End buds: non-ampullary electroreceptors in adult lampreys

Summary Shared anatomical and physiological characters indicate that the low-frequency sensitive electrosensory system of lampreys is homologous with those of non-teleost fishes and amphibians. However, the ampullary electroreceptor organs which characterize all of these gnathostomes are not found in lampreys. Experimental anatomical and physiological studies reported here demonstrate that the epidermal end buds are the electroreceptors of adult lampreys.End buds, consisting of both sensory and supporting cells, are goblet-shaped with the top (25–60 m diameter) at the epidermal surface and the stem directed toward the dermis (Fig. 1A). Short lines or clusters of 2–8 end buds (Fig. 1B) are distributed over both trunk and head. Injections of horseradish peroxidase (HRP) into vitally-stained end buds labeled anterior lateral line afferents terminating in the ipsilateral dorsal nucleus (Fig. 2A) — the primary electrosensory nucleus of the lamprey medulla. Conversely, after HRP injection into the dorsal nucleus HRP-filled fibers and terminals were present on ipsilateral end buds (Fig. 2B).End buds are usually not visible without staining. However, in adult sea lampreys the presence of end buds was histologically confirmed in skin patches containing the receptive fields of electroreceptor fibers recorded in the anterior lateral line nerve. Additionally, in the rare instance of two silver lampreys in which end buds were visible without staining, electrosensory activity indistinguishable from that of the primary electroreceptor afferents was recorded from the end bud surface (Figs. 3, 4).End buds were initially characterized as chemoreceptors (Johnston 1902) but were later correctly advanced as lateralis receptors based on the presence of presynaptic dense bodies in the receptor cells (Whitear and Lane 1981). Unlike all other low-frequency electroreceptors, end buds lack canals. The receptor cells contact the epidermal surface and possess apical microvilli rather than the kinocilium of most gnathostomes with homologous electrosensory systems of the primitive (non-teleost) type.Larval lampreys and newly transformed adults lack end buds although at least the latter are electroreceptive. End buds, therefore, may be the form taken by electroreceptors only in the final portion of a lamprey's life.     

Amino acid sequence of human plasma apolipoprotein C-III from normolipidemic subjects

The complete amino acid sequence of human plasma apolipoprotein C-III (apoC-III) isolated from normal subjects is described. ApoC-III is a linear polypeptide chain of 79 amino acids. Tryptic digestion of intact apoC-III produced 5 major peptides, while tryptic digestion of the citraconylated protein yielded two peptides. The complete amino acid sequence of apoC-III was determined by the automated Edman degradation of the intact protein as well as the various tryptic peptides. Phenylthiohydantoin amino acids were identified by high-performance liquid chromatography and chemical ionization mass spectrometry. The amino acid sequence of apoC-III isolated from normolipidemic subjects is identical to the apoC-III sequence derived from the cDNA sequence and differs at 4 positions from the previously reported sequence of apoC-III derived from a patient with type V hyperlipoproteinemia.     

Acute lymphoblastic leukemia-derived extracellular vesicles affect quiescence of hematopoietic stem and progenitor cells

Patient-derived xenografted (PDX) models were generated through the transplantation of primary acute lymphoblastic leukemia (ALL) cells into immunodeficient NSG mice. We observed that ALL cells from mouse bone marrow (BM) produced extracellular vesicles (EVs) with specific expression of inducible heat shock protein HSP70, which is commonly activated in cancer cells. Taking advantage of this specific expression, we designed a strategy to generate fluorescent HSP70-labeled ALL EVs and monitor the impact of these EVs on endogenous murine BM cells ex vivo and in vivo. We discovered that hematopoietic stem and progenitor cells (HSPC) were mainly targeted by ALL EVs, affecting their quiescence and maintenance in the murine BM environment. Investigations revealed that ALL EVs were enriched in cholesterol and other metabolites that contribute to promote the mitochondrial function in targeted HSPC. Furthermore, using CD34⁺ cells isolated from cord blood, we confirmed that ALL EVs can modify quiescence of human HSPC. In conclusion, we have discovered a new oncogenic mechanism illustrating how EVs produced by proliferative ALL cells can target and compromise a healthy hematopoiesis system during leukemia development.Subject terms: Acute lymphocytic leukaemia, Cancer models, Cancer metabolism     

Deoxycholic acid promotes development of gastroesophageal reflux disease and Barrett's oesophagus by modulating integrin‐αv trafficking

