Identity and nature of neural stem cells in the adult human subventricular zone

The existence of neural stem cells (NSCs) in adult human brain neurogenic regions remains unresolved. To address this, we created a cell atlas of the adult human subventricular zone (SVZ) derived from fresh neurosurgical samples using single-cell transcriptomics. We discovered 2 adult radial glia (RG)-like populations, aRG1 and aRG2. aRG1 shared features with fetal early RG (eRG) and aRG2 were transcriptomically similar to fetal outer RG (oRG). We also captured early neuronal and oligodendrocytic NSC states. We found that the biological programs driven by their transcriptomes support their roles as early lineage NSCs. Finally, we show that these NSCs have the potential to transition between states and along lineage trajectories. These data reveal that multipotent NSCs reside in the adult human SVZ.

Single-cell RNA-seq reveals that glioblastoma recapitulates a normal neurodevelopmental hierarchy

Cancer stem cells are critical for cancer initiation, development, and treatment resistance. Our understanding of these processes, and how they relate to glioblastoma heterogeneity, is limited. To overcome these limitations, we performed single-cell RNA sequencing on 53586 adult glioblastoma cells and 22637 normal human fetal brain cells, and compared the lineage hierarchy of the developing human brain to the transcriptome of cancer cells. We find a conserved neural tri-lineage cancer hierarchy centered around glial progenitor-like cells. We also find that this progenitor population contains the majority of the cancer's cycling cells, and, using RNA velocity, is often the originator of the other cell types. Finally, we show that this hierarchal map can be used to identify therapeutic targets specific to progenitor cancer stem cells. Our analyses show that normal brain development reconciles glioblastoma development, suggests a possible origin for glioblastoma hierarchy, and helps to identify cancer stem cell-specific targets.

Evaluation of Resident Palpation Skills in Foot and Ankle Anatomic Structures Using Bedside Ultrasound

Objective

The objective is to determine the accuracy of foot and ankle joint and soft tissue structure palpation in Physical Medicine and Rehabilitation (PM&R) residents using ultrasonography (US) verification.

Methods

PM&R residents were tested in an outpatient musculoskeletal (MSK) clinic on palpated foot and ankle anatomic structures in a human model. Once the presumed structures were localized, residents marked a 1 cm size circle on the overlying skin with a ink marker. The accuracy of the circle over the joint line and soft tissue structures was verified using US.

Results

The overall palpation accuracy for 22 joint line and soft tissue structures was 38.0%. Accuracy by foot and ankle region, including the posterior, medial, lateral, plantar, and dorsal were 72.9%, 47.5%, 42.5%, 35% and 7.8% respectively. There was a positive trend with level of education without a statistically significant difference in palpation accuracy (30.4% in PGY-2, 38.3% in PGY-3, 44.2% in PGY-4, p = 0.11).

Conclusions

Residents in this study demonstrated suboptimal accuracy of foot and ankle anatomic structure identification by palpation. US may be a useful adjunctive tool to advance current methods of teaching musculoskeletal examination skills to PM&R residents.

Antibody-Antisense Oligonucleotide Conjugate Downregulates a Key Gene in Glioblastoma Stem Cells

Glioblastoma stem cells (GSCs) are invasive, treatment-resistant brain cancer cells that express downregulated in renal cell carcinoma (DRR), also called FAM107A, a genetic driver of GSC invasion. We developed antibody-antisense oligonucleotide (AON) conjugates to target and reduce DRR/FAM107A expression. Specifically, we used antibodies against antigens expressed on the GSCs, such as CD44 and EphA2, conjugated to chemically modified AONs against DRR/FAM107A, which were designed as chimeras of DNA and 2'-deoxy-2'-fluoro-beta-D-arabinonucleic acid (FANA) for increased nuclease stability and mRNA affinity. We demonstrate that these therapeutic conjugates successfully internalize, accumulate, and reduce DRR/FAM107A expression in patient-derived GSCs. This is the first example of an antibody-antisense strategy against cancer stem cells.

Evaluation of the risk of anti-SSA/Ro-SSB/La antibody-associated cardiac manifestations of neonatal lupus in fetuses of mothers with systemic lupus erythematosus exposed to hydroxychloroquine

BACKGROUND

Based on the potential involvement of Toll-like receptor (TLR) signalling in the pathogenesis of neonatal lupus (NL), it was hypothesised that fetal exposure to hydroxychloroquine (HCQ), a TLR inhibitor, might reduce the risk of anti-SSA/Ro/SSB/La antibody-associated cardiac manifestations of NL (cardiac-NL).

