myelin-basic-protein and Hemorrhage

Mutations in the human NOTCH3 gene cause CADASIL syndrome (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). CADASIL is an inherited small vessel disease characterized by diverse clinical manifestations including vasculopathy, neurodegeneration and dementia. Here we report two mutations in the zebrafish notch3 gene, one identified in a previous screen for mutations with reduced expression of myelin basic protein (mbp) and another caused by a retroviral insertion. Reduced mbp expression in notch3 mutant embryos is associated with fewer oligodendrocyte precursor cells (OPCs). Despite an early neurogenic phenotype, mbp expression recovered at later developmental stages and some notch3 homozygous mutants survived to adulthood. These mutants, as well as adult zebrafish carrying both mutant alleles together, displayed a striking stress-associated accumulation of blood in the head and fins. Histological analysis of mutant vessels revealed vasculopathy, including: an enlargement (dilation) of vessels in the telencephalon and fin, disorganization of the normal stereotyped arrangement of vessels in the fin, and an apparent loss of arterial morphological structure. Expression of hey1, a well-known transcriptional target of Notch signaling, was greatly reduced in notch3 mutant fins, suggesting that Notch3 acts via a canonical Notch signaling pathway to promote normal vessel structure. Ultrastructural analysis confirmed the presence of dilated vessels in notch3 mutant fins and revealed that the vessel walls of presumed arteries showed signs of deterioration. Gaps in the arterial wall and the presence of blood cells outside of vessels in mutants indicated that compromised vessel structure led to hemorrhage. In notch3 heterozygotes, we found elevated expression of both notch3 itself and target genes, indicating that specific alterations in gene expression due to partial loss of Notch3 function might contribute to the abnormalities observed in heterozygous larvae and adults. Our analysis of zebrafish notch3 mutants indicates that Notch3 regulates OPC development and mbp gene expression in larvae, and maintains vascular integrity in adults.

Topics: Animals; Apoptosis; Blood Vessels; Body Patterning; Hemorrhage; Heterozygote; Humans; Larva; Mutation; Myelin Basic Protein; Neurogenesis; Oligodendroglia; Phenotype; Receptor, Notch3; Receptors, Notch; RNA, Messenger; Telencephalon; Vasodilation; Zebrafish; Zebrafish Proteins

One characteristic of experimental allergic encephalomyelitis (EAE) in all species is the presence of a considerable leukocyte infiltrate in the central nervous system (CNS). By adoptive transfer of EAE into irradiated or nonirradiated Lewis strain rats we now show that the bulk (greater than 90%) of infiltrating cells in the CNS are superfluous to the induction of disease, as lethally irradiated recipients, despite having very few infiltrating cells in the CNS, acquire severe paralytic EAE. The reduction in the level of infiltration in irradiated recipients is selective, however, as both irradiated and nonirradiated diseased animals have very similar numbers of cells expressing IL-2-R. Disease in irradiated recipient animals is associated with substantial submeningeal hemorrhage in the spinal cord and brain stem and similar hemorrhages are found in recipients rendered leukopenic with cytotoxic drugs. Clinical signs of disease and hemorrhage are preventable, however, by administration to the recipient rats of mAbs specific for the CD4 antigen. Classic delayed-type hypersensitivity (DTH) reactions are transferable with the same cells that produce EAE in both irradiated and nonirradiated recipient rats, but such transfer of DTH is observed only in nonirradiated recipient animals and not in irradiated rats. Collectively, the findings reported herein support the conclusion that the paralysis characteristic of acute EAE is mediated by the direct action of very small numbers of activated CD4+ lymphocytes that infiltrate the CNS and produce their effects by inducing vascular damage. The findings are not consistent with reports that the lesions in EAE are produced by a classic DTH reaction.

Topics: Animals; Busulfan; Cells, Cultured; Central Nervous System; Cerebral Hemorrhage; Chlorambucil; Encephalomyelitis, Autoimmune, Experimental; Female; Hemorrhage; Hypersensitivity, Delayed; Immunization, Passive; Leukopenia; Male; Myelin Basic Protein; Ovalbumin; Rats; Rats, Inbred Lew; Receptors, Immunologic; Receptors, Interleukin-2; Spinal Cord Diseases; Spleen; T-Lymphocytes, Helper-Inducer; Whole-Body Irradiation