Vertebrate endothelial lipase: comparative studies of an ancient gene and protein in vertebrate evolution

Endothelial lipase (gene: LIPG; enzyme: EL) is one of three members of the triglyceride lipase family that contributes to lipoprotein degradation within the circulation system and plays a major role in HDL metabolism in the body. In this study, in silico methods were used to predict the amino acid sequences, secondary and tertiary structures, and gene locations for LIPG genes and encoded proteins using data from several vertebrate genome projects. LIPG is located on human chromosome 18 and is distinct from other human ‘neutral lipase’ genes, hepatic lipase (gene: LIPC; enzyme: HL) and lipoprotein lipase (gene: LPL; enzyme: LPL) examined. Vertebrate LIPG genes usually contained 10 coding exons located on the positive strand for most primates, as well as for horse, bovine, opossum, platypus and frog genomes. The rat LIPG gene however contained only 9 coding exons apparently due to the presence of a ‘stop’ codon’ within exon 9. Vertebrate EL protein subunits shared 58–97% sequence identity as compared with 38–45% sequence identities with human HL and LPL. Four previously reported human EL N-glycosylation sites were predominantly conserved among the 10 potential N-glycosylation sites observed for the vertebrate EL sequences examined. Sequence alignments and identities for key EL amino acid residues were observed as well as conservation of predicted secondary and tertiary structures with those previously reported for horse pancreatic lipase (PL) (Bourne et al. 1994). Several potential sites for regulating LIPG gene expression were observed including CpG islands near the LIPG gene promoter and a predicted microRNA binding site near the 3’-untranslated region. Promoter regions containing functional polymorphisms that regulate HDL cholesterol in baboons were conserved among primates but not retained between primates and rodents. Phylogenetic analyses examined the relationships and potential evolutionary origins of the vertebrate LIPG gene subfamily with other neutral triglyceride lipase gene families, LIPC and LPL. It is apparent that the triglyceride lipase ancestral gene for the vertebrate LIPG gene predated the appearance of fish during vertebrate evolution >500 million years ago.     

A comparative study of microtubules in some vertebrate and invertebrate cells

Summary An electron microscope study of a variety of invertebrate and vertebrate cell types has supported the postulate that the microtubule is a universal cellular organelle. Microtubules of similar dimensions have been observed in the flagellum and beneath the plasma membrane of Trypanosoma lewisi, in the flagellum, manchette and mitotic spindle of the earthworm (Lumbricus terrestris) spermatid; and in fibroblasts, proximal convoluted and collecting tubule cells of the hypertrophying rat kidney. The specific occurrence and organization of the microtubules in cells undergoing morphological and developmental changes have suggested that these organelles are contractile and that they effectively contribute to the maintenance of cellular form. The possibility that microtubules may function as an intracellular transport system is also suggested.This work was supported by grants CA-04046, GM-08380, and K 3-AM-4932 from the U. S. Public Health Service.     

Fine structure and immunocytochemistry of monotreme hairs, with emphasis on the inner root sheath and trichohyalin-based cornification during hair evolution

The fine structure of hairs in the most ancient extant mammals, the monotremes, is not known. The present study analyzes the ultrastructure and immunocytochemistry for keratins, trichohyalin, and transglutaminase in monotreme hairs and compares their distribution with that present in hairs of the other mammals. The overall ultrastructure of the hair and the distribution of keratins is similar to that of marsupial and placental hairs. Acidic and basic keratins mostly localize in the outer root sheath. The inner root sheath (IRS) comprises 4-8 cell layers in most hairs and forms a tile-like sheath around the hair shaft. No cytological distinction between the Henle and Huxley layers is seen as cells become cornified about at the same time. Externally to the last cornified IRS cells (homologous to the Henle layer), the companion layer contains numerous bundles of keratin. Occasionally, some granules in the companion layer show immunoreactivity for the trichohyalin antibody. This further suggests that the IRS in monotremes is ill-defined, as the companion layer of placental hairs studied so far does not express trichohyalin. A cross-reactivity with an antibody against sheep trichohyalin is present in the IRS of monotremes, suggesting conserved epitopes across mammalian trichohyalin. Trichohyalin granules in the IRS consist of a framework of immunolabeled coarse filaments of 10-12 nm. The latter assume a parallel orientation and lose the immunoreactivity in fully cornified cells. Transglutaminase immunolabeling is diffuse among trichohyalin granules and among the parallel 10-12 nm filaments of maturing inner root cells. Transglutaminase is present where its substrate, trichohyalin, is modified as matrix protein. Cornification of IRS is different from that of hair fiber cuticle and from that of the cornified layer of the epidermis above the follicle. The different consistency among cuticle, IRS, and corneous layer of the epidermis determines separation between hair fiber, IRS, and epidermis. This allows the hair to exit on the epidermal surface after shedding from the IRS and epidermis. Based on comparative studies of reptilian and mammalian skin, a speculative hypothesis on the evolution of the IRS and hairs from the skin of synapsid reptiles is presented.     

