investigation of ROMP and RCM Reactions with Grubbs\u27 Catalyst

The metathesis activity of Grubbs\u27 catalyst 1 was investigated in the presence of N-donor ligands (1-methylimidazole [MIM], 4-(N,N-dimethylamino)pyridine [DMAP], pyridine, and 1-octylimidazole [OIM]). Ring opening metathesis polymerization (ROMP) reactions of cyclooctene (COE), bulk-ROMP reactions of COE and norbornadiene (NBD), and ring closing metathesis (RCM) reactions of diethyl diallylmalonate (DEDAM) were conducted containing various equivalents of N-donor with respect to catalyst. ROMP reactions could be stopped using MIM (1−5 equiv) and DMAP (2−5 equiv), and slowed with pyridine (1−5 equiv) by factors \u3e100, in benzene solution for 24 h. The stopped reactions could be initiated with excess phosphoric acid (H3PO4), and the reactions proceeded faster than with uninhibited Grubbs\u27 catalyst in the first 4 min after reactivation. Thereafter, the reaction proceeded at the same rate as the reaction with the uninhibited catalyst. ROMP reactions in neat COE and NBD could be inhibited for 72 h using 2 equiv of MIM, DMAP, or OIM and activated with H3PO4 to give polymer gels within minutes or less. RCM reactions could be completely inhibited with MIM (1−5 equiv), but upon treatment with H3PO4, the reaction would proceed at a fraction of the initial rate accomplished by uninhibited Grubbs\u27 catalyst 1. A structural investigation of the inhibited species showed that MIM and DMAP completely or partially transform catalyst 1 into the hexacoordinate species 5a or 5b producing free PCy3, which additionally acts as an inhibitor for the ROMP reaction. Upon reactivation, the PCy3 is protonated along the N-donor ligand; however, over the period of 5 min, the phosphine has been found to coordinate back to the ruthenium catalyst. Therefore, the reaction slows to the same polymerization rate as the reaction using the uninhibited catalyst at this point. Complexes 5a and 5b were isolated, characterized, and employed in ROMP and RCM experiments where they exhibited very low catalytic activity

Indenylidene-imidazolylidene complexes of ruthenium as ring-closing metathesis catalysts

The indenylidene-imidazolylidene complexes of ruthenium (IMes)(PR3)Cl2Ru(3-phenylindenylid-1-ene) and (IPr)(PR3)Cl2Ru(3-phenylindenylid-1-ene) (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, IPr = 1,3-bis(2, 6-diisopropylphenyl)imidazol-2-ylidene and R = Ph, Cy) were prepared and found to be efficient catalyst precursors for ring-closing metathesis

Stereoelectronic effects characterizing nucleophilic carbene ligands bound to the Cp*RuCl (Cp* = η5-C5Me5) moiety : a structural and thermochemical investigation

The reaction of [Cp*RuCl](4) (1) with carbene ligands affords unsaturated Cp*Ru(L)Cl [Cp* = eta(5)-C5Me5; L = 1,3-R-2-imidazol-2-ylidene [R = cyclohexyl (ICy, 2); 4-methylphenyl (ITol, 3); 4-chlorophenyl (IpCl, 4); adamantyl (IAd, 5)] and 4,5-dichloro-1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMesCl, 6)] complexes 2-6 in high yield. Solution calorimetric investigations of this series provides a measure of the electron donor properties of all ligands, and comparisons are made with IMes [1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] and the widely used PCy3. Structural information from single X-ray studies for complexes 2, 3, 5, 6, Cp*Ru(IMes)Cl (7), Cp*Ru(PCy3)Cl (8), and Cp*Ru((PPr3)-Pr-i)Cl (9) permits a quantitative treatment of steric parameters associated with these Ligands

Coordinatively unsaturated 16-electron ruthenium allenylidene complexes : synthetic, structural, and catalytic studies

The one-pot reactions of [(p-cymene)RuCl2](2) (1) or (PPh3)(4)RuCl2 (2) with 2 equiv of PCy3 and 3,3-diphenylpropyn-3-ol afford the novel 16-electron ruthenium allenylidene complex (PCy3)(2)Cl2Ru(=C=C=CPh2) (3) in high yields. Substitution of one PCy3 ligand in 3 for one nucleophilic carbene ligand, IMes [1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene], affords the novel complex (PCy3)(IMes)Cl2Ru(=C=C=CPh2) (4). Single-crystal X-ray structure analyses of complexes 3 and 4 were performed. Thermal stability of complexes 3 and 4 was investigated, and their catalytic activity promoting ring-closing metathesis (RCM) of various substrates was tested

Influence of sterically demanding carbene ligation on catalytic behavior and thermal stability of ruthenium olefin metathesis catalysts

The exchange reaction of one phosphine ligand in Cl-2(PCy3)(2)Ru=CHPh (1; Cy = cyclohexyl, C6H11 with the sterically demanding carbene ligands 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), 1,3-bis(4-methylphenyl)imidazol-2-yliden (ITol), and 1,3-bis(4-chlorophenyl)imidazol-2-ylidene (IpCl) leads to the isolation of the new complexes (PCy3)(IMes)Cl2Ru=CHPh (2), (PCy3)(ITol)Cl2Ru=CHPh (3), and (PCy3)(IpCl)Cl2Ru=CHPh (4). Similarly, one IMes ligand can be substituted for one PCyp(3) ligand in Cl-2(PCyp(3))(2)Ru=CHCH=C(CH3)(2) (5; Cyp = cyclopentyl, C5H9) to produce (PCyp(3))(IMes)Cl2Ru=CHPh (6) in high yield. X-ray structure analysis of 6 confirmed a near-square-pyramidal coordination sphere around the metal center. Improved catalytic properties and thermal stability are observed for 2 and 6 in comparison to the parent 1 and 5

A competitive advantage by neonatally engrafted human glial progenitors yields mice whose brains are chimeric for human glia

Neonatally transplanted human glial progenitor cells (hGPCs) densely engraft and myelinate the hypomyelinated shiverer mouse. We found that, in hGPC-xenografted mice, the human donor cells continue to expand throughout the forebrain, systematically replacing the host murine glia. The differentiation of the donor cells is influenced by the host environment, such that more donor cells differentiated as oligodendrocytes in the hypomyelinated shiverer brain than in myelin wild-types, in which hGPCs were more likely to remain as progenitors. Yet in each recipient, both the number and relative proportion of mouse GPCs fell as a function of time, concomitant with the mitotic expansion and spread of donor hGPCs. By a year after neonatal xenograft, the forebrain GPC populations of implanted mice were largely, and often entirely, of human origin. Thus, neonatally implanted hGPCs outcompeted and ultimately replaced the host population of mouse GPCs, ultimately generating mice with a humanized glial progenitor population. These human glial chimeric mice should permit us to define the specific contributions of glia to a broad variety of neurological disorders, using human cells in vivo