METHODS

Cardiac-NL children (N=50) and controls (N=151) were drawn from the following overlapping pregnancy studies: Research Registry for NL; PR Interval and Dexamethasone Evaluation in Cardiac-NL; and Predictors of Pregnancy Outcomes: Biomarkers in Antiphospholipid Syndrome and Systemic Lupus Erythematosus (SLE). Pregnancies met the following inclusion criteria: documentation of maternal anti-SSA/Ro/SSB/La antibodies at pregnancy, confirmation of medication use and child's outcome, a diagnosis of SLE before pregnancy and birth by 31 December 2007.

RESULTS

Seven (14%) of the cardiac-NL children were exposed to HCQ compared with 56 (37%) of the controls (p=0.002; OR 0.28; 95% CI 0.12 to 0.63). Cases and controls were similar with respect to demographic and antibody status. Multivariable analysis adjusting for birth year, maternal race/ethnicity, antibody status, non-fluorinated steroid use and prior cardiac-NL risk yielded an OR associated with HCQ use of 0.46 (95% CI 0.18 to 1.18; p=0.10).

CONCLUSION

This case-control study suggests that, in mothers with SLE with anti-SSA/Ro/SSB/La antibodies, exposure to HCQ during pregnancy may decrease the risk of fetal development of cardiac-NL. Prospective studies are needed for confirmation.

Raft-dependent Endocytosis of Autocrine Motility Factor Is Phosphatidylinositol 3-Kinase-dependent in Breast Carcinoma Cells

Autocrine motility factor (AMF) is internalized via a receptor-mediated, dynamin-dependent, cholesterol-sensitive raft pathway to the smooth endoplasmic reticulum that is negatively regulated by caveolin-1. Expression of AMF and its receptor (AMFR) is associated with tumor progression and malignancy; however, the extent to which the raft-dependent uptake of AMF is tumor cell-specific has yet to be addressed. By Western blot and cell surface fluorescence-activated cell sorter (FACS) analysis, AMFR expression is increased in tumorigenic MCF7 and metastatic MDA-231 and MDA-435 breast cancer cell lines relative to dysplastic MCF10A mammary epithelial cells. AMF uptake, determined by FACS measurement of protease-insensitive internalized fluorescein-conjugated AMF, was increased in MCF7 and MDA-435 cells relative to MCF-10A and caveolin-1-expressing MDA-231 cells. Uptake of fluorescein-conjugated AMF was dynamin-dependent, methyl-beta-cyclodextrin- and genistein-sensitive, reduced upon overexpression of caveolin-1 in MDA-435 cells, and increased upon short hairpin RNA reduction of caveolin-1 in MDA-231 cells. Tissue microarray analysis of invasive primary human breast carcinomas showed that AMFR expression had no impact on survival but did correlate significantly with expression of phospho-Akt. Phospho-Akt expression was increased in AMF-internalizing MCF7 and MDA-435 breast carcinoma cells. AMF uptake in these cells was reduced by phosphatidylinositol 3-kinase inhibition but not by regulators of macropinocytosis such as amiloride, phorbol ester, or actin cytoskeleton disruption by cytochalasin D. The raft-dependent endocytosis of AMF therefore follows a distinct phosphatidylinositol 3-kinase-dependent pathway that is up-regulated in more aggressive tumor cells.

The gene product of the gp78/AMFR ubiquitin E3 ligase cDNA is selectively recognized by the 3F3A antibody within a subdomain of the endoplasmic reticulum

The receptor for the autocrine motility factor/phosphoglucose isomerase cytokine (gp78 or AMFR) has been extensively characterized using the 3F3A monoclonal antibody. Cloning of AMFR identified a seven-transmembrane domain G-protein-coupled receptor ubiquitin E3 ligase whose identity as AMFR was based on prior expression cloning with the 3F3A mAb that generated a truncated sequence. We show here that the gp78/AMFR gene product is indeed recognized by the 3F3A mAb. The FLAG-taggedAMFR immunoprecipitated with an anti-FLAG antibody was recognized by the 3F3A mAb in Western blot analysis and cells transfected with AMFR exhibit increased labeling with the 3F3A mAb. The 3F3A mAb does not however recognize higher molecular weight isoforms of AMFR. 3F3A labeling colocalizes with tagged AMFR in a peripheral ER network but does not recognize FLAG- or GFP-tagged AMFR localized to a perinuclear ER domain that likely corresponds to misfolded forms of the protein retained in the ER. These data indicate that 3F3A antibody binding is highly specific for a subpopulation of AMFR localized to an ER subdomain. Coexpression of AMFR-GFP and a lumenal ER-targeted RFP presented extensive colocalization in living cells andAMFR-GFP is concentrated in a basal ER network morphologically similar to that labeled by the 3F3A mAb in fixed cells. The3F3A anti-AMFR mAb therefore selectively recognizes a subpopulation of expressed AMFR localized to a subdomain of the ER.

