DOCSLIB.ORG

Mechanism of Skin Morphogenesis. II. Retinoic Acid Modulates Axis Orientation and Phenotypes of Skin Appendages

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Development 115, 839-852 (1992) 839 Printed in Great Britain © The Company of Biologists Limited 1992 Mechanism of skin morphogenesis. II. Retinoic acid modulates axis orientation and phenotypes of skin appendages CHENG-MING CHUONG*, SHEREE A. TING, RANDALL B. WIDELITZ andYUN-SHAIN LEE Department of Pathology, HMR 204, 2011 Zonal Ave, School of Medicine, University of Southern California, Los Angeles, CA 90033, USA *Author for correspondence Summary The factors that determine the axial orientation and Both all-trans and 13-cis RA have morphogenetic phenotypes of skin appendages were analyzed by study- activity. Retinol has no effect and retinal has a small ing the effect of retinoic acid (RA) on embryonic chicken inhibitory effect but neither phenotypic transformation skin explant cultures. With RA uniformly distributed in nor axial disorientation were observed. The antero-pos- the culture media, the feather buds became smaller, were terior gradient of homeoprotein XlHbox 1 in feather disoriented or were transformed into scale-like struc- buds became diffusive after RA treatment. RA dissolves tures in a concentration-dependent manner (from 0.05 - dermal condensations and the distribution of N-CAM is 2.5 M). With RA distributed as a gradient created by a altered from an anterior localized pattern to a diffusive RA-soaked anion exchange bead, a radial zone of inhibi- presence in the bud cores. Endogenous retinoids in devel- tion with a rim of disoriented buds was observed. The oping skins show developmental stage-dependent new axis of the disoriented buds appeared to be deter- changes both quantitatively and qualitatively. The mined by a combination of the original feather axis deter- results suggest that RA either is or can modulate the mining force and a new axial force pointing centrifugally endogenous morphogen(s) that determine the orientation away from the RA source. This observed result can be and phenotype of skin appendages, and that this morpho- simulated with a computer model using a vectorial sum of genetic pathway involves Hox genes and adhesion mole- different feather axial determination forces. The size of cules. the inhibited zone is linearly correlated to the RA concen- tration and may be used to quantify the morphogenetic activity of retinoids. These effects are specific to develop- Key words: homeoprotein gradient, Hox, feather buds, scale, mental stages (Hamburg and Hamilton stage 31-34). polarity, skin morphogenesis, retinoic acid, axis orientation. Introduction mice (Kessel and Gruss, 1991). Localized application of RA in vivo by implanting a RA-soaked bead into the anterior Pattern formation is a crucial event in embryonic develop- limb bud can cause a mirror-image axis duplication in the ment (summarized in Gilbert, 1991) This process requires limb digit pattern (Tickle et al., 1982). In the latter two cases, cells to form ordered spatial arrangements and to differen- there are also corresponding changes in the homeobox gene tially express genes at specific positions. Positional infor- expression patterns (Nohno et al., 1991; Izpisua-Belmonte et mation mediated by some diffusible morphogen(s) has been al., 1991; Kessel and Gruss, 1991), implying a series of mol- proposed (Wolpert, 1978), but the nature of these hypotheti- ecular events involving retinoid-related molecules and Hox cal morphogens remains elusive. Recent progress has identi- genes along the pattern formation pathway. fied that homeobox (Hox) genes and retinoids are involved in One of the classical models in the study of pattern forma- the phenotype and axis determination during morphogenesis tion is the induction of skin appendages. Studies of morpho- (Gehring, 1985; Tickle, 1991; De Robertis et al., 1991). For logical and biochemical events in the various stages of devel- example, mutation of Hox genes causes transformation of opment of feathers, hairs and scales have been described appendages in Drosophila. Exogenous delivery of RA can (Lucas and Sttenheim, 1972). The central concern is to deter- induce the homeotic conversion of tail structures to legs in mine how genes are locally regulated to form many different the marbled balloon frog (Mohanty-Hejmadi et al., 1992). types of skin appendages from the genomic DNA of a single RA can cause an antero-posterior reversal of axis in the organism. A variety of epithelial-mesenchymal recombina- developing nervous system of Xenopus laevis (Durston et al., tion experiments have been performed which led to the con- 1989; Ruiz i Altaba and Jessell, 1991) and in the spine of clusion that the message for the phenotype of skin 840 C.