The rhombic lip (RL) is the neuroepithelium immediately adjacent to the roof plate of the fourth ventricle, and it gives rise to various brainstem and cerebellar cell types. Our study shows that the bHLH (basic helix-loop-helix) transcription factor Olig3 is expressed in the progenitors of RL, and ablation of Olig3 significantly affects the development of RL. In Olig3؊/؊ caudal RL, the expression level of Math1 in the dorsal interneuron 1 (dI1) domain is reduced, and the formation of four mossy-fiber nuclei is compromised; dI2-dI3 neurons are misspecified to dI4 interneurons, and the climbing-fiber neurons (inferior olive nucleus) are completely lost. In addition, the formation of brainstem (nor)adrenergic centers and first-order relay visceral sensory neurons is also dependent on Olig3. Therefore, Olig3 plays an important role in the fate specification and differentiation of caudal RL-derived neurons.

We previously found that the T24 Ha-ras oncogene induces metastatic ability in NIH 3T3 cells and that this change depends on expression of the ras oncogene. As part of our studies on mechanisms by which ras may induce metastasis, we investigated expression and activity of two cysteine proteinases, cathepsin L (major excreted protein) and cathepsin B, as well as cysteine proteinase inhibitor activity, in ras-transformed NIH 3T3 cells. In a series of cel lines that expressed differing amounts of ras, we found a good correlation between levels of ras expression and cathepsin L expression (r = 0.80). There was also a good correlation between secreted procathepsin L protein levels and experimental metastatic ability (r = 0.88). We found a similar but less strong association between cathepsin B levels and metastatic ability in these cells (r = 0.76 and r = 0.72 for 2.2-kb and 4.1-kb transcripts, respectively). Functional cathepsin L plus B activity (both secreted and cell-associated) was found to be higher in ras-transformed cells and was dependent on cell confluency in culture. Coupled with increased expression and activity of cysteine proteinases, ras-transformed NIH 3T3 cells showed reduced cysteine proteinase inhibitor activity. We conclude that the balance between expression of cysteine proteinases and their inhibitors may be coregulated by ras expression. Our results suggest that ras-induced increases in production of degradative enzymes such as cathepsins L and B, along with decreased activities of their inhibitors, may contribute to the increased malignant properties of ras-transformed NIH 3T3 cells.

Cathepsins L and B are lysosomal cysteine proteinases whose activities and cellular location are altered in many types of cancers and cancer cell lines. Cathepsins L and B play an unspecified role in cancer invasion and metastasis. The purpose of our study was to determine whether cathepsins L and B are important for the ability of two prostate cancer cell lines, PC3 and DU 145, to invade the basement membrane-like preparation, Matrigel. Exposure of PC3 and DU145 to the irreversible cysteine proteinase inhibitor, E64, decreases the invasive ability of DU145, but not PC3. PC3 and DU145 were treated with the phorbol ester analogue, phorbol 12-myristate 13-acetate (PMA), a known tumor promoter that activates protein kinase C and contributes to the metastatic phenotype. PMA increased secreted cathepsin L+B activity and the invasive ability of PC3 and DU145; co-exposure to E64 and PMA decreased both cathepsin L+B activity and invasion. We conclude that DU145 requires cathepsin L+B activity more than PC3 for the invasion of the Matrigel. When the amount of secreted cathepsin L+B activity is increased by PMA treatment, however, PC3 becomes dependent on cathepsin L+B for invasion. Our study demonstrates that modulation of the amount of secreted cathepsin L+B activity influences the invasive phenotype of PC3 and DU145.

The Pelger-Huët anomaly (PHA) is a recognized morphologic variant affecting all granulocytes but is most evident in polymorphonuclear neutrophils (PMNs). PHA is caused by a decreased amount of the lamin B receptor (LBR). Recognition of PHA morphologic features serves as a marker for mutations in the LBR gene. This review summarizes the history of PHA and the current knowledge of the functions of the LBR. Guidance is given for distinguishing PHA from other hematologic disorders in which granulocytes may show similar changes. Recognition of PHA in the laboratory should prompt communication to the patient's physician about the possible clinical significance of this finding and the recommended screening for the anomaly in other family members by CBC and review of a peripheral blood smear.

To investigate mechanisms of neurite outgrowth, murine Neuro-2a neuroblastoma cells were exposed to ganglioside GM1 in the presence or absence of specific protein kinase inhibitors. Isoquinolinesulfonamide (H-89), an inhibitor of cyclic AMP dependent protein kinase A (PKA), and bisindolylmaleimide I (BIM), which inhibits protein kinase C, each stimulated neurite outgrowth in a dose-dependent manner in the absence of exogenous GM1. Minimally effective (threshold) concentrations of H-89 or BIM potentiated outgrowth when they were used in combination with GM1. To search for a shared component in the mechanisms of GM1, H-89 and BIM, phosphorylation of ERK1/2 was examined. Inhibition of the activation of extracellular signal regulated kinases (ERK1/2) by U0126, prevented neuritogenesis of Neuro-2a by all the three agents. Pretreatment of serum-depleted Neuro-2a cultures with GM1 or BIM enhanced ERK1/2 phosphorylation when the serum level was restored to 10%. In contrast, H-89 did not alter the serum-mediated response. In cells exposed to GM1 or BIM without additional serum, a transitory decrease in ERK phosphorylation occurred. These data suggest that GM1 influences two neuritogenic pathways, one modulated by PKC and the other regulated by PKA. Therefore, GM1 may have the potential to stimulate alternate pathways resulting in outgrowth.