Exon-Intron Structure and Evolution of the Lipocalin Gene Family

Innovación EducativaThe Lipocalins are an ancient protein family whose expression is currently confirmed in bacteria, protoctists, plants, arthropods, and chordates. The evolution of this protein family has been assessed previously using amino acid sequence phylogenies. In this report we use an independent set of characters derived from the gene structure (exon-intron arrangement) to infer a new lipocalin phylogeny. We also present the novel gene structure of three insect lipocalins. The position and phase of introns are well preserved among lipocalin clades when mapped onto a protein sequence alignment, suggesting the homologous nature of these introns. Because of this homology, we use the intron position and phase of 23 lipocalin genes to reconstruct a phylogeny by maximum parsimony and distance methods. These phylogenies are very similar to the phylogenies derived from protein sequence. This result is confirmed by congruence analysis, and a consensus tree shows the commonalities between the two source trees. Interestingly, the intron arrangement phylogeny shows that metazoan lipocalins have more introns than other eukaryotic lipocalins, and that intron gains have occurred in the C-termini of chordate lipocalins. We also analyze the relationship of intron arrangement and protein tertiary structure, as well as the relationship of lipocalins with members of the proposed structural superfamily of calycins. Our congruence analysis validates the gene structure data as a source of phylogenetic information and helps to further refine our hypothesis on the evolutionary history of lipocalins.2015-09-1

Grasshopper Lazarillo, a GPI-anchored Lipocalin, increases Drosophila longevity and stress resistance, and functionally replaces its secreted homolog NLaz

Producción CientíficaLazarillo (Laz) is a glycosyl-phosphatidylinositol (GPI)-linked glycoprotein first characterized in the developing nervous system of the grasshopper Schistocerca americana. It belongs to the Lipocalins, a functionally diverse family of mostly secreted proteins. In this work we test whether the protective capacity known for Laz homologs in flies and vertebrates (NLaz, GLaz and ApoD) is evolutionarily conserved in grasshopper Laz, and can be exerted from the plasma membrane in a cell-autonomous manner. First we demonstrate that extracellular forms of Laz have autocrine and paracrine protecting effects for oxidative stress-challenged Drosophila S2 cells. Then we assay the effects of overexpressing GPI-linked Laz in adult Drosophila and whether it rescues both known and novel phenotypes of NLaz null mutants. Local effects of GPI-linked Laz inside and outside the nervous system promote survival upon different stress forms, and extend lifespan and healthspan of the flies in a cell-type dependent manner. Outside the nervous system, expression in fat body cells but not in hemocytes results in protection. Within the nervous system, glial cell expression is more effective than neuronal expression. Laz actions are sexually dimorphic in some expression domains. Fat storage promotion and not modifications in hydrocarbon profiles or quantities explain the starvationedesiccation resistance caused by Laz overexpression. This effect is exerted when Laz is expressed ubiquitously or in dopaminergic cells, but not in hemocytes. Grasshopper Laz functionally restores the loss of NLaz, rescuing stress-sensitivity as well as premature accumulation of aging-related damage, monitored by advanced glycation end products (AGEs). However Laz does not rescue NLaz courtship behavioral defects. Finally, the presence of two new Lipocalins with predicted GPI-anchors in mosquitoes shows that the functional advantages of GPI-linkage have been commonly exploited by Lipocalins in the arthropodan lineage

Sex-dependent modulation of longevity by two Drosophila homologues of human Apolipoprotein D, GLaz and NLaz

Producción CientíficaApolipoprotein D (ApoD), a member of the Lipocalin family, is the gene most up-regulated with age in the mammalian brain. Its expression strongly correlates with aging-associated neurodegenerative and metabolic diseases. Two homologues of ApoD expressed in the Drosophila brain, Glial Lazarillo (GLaz) and Neural Lazarillo (NLaz), are known to alter longevity in male flies. However, sex differences in the aging process have not been explored so far for these genes. Here we demonstrate that NLaz alters lifespan in both sexes, but unexpectedly the lack of GLaz influences longevity in a sex-specific way, reducing longevity in males but not in females. While NLaz has metabolic functions similar to ApoD, the regulation of GLaz expression upon aging is the closest to ApoD in the aging brain. A multivariate analysis of physiological parameters relevant to lifespan modulation uncovers both common and specialized functions for the two Lipocalins, and reveals that changes in protein homeostasis account for the observed sex-specific patterns of longevity. The response to oxidative stress and accumulation of lipid peroxides are among their common functions, while the transcriptional and behavioral response to starvation, the pattern of daily locomotor activity, storage of fat along aging, fertility, and courtship behavior differentiate NLaz from GLaz mutants. We also demonstrate that food composition is an important environmental parameter influencing stress resistance and reproductive phenotypes of both Lipocalin mutants. Since ApoD shares many properties with the common ancestor of invertebrate Lipocalins, we must benefit from this global comparison with both GLaz and NLaz to understand the complex functions of ApoD in mammalian aging and neurodegeneration