-M. Chuong and others appendages is stored in the mesenchyme (reviewed in (Promega) were used as substrates in which a positive reaction Sengel, 1976). However, the molecular basis of this stored results in purple staining. The sections were mounted in glycerin message remains unknown. mounting media. We have recently discovered that there are anterior-pos- Antibodies to N-CAM were described in Chuong and Edelman terior (A-P) homeoprotein gradients present transiently in (1985). Polyclonal antibodies to XlHBox 1 were produced by developing feather buds (Chuong et al., 1990). This and immunizing with rabbit fusion proteins (Oliver et al., 1988) and its expression pattern in chicken feather development was described in other’s previous results (reviewed in De Robertis et al., Chuong et al. (1990). We will tentatively call the chicken protein(s) 1991) led us to hypothesize that homeoproteins may be recognized by anti-Xenopus XlHbox 1 as cXlHbox 1. DNA involved in setting up the A-P axis of cell fields at different sequence data so far suggests that XlHBox 1 most closely resembles levels, first for the body axis, then for the limb axis, and mouse Hox 3.3. Whether cXlHbox 1 is indeed one or several finally for the feather axis. With further characterization, we homeoproteins is unknown, but the distribution pattern of cXlHbox have shown that there are position-specific expression pat- 1 provides a useful markers for homeoprotein distribution. Anti- terns of homeoproteins (Chuong, 1991). If this hypothesis is bodies to alpha and beta keratin were kindly provided by Dr. R. H. correct, alteration of Hox genes should cause changes in the Sawyer and L. Knapp and was performed according to O’Guin et al. orientation or phenotypes of skin appendages. (1982) and Zeltinger and Sawyer (1992). RA has been shown to regulate homeobox gene expression both in vitro (Simeone et al., 1990) and in vivo Retinoid (Nohno et al., 1991; Izpisua-Belmonte et al., 1991; Kessel and Gruss, 1991) and the human homeobox 3D promoter has Retinoids including all-trans RA, 13-cis-RA, retinol and retinal were obtained from Sigma. Retinoids were weighed and dissolved been shown to be regulated by RA in embryonal carcinoma in dimethyl sulfoxide (DMSO) to make 10 mg/ml stock solution. cells (Alcioni et al., 1992). Therefore in the present study, we They were aliquoted into 20 ml aliquots, wrapped in aluminum foil exposed developing feather buds to RA in culture media or a and stored at - 40°C. One aliquot was thawed immediately before local micro RA gradient. We observed alterations of orienta- use and discarded in the same day. For experiments using retinoid in tion and phenotypes of skin appendages concomitant with culture media, aliquots of stock solution were added to the media to alterations of the distribution of homeoprotein and N-CAM make various final concentrations (0.05 - 9.0 mM). In some experi- expression. ments, absolute ethanol was used instead of DMSO, and the results were the same. For preparation of retinoid beads, we followed Tickle et al. (1982) with some modification. AG1-X8 ion exchange Material and method beads (Bio-rad) of 100-200 mm diameter were soaked for 2 hours in either DMSO only or in solutions containing 0.01 - 5 mg/ml of retinol, retinal, all-trans RA, or 13-cis-RA. The beads were then Chicken embryos washed in DMEM and placed on skin explant cultures using micro- Fertilized White Leghorn chicken eggs were obtained from Red manipulator (Narishigi) under dissection microscope. Cultures con- Wing Farm (Los Angeles) and incubated in a humidified chamber at taining retinoids were kept away from light as much as possible. 38°C (Humidare). The embryos were staged according to Ham- burger and Hamilton (1951). Scanning electron microscopy Skin explant cultures intended for scanning electron microscopy Skin explants culture were fixed in 1/2 strength Karnovsky’s fixative overnight at 4°C, White Leghorn chicken embryos between 6.5 (stage 30) and 8 post-fixed in thio-carbohydrazide, and followed by osmium fixa- (stage 34) days of incubation were obtained from K and R Farm tion. The specimen were critically pointed dried and coated with (Westminster, CA). The dorsal skins between the lower neck to the gold palladium. They were viewed with an Hitachi S-570 scanning tail were dissected in Hank’s buffered saline solution (Gibco/BRL) microscope. We thank Dr Janet Blanks and Ms Chris Spee of the under dissection microscope and placed on culture inserts in 6-well Doheny Eye Institute for their expertise and help in processing these culture dishes (Falcon). The culture media contains DMEM with samples. 2% fetal calf serum and was changed every two days. The cultures were incubated at 37°C at an atmosphere of 5% CO2 and 95% air. The morphogenesis of feather buds were recorded with Olympus Computer model OMT 4 camera using inverted microscope (Olympus IMT-2) or dis- We have generated a computer model to simulate the effects of RA section microscope. on feather axis determination. This model was written under the premise that RA supplies an axial force which radiates out from the central bead in a concentration-dependent manner. In this model, Immunostaining the axial vector provided by the RA bead is added to the endogenous Immuno-alkaline phosphatase stainings were performed on paraffin axis generating vector to determine the predicted feather axis.
Recommended publications
  • Gene Regulatory Networks

