AP4 deficiency: A novel form of neurodegeneration with brain iron accumulation?

OBJECTIVE: To describe the clinico-radiological phenotype of 3 patients harboring a homozygous novel AP4M1 pathogenic mutation. METHODS: The 3 patients from an inbred family who exhibited early-onset developmental delay, tetraparesis, juvenile motor function deterioration, and intellectual deficiency were investigated by magnetic brain imaging using T1-weighted, T2-weighted, T2*-weighted, fluid-attenuated inversion recovery, susceptibility weighted imaging (SWI) sequences. Whole-exome sequencing was performed on the 3 patients. RESULTS: In the 3 patients, brain imaging identified the same pattern of bilateral SWI hyposignal of the globus pallidus, concordant with iron accumulation. A novel homozygous nonsense mutation was identified in AP4M1, segregating with the disease and leading to truncation of half of the adap domain of the protein. CONCLUSIONS: Our results suggest that AP4M1 represents a new candidate gene that should be considered in the neurodegeneration with brain iron accumulation (NBIA) spectrum of disorders and highlight the intersections between hereditary spastic paraplegia and NBIA clinical presentations

Bioinformatic analyses of integral membrane transport proteins encoded within the genome of the planctomycetes species, Rhodopirellula baltica

Rhodopirellula baltica (R. baltica) is a Planctomycete, known to have intracellular membranes. Because of its unusual cell structure and ecological significance, we have conducted comprehensive analyses of its transmembrane transport proteins. The complete proteome of R. baltica was screened against the Transporter Classification Database (TCDB) to identify recognizable integral membrane transport proteins. 342 proteins were identified with a high degree of confidence, and these fell into several different classes. R. baltica encodes in its genome channels (12%), secondary carriers (33%), and primary active transport proteins (41%) in addition to classes represented in smaller numbers. Relative to most non-marine bacteria, R. baltica possesses a larger number of sodium-dependent symporters but fewer proton-dependent symporters, and it has dimethylsulfoxide (DMSO) and trimethyl-amine-oxide (TMAO) reductases, consistent with its Na-rich marine environment. R. baltica also possesses a Na-translocating NADH:quinone dehydrogenase (Na-NDH), a Na efflux decarboxylase, two Na-exporting ABC pumps, two Na-translocating F-type ATPases, two Na:H antiporters and two K:H antiporters. Flagellar motility probably depends on the sodium electrochemical gradient. Surprisingly, R. baltica also has a complete set of H-translocating electron transport complexes similar to those present in α-proteobacteria and eukaryotic mitochondria. The transport proteins identified proved to be typical of the bacterial domain with little or no indication of the presence of eukaryotic-type transporters. However, novel functionally uncharacterized multispanning membrane proteins were identified, some of which are found only in Rhodopirellula species, but others of which are widely distributed in bacteria. The analyses lead to predictions regarding the physiology, ecology and evolution of R. baltica

The Watchers Team Self Diagnosis

This paper is a self-diagnosis of The Watchers team. It outlines the stages of the team development, decision making process, conflicts, the up and down periods, and many other elements regarding team values

Zebrafish Prion Protein PrP2 Controls Collective Migration Process during Lateral Line Sensory System Development

<div><p>Prion protein is involved in severe neurodegenerative disorders but its physiological role is still in debate due to an absence of major developmental defects in knockout mice. Previous reports in zebrafish indicate that the two prion genes, <i>PrP1</i> and <i>PrP2</i>, are both involved in several steps of embryonic development thus providing a unique route to discover prion protein function. Here we investigate the role of PrP2 during development of a mechano-sensory system, the posterior lateral line, using morpholino knockdown and PrP2 targeted inactivation. We confirm the efficiency of the translation blocking morpholino at the protein level. Development of the posterior lateral line is altered in <i>PrP2</i> morphants, including nerve axonal outgrowth and primordium migration defects. Reduced neuromast deposition was observed in <i>PrP2</i> morphants as well as in <i>PrP2^−/−</i> mutants. Rosette formation defects were observed in <i>PrP2</i> morphants, strongly suggesting an abnormal primordium organization and reflecting loss of cell cohesion during migration of the primordium. In addition, the adherens junction proteins, E-cadherin and ß-catenin, were mis-localized after reduction of PrP2 expression and thus contribute to the primordium disorganization. Consequently, hair cell differentiation and number were affected and this resulted in reduced functional neuromasts. At later developmental stages, myelination of the posterior lateral line nerve was altered. Altogether, our study reports an essential role of PrP2 in collective migration process of the primordium and in neuromast formation, further implicating a role for prion protein in cell adhesion.</p></div

PrP2 is involved in PLL development.

