Identification and functional characterization of mouse TPO1 as a myelin membrane protein

Gene expression analysis at multiple time-points identifies key genes for nerve regeneration

INTRODUCTION

The purpose of this study was to provide a comprehensive understanding of gene expression during Wallerian degeneration and axon regeneration after peripheral nerve injury.

METHODS

A microarray was used to detect gene expression in the distal nerve 0, 3, 7, and 14 days after sciatic nerve crush. Bioinformatic analysis was used to predict function of the differentially expressed mRNAs. Microarray results and the key pathways were validated by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Differentially expressed mRNAs at different time-points (3, 7, and 14 days) after injury were identified and compared with a control group (0 day). Nine general trends of changes in gene expression were identified. Key signal pathways and 9 biological processes closely associated with nerve regeneration were identified and verified.

CONCLUSIONS

Differentially expressed genes and biological processes and pathways associated with axonal regeneration may elucidate the molecular-biological mechanisms underlying peripheral nerve regeneration. Muscle Nerve 55: 373-383, 2017.

Endothelin/endothelin-B receptor signals regulate ventricle-directed interkinetic nuclear migration of cerebral cortical neural progenitors

We determined the expression profile of ∼300 G protein-coupled receptors (GPCRs) in embryonic cortical neural progenitor cells (NPCs) and identified a number of highly expressed GPCRs, among which endothelin-B receptor (ET(B)-R) was expressed at the highest level. We also revealed that endothelins (ETs) were predominantly expressed in CD31-positive endothelial cells of the embryonic cerebral cortex. Activation of ET(B)-R induced NPC assembly in vitro by promoting fibronectin-dependent-motility and N-cadherin-associated cell contact. NPC assembly also required a Rho-family GTPase(s) and phosphatidylinositol-3-kinase. In the embryonic cerebral cortex, a specific ET(B)-R agonist, IRL-1620, accelerated interkinetic nuclear migration (INM) of NPCs toward the ventricular wall (VW) ex vivo. Conversely, a specific ET(B)-R antagonist, BQ788, slowed INM, thereby inducing mislocalization of phospho-histone H3-positive M-phase nuclei in the ventricular zone (VZ) and decreasing the number of Tuj1-positive newborn neurons. Our results suggest that ET(B)-R-mediated assembly signals drive INM that precedes neurogenesis.

Characterization of Fyn signaling on the age-dependent immuno-modulation on traumatic rats

Traumatic stress is well characterized to develop immuno-depression in our previous report. Here, we provide evidence that adult and aged rats showed similar decrease in lymphocyte proliferation and natural killer (NK) cell activity. However, compared with beginning recovering from traumatic stress after 3 day and fully recovered by 7 day in adult rats, aged rats begin the recovery phage later than 3 day and do not fully recovered by 7 day. In parallel, Fyn expression in cerebral cortex was augmented with the highest level at 3 day of trauma in both age groups of rats, although aged rats exhibited lower level than the younger cohorts. Immune consequences were consequently modified by intracerebroventricular (i.c.v.) injection of Fyn antibody or recombinant adenovirus expressing active Fyn. Finally, the increase in Fyn expression was converged on ERK1/2 (extracellular signal regulated kinase 1/2) activation. Taken together, the data indicated that immunological processes in response to traumatic stress was age dependent, Fyn-ERK1/2 signal pathway was required to convey the recovery signals.

Alpha 1-adrenoceptor agonists protect against stress-induced death of neural progenitor cells

Here, we show that alpha(1)-adrenoceptor agonists suppress stress-induced death of mouse embryonic brain-derived neural progenitor cells (NPCs). NPCs highly expressed both alpha(1A)- and alpha(1B)-adrenoceptor genes, whereas the gene encoding alpha(1D)-adrenoceptor was expressed at low levels. Application of the alpha(1)-adrenoceptor agonists phenylephrine and cirazoline significantly promoted cell survival of embryonic NPCs that had been exposed to stress, as measured by a lactate dehydrogenase release assay, but had no remarkable effect on differentiation of the NPCs. Both phenylephrine and cirazoline protected NPCs from death induced by growth factor deprivation, N2 nutrient deprivation, tunicamycin treatment or staurosporine treatment. Phenylephrine and cirazoline treatments both maximally reduced stress-induced cell death by approximately 60% but did not change the percentage of undifferentiated cells as measured by nestin staining. Moreover, phenylephrine and cirazoline treatments did not affect the cellular activities of caspase-3 and caspase-7 but markedly reduced propidium iodide penetration into the cytoplasm, suggesting that alpha(1)-adrenoceptor agonists inhibit caspase-3/7-independent death of the embryonic NPCs.

Detection of novel skeletogenesis target genes by comprehensive analysis of a Runx2(-/-) mouse model

Runx2 is an essential factor for skeletogenesis and heterozygous loss causes cleidocranial dysplasia in humans and a corresponding phenotype in the mouse. Homozygous Runx2-deficient mice lack hypertrophic cartilage and bone. We compared the expression profiles of E14.5 wildtype and Runx2(-/-) murine embryonal humeri to identify new transcripts potentially involved in cartilage and bone development. Seventy-one differentially expressed genes were identified by two independent oligonucleotide-microarray hybridizations and quantitative RT-PCR experiments. Gene Ontology analysis demonstrated an enrichment of the differentially regulated genes in annotations to terms such as extracellular, skeletal development, and ossification. In situ hybridization on E15.5 limb sections was performed for all 71 differentially regulated genes. For 54 genes conclusive in situ hybridization results were obtained and all of them showed skeletal expression. Co-expression with Runx2 was demonstrated for 44 genes. While 41 of the 71 differentially expressed genes have a known role in bone and cartilage, we identified 21 known genes that have not yet been implicated in skeletal development and 9 entirely new transcripts. Expression in the developing skeleton was demonstrated for 21 of these genes.