    Gene Regulatory Networks

    Gene Regulatory Networks 02-710 Computaonal Genomics Seyoung Kim Transcrip6on Factor Binding Transcrip6on Control • Gene transcrip.on is influenced by – Transcrip.on factor binding affinity for the regulatory regions of target genes – Transcrip.on factor concentraon – Nucleosome posi.oning and chroman states – Enhancer ac.vity Gene Transcrip6onal Regulatory Network • The expression of a gene is controlled by cis and trans regulatory elements – Cis regulatory elements: DNA sequences in the regulatory region of the gene (e.g., TF binding sites) – Trans regulatory elements: RNAs and proteins that interact with the cis regulatory elements Gene Transcrip6onal Regulatory Network • Consider the following regulatory relaonships: Target gene1 Target TF gene2 Target gene3 Cis/Trans Regulatory Elements Binding site: cis Target TF regulatory element TF binding affinity gene1 can influence the TF target gene Target gene2 expression Target TF gene3 TF: trans regulatory element TF concentra6on TF can influence the target gene TF expression Gene Transcrip6onal Regulatory Network • Cis and trans regulatory elements form a complex transcrip.onal regulatory network – Each trans regulatory element (proteins/RNAs) can regulate mul.ple target genes – Cis regulatory modules (CRMs) • Mul.ple different regulators need to be recruited to ini.ate the transcrip.on of a gene • The DNA binding sites of those regulators are clustered in the regulatory region of a gene and form a CRM How Can We Learn Transcriponal Networks? • Leverage allele specific expressions – In diploid organisms, the transcript levels from the two copies of the genes may be different – RNA-seq can capture allele- specific transcript levels How Can We Learn Transcriponal Networks? • Leverage allele specific gene expressions – Teasing out cis/trans regulatory divergence between two species (WiZkopp et al.
  • Spectrum of Mutations and Genotype ± Phenotype Analysis in Currarino Syndrome

    Spectrum of Mutations and Genotype ± Phenotype Analysis in Currarino Syndrome

    European Journal of Human Genetics (2001) 9, 599 ± 605 ã 2001 Nature Publishing Group All rights reserved 1018-4813/01 $15.00 www.nature.com/ejhg ARTICLE Spectrum of mutations and genotype ± phenotype analysis in Currarino syndrome Joachim KoÈchling1, Mohsen Karbasiyan2 and Andre Reis*,2,3 1Department of Pediatric Oncology/Hematology, ChariteÂ, Humboldt University, Berlin, Germany; 2Institute of Human Genetics, ChariteÂ, Humboldt University, Berlin, Germany; 3Institute of Human Genetics, Friedrich- Alexander University Erlangen-NuÈrnberg, Erlangen, Germany The triad of a presacral tumour, sacral agenesis and anorectal malformation constitutes the Currarino syndrome which is caused by dorsal-ventral patterning defects during embryonic development. The syndrome occurs in the majority of patients as an autosomal dominant trait associated with mutations in the homeobox gene HLXB9 which encodes the nuclear protein HB9. However, genotype ± phenotype analyses have been performed only in a few families and there are no reports about the specific impact of HLXB9 mutations on HB9 function. We performed a mutational analysis in 72 individuals from nine families with Currarino syndrome. We identified a total of five HLXB9 mutations, four novel and one known mutation, in four out of four families and one out of five sporadic cases. Highly variable phenotypes and a low penetrance with half of all carriers being clinically asymptomatic were found in three families, whereas affected members of one family showed almost identical phenotypes. However, an obvious genotype ± phenotype correlation was not found. While HLXB9 mutations were diagnosed in 23 patients, no mutation or microdeletion was detected in four sporadic patients with Currarino syndrome. The distribution pattern of here and previously reported HLXB9 mutations indicates mutational predilection sites within exon 1 and the homeobox.
  • Solutions for Practice Problems for Molecular Biology, Session 5