Immunological studies on vertebrate photoreceptors

Many monoclonal antibodies to the rhodopsin and other visual pigments have been reported by a number of research groups. The antibodies are available for cell classification, detecting some molecular difference(s) among various visual pigments, and also recently for protein purification and gene cloning. In this review article, we paid attention to precedingly reported 20 anti-photoreceptor antibodies in order to compare them with our own two anti-lamprey photoreceptor antibodies, H16 and B11. From the point of view of immunohistochemical reactivity, the H16 antibody was regarded as a marker for a universal component of vertebrate rhodopsins and a certain number of cone pigments; meanwhile the B11 antibody would recognize more specifically lower-vertebrate rhodopsins and, perhaps, blue-sensitive cone pigments in higher vertebrate retinas.     

Lineage-specific evolution of the vertebrate Otopetrin gene family revealed by comparative genomic analyses

Background  

Mutations in the Otopetrin 1 gene (Otop1) in mice and fish produce an unusual bilateral vestibular pathology that involves the absence of otoconia without hearing impairment. The encoded protein, Otop1, is the only functionally characterized member of the Otopetrin Domain Protein (ODP) family; the extended sequence and structural preservation of ODP proteins in metazoans suggest a conserved functional role. Here, we use the tools of sequence- and cytogenetic-based comparative genomics to study the Otop1 and the Otop2-Otop3 genes and to establish their genomic context in 25 vertebrates. We extend our evolutionary study to include the gene mutated in Usher syndrome (USH) subtype 1G (Ush1g), both because of the head-to-tail clustering of Ush1g with Otop2 and because Otop1 and Ush1g mutations result in inner ear phenotypes.     

脊椎动物视蛋白基因分子进化的研究进展

视觉是动物获取外界信息的重要途径,在动物的捕食、配偶选择及讯息传递等方面均有重要作用,对动物的进化具有深远而广泛的影响[1].经过科学家的不懈努力,生态因素被认为是引导视觉系统进化的一个主要因素[1,2].     

Brain structure evolution in a basal vertebrate clade: evidence from phylogenetic comparative analysis of cichlid fishes

Background  

The vertebrate brain is composed of several interconnected, functionally distinct structures and much debate has surrounded the basic question of how these structures evolve. On the one hand, according to the 'mosaic evolution hypothesis', because of the elevated metabolic cost of brain tissue, selection is expected to target specific structures mediating the cognitive abilities which are being favored. On the other hand, the 'concerted evolution hypothesis' argues that developmental constraints limit such mosaic evolution and instead the size of the entire brain varies in response to selection on any of its constituent parts. To date, analyses of these hypotheses of brain evolution have been limited to mammals and birds; excluding Actinopterygii, the basal and most diverse class of vertebrates. Using a combination of recently developed phylogenetic multivariate allometry analyses and comparative methods that can identify distinct rates of evolution, even in highly correlated traits, we studied brain structure evolution in a highly variable clade of ray-finned fishes; the Tanganyikan cichlids.     

The evolution of developmental gene networks: lessons from comparative studies on holometabolous insects

Recent comparative studies have revealed significant differences in the developmental gene networks operating in three holometabolous insects: the beetle Tribolium castaneum, the parasitic wasp Nasonia vitripennis and the fruitfly Drosophila melanogaster. I discuss these differences in relation to divergent and convergent changes in cellular embryology. I speculate on how segmentation gene networks have evolved to operate in divergent embryological contexts, and highlight the role that co-option might have played in this process. I argue that insects represent an important example of how diversification in life-history strategies between lineages can lead to divergence in the genetic and cellular mechanisms controlling the development of homologous adult structures.     

Symposium on the evolution and development of the vertebrate head

Among the symposia held at the seminal meeting of the European Society for Evolutionary Developmental Biology was one centered on the development and evolution of the vertebrate head, an exquisitely complex anatomical system. The articles presented at this meeting have been gathered in a special issue of the Journal of Experimental Zoology, and are here reviewed by the organizers of the symposia. These articles cover a breadth of subjects, including interactions between cells derived from the different germ layers, such as those underlying neural crest cell migration and fate and cranial muscle specification, as well as placode development and the origin, development, and evolution of important evolutionary innovations such as jaws and the trabecula cranii. In this introduction, we provide a short historical overview of themes of research into the fundamental organization, structure, and development of the vertebrate head, including the search for head segmentation and the relevance of the New Head Hypothesis, and subsequently present the topics discussed in each of the articles. This overview of the past and the present of head evo-devo is then followed by a glimpse at its possible future and a brief examination of the utility of the notions of heterochrony, heterotopy, and heterofacience in describing evolutionarily important changes in developmental events.     

