Single-cell transcriptomics reveals heterogeneous progression and EGFR activation in pancreatic adenosquamous carcinoma

Pancreatic adenosquamous carcinoma (PASC) — a rare pathological pancreatic cancer (PC) type — has a poor prognosis due to high malignancy. To examine the heterogeneity of PASC, we performed single-cell RNA sequencing (scRNA-seq) profiling with sample tissues from a healthy donor pancreas, an intraductal papillary mucinous neoplasm, and a patient with PASC. Of 9,887 individual cells, ten cell subpopulations were identified, including myeloid, immune, ductal, fibroblast, acinar, stellate, endothelial, and cancer cells. Cancer cells were divided into five clusters. Notably, cluster 1 exhibited stem-like phenotypes expressing UBE2C, ASPM, and TOP2A. We found that S100A2 is a potential biomarker for cancer cells. LGALS1, NPM1, RACK1, and PERP were upregulated from ductal to cancer cells. Furthermore, the copy number variations in ductal and cancer cells were greater than in the reference cells. The expression of EREG, FCGR2A, CCL4L2, and CTSC increased in myeloid cells from the normal pancreas to PASC. The gene sets expressed by cancer-associated fibroblasts were enriched in the immunosuppressive pathways. We demonstrate that EGFR-associated ligand-receptor pairs are activated in ductal-stromal cell communications. Hence, this study revealed the heterogeneous variations of ductal and stromal cells, defined cancer-associated signaling pathways, and deciphered intercellular interactions following PASC progression.     

Complete genome sequence of an H10N8 avian influenza virus isolated from a live bird market in Southern China

An H10N8 avian influenza virus (AIV), designated A/Duck/Guangdong/E1/2012 (H10N8), was isolated from a duck in January 2012. This is first report that this subtype of AIV was isolated from a live bird market (LBM) in Guangdong Province in southern China. Furthermore, the complete genome of this strain was analyzed. The availability of genome sequences is helpful to further investigations of epidemiology and molecular characteristics of AIV in southern China.     

Helper virus-free transfer of herpes simplex virus type 1 plasmid vectors into neural cells.

Herpes simplex virus type 1 (HSV-1) plasmid vectors have promise for genetic intervention in the brain, but several problems caused by the helper virus have compromised their utility. To develop a helper virus-free packaging system for these vectors, the DNA cleavage/packaging signals were deleted from a set of cosmids that represents the HSV-1 genome. Following cotransfection into cells, this modified cosmid set supported replication and packaging of vector DNA. However, in the absence of the DNA cleavage/packaging signals, the HSV-1 genome was not packaged, and consequently vector stocks were free of detectable helper virus. In the absence of helper virus, the vectors efficiently infected rat neural cells in culture or in the brain with minimal cytopathic effects. beta-galactosidase-positive cells were observed for at least 1 month in vivo, and vector DNA persisted for this period. This system may facilitate studies on neuronal physiology and potential therapeutic applications.     

Membrane-integration Characteristics of Two ABC Transporters, CFTR and P-glycoprotein

To what extent do corresponding transmembrane helices in related integral membrane proteins have different membrane-insertion characteristics? Here, we compare, side-by-side, the membrane insertion characteristics of the 12 transmembrane helices in the adenosine triphosphate-binding cassette (ABC) transporters, P-glycoprotein (P-gp) and the cystic fibrosis transmembrane conductance regulator (CFTR). Our results show that 10 of the 12 CFTR transmembrane segments can insert independently into the ER membrane. In contrast, only three of the P-gp transmembrane segments are independently stable in the membrane, while the majority depend on the presence of neighboring loops and/or transmembrane segments for efficient insertion. Membrane-insertion characteristics can thus vary widely between related proteins.     

Dolichyl phosphate-dependent glycosyltransferases utilize truncated cofactors.