    Solutions for Practice Problems for Molecular Biology, Session 5

    Solutions to Practice Problems for Molecular Biology, Session 5: Gene Regulation and the Lac Operon Question 1 a) How does lactose (allolactose) promote transcription of LacZ? 1) Lactose binds to the polymerase and increases efficiency. 2) Lactose binds to a repressor protein, and alters its conformation to prevent it from binding to the DNA and interfering with the binding of RNA polymerase. 3) Lactose binds to an activator protein, which can then help the RNA polymerase bind to the promoter and begin transcription. 4) Lactose prevents premature termination of transcription by directly binding to and bending the DNA. Solution: 2) Lactose binds to a repressor protein, and alters its conformation to prevent it from binding to the DNA and interfering with the binding of RNA polymerase. b) What molecule is used to signal low glucose levels to the Lac operon regulatory system? 1) Cyclic AMP 2) Calcium 3) Lactose 4) Pyruvate Solution: 1) Cyclic AMP. Question 2 You design a summer class where you recreate experiments studying the lac operon in E. coli (see schematic below). In your experiments, the activity of the enzyme b-galactosidase (β -gal) is measured by including X-gal and IPTG in the growth media. X-gal is a lactose analog that turns blue when metabolisize by b-gal, but it does not induce the lac operon. IPTG is an inducer of the lac operon but is not metabolized by b-gal. I O lacZ Plac Binding site for CAP Pi Gene encoding β-gal Promoter for activator protein Repressor (I) a) Which of the following would you expect to bind to β-galactosidase? Circle all that apply.
  • Evolutionary Developmental Biology 573

    Evolutionary Developmental Biology 573

    EVOC20 29/08/2003 11:15 AM Page 572 Evolutionary 20 Developmental Biology volutionary developmental biology, now often known Eas “evo-devo,” is the study of the relation between evolution and development. The relation between evolution and development has been the subject of research for many years, and the chapter begins by looking at some classic ideas. However, the subject has been transformed in recent years as the genes that control development have begun to be identified. This chapter looks at how changes in these developmental genes, such as changes in their spatial or temporal expression in the embryo, are associated with changes in adult morphology. The origin of a set of genes controlling development may have opened up new and more flexible ways in which evolution could occur: life may have become more “evolvable.” EVOC20 29/08/2003 11:15 AM Page 573 CHAPTER 20 / Evolutionary Developmental Biology 573 20.1 Changes in development, and the genes controlling development, underlie morphological evolution Morphological structures, such as heads, legs, and tails, are produced in each individual organism by development. The organism begins life as a single cell. The organism grows by cell division, and the various cell types (bone cells, skin cells, and so on) are produced by differentiation within dividing cell lines. When one species evolves into Morphological evolution is driven another, with a changed morphological form, the developmental process must have by developmental evolution changed too. If the descendant species has longer legs, it is because the developmental process that produces legs has been accelerated, or extended over time.
  • Myths and Legends of the Baldwin Effect