Cocyclic Hadamard matrices over Latin rectangles

In the literature, the theory of cocyclic Hadamard matrices has always been developed over finite groups. This paper introduces the natural generalization of this theory to be developed over Latin rectangles. In this regard, once we introduce the concept of binary cocycle over a given Latin rectangle, we expose examples of Hadamard matrices that are not cocyclic over finite groups but they are over Latin rectangles. Since it is also shown that not every Hadamard matrix is cocyclic over a Latin rectangle, we focus on answering both problems of existence of Hadamard matrices that are cocyclic over a given Latin rectangle and also its reciprocal, that is, the existence of Latin rectangles over which a given Hadamard matrix is cocyclic. We prove in particular that every Latin square over which a Hadamard matrix is cocyclic must be the multiplication table of a loop (not necessarily associative). Besides, we prove the existence of cocyclic Hadamard matrices over non-associative loops of order 2t+3, for all positive integer t > 0.Junta de Andalucía FQM-01

Genetic deficiency of apolipoprotein D in the mouse is associated with nonfasting hypertriglyceridemia and hyperinsulinemia

Producción CientíficaApolipoprotein D (ApoD) is an atypical apolipoprotein with an incompletely understood function in the regulation of triglyceride and glucose metabolism. We have demonstrated that elevated ApoD production in mice results in improved postprandial triglyceride clearance. This work studies the role of ApoD deficiency in the regulation of triglyceride and glucose metabolism and its dependence on aging. We used ApoD knockout (ApoD-KO) mice of 3 and 21 months of age. Body weight and food intake were measured. Hepatic histology, triglyceride content, lipoprotein lipase levels, and plasma metabolites were studied. Phenotypic characterization of glucose metabolism was performed using glucose tolerance test. β-Cell mass, islet volume, and islet number were analyzed by histomorphometry. Apolipoprotein D deficiency results in nonfasting hypertriglyceridemia in young (P = .01) and aged mice (P = .002). In young ApoD-KO mice, hypertriglyceridemiawas associated with 30% to 50% increased food intake in nonfasting and fasting conditions, respectively, without changes in body weight. In addition, lipoprotein lipase levels were reduced by 35% in adipose tissue (P = .006). In aged ApoD-KO mice, hypertriglyceridemia was not associated with changes in food intake or body weight, whereas hepatic triglyceride levels were reduced by 35% (P = .02). Furthermore, nonfasting plasma insulin levels were elevated by 2-fold in young (P = .016) and aged (P = .004) ApoD-KO mice, without changes in blood glucose levels, glucose tolerance, β-cell mass, or islet number. These findings underscore the importance of ApoD in the regulation of plasma insulin levels and triglyceride metabolism, suggesting that ApoD plays an important role in the pathogenesis of dyslipidemia

A Mixed Heuristic for Generating Cocyclic Hadamard Matrices

A way of generating cocyclic Hadamard matrices is described, which combines a new heuristic, coming from a novel notion of fitness, and a peculiar local search, defined as a constraint satisfaction problem. Calculations support the idea that finding a cocyclic Hadamard matrix of order 4 · 47 might be within reach, for the first time, progressing further upon the ideas explained in this work.Junta de Andalucía FQM-01

ApoD, a Glia-Derived Apolipoprotein, Is Required for Peripheral Nerve Functional Integrity and a Timely Response to Injury