<p><b>A, C.</b> Alkaline phosphatase staining of the trunk neuromasts (arrows) in wild type embryos at 72 hpf. <b>C</b>. High magnification of boxed area in A. <b>B, D.</b> In <i>Prp2^−/−</i> mutant, less neuromasts are visible with the first neuromast displaced anteriorly (<b>B</b>, white arrow) <b>D</b>. High magnification of boxed area in B. <b>E–G.</b> In Control <b>(E)</b>, <i>PrP2</i>-MO/<i>p53</i>-MO (<b>F</b>) and <i>PrP2</i>-MO (<b>G</b>), the total neuromast number is decreased in morphants. <b>H.</b> Quantification of total neuromast number shows a significant decrease in morphants and mutants compared to control. <b>I.</b> Neuromast position along the somite axis, scheme adapted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113331#pone.0113331-Matsuda1" target="_blank">[28]</a>. In <i>Prp2^−/−</i> mutant, L1 is retrieved anteriorly to the normal L1 position while in morphants, the present neuromasts are displaced posteriorly. *: p<0.05, ***: p<0.001.</p

Loss of cell-cell contact and disorganization of collective migration of the primordium.

<p>Select time points from time-lapse recording of primordium migration in <i>claudinB-GFP</i> embryos. In control embryos, primordium migration is continuous, with a neuromast deposition (time point 2h30) and out of view at the time point 4h30 (not shown). In contrast in one <i>PrP2</i> morphant example, representative of the observed phenotypes, primordium migration shows a progressive rounded shape and arrest. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113331#pone.0113331.s007" target="_blank">Movies S6</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113331#pone.0113331.s008" target="_blank">S7</a>.</p

Primodium disorganisation and absence of rosette formation.

<p><b>A′.</b> Schematic representation of a normal <i>claudinB-GFP</i> embryo at 30 hpf and detailed organization of the primordium with rosette structure. Red spot indicates a normal concentration point of actin. <b>A, B.</b> Phalloidin staining (Phalloidin-TRITC) in control embryo <i>claudinB-GFP</i>, at 30 hpf, is observed in muscle cells and within the primodium at the center of the rosette (arrows), on the apical side. <b>C, D.</b> Phalloidin-TRITC staining in <i>PrP2</i>-MO, no rosette structure is observed and no actin concentration is found. <b>E, F.</b> Higher magnification shows the co-localization of central actin concentration with <i>claudinB-GFP</i> at the rosette center in control. In morphants, cell disorganization is observed and no actin concentration is observed associated with the absence of a rosette. <b>G–I.</b> Phalloidin staining and DAPI nuclei labeling highlight the primordium and rosette center (arrows) in control embryos. <b>J–L.</b> In <i>PrP2^−/−</i> mutants, actin apical localization in rosette was severely reduced or barely detectable (arrow) and primordium organization at the periphery was impaired: loose cells were visible on the border (arrowheads). <b>I′, L′.</b> In <i>PrP2^−/−</i> mutant, the primordium position was often delayed and the first neuromast deposited close to the ear. <b>M</b>. Quantification of rosette number was established in control (n = 20), <i>PrP2</i>-MO (n = 84) and <i>PrP2^−/−</i> mutant (n = 28) using actin staining at the center, **: p<0.01, ***: p<0.001, Student t test. See also associated <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113331#pone.0113331.s002" target="_blank">Movies S1</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113331#pone.0113331.s006" target="_blank">S5</a>.</p

Delocalisation of E-cadherin and beta-catenin in primordium cells in absence of PrP2.

<p><b>A</b>. Schematic representation of <i>claudinB-GFP</i> embryo at 30 hpf, primordium structure, and transversal view of a rosette showing the level of confocal focus plan. <b>B–B″</b>. In control embryos at 30 hpf, E-cadherin is expressed at the membrane level at the basal side of the primordium. <b>C–C″.</b> In morphant embryos, E-cadherin is observed in the cytoplasm and cellular membrane at basal and apical levels. The staining pattern is more punctuated in morphant compared to control. <b>D, E.</b> In control embryos, beta catenin expression is observed at the membrane level and at the center of rosette structures. <b>F, G</b>. In morphant, small rounded primordium shows a membrane homogeneous pattern with no rosette.</p

Decreased hair cell number of PLL neuromast in <i>PrP2</i>-MO.

<p><b>A–C.</b> In control embryos at 48 hpf, <i>Brn3-GFP</i> fluorescence labels hair cells of neuromasts and ear. High magnification of the first 3 neuromasts and zoom of the first neuromast show 8 hair cells. <b>D–F</b>. Morphants displays reduced number of neuromasts. High magnification shows smaller hair cells number. <b>G</b>. Quantification indicates significant reduction of hair cells/neuromast, independently of the neuromast position (mean hair cell number: 5.5±0.4, n = 36, compare to control 7.9±0.2, n = 20, p<0.001).</p