The role of PNPLA1 in ω-O-acylceramide synthesis and skin barrier function

The human genome encodes nine enzymes belonging to the patatin-like phospholipase domain-containing lipase (PNPLA)/Ca²⁺-independent phospholipase A₂ (iPLA₂) family. Although most PNPLA/iPLA₂ enzymes are widely distributed and act on phospholipids or neutral lipids as (phospho)lipases to play homeostatic roles in lipid metabolism, the function of PNPLA1 remained a mystery until a few years ago. However, the recent finding that mutations in the human PNPLA1 gene are linked to autosomal recessive congenital ichthyosis (ARCI), as well as evidence obtained from biochemical and gene knockout studies, has shed light on the function of this enzyme in skin-specific sphingolipid metabolism rather than glycerophospholipid metabolism. PNPLA1 is specifically expressed in differentiated keratinocytes and plays a crucial role in the biosynthesis of ω-O-acylceramide, a particular class of sphingolipids that is essential for skin barrier function. PNPLA1 acts as a unique transacylase that specifically transfers linoleic acid from triglyceride to ω-hydroxy fatty acid in ceramide, thus giving rise to ω-O-acylceramide. In this review, we overview the biosynthetic route and biological role of epidermal ω-O-acylceramide, highlight the function of PNPLA1 as a bona fide acylceramide synthase required for proper skin barrier function and keratinocyte differentiation, and summarize the mutations of PNPLA1 currently identified in ARCI patients.This article is part of a Special Issue entitled Novel functions of phospholipase A₂ Guest Editors: Makoto Murakami and Gerard Lambeau     

The role of iron in the formation of Ediacaran ‘death masks’

The Ediacara biota are an enigmatic group of Neoproterozoic soft-bodied fossils that mark the first major radiation of complex eukaryotic and macroscopic life. These fossils are thought to have been preserved via pyritic “death masks” mediated by seafloor microbial mats, though little about the chemical constraints of this preservational pathway is known, in particular surrounding the role of bioavailable iron in death mask formation and preservational fidelity. In this study, we perform decay experiments on both diploblastic and triploblastic animals under a range of simulated sedimentary iron concentrations, in order to characterize the role of iron in the preservation of Ediacaran organisms. After 28 days of decay, we demonstrate the first convincing “death masks” produced under experimental laboratory conditions composed of iron sulfide and probable oxide veneers. Moreover, our results demonstrate that the abundance of iron in experiments is not the sole control on death mask formation, but also tissue histology and the availability of nucleation sites. This illustrates that Ediacaran preservation via microbial death masks need not be a “perfect storm” of paleoenvironmental porewater and sediment chemistry, but instead can occur under a range of conditions.     

The ‘requirement of total evidence’ and its role in phylogenetic systematics

The question of whether or not to partition data for the purposes of inferring phylogenetic hypotheses remains controversial. Opinions have been especially divided since Kluge's (1989, Systematic Zoology 38, 7–25) claim that data partitioning violates the requirement of total evidence (RTE). Unfortunately, advocacy for or against the RTE has not been based on accurate portrayals of the requirement. The RTE is a basic maxim for non-deductive inference, stipulating that evidence must be considered if it has relevance to an inference. Evidence is relevant if it has a positive or negative effect on a given conclusion. In the case of ℈partitioned’ phylogenetic inferences, the RTE is violated, and the basis for rational belief in any conclusion is compromised, unless it is shown that the partitions are evidentially irrelevant to one another. The goal of phylogenetic systematics is to hypothesize past causal conditions to account for observed shared similarities among two or more species. Such inferences are non-deductive, necessitating consideration of the RTE. Some phylogeneticists claim the parsimony criterion as justification for the RTE. There is no relation between the two – parsimony is a relation between a hypothesis and causal question(s). Parsimony does not dictate the content of premises prior to an inference. ℈Taxonomic congruence,’ ℈supertrees,’ and ℈conditional combination’ methods violate the RTE. Taxonomic congruence and supertree methods also fail to achieve the intended goal of phylogenetic inference, such that ℈consensus trees’ and ℈supertrees’ lack an empirical basis. ℈Conditional combination’ is problematic because hypotheses derived from partitioned data cannot be compared – a causal hypothesis inferred to account for a set of effects only has relevance to those effects, not any comparative relevance to other causal hypotheses. A similar problem arises in the comparisons of hypotheses derived from different causal theories.     