Producción CientíficaGlial cells are a key element to the process of axonal regeneration, either promoting or inhibiting axonal growth. The study of glial derived factors induced by injury is important to understand the processes that allow or preclude regeneration, and can explain why the PNS has a remarkable ability to regenerate, while the CNS does not. In this work we focus on Apolipoprotein D (ApoD), a Lipocalin expressed by glial cells in the PNS and CNS. ApoD expression is strongly induced upon PNS injury, but its role has not been elucidated. Here we show that ApoD is required for: (1) the maintenance of peripheral nerve function and tissue homeostasis with age, and (2) an adequate and timely response to injury. We study crushed sciatic nerves at two ages using ApoD knock-out and transgenic mice over-expressing human ApoD. The lack of ApoD decreases motor nerve conduction velocity and the thickness of myelin sheath in intact nerves. Following injury, we analyze the functional recovery, the cellular processes, and the protein and mRNA expression profiles of a group of injury-induced genes. ApoD helps to recover locomotor function after injury, promoting myelin clearance, and regulating the extent of angiogenesis and the number of macrophages recruited to the injury site. Axon regeneration and remyelination are delayed without ApoD and stimulated by excess ApoD. The mRNA and protein expression profiles reveal that ApoD is functionally connected in an age-dependent manner to specific molecular programs triggered by injury.2015-09-1

Phylogeny and regulation of four lipocalin genes clustered in the chicken genome: evidence of a functional diversification after gene duplication

Producción CientíficaA novel lipocalin gene is here reported that represents the fourth member of a cluster we have identified in the chicken genome. This cluster also includes Chondrogenesis-Associated Lipocalins h and g (CALh, CALg) and Extracellular Fatty Acid Binding Protein (Ex- FABP). The new gene codes for a 22-kDa secreted protein with three cysteine residues and a series of sequence features well conserved in the lipocalin family. All the genes in the cluster are structurally similar presenting comparable exon/intron boundary positions and exon sizes. A phylogenetic analysis indicates the monophyletic grouping of these genes, and their relationship with the lipocalins a-1-microglobulin (A1mg), complement factor 8g chain (C8GC), prostaglandin D synthase (PGDS), and neutrophil-gelatinase-associated lipocalin (NGAL). The new cluster gene appears to be the ortholog of the mammalian C8GC and was thus named Ggal-C8GC. This orthology also suggests that this lipocalin was present in the ancestor common to reptiles and mammals. In addition to other expressing tissues, Ex-FABP, CALh and CALg genes are highly transcribed in chondrocytes at late stages of chondrogenesis during endochondral bone formation and/or upon inflammatory stimulation. Here, we show that they are also transcriptionally induced when chondrocytes are subjected to various biological events as cell quiescence, cell shape transition, and hormonal stimulation. By contrast, Ggal-C8GC transcripts are only barely detectable in chondrocytes, but are more abundant in liver, kidney, brain, heart, skeletal muscle and particularly in skin. Moreover, no expression induction was observed neither during chondrocyte differentiation, nor upon any of the stimulations mentioned above. This indicates that the Ggal-C8GC gene was co-opted for a novel function after the duplication events that gave rise to the cluster. The peculiar coordinated regulation of Ex-FABP, CALh and CALg, and the apparent divergent role of Ggal-C8GC suggest that these gene duplications may have been maintained during evolution by a sub-functionalization mechanism where some common function(s) are shared by several members of the cluster and some other specialized function(s) are unique to other members

Decreased kainate receptors in the hippocampus of apolipoprotein D knockout mice

Producción CientíficaApolipoprotein D (ApoD) has many actions critical to maintaining mammalian CNS function. It is therefore significant that levels of ApoD have been shown to be altered in the CNS of subjects with schizophrenia, suggesting a role for ApoD in the pathophysiology of the disorder. There is also a large body of evidence that cortical and hippocampal glutamatergic, serotonergic and cholinergic systems are affected by the pathophysiology of schizophrenia. Thus, we decided to use in vitro radioligand binding and autoradiography tomeasure levels of ionotropic glutamate, somemuscarinic and serotonin 2Areceptors in theCNS ofApoD-/- and isogenic wild-type mice. These studies revealed a 20% decrease(mean±SEM: 104±10.2 vs. 130±10.4 fmol/mg ETE) in the density of kainate receptors in the CA 2–3 of the ApoD-/- mice. In addition therewas a global decrease inAMPA receptors (F1,214=4.67, pb0.05) and a global increase in muscarinic M2/M4 receptors (F1,208=22.77, pb0.0001) in the ApoD-/- mice that did not reach significance in any single cytoarchitectural region. We conclude that glutamatergic pathways seem to be particularly affected in ApoD-/- mice and this may contribute to the changes in learning and memory, motor tasks and orientation-based tasks observed in these animals, all of which involve glutamatergic neurotransmission