Ganglioside GM1 levels are a determinant of the extent of caveolae/raft-dependent endocytosis of cholera toxin to the Golgi apparatus

Cholera toxin is associated with caveolae and raft domains in various cell types and previous studies have shown that cholera toxin can be internalized by caveolae/raft-dependent endocytosis as well as by other pathways. We undertook the study of cholera toxin endocytosis in CaCo-2 and HeLa cells. CaCo-2 cells do not express detectable levels of caveolin and, relative to HeLa cells, also present significantly reduced expression of ganglioside GM1, the cholera toxin receptor, that remains Triton X-100 insoluble. Amongst the HeLa cell population, caveolin expression is constant, however, GM1 expression is highly variable. Cholera toxin is internalized to the Golgi apparatus via a caveolae/raft-dependent pathway sensitive to methyl-β-cyclodextrin and genistein in high-GM1-expressing HeLa cells but not in low-GM1 HeLa cells or in CaCo-2 cells. Limited cholera toxin endocytosis to endosomes sensitive to neither methyl-β-cyclodextrin nor genistein is also observed in all cells and corresponds to a non-caveolae/raft endocytic pathway. Increasing cell-associated GM1 by adding GM1 to the cell media of both HeLa and CaCo-2 cells selectively enhances the methyl-β-cyclodextrin-, genistein-sensitive delivery of cholera toxin to the Golgi apparatus but not to endosomes. GM1 expression levels are therefore a selective determinant of caveolae/raft-dependent endocytosis of cholera toxin to the Golgi apparatus and variable expression of GM1 between cells can impact on the endocytosis and choice of pathway followed by cholera toxin.

Caveolae/raft-dependent endocytosis

Although caveolae are well-characterized subdomains of glycolipid rafts, their distinctive morphology and association with caveolins has led to their internalization being considered different from that of rafts. In this review, we propose that caveolae and rafts are internalized via a common pathway, caveolae/raft-dependent endocytosis, defined by its clathrin independence, dynamin dependence, and sensitivity to cholesterol depletion. The regulatory role of caveolin-1 and ligand sorting in this complex endocytic pathway are specifically addressed.

Synaptojanin 2 functions at an early step of clathrin-mediated endocytosis

Synaptojanin 2 is a ubiquitously expressed polyphosphoinositide phosphatase that displays a high degree of homology in its catalytic domains with synaptojanin 1 [1,2]. Neurons of synaptojanin 1-deficient mice display an increase in clathrin-coated vesicles and delayed reentry of recycling vesicles into the fusion-competent vesicle pool, but no defects in early steps of endocytosis [3,4]. Here we show that inhibition of synaptojanin 2 expression via small interfering (si) RNA causes a strong defect in clathrin-mediated receptor internalization in a lung carcinoma cell line. This inhibitory phenotype is rescued by overexpression of wild-type synaptojanin 2, but not of wild-type synaptojanin 1 or mutant synaptojanin 2 that is deficient in 5'-phosphatase activity. In addition, electron-microscopic analysis shows that synaptojanin 2 depletion causes a decrease in clathrin-coated pits and vesicles. These results suggest a role for synaptojanin 2 in clathrin-coated pit formation and imply that lipid hydrolysis is required at an early stage of clathrin-mediated endocytosis. Taken together, our results also indicate that synaptojanin 2 is functionally distinct from synaptojanin 1.

Distinct caveolae-mediated endocytic pathways target the Golgi apparatus and the endoplasmic reticulum

Internalization of autocrine motility factor (AMF) into the endoplasmic reticulum is sensitive to the cholesterol-extracting reagent methyl-beta-cyclodextrin, inhibited by the dynamin-1 K44A mutant and negatively regulated by caveolin-1. Thus, AMF internalization requires a caveolae-mediated endocytic pathway. Similarly, we show here that endocytosis of cholera toxin (CTX) in NIH-3T3 fibroblasts is inhibited by adenoviral expression of the dynamin-1 K44A mutant but only partially by expression of the clathrin hub. Treatment with methyl-beta-cyclodextrin and overexpression of caveolin-1, but not the clathrin hub, selectively diminishes CTX endocytosis to the Golgi apparatus but not to endosomes. CTX is therefore targeted via a caveolin-1-regulated caveolae-mediated pathway to the Golgi. Disruption of Golgi-, caveosome- or endosome-mediated trafficking with brefeldin A, nocodazole or a 20 degrees C temperature block, respectively, inhibit CTX endocytosis to the Golgi but do not affect AMF delivery to the endoplasmic reticulum. Following an incubation of only five minutes in the presence of the clathrin hub, AMF and CTX are not cointernalized, and AMF is delivered to the AMF-R-positive smooth ER. The internalization of both ligands is nevertheless sensitive to the tyrosine kinase inhibitor genistein, confirming that they are both internalized via caveolae/raft pathways. Two distinct caveolae-mediated endocytic pathways therefore exist, including a novel direct pathway to the ER from the plasma membrane.