Comprehensive analysis of the roles of ‘black’ and ‘gray’ clusters in structure and function of rat β-parvalbumin

Recently we found two highly conserved structural motifs in the proteins of the EF-hand calcium binding protein family. These motifs provide a supporting scaffold for the Ca²⁺ binding loops and contribute to the hydrophobic core of the EF-hand domain. Each structural motif forms a cluster of three amino acids called cluster I (‘black’ cluster) and cluster II (‘grey’ cluster). Cluster I is much more conserved and mostly incorporates aromatic amino acids. In contrast, cluster II includes a mix of aromatic, hydrophobic, and polar amino acids. The ‘black’ and ‘gray’ clusters in rat β-parvalbumin consist of F48, A100, F103 and G61, L64, M87, respectively. In the present work, we sequentially substituted these amino acids residues by Ala, except Ala100, which was substituted by Val. Physical properties of the mutants were studied by circular dichroism, scanning calorimetry, dynamic light scattering, chemical crosslinking, and fluorescent probe methods. The Ca²⁺ and Mg²⁺ binding affinities of these mutants were evaluated by intrinsic fluorescence and equilibrium dialysis methods. In spite of a rather complicated pattern of contributions of separate amino acid residues of the ‘black’ and ‘gray’ clusters into maintenance of rat β-parvalbumin structural and functional status, the alanine substitutions in the cluster I cause noticeably more pronounced changes in various structural parameters of proteins, such as hydrodynamic radius of apo-form, thermal stability of Ca²⁺/Mg²⁺-loaded forms, and total energy of Ca²⁺ binding in comparison with the changes caused by amino acid substitutions in the cluster II. These findings were further supported by the outputs of computational analysis of the effects of these mutations on the intrinsic disorder predisposition of rat β-parvalbumin, which also indicated that local intrinsic disorder propensities and the overall levels of predicted disorder were strongly affected by mutations in the cluster I, whereas mutations in cluster II had less pronounced effects. These results demonstrate that amino acids of the cluster I provide more essential contribution to the maintenance of structuraland functional properties of the protein in comparison with the residues of the cluster II.     

Squamous cell carcinoma of the head and neck—The role of diffusion and perfusion imaging in tumor recurrence and follow-up

Computed tomography and magnetic resonance imaging-based techniques of functional imaging are proven to be sensitive and reliable tools for detection and staging of head and neck cancer.These new techniques enable to visualize and differentiate subtle pathologic changes before they become evident on standard cross-sectional images.However, it is their role in evaluating possible recurrence and estimation of treatment response that holds the biggest promise.This article describes the role and usefulness of diffusion and perfusion in detecting recurrence and follow-up in patients with head and neck squamous cell carcinoma.     

Polyphenol gene expression and changes in anthocyanins and polyphenols in the skin of ‘Braeburn’ apples after the autumn application of prohexadione-calcium

Prohexadione-calcium (Pro-Ca) transient inhibits 2-Oxoglutarate-dependent dioxygenases and causes significant changes in the flavonoid spectrum of apple. In the present study the influence of two autumn preharvest applications of Pro-Ca on the polyphenol metabolism in apple peel during the advanced maturation was investigated. Pro-Ca was sprayed in two doses, approximately five and 3 weeks before the technological maturity. Changes in the concentrations of hydroxycinnamic acids, dihydrochalcones, flavonols, flavanols and anthocyanins as well as their related gene expression and enzyme activities in the apple peel were monitored six times during the advanced maturation until the technological maturity of the fruits. To evaluate its influence on red coloration differences in the chromatic values a*, h° and L* between the treated and untreated apples were monitored. The parameters showed a temporary effect of Pro-Ca on the intensity of red coloration, which was not detected anymore at the technological maturity of apples. The application of Pro-Ca decreased the flavanone 3-hydroxylase activity and slightly inhibited activities of all the enzymes analyzed. Concomitantly, the concentrations of anthocyanins in the peel of the treated apples decreased, whereas the concentrations of hydroxycinnamic acids, dihydrochalcones and flavan 3-ols increased. Flavonol concentrations, however, remained unchanged. The expression of ANS, ANR, FGT and MYB10 was downregulated after the Pro-Ca treatment. The results indicate that the autumn application of Pro-Ca modulates the biosynthetic pathway resulting in distinct changes in the flavonoid composition in the apple peel of ‘Braeburn’ apples. However, the changes are temporary and are generally suspended during apple storage.     

The ‘fluid mosaic model’ and the ‘lattice model’ as two nonequilibrium states of the same membrane and the significance for biochemical control

Summary Biochemical control involves steep and hysteretic response. But the law of mass action does not allow for cooperativity. Therefore resort is classically made to concerted conformational change of protomers. This explanation of steepness and hysteresis by cooperativity is supported by regular surface patterns often observed by electron microscopy. But at other times the lattice appearance which gave rise to the lattice model is not observed. By contrast, a random appearance is observed and the fluid mosaic model of the membrane is assumed. So we are faced with the choice between the fluid mosaic model and the lattice model. Recently the fluid mosaic model is favoured but unlike the lattice model it does not explain the steep hyteretic response.It is suggested that the lattice model and the fluid mosaic model are in fact expression of two states of the very same membrane. The random state corresponds to a resting state. The lattice state corresponds to an active or inhibited state. Thus the transition from random distribution to hexagonal distribution provides simultaneously for triggering and hysteretic cycle with respect to both chemical production and transport across the membrane. This is a universal mechanism for rapid responsiveness and cyclic activity which is largely independent of the chemical mechanism assumed. It is based on the law of mass action supplemented by lateral diffusion. Conformational change and cooperativity are not invoked at all.     

