Faculty Bibliography

A 4-year-old girl presented with a 3-year history of demarcated, salmon-pink, hyperkeratotic plaques, which were symmetrically distributed on the elbows, knees, ankles, and dorsal aspects of the hands and feet. A diffuse, orange-pink palmoplantar keratoderma was also evident. Clinical and histologic findings were consistent with a diagnosis of pityriasis rubra pilaris (PRP), type IV (circumscribed juvenile). Type IV PRP develops in prepubertal children, is typically localized to the distal aspects of the extremities, and has an unpredictable course. Although ultraviolet (UV) radiation can potentially exacerbate PRP, our patient has improved with broad-band UVB phototherapy

Gene products provided by the mother to the embryo determine the body axes in most animals. A recent study in zebrafish proposes that the TGFss signal Squint is one such factor.

The biochemistry of early stages of hematopoietic differentiation is difficult to study because only relatively small numbers of precursor cells are available. The murine EML cell line is a multipotential cell line that can be used to model some of these steps. We found that the lineage- EML precursor cells can be separated into two populations based on cell surface markers including CD34. Both populations contain similar levels of stem cell factor (SCF) receptor (c-Kit) but only the CD34+ population shows a growth response when treated with SCF. Conversely, the CD34- population will grow in the presence of the cytokine IL-3. The human beta-globin locus control region hypersensitive site 2 plays different roles on beta-globin transcription in the CD34+ and CD34- populations. The two populations are present in about equal amounts in culture, and the CD34+ population rapidly regenerates the mixed population when grown in the presence of SCF. We suggest that this system may mimic a normal developmental transition in hematopoiesis.

Nodes of Ranvier are regularly placed, nonmyelinated axon segments along myelinated nerves. Here we show that nodal membranes isolated from the central nervous system (CNS) of mammals restricted neurite outgrowth of cultured neurons. Proteomic analysis of these membranes revealed several inhibitors of neurite outgrowth, including the oligodendrocyte myelin glycoprotein (OMgp). In rat spinal cord, OMgp was not localized to compact myelin, as previously thought, but to oligodendroglia-like cells, whose processes converge to form a ring that completely encircles the nodes. In OMgp-null mice, CNS nodes were abnormally wide and collateral sprouting was observed. Nodal ensheathment in the CNS may stabilize the node and prevent axonal sprouting.

Overcoming the androgen independence of prostate tumors is considered the most critical therapeutic end point for improving survival in patients with metastatic prostate cancer. Normal epithelial and endothelial cells can undergo apoptosis when detached from the extracellular matrix (ECM), via the anoikis phenomenon. In contrast, tumor cells upon detachment from the ECM are capable of evading anoikis and metastasizing to different distant organs. Is the biological repertoire of the epithelial and endothelial cells sufficient to account for the events associated with the process of anoikis during prostate cancer metastasis? Although there is no clear answer to this question, what has become increasingly evident from the existing evidence is that molecules that induce anoikis in tumor epithelial and endothelial cells provide exciting new leads into effective therapeutic targeting as well as markers of prostate cancer progression and prediction of therapeutic resistance. This review analyzes recent findings on anoikis regulators and discusses the relevance of this unique apoptosis mode in the development of metastatic prostate cancer and identification of molecular signatures for treatment of advanced disease.

Until recently, studies in this field of signal transduction have involved the 'what' and 'when' of signaling. Who talks to whom and for how long? With the advent of genetically encoded fluorescent proteins, it has become possible to monitor signaling events in living cells in real time. This has added the dimension of 'where' to the study of cellular signaling. This lecture, which is a part of 'Cell Signaling Systems: A Course for Graduate Students,' provides a survey of how green fluorescent protein (GFP)-tagged probes for signaling events have been used to elucidate new pathways, to describe the kinetics of signaling events at the single-cell level, and to reveal upon which subcellular compartments these events take place. Some of the findings confirm previous ones using biochemical techniques, and others have been surprising. Examples include those utilizing protein localization, relocalization, fluorescence recovery after photobleaching (FRAP), and fluorescence resonance energy transfer (FRET). The design of FRET probes is described. The detection of small guanosine triphosphatase (GTPase) signaling in living cells is used as an example to explore the creative and diverse ways investigators have developed to look at this system