The fundamental mechanisms underlying erosive oesophagitis and subsequent development of Barrett's oesophagus (BO) are poorly understood. Here, we investigated the contribution of specific components of the gastric refluxate on adhesion molecules involved in epithelial barrier maintenance. Cell line models of squamous epithelium (HET‐1A) and BO (QH) were used to examine the effects of bile acids on cell adhesion to extracellular matrix proteins (Collagen, laminin, vitronectin, fibronectin) and expression of integrin ligands (α₃, α_4, α₅, α₆ and α_ν). Experimental findings were validated in human explant oesophageal biopsies, a rat model of gastroesophageal reflux disease (GORD) and in patient tissue microarrays. The bile acid deoxycholic acid (DCA) specifically reduced adhesion of HET‐1A cells to vitronectin and reduced cell‐surface expression of integrin‐α_ν via effects on endocytic recycling processes. Increased expression of integrin‐α_v was observed in ulcerated tissue in a rat model of GORD and in oesophagitis and Barrett's intestinal metaplasia patient tissue compared to normal squamous epithelium. Increased expression of integrin‐α_ν was observed in QH BO cells compared to HET‐1A cells. QH cells were resistant to DCA‐mediated loss of adhesion and reduction in cell‐surface expression of integrin‐α_ν. We demonstrated that a specific component of the gastric refluxate, DCA, affects the epithelial barrier through modulation of integrin α_ν expression, providing a novel mechanism for bile acid‐mediated erosion of oesophageal squamous epithelium and promotion of BO. Strategies aimed at preventing bile acid‐mediated erosion should be considered in the clinical management of patients with GORD.     

Foliose Ulva Species Show Considerable Inter‐Specific Genetic Diversity,Low Intra‐Specific Genetic Variation,and the Rare Occurrence of Inter‐Specific Hybrids in the Wild

Foliose Ulva spp. have become increasingly important worldwide for their environmental and financial impacts. A large number of such Ulva species have rapid reproduction and proliferation habits, which explains why they are responsible for Ulva blooms, known as “green tides”, having dramatic negative effects on coastal ecosystems, but also making them attractive for aquaculture applications. Despite the increasing interest in the genus Ulva, particularly on the larger foliose species for aquaculture, their inter‐ and intra‐specific genetic diversity is still poorly described. We compared the cytoplasmic genome (chloroplast and mitochondrion) of 110 strains of large distromatic foliose Ulva from Ireland, Brittany (France), the Netherlands and Portugal. We found six different species, with high levels of inter‐specific genetic diversity, despite highly similar or overlapping morphologies. Genetic variation was as high as 82 SNPs/kb between Ulva pseudorotundata and U. laetevirens, indicating considerable genetic diversity. On the other hand, intra‐specific genetic diversity was relatively low, with only 36 variant sites (0.03 SNPs/kb) in the mitochondrial genome of the 29 Ulva rigida individuals found in this study, despite different geographical origins. The use of next‐generation sequencing allowed for the detection of a single inter‐species hybrid between two genetically closely related species, U. laetevirens, and U. rigida, among the 110 strains analyzed in this study. Altogether, this study represents an important advance in our understanding of Ulva biology and provides genetic information for genomic selection of large foliose strains in aquaculture.     

Different Epidermal Growth Factor Receptor (EGFR) Agonists Produce Unique Signatures for the Recruitment of Downstream Signaling Proteins

The EGF receptor can bind seven different agonist ligands. Although each agonist appears to stimulate the same suite of downstream signaling proteins, different agonists are capable of inducing distinct responses in the same cell. To determine the basis for these differences, we used luciferase fragment complementation imaging to monitor the recruitment of Cbl, CrkL, Gab1, Grb2, PI3K, p52 Shc, p66 Shc, and Shp2 to the EGF receptor when stimulated by the seven EGF receptor ligands. Recruitment of all eight proteins was rapid, dose-dependent, and inhibited by erlotinib and lapatinib, although to differing extents. Comparison of the time course of recruitment of the eight proteins in response to a fixed concentration of each growth factor revealed differences among the growth factors that could contribute to their differing biological effects. Principal component analysis of the resulting data set confirmed that the recruitment of these proteins differed between agonists and also between different doses of the same agonist. Ensemble clustering of the overall response to the different growth factors suggests that these EGF receptor ligands fall into two major groups as follows: (i) EGF, amphiregulin, and EPR; and (ii) betacellulin, TGFα, and epigen. Heparin-binding EGF is distantly related to both clusters. Our data identify differences in network utilization by different EGF receptor agonists and highlight the need to characterize network interactions under conditions other than high dose EGF.