Caveolin-1 is a negative regulator of caveolae-mediated endocytosis to the endoplasmic reticulum

Caveolae are flask-shaped invaginations at the plasma membrane that constitute a subclass of detergent-resistant membrane domains enriched in cholesterol and sphingolipids and that express caveolin, a caveolar coat protein. Autocrine motility factor receptor (AMF-R) is stably localized to caveolae, and the cholesterol extracting reagent, methyl-beta-cyclodextrin, inhibits its internalization to the endoplasmic reticulum implicating caveolae in this distinct receptor-mediated endocytic pathway. Curiously, the rate of methyl-beta-cyclodextrin-sensitive endocytosis of AMF-R to the endoplasmic reticulum is increased in ras- and abl-transformed NIH-3T3 cells that express significantly reduced levels of caveolin and few caveolae. Overexpression of the dynamin K44A dominant negative mutant via an adenovirus expression system induces caveolar invaginations sensitive to methyl-beta-cyclodextrin extraction in the transformed cells without increasing caveolin expression. Dynamin K44A expression further inhibits AMF-R-mediated endocytosis to the endoplasmic reticulum in untransformed and transformed NIH-3T3 cells. Adenoviral expression of caveolin-1 also induces caveolae in the transformed NIH-3T3 cells and reduces AMF-R-mediated endocytosis to the endoplasmic reticulum to levels observed in untransformed NIH-3T3 cells. Cholesterol-rich detergent-resistant membrane domains or glycolipid rafts therefore invaginate independently of caveolin-1 expression to form endocytosis-competent caveolar vesicles via rapid dynamin-dependent detachment from the plasma membrane. Caveolin-1 stabilizes the plasma membrane association of caveolae and thereby acts as a negative regulator of the caveolae-mediated endocytosis of AMF-R to the endoplasmic reticulum.

Regulation of the formation of tumor cell pseudopodia by the Na(+)/H(+) exchanger NHE1

The Na(+)/H(+) exchanger NHE1 is involved in intracellular pH homeostasis and cell volume regulation and accumulates with actin in the lamellipodia of fibroblasts. In order to determine the role of NHE1 following epithelial transformation and the acquisition of motile and invasive properties, we studied NHE1 expression in polarized MDCK cells, Moloney Sarcoma virus (MSV) transformed MDCK cells and an invasive MSV-MDCK cell variant (MSV-MDCK-INV). Expression of NHE1 was significantly increased in MSV-MDCK-INV cells relative to MSV-MDCK and MDCK cells. NHE1 was localized with b-actin to the tips of MSV-MDCK-INV cell pseudopodia by immunofluorescence. Sensitivity of NHE1-mediated (22)Na uptake to ethylisopropylamiloride, a specific inhibitor of NHE1, was increased in MSV-MDCK cells relative to MDCK cells. Changes in intracellular pH induced upon EIPA treatment were also of higher magnitude in MSV-MDCK and MSV-MDCK-INV cells compared to wild-type MDCK cells, especially in Hepes-buffered DMEM medium. Inhibition of NHE1 by 50 microM ethylisopropylamiloride induced the disassembly of actin stress fibers and redistribution of the actin cytoskeleton in all cell types. However, in MSV-MDCK-INV cells, the effect of ethylisopropylamiloride treatment was more pronounced and associated with the increased reversible detachment of the cells from the substrate. Videomicroscopy of MSV-MDCK-INV cells revealed that within 20 minutes of addition, ethylisopropylamiloride induced pseudopodial retraction and inhibited cell motility. The ability of ethylisopropylamiloride to prevent nocodazole-induced formation of actin stress fibers in MSV-MDCK cells was more pronounced in Hepes medium relative to NaHCO(3) medium, showing that NHE1 can regulate actin stress fiber assembly in transformed MSV-MDCK cells via its intracellular pH regulatory effect. These results implicate NHE1 in the regulation of the actin cytoskeleton dynamics necessary for the adhesion and pseudopodial protrusion of motile, invasive tumor cells.