During tRNA translocation on the ribosome, an arc-like connection (ALC) is formed between the G' domain of elongation factor G (EF-G) and the L7/L12-stalk base of the large ribosomal subunit in the GDP state. To delineate the boundary of EF-G within the ALC, we tagged an amino acid residue near the tip of the G' domain of EF-G with undecagold, which was then visualized with three-dimensional cryo-electron microscopy (cryo-EM). Two distinct positions for the undecagold, observed in the GTP-state and GDP-state cryo-EM maps of the ribosome bound EF-G, allowed us to determine the movement of the labeled amino acid. Molecular analyses of the cryo-EM maps show: (1) that three structural components, the N-terminal domain of ribosomal protein L11, the C-terminal domain of ribosomal protein L7/L12, and the G' domain of EF-G, participate in formation of the ALC; and (2) that both EF-G and the ribosomal protein L7/L12 undergo large conformational changes to form the ALC

Calcium entry into myocytes drives contraction of the embryonic heart. To prepare for the next contraction, myocytes must extrude calcium from intracellular space via the Na+/Ca2+ exchanger (NCX1) or sequester it into the sarcoplasmic reticulum, via the sarcoplasmic reticulum Ca2+-ATPase2 (SERCA2). In mammals, defective calcium extrusion correlates with increased intracellular calcium levels and may be relevant to heart failure and sarcoplasmic dysfunction in adults. We report here that mutation of the cardiac-specific NCX1 (NCX1h) gene causes embryonic lethal cardiac arrhythmia in zebrafish tremblor (tre) embryos. The tre ventricle is nearly silent, whereas the atrium manifests a variety of arrhythmias including fibrillation. Calcium extrusion defects in tre mutants correlate with severe disruptions in sarcomere assembly, whereas mutations in the L-type calcium channel that abort calcium entry do not produce this phenotype. Knockdown of SERCA2 activity by morpholino-mediated translational inhibition or pharmacological inhibition causes embryonic lethality due to defects in cardiac contractility and morphology but, in contrast to tre mutation, does not produce arrhythmia. Analysis of intracellular calcium levels indicates that homozygous tre embryos develop calcium overload, which may contribute to the degeneration of cardiac function in this mutant. Thus, the inhibition of NCX1h versus SERCA2 activity differentially affects the pathophysiology of rhythm in the developing heart and suggests that relative levels of NCX1 and SERCA2 function are essential for normal development

Although the epithelial lining of much of the mammalian urinary tract is known simply as the urothelium, this epithelium can be divided into at least three lineages of renal pelvis/ureter, bladder/trigone, and proximal urethra based on their embryonic origin, uroplakin content, keratin expression pattern, in vitro growth potential, and propensity to keratinize during vitamin A deficiency. Moreover, these cells remain phenotypically distinct even after they have been serially passaged under identical culture conditions, thus ruling out local mesenchymal influence as the sole cause of their in vivo differences. During vitamin A deficiency, mouse urothelium form multiple keratinized foci in proximal urethra probably originating from scattered K14-positive basal cells, and the keratinized epithelium expands horizontally to replace the surrounding normal urothelium. These data suggest that the urothelium consists of multiple cell lineages, that trigone urothelium is closely related to the urothelium covering the rest of the bladder, and that lineage heterogeneity coupled with cell migration/replacement form the cellular basis for urothelial squamous metaplasia

The adaptive unfolded protein response (UPR) is essential for the development of antibody-secreting plasma cells. B cells induced by lipopolysaccharide (LPS) to differentiate into plasma cells exhibit a nonclassical UPR reported to anticipate endoplasmic reticulum stress prior to immunoglobulin production. Here we demonstrate that activation of a physiologic UPR is not limited to cells undergoing secretory cell differentiation. We identify B cell receptor (BCR) signaling as an unexpected physiologic UPR trigger and demonstrate that in mature B cells, BCR stimulation induces a short lived UPR similar to the LPS-triggered nonclassical UPR. However, unlike LPS, BCR stimulation does not induce plasma cell differentiation. Furthermore, the BCR-induced UPR is not limited to cells in which BCR induces activation, since a UPR is also induced in transitional immature B cells that respond to BCR stimulation with a rapid apoptotic fate. This response involves sustained up-regulation of Chop mRNA indicative of a terminal UPR. Whereas sustained Chop expression correlates with the ultimate fate of the BCR-triggered B cell and not its developmental stage, Chop-/- B cells undergo apoptosis, indicating that CHOP is not required for this process. These studies establish a system whereby a terminal or adaptive UPR can be alternatively triggered by physiologic stimuli