    Myths and Legends of the Baldwin Effect

    Myths and Legends of the Baldwin Effect Peter Turney Institute for Information Technology National Research Council Canada Ottawa, Ontario, Canada, K1A 0R6 [email protected] Abstract ary computation when there is an evolving population of learning individuals (Ackley and Littman, 1991; Belew, This position paper argues that the Baldwin effect 1989; Belew et al., 1991; French and Messinger, 1994; is widely misunderstood by the evolutionary Hart, 1994; Hart and Belew, 1996; Hightower et al., 1996; computation community. The misunderstandings Whitley and Gruau, 1993; Whitley et al., 1994). This syn- appear to fall into two general categories. Firstly, ergetic effect is usually called the Baldwin effect. This has it is commonly believed that the Baldwin effect is produced the misleading impression that there is nothing concerned with the synergy that results when more to the Baldwin effect than synergy. A myth or legend there is an evolving population of learning indi- has arisen that the Baldwin effect is simply a special viduals. This is only half of the story. The full instance of synergy. One of the goals of this paper is to story is more complicated and more interesting. dispel this myth. The Baldwin effect is concerned with the costs Roughly speaking (we will be more precise later), the and benefits of lifetime learning by individuals in Baldwin effect has two aspects. First, lifetime learning in an evolving population. Several researchers have individuals can, in some situations, accelerate evolution. focussed exclusively on the benefits, but there is Second, learning is expensive. Therefore, in relatively sta- much to be gained from attention to the costs.
  • Principles of Differentiation and Morphogenesis

    Principles of Differentiation and Morphogenesis

    Swarthmore College Works Biology Faculty Works Biology 2016 Principles Of Differentiation And Morphogenesis Scott F. Gilbert Swarthmore College, [email protected] R. Rice Follow this and additional works at: https://works.swarthmore.edu/fac-biology Part of the Biology Commons Let us know how access to these works benefits ouy Recommended Citation Scott F. Gilbert and R. Rice. (2016). 3rd. "Principles Of Differentiation And Morphogenesis". Epstein's Inborn Errors Of Development: The Molecular Basis Of Clinical Disorders On Morphogenesis. 9-21. https://works.swarthmore.edu/fac-biology/436 This work is brought to you for free by Swarthmore College Libraries' Works. It has been accepted for inclusion in Biology Faculty Works by an authorized administrator of Works. For more information, please contact [email protected]. 2 Principles of Differentiation and Morphogenesis SCOTT F. GILBERT AND RITVA RICE evelopmental biology is the science connecting genetics with transcription factors, such as TFHA and TFIIH, help stabilize the poly­ anatomy, making sense out of both. The body builds itself from merase once it is there (Kostrewa et al. 2009). Dthe instructions of the inherited DNA and the cytoplasmic system that Where and when a gene is expressed depends on another regula­ interprets the DNA into genes and creates intracellular and cellular tory unit of the gene, the enhancer. An enhancer is a DNA sequence networks to generate the observable phenotype. Even ecological fac­ that can activate or repress the utilization of a promoter, controlling tors such as diet and stress may modify the DNA such that different the efficiency and rate of transcription from that particular promoter.
  • Lamarck's Ladder

    Lamarck's Ladder

    Lamarck’s Ladder Overview Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others. It states that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce. The environment plays a critical role in the natural selection process of Darwinian evolution through the phenotypic variation produced over time by small genetic changes to the DNA sequence, such as beneficial random mutations. However, the vast majority of environmental factors cannot directly alter DNA sequence. Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1744 – 1829), often known simply as Lamarck, was a French naturalist. Before Darwin, Lamarck was one of the first scientists to support the Theory of Evolution. His theory was that species evolved based on the behavior of their parents. His hypothesis stated that an organism can pass on phenotypes acquired because of environmental pressures within their lifetime and pass them to its offspring. One of his most famous examples is his explanation of a giraffe’s long neck. He proposed that the continuous stretching of the neck by the giraffe to reach higher and higher leaves caused the muscles in the neck to strengthen and gradually lengthen over a period of time, which gave rise to longer necks in giraffes. Lamarck’s hypothesis was rejected and later became associated with flawed science concepts. However, scientists today debate whether advances in the field of transgenerational epigenetics indicate that Lamarck was correct, at least to some extent.
  • From Genotype to Phenotype: a Shortcut Through the Library