The outcome of failed free flaps in head and neck and extremity reconstruction: what is next in the reconstructive ladder?

The indications for free flaps have been more or less clarified; however, the course of reconstruction after the failure of a free flap remains undetermined. Is it better to insist on one's initial choice, or should surgeons downgrade their reconstructive goals? To establish a preliminary guideline, this study was designed to retrospectively analyze the outcome of failed free-tissue transfers performed in the authors hospital. Over the past 8 years (1990 through 1997), 3361 head and neck and extremity reconstructions were performed by free-tissue transfers, excluding toe transplantations. Among these reconstructions, 1235 flaps (36.7 percent) were transferred to the head and neck region, and 2126 flaps (63.3 percent) to the extremities. A total of 101 failures (3.0 percent total plus the partial failure rate) were encountered. Forty-two failures occurred in the head and neck region, and 59 in the extremities. Evaluation of the cases revealed that one of three following approaches to handling the failure was taken: (1) a second free-tissue transfer; (2) a regional flap transfer; or (3) conservative management with debridement, wound care, and subsequent closure by secondary intention, whether by local flaps or skin grafting. In the head and neck region, 17 second free flaps (40 percent) and 15 regional flaps (36 percent) were transferred to salvage the reconstruction, whereas conservative management was undertaken in the remaining 10 cases (24 percent). In the extremities, 37 failures were treated conservatively (63 percent) in addition to 17 second free flaps (29 percent) and three regional flaps (5 percent) used to salvage the failed reconstruction. Two cases underwent amputation (3 percent). The average time elapsed between the failure and second free-tissue transfer was 12 days (range, 2 to 60 days) in the head and neck region and 18 days (range, 2 to 56 days) in the extremities. In a total of 34 second free-tissue transfers at both localizations, there were only three failures (9 percent). However, in the head and neck region, seven of the regional flaps transferred (47 percent) and four cases that were conservatively treated (40 percent) either failed or developed complications that lengthened the reconstruction period because of additional procedures. Six other free-tissue transfers had to be performed to manage these complicated cases. Conservative management was quite successful in the extremities; most patients' wounds healed, although more than one skin-graft procedure was required in 10 patients (27 percent). In conclusion, a second free-tissue transfer is, in general, a relatively more reliable and more effective procedure for the treatment of flap failure in the head and neck region, as well as failed vascularized bone flaps in the reconstruction of the extremities. Conservative treatment may be a simple and valid alternative to second (free) flaps for soft-tissue coverage in extremities with partial and even total losses.     

The role of ‘Norin 10’ dwarfing genes in photosynthetic and respiratory activity of wheat leaves

Summary A comparative analysis of eight cultivars of spring wheat (Triticum aestivum) classified by height as tall (T), semi-dwarf (D₁), dwarf (D₂) and very dwarf (D₃) was conducted to study their efficiency of oxygen exchange during photosynthesis and dark respiration. Two cultivars were included in each height group.Cultivars carrying Norin 10 dwarfing genes (D₁, D₂ and D₃) were found to have a significantly higher photosynthetic rate per unit leaf area than talls (T) that lack these genes. Among the Norin gene carriers, dwarf group (D₂) was most efficient, followed by very dwarf (D₃) and semi-dwarf (D₁).Photosynthetic rate and respiratory rate were found to have a positive relationship.     

The role of Schmidt ‘Antonovka’ in apple scab resistance breeding

??Antonovka?? has long been recognised as a major source of scab (Venturia inaequalis) resistance useful for apple breeding worldwide. Both major gene resistances in the form of the Rvi10 and Rvi17 and quantitative resistance, collectively identified as VA, have been identified in different accessions of ??Antonovka??. Most of the ??Antonovka?? scab resistance used in apple-breeding programmes around the world can be traced back to Schmidt ??Antonovka?? and predominantly its B VIII progenies 33,25 (PI 172623), 34,6 (PI 172633), 33,8 (PI 172612) and 34,5 (PI 172632). Using genetic profile reconstruction, we have identified ??common ??Antonovka?? ?? as the progenitor of the B VIII family, which is consistent with it having been a commercial cultivar in Poland and the single source of scab resistance used by Dr. Martin Schmidt. The major ??Antonovka?? scab resistance genes mapped to date are located either very close to Rvi6, or about 20?C25?cM above it, but their identities need further elucidation. The presence of the 139?bp allele of the CH-Vf1 microsatellite marker known to be associated with Rvi17 (Va1) in most of the ??Antonovka?? germplasm used in breeding suggests that it plays a central role in the resistance. The nature and the genetic relationships of the scab resistance in these accessions as well as a number of apple cultivars derived from ??Antonovka??, such as, ??Freedom??, ??Burgundy?? and ??Angold??, are discussed. The parentage of ??Reglindis?? is unclear, but the cultivar commercialised as ??Reglindis?? was confirmed to be an Rvi6 cultivar.     