Synthetic truncated dolichyl phosphates of chain lengths from four to thirteen isoprene units (Jaenicke L. and Siegmund H.-U., Chem. Phys. Lipids 51 (1989) 159-170) were assayed for their cofactor activity in the enzymatic transfer of hexoses and hexosamines. The enzymes were microsomal preparations from the green alga Volvox carteri, baker's yeast, and mammalian liver cells. Under saturating conditions, the acceptor activities of the truncated dolichyl phosphates increased from zero to full strength as compared to the mixture of long-chain dolichyl phosphates from natural sources with growing chain length from five to nine isoprene units. Km determinations confirmed the results. Of the geometric isomers of dolichyl 7-phosphate (35 carbon atoms), the 14-trans compound has unchanged acceptor activity; all-trans dolichyl 7-phosphate, however, was almost inactive. The data suggest that hydrophobicity may be an important, but not the only criterion for the binding of the isoprene moiety to the active sites of the transferase enzyme(s) and that the geometry of more than only one double bond in the dolichols is recognized.     

Digestive tract motor correlates of vomiting and nausea

The digestive tract from the upper esophageal sphincter to the ileum participates in the vomiting process, but the role of the digestive tract in nausea is unclear. In preparation for vomiting, the proximal stomach relaxes and the small intestine is evacuated orad in a single mass movement by a retrograde giant contraction and caudad in a stripping fashion by a series of phasic contractions. Orad evacuation of the small intestine may not only remove offending substances but may also dilute. or buffer gastric contents with intestinal and pancreaticobiliary secretions. In association with retching and vomiting, the striated muscle of the esophagus contracts longitudinally, pulling the relaxed proximal stomach into the thoracic cavity forming a funnel from stomach to esophagus. However, gastric evacuation does not occur until the hiatal fibers of the diaphragm relax during vomitus expulsion. Nausea is a subjective feeling in humans that is difficult to identify in animals. Various changes in digestive tract activity have been associated with nausea, but no evidence suggests that these events cause nausea. The prodromal signs of vomiting (e.g., increased heart rate and respiration) that occur concomitantly with the gastrointestinal motor correlates of vomiting have been considered autonomic indices of nausea in animals, but this has not been proven. Regardless, the gastrointestinal motor correlates of vomiting do not cause the prodromata. The emetic central pattern generator may be organized in parallel with respect to its individual autonomic correlates, but as groups of responses, the autonomic and somatomotor correlates may be organized in series.     

Proteolytic enzymes in Chlamydomonas I. A survey on the aminopeptidase pattern in asynchronous vegetative cells of Chlamydomonas reinhardii

The supernatant of a crude extract from vegetative cells ofChlamydomonas reinhardii contains three different types of aminopeptidases.They are similar in their substrate specificities to the relativealanine specific aminopeptidases, the relative leucine specificaminopeptidases and the specific proline iminopeptidases describedin many other systems. Relative alanine specific aminopeptidasewhich also cleaves N-terminal Lys and Leu residues has a molecularweight of 92,000 daltons and is inhibited by zinc and manganeseions.Relative leucine specific aminopeptidase shows high activitywith N-terminal Phe besides Leu, and is capable of cleavingTyr, Pro, and to a minor degree Ala. It has a molecular weightof 76,000 daltons. No effects on its activity were detectedin the presence of divalent cations or chelating agents. Theiminopeptidase specifically splits N-terminal Pro and has amolecular weight of about 255,000 daltons. All the enzymes showoptimal activity at pH 8.0–8.5. The two aminopeptidases can be separated from the iminopeptidaseby ammonium sulfate solubilization and from each other by subsequentfractionation on DEAE-cellulose. Relative leucine specific activityappeared as a single enzyme in all the fractionation techniquesused, but it gave two distinct bands when crude extracts wererun on native polyacrylamide gels. Therefore, this enzyme mayexist in multiple molecularforms. (Received October 17, 1978; )     

The mechanism and function of active DNA demethylation in plants

DNA methylation is a conserved and important epigenetic mark in both mammals and plants.DNA methylation can be dynamically established,maintained,and removed through different pathways.In plants,active DNA demethylation is initiated by the RELEASE OF SILENCING 1(ROS1)family of bifunctional DNA glycosylases/lyases.Accumulating evidence suggests that DNA demethylation is important in many processes in plants.In this review,we summarize recent studies on the enzymes and regulatory factors that have been identified in the DNA demethylation pathway.We also review the functions of active DNA demethylation in plant development as well as biotic and abiotic stress responses.Finally,we highlight those aspects of DNA demethylation that require additional research.