    From Genotype to Phenotype: a Shortcut Through the Library

    RESEARCH HIGHLIGHTS URLs BIOINFORMATICS From genotype to phenotype: a shortcut through the library A list of genes tells you little about 11,026 orthologous gene sets were PLoS Biol. 3, e134 (2005) WEB SITES their biological roles: understanding identified from the STRING (search Peer Bork’s laboratory: http://www-db.embl.de/ this generally requires time-con- tool for the retrieval of interacting jss/EmblGroupsHD/g_27.html suming functional or comparative genes/proteins) database, defining The STRING database: http://string.embl.de studies. A new method provides a shared sets of genes. shortcut on this path from genotype The final stage was to look for to phenotype — it uses a combina- correlations between the groupings tion of comparative genomics and of MEDLINE nouns and the group- literature mining to predict the ings of shared genes. Bork and col- functions of large sets of sequenced leagues identified 2,700 significant genes. associations between orthologous Peer Bork and colleagues rea- groups and trait words, which soned that if a group of species has a allowed them to relate 28,888 genes shared phenotypic trait, orthologous to at least one trait. Among these genes shared among the species are associations, many of the gene–phe- likely to be involved in the underly- notype associations were already ing biological process. Such geno- known, confirming the validity of type–phenotype correlations have the method. However, many new been made in the past, but required discoveries were also made. For initial manual collection of pheno- example, previously unknown asso- typic information for each species, ciations were made between a group which is labour-intensive and might of metabolic genes and trait words lead to biases in the phenotypes linked to food poisoning.
  • Inference of Phenotype-Relevant Transcriptional Regulatory Networks Elucidates Cancer Type-Specific Regulatory Mechanisms In

    Inference of Phenotype-Relevant Transcriptional Regulatory Networks Elucidates Cancer Type-Specific Regulatory Mechanisms In

    www.nature.com/npjsba ARTICLE OPEN Inference of phenotype-relevant transcriptional regulatory networks elucidates cancer type-specific regulatory mechanisms in a pan-cancer study ✉ ✉ Amin Emad 1 and Saurabh Sinha2,3,4 Reconstruction of transcriptional regulatory networks (TRNs) is a powerful approach to unravel the gene expression programs involved in healthy and disease states of a cell. However, these networks are usually reconstructed independent of the phenotypic (or clinical) properties of the samples. Therefore, they may confound regulatory mechanisms that are specifically related to a phenotypic property with more general mechanisms underlying the full complement of the analyzed samples. In this study, we develop a method called InPheRNo to identify “phenotype-relevant” TRNs. This method is based on a probabilistic graphical model that models the simultaneous effects of multiple transcription factors (TFs) on their target genes and the statistical relationship between the target genes’ expression and the phenotype. Extensive comparison of InPheRNo with related approaches using primary tumor samples of 18 cancer types from The Cancer Genome Atlas reveals that InPheRNo can accurately reconstruct cancer type-relevant TRNs and identify cancer driver TFs. In addition, survival analysis reveals that the activity level of TFs with many target genes could distinguish patients with poor prognosis from those with better prognosis. npj Systems Biology and Applications (2021) 7:9 ; https://doi.org/10.1038/s41540-021-00169-7 1234567890():,; INTRODUCTION among samples. In this example, the expression levels of TF and Gene expression programs are responsible for many biological gene are only weakly correlated in each phenotypic class (case or processes in a cell and extensive efforts have been devoted to control) separately, possibly owing to noisy data and small sample elucidating these programs in healthy and disease states.
  • Evolutionary Dynamics of Morphogenesis

    Evolutionary Dynamics of Morphogenesis

    Shapes in the Shadow: P. Hogeweg Theoretical Biology and Evolutionary Dynamics of Bioinformatics Group Morphogenesis Utrecht University Padualaan 8, 3584 CH Utrecht, The Netherlands [email protected] Abstract This article investigates the evolutionary dynamics Keywords evolution, morphogenesis, develop- of morphogenesis. In this study, morphogenesis arises as a ment, EvoDevo, fitness landscapes, side-effect of maximization of number of cell types. Thus, it cell adhesion, gene networks investigates the evolutionary dynamics of side-effects. Morphogenesis is governed by the interplay between differential cell adhesion, gene-regulation, and intercellular signaling. Thus, it investigates the potential to generate complex behavior by entanglement of relatively “boring” processes, and the (automatic) coordination between these processes. The evolutionary dynamics shows all the hallmarks of evolutionary dynamics governed by nonlinear genotype phenotype mapping: for example, punctuated equilibria and diffusion on neutral paths. More striking is the result that interesting, complex morphogenesis occurs mainly in the “shadow” of neutral paths which preserve cell differentiation, that is, the interesting morphologies arise as mutants of the fittest individuals. Characteristics of the evolution of such side-effects in the shadow appear to be the following: (1) The specific complex morphologies are unique (or at least very rare) among the set of de novo initiated evolutionary histories. (2) Similar morphologies are reinvented at large temporal distances during one evolutionary history and also when evolution is restarted after the main cell differentiation pattern has been established. (3) A mosaic-like evolution at the morphological level, where different morphological features occur in many combinations, while at the genotypic level recombination is not implemented and genotypes diverge linearly and at a constant rate.
  • Bullwinkle Is Required for Epithelial Morphogenesis During Drosophila Oogenesis$