Perspectives on protein evolution from simple exact models

Understanding the evolution of biopolymers is important to rationalise the directed and undirected design of functional molecules. Large scale experiments or detailed computational studies are often impractical. Therefore, simple model systems, such as RNA secondary structure and lattice proteins have been adapted to study general statistical and topological features of genotype (sequence) to phenotype (structure) maps. We review findings from such models that address aspects of thermodynamic and mutational robustness, neutral evolution and recombination of proteins. We compare various modelling approaches, and discuss their generality, parameter dependency and experimental verifications of their predictions. The most striking observation is the universal emergence of neutral nets--sets of phenotypically identical genotypes that are interconnected by series of point mutations. However, fast adaptation by point mutations appears to be problematic for proteins. This may explain why proteins appear to be more specific while RNA is rather versatile. This could even be the reason why RNA had to evolve before proteins. Similar principles of biological organisation are reflected in sequence and structure databases of real proteins. Insights gained from modelling are useful for designing more efficient database organisation and search strategies.     

Studies on isozymes of sorbitol dehydrogenase in some vertebrate species

Summary In swine, the enzyme sorbitol dehydrogenase exhibits a genetically determined polymorphism as identified by multiple electrophoretic bands suggesting a tetrameric structure (Op't Hof, 1969). In order to obtain further information on the genetics of this polymorphism, a number of other vertebrate species were examined. Multiple alleles at the SDH gene locus were found in the Cyprinid fishes Leuciscus and Rutilus, and in the Salmonid fish Salmo trutta. The electrophoretic patterns found in these species are compatible with the model of a tetrameric structure of the enzyme. This model was further verified by dissociation-reassociation studies with the homomeric enzymes of swine and Leuciscus. Since in the heterozygote an intensity gradient of the isozymes was seen, the three phenotypes observed in swine were further characterized by means of activity measurements and application of different substrates. The results point to a differential activity of the two different homomeres.Supported by the Deutsche Forschungsgemeinschaft.     

Histochemical studies on the mucins of the vertebrate tongues

Summary With a view to augment the understanding of the tongue mucosubstances and their significance in the physiology of taste, tongues of two amphibians were investigated histochemically to determine the distribution and nature of the mucosubstances by employing recent techniques, and the results were considered comparatively with the tongue mucins of other vertebrates and the animal mucosubstances in general. A heterogenous distribution of neutral mucins, sulfomucins and sialomucins in fungiform and filiform papillae, ventral epithelium, lingual glands and connectives tissue could be significantly noted on the basis of which various cell types having specialised mucosubstances were identified in the papillae and the ventral epithelium.The tongue mucosubstances, especially sulfomucins and sialomucins, exhibited inharent heterogenity. Sulfomucins at some sites were hyaluronidas-labile and at other hyaluronidaseresistant, their azurophilia especially at low pH was also different, some being azurophilic and others nonazurophilic. Sialomucins also exhibited such heterogenity, at some sites they were labile to acid hydrolysis and mild methylation but in others they were resistant to the latter, though sialomucins at both sites were sialidase-labile. The mucosubstances localised in the serous glands were highly typical, since they exhibited extraordinary histochemical reactions, they possessed intensely PAS positive reactivity resistant to diastase, hyaluronidase and sialidase, negative to alcian blue both at pH 1 and 2.5, and exhibited no metachromasia at both low and high pH levels, but showed alcianophilia only at high pH levels. Such high pH alcianophilia was sialidase and hyaluronidase resistant but labile to mild methylation. These mucosubstances bear some similarity to those of mammalian parotid.Such heterogenity was reflected at species-specific level, since some interesting speciesspecific differences were observed in mucosubstances of histologically identical cells and tissues of tongues of the two species of amphibians which might assist in the elucidation of phylogenetic importance of mucins.This investigation forms a part of Ph. D. Thesis to be submitted by Mr. M. N. Nalavade to Shivaji University, Kolhapur, under the guidance of Dr. A. T. Varute.     

Perspectives on dimensional analysis in scaling studies

Scaling, as defined here, refers to the precise identification of those structural and functional aspects of selected systems that are size-independent, over some specified size-range. Small and large instances of such systems are said to be similar in respect to those aspects. Physicists and engineers have developed an elaborate methodology for identifying quantitative similarity criteria applicable to physical systems.These criteria are usually derived by dimensional analysis of physical laws pertinent to a given system. Knowledge of similarity criteria allows one to predict quantitatively the behavior of a large-scale prototype from measurements made on a small-scale model (e.g., in a wind tunnel). Numerous workers have sought to apply this elegant methodology to scale-up in biology. After briefly reviewing dimensional analysis, scaling, and modeling, as deployed in physics and engineering, this article discusses several well-known examples of their application to bioscaling problems (chiefly in mammals) and gives reasons for doubting their validity. It concludes that this methodology is unlikely to provide explanations applicable to scale-up in diverse species.