The role of Apodemus mice and Microtus voles in the diet of the Tengmalm’s owl in Central Europe

Based on a long-term dataset (1999–2010), we investigated how the availability of main prey affects the breeding density and food ecology of the Tengmalm’s owl (Aegolius funereus) in the Czech Republic. In particular, we assessed the role of Microtus voles and Apodemus mice in the diet, based on the main predictions of the optimal diet theory that the diet composition depends on the availability of the main prey. We found that (i) the Tengmalm’s owl exhibited no numerical response to the availability of Microtus voles and Apodemus mice in the field; (ii) the availability of Apodemus mice in the field positively affected their proportion in the diet (26 %), and despite a high proportion of Microtus voles in the owls’ diet (47 %), no relationship was found between their availability in the field and proportion in the diet; (iii) the proportion of Apodemus mice was negatively correlated to the proportion of Microtus voles, Sorex shrews and birds in the diet, but no similar relationship was detected for Microtus voles; (iv) the reproductive output of Tengmalm’s owls was positively correlated to the proportion of Apodemus mice in the diet, as well as to Apodemus mice and Microtus vole availability in the field; and (v) diet diversity and diet overlap were not significantly affected by the abundance of Apodemus mice and Microtus voles. Therefore, the validity of these main optimal diet theory predictions was not confirmed, especially for Microtus vole prey, due to an opportunistic choice between Apodemus mice and Microtus voles. We suggest that the reproductive output of nocturnal raptors in Central Europe may be less dependent on Microtus vole supply than that of their northern counterparts.     

The use of cluster and discriminant analysis in the investigations of the role of trace metals in the pathogenesis of Parkinson’s disease

X-ray fluorescence microscopy was applied for two-dimensional elemental analysis of substantia nigra (SN) tissue. The samples representing Parkinson’s disease (PD) and control cases were examined at HASYLAB beamline L and at ESRF beamline ID22. Two-dimensional mapping of P, S, Cl, K, Ca, Fe, Cu, Zn, Se and Br was done with the spatial resolution of 15 and 5 μm. The masses per unit area of elements in neuromelanin reach nerve cells of SN were determined.The elemental data were processed using two multivariate techniques, namely cluster and discriminant analysis. The statistical methods were used for data reduction, both unsupervised and supervised classification as well as for the creation of a model that would simplify case identification based on the elemental analysis of SN tissue. The results of cluster analysis confirmed the statistical significance of the differences in elemental composition of PD and control SN nerve cells. Based on the results of discriminant analysis, the elements (P, Cl, Fe, Cu and Zn) that played the greatest role in the process of differentiation between neurons from examined groups were determined.     

The role of nodal roots in prostrate clonal herbs: ‘phalanx’ versus ‘guerrilla’

The influence of nodal rooting on branching was studied in three evolutionarily and morphologically diverse species of prostrate clonal herbs: Tradescantia fluminensis (a monocotyledonous extreme ‘phalanx’ species), Calystegia silvatica (a dicotyledonous extreme ‘guerrilla’ species) and Trifolium repens (a dicotyledonous intermediate species). In all three, branch development from axillary buds is regulated by a positive signal produced by roots together with inhibitory influences from both pre-existing branches and shoot apical buds (apical dominance). Responses to nodal roots are cumulative and increased root activity leads to more vigorous bud outgrowth. In the absence of nodal roots, a single basal root system is unable to maintain continued extension growth of the shoot. We suggest that as individual nodal roots and stem internodes are both short-lived in these nodally-rooting clonal species, the plants’ investment in them is minimal. Thus, in contrast to perennial species lacking nodal roots, individual root systems in prostrate clonal herbs are small and stems have little secondary thickening and development of long-distance transport tissues. Hence the decline in extension growth of the shoot in the absence of nodal roots could be linked to the weak development of long-distance transport tissues in their relatively thin horizontal stems and to resource sharing between primary stems and lateral branches (as suggested by the greater retardation of primary stem growth in the more profusely branched ‘phalanx’ species (Trifolium and Tradescantia) than in the weakly branched ‘guerrilla’ species, Calystegia). These findings are consistent with the view that the long-term persistence of genotypes of nodally-rooting prostrate species is dependent upon them encountering the moist conditions required to facilitate the continual development of new young nodal root systems.