    Bullwinkle Is Required for Epithelial Morphogenesis During Drosophila Oogenesis$

    Developmental Biology 267 (2004) 320–341 www.elsevier.com/locate/ydbio bullwinkle is required for epithelial morphogenesis during Drosophila oogenesis$ Jennie B. Dorman,a,b Karen E. James,a Scott E. Fraser,c Daniel P. Kiehart,d and Celeste A. Berga,b,* a Department of Genome Sciences, University of Washington, Seattle, WA 98195-7730, USA b Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195-7275, USA c Biology Division, Caltech, Beckman Institute 139-74, Pasadena, CA 91125, USA d Developmental, Cell and Molecular Biology Group, Department of Biology, Duke University, Durham, NC 27708-1000, USA Received for publication 29 July 2003, revised 4 October 2003, accepted 7 October 2003 Abstract Many organs, such as the liver, neural tube, and lung, form by the precise remodeling of flat epithelial sheets into tubes. Here we investigate epithelial tubulogenesis in Drosophila melanogaster by examining the development of the dorsal respiratory appendages of the eggshell. We employ a culture system that permits confocal analysis of stage 10–14 egg chambers. Time-lapse imaging of GFP-Moesin- expressing egg chambers reveals three phases of morphogenesis: tube formation, anterior extension, and paddle maturation. The dorsal- appendage-forming cells, previously thought to represent a single cell fate, consist of two subpopulations, those forming the tube roof and those forming the tube floor. These two cell types exhibit distinct morphological and molecular features. Roof-forming cells constrict apically and express high levels of Broad protein. Floor cells lack Broad, express the rhomboid-lacZ marker, and form the floor by directed cell elongation. We examine the morphogenetic phenotype of the bullwinkle (bwk) mutant and identify defects in both roof and floor formation.
  • Evolutionary Developmental Psychology

    Evolutionary Developmental Psychology

    Psicothema 2010. Vol. 22, nº 1, pp. 22-27 ISSN 0214 - 9915 CODEN PSOTEG www.psicothema.com Copyright © 2010 Psicothema Evolutionary developmental psychology Ashley C. King and David F. Bjorklund* University of Arizona and * Florida Atlantic University The field of evolutionary developmental psychology can potentially broaden the horizons of mainstream evolutionary psychology by combining the principles of Darwinian evolution by natural selection with the study of human development, focusing on the epigenetic effects that occur between humans and their environment in a way that attempts to explain how evolved psychological mechanisms become expressed in the phenotypes of adults. An evolutionary developmental perspective includes an appreciation of comparative research and we, among others, argue that contrasting the cognition of humans with that of nonhuman primates can provide a framework with which to understand how human cognitive abilities and intelligence evolved. Furthermore, we argue that several «immature» aspects of childhood (e.g., play and immature cognition) serve both as deferred adaptations as well as imparting immediate benefits. Intense selection pressure was surely exerted on childhood over human evolutionary history and, as a result, neglecting to consider the early developmental period of children when studying their later adulthood produces an incomplete picture of the evolved adaptations expressed through human behavior and cognition. Psicología evolucionista del desarrollo. El campo de la psicología evolucionista del desarrollo puede am- pliar potencialmente los horizontes de la psicología evolucionista, combinando los principios darwinistas de la evolución por selección natural con el estudio del desarrollo humano, centrándose en los efectos epi- genéticos entre los seres humanos y su entorno, de manera que explique cómo los mecanismos psicológi- cos evolucionados se acaban expresando en el fenotipo de los sujetos adultos.