Clathrin-mediated endocytosis and recycling of autocrine motility factor receptor to fibronectin fibrils is a limiting factor for NIH-3T3 cell motility

Autocrine motility factor receptor (AMF-R) is internalized via a clathrin-independent pathway to smooth endoplasmic reticulum tubules. This endocytic pathway is shown here to be inhibited by methyl-(beta)-cyclodextrin (m(beta)CD) implicating caveolae or caveolae-like structures in AMF internalization to smooth ER. AMF-R is also internalized via a clathrin-dependent pathway to a transferrin receptor-negative, LAMP-1/lgpA-negative endocytic compartment identified by electron microscopy as a multivesicular body (MVB). Endocytosed AMF recycles to cell surface fibrillar structures which colocalize with fibronectin; AMF-R recycling is inhibited at 20 degrees C, which blocks endocytosis past the early endosome, but not by m(beta)CD demonstrating that AMF-R recycling to fibronectin fibrils is mediated by clathrin-dependent endocytosis to MVBs. Microtubule disruption with nocodazole did not affect delivery of bAMF to cell surface fibrils indicating that recycling bAMF traverses the MVB but not a later endocytic compartment. Plating NIH-3T3 cells on an AMF coated substrate did not specifically affect cell adhesion but prevented bAMF delivery to cell surface fibronectin fibrils and reduced cell motility. AMF-R internalization and recycling via the clathrin-mediated pathway are therefore rate-limiting for cell motility. This recycling pathway to the site of deposition of fibronectin may be implicated in the de novo formation of cellular attachments or the remodeling of the extracellular matrix during cell movement.

Localization of autocrine motility factor receptor to caveolae and clathrin-independent internalization of its ligand to smooth endoplasmic reticulum

Autocrine motility factor receptor (AMF-R) is a cell surface receptor that is also localized to a smooth subdomain of the endoplasmic reticulum, the AMF-R tubule. By postembedding immunoelectron microscopy, AMF-R concentrates within smooth plasmalemmal vesicles or caveolae in both NIH-3T3 fibroblasts and HeLa cells. By confocal microscopy, cell surface AMF-R labeled by the addition of anti-AMF-R antibody to viable cells at 4 degreesC exhibits partial colocalization with caveolin, confirming the localization of cell surface AMF-R to caveolae. Labeling of cell surface AMF-R by either anti-AMF-R antibody or biotinylated AMF (bAMF) exhibits extensive colocalization and after a pulse of 1-2 h at 37 degreesC, bAMF accumulates in densely labeled perinuclear structures as well as fainter tubular structures that colocalize with AMF-R tubules. After a subsequent 2- to 4-h chase, bAMF is localized predominantly to AMF-R tubules. Cytoplasmic acidification, blocking clathrin-mediated endocytosis, results in the essentially exclusive distribution of internalized bAMF to AMF-R tubules. By confocal microscopy, the tubular structures labeled by internalized bAMF show complete colocalization with AMF-R tubules. bAMF internalized in the presence of a 10-fold excess of unlabeled AMF labels perinuclear punctate structures, which are therefore the product of fluid phase endocytosis, but does not label AMF-R tubules, demonstrating that bAMF targeting to AMF-R tubules occurs via a receptor-mediated pathway. By electron microscopy, bAMF internalized for 10 min is located to cell surface caveolae and after 30 min is present within smooth and rough endoplasmic reticulum tubules. AMF-R is therefore internalized via a receptor-mediated clathrin-independent pathway to smooth ER. The steady state localization of AMF-R to caveolae implicates these cell surface invaginations in AMF-R endocytosis.

Increased beta-actin expression in an invasive moloney sarcoma virus-transformed MDCK cell variant concentrates to the tips of multiple pseudopodia

An invasive variant of Moloney sarcoma virus-transformed MDCK cells (MSV-MDCK-INV), which was isolated by the repeated selection of cells that successfully traversed a Matrigel-coated filter, exhibits increased motile ability and presents an elongated cell shape and numerous pseudopodia. Although stress fibers are present in both MDCK and MSV-MDCK cells, MSV-MDCK-INV cells contain no stress fibers and exhibit a dense concentration of actin at the tips of pseudopodia. Relative to both MDCK and MSV-MDCK cells, the MSV-MDCK-INV cells exhibit increased expression of beta-actin and redistribution of beta-actin to the tips of pseudopodia. These actin concentrations are enriched in both F- and G-actin and, thus, represent dynamic regions of actin cytoskeleton remodeling. The acquisition of invasive properties by epithelial transformants is, therefore, associated with the increased expression of beta-actin and its concentration in actin-rich domains, which may drive pseudopodial extension and facilitate tumor cell invasion.