SICB Annual Meeting 2008

Symposium: "Reptile genomics and evolutionary genetics"

(Organized by D. Janes & C. Organ)

Symposium Abstract:

Birds and mammals exhibit tremendous variation in reproductive traits and genomic landscapes.  Although both are genotypically sex-determined, inheritance of avian and mammalian sex chromosomes is different.  Also, avian genomes are, on average, smaller than mammalian genomes.  As more reptilian genomic data become available, more opportunities arise for study of seemingly avian or mammalian traits in their common reptilian ancestors.  Researchers can now more easily compare avian and mammalian genes to their reptilian orthologs.  This symposium will highlight advances and progress made in sequencing of reptile (including birds) genomes, characteristics of reptile genome architecture, and the evolution of reptilian traits (i.e., sex-determining mechanisms, cleidoic eggs, complex behavioral and learning patterns, microchromosomes and sex chromosomes).  The first non-avian reptile (Green Anole, Anolis carolinensis) genome project will be published soon.  It is therefore an opportune time to organize a symposium concerning reptile genomics and discuss the impact these data will have on the study of evolution and development in reptiles, birds and mammals.

Sources of Support:

SICB Division of Developmental and Cell Biology ( divisions/ddcb.php3)

SICB Division of Evolutionary Developmental Biology ( divisions/dedb.php3)



Daniel E. Janes
26 Oxford St.
Cambridge, MA 02138
Phone: (617) 496-2375
Fax: (617) 495-5667

Christopher L. Organ
26 Oxford St.
Cambridge, MA 02138
Phone: (617) 496-9389
Fax: (617) 495-5667






List of Speakers:

S1-1.1 Thu, Jan. 3, 08:00 CHOJNOWSKI, JL*; BRAUN, EL: Candidate genes in a turtle with temperature-dependent sex determination

S1-1.2 Thu, Jan. 3, 08:30 GLENN, Travis C.*; JONES, Kenneth L.; SAWYER, Roger H.; GREENWOLD, Matthew J.; CRAWFORD, Nicholas G.: Challenges and opportunities in comparative reptilian genomics

S1-1.3 Thu, Jan. 3, 09:00 KOHNO, Satomi*; KATSU, Yoshinao; IGUCHI, Taisen; GUILLETTE, Louis J Jr: The Functional Evolution of Steroid Hormone Receptors: Insights from Reptiles

S1-1.4 Thu, Jan. 3, 10:00 JANES, D.E.*; EDWARDS, S.V.: Comparative expression and genomic organization of sex-differentiating genes in a bird and a reptile

S1-1.5 Thu, Jan. 3, 10:30 ELF, P: Maternally derived yolk steroid hormones in TSD reptiles: A comparison among species and their possible roles in embryonic development

S1-1.6 Thu, Jan. 3, 11:00 OLMO, Ettore: Rate of chromosome changes and speciation in reptiles

S1-1.7 Thu, Jan. 3, 11:30 ORGAN, Chris*; EDWARDS, Scott: Genome Architecture and Diversity in Reptiles

S1-2.1 Thu, Jan. 3, 13:00 SCHNEIDER, Christopher: Exploiting Genomic Resources in Studies of Speciation and Adaptive Radiation of Anolis Lizards.

S1-2.2 Thu, Jan. 3, 13:30 BERMUDEZ, DS*; GUILLETTE, LJ: The Thyroid-Gonad axis: Insights on a novel mechanism of communication in the American Alligator

S1-2.3 Thu, Jan. 3, 14:00 THOMSON, R.C.*; SHAFFER, H.B.: Moving towards many-marker datasets: progress and challenges for turtle phylogenetics

S1-2.4 Thu, Jan. 3, 14:30 NICOLE, Valenzuela: Evolution of the gene regulatory network underlying sexual differentiation in turtles with alternative sex determining mechanisms

Speakers and Topics:

11 Jena Chojnowski
Graduate Student
Department of Zoology
223 Bartram Hall
University of Florida
Gainesville, FL 32611, USA

My interests are broadly categorized as evolution of genomes and genetic systems.  More specifically, my dissertation research is determining and characterizing the genes involved in temperature-dependent sex determination in the developing embryo of the Red-eared Slider turtle.  I am also heavily involved in a project regarding isochore evolution, defined as the evolution of long (> 100 kb) regions with relatively homogeneous within-region base composition, and its implications on genome stability. In addition to isochore evolution, I am also involved in the Early Bird Project, a long term collaborative project determining avian phylogeny.  My contribution to the Early Bird Project is the design of two loci, Clathrin Heavy Chain and Clathrin Heavy Chain-like 1, and furthermore, using those specific loci in understanding intron evolution and its benefits in determining deep avian nodes.  Genome evolution and the interactions of genes are both important in understanding the evolution of organisms over time (i.e. their body plans, innovative structures, regulation of body temperature and so forth).

6 Travis Glenn
Associate Research Scientist
University of Georgia
Savannah River Ecology Laboratory
PO Drawer E, Aiken, SC 29802

I develop and use DNA techniques and technologies to address problems in ecology, evolution, environmental remediation, and natural resource management.  Although I have worked with DNA from organisms of all kingdoms, much of my research focuses on evolutionary processes of vertebrates, especially processes which can be impacted by human activities.  Reptilians offer a variety of unique challenges and opportunities to study such processes.

6 Satomi Kohno
Assistant Scientist
University of Florida
528 Bartram Hall
Box 118525
Gainesville, FL 32611

Steroid hormones are essential for the normal function of most organ systems in vertebrates. Reproductive activity in females and males, such as the differentiation, growth and maintenance of the reproductive system, requires signaling by sex steroids.  Although extensively studied in mammals and a few fish, amphibians and bird species, the evolution of and molecular mechanisms associated with the nuclear steroid hormone receptors are poorly understood in reptiles.  Given our interest in environmental signaling of sex determination as well as a major interest in environmental contaminants that can mimic steroid hormone signaling, we have established an approach to study the molecular function (ligand binding and gene transcription) of steroid receptors from an array of reptiles.  This approach involves cloning and sequencing of the receptors, phylogenetic analysis and in vitro transfection /gene expression studies using natural and exogenous ligands.

7 Daniel Janes
NIH Postdoctoral Fellow
Department of Organismic and Evolutionary Biology
Harvard University
26 Oxford St.
Cambridge, MA 02138

Although sex is one of the most fundamental phenotypes in living systems, the evolution of sex and the maintenance of sex by genetic or environmental controls remain unresolved.  Also, the history of heteromorphic sex chromosomes and the functions of sex-determining (SD) genes found on either recognized sex chromosomes or autosomes remain poorly understood, especially in non-mammalian vertebrates.  Several SD genes have been identified across chordates that must be present in either one or two copies and expressed at the appropriate time during embryonic development for male or female sexual development to occur.  These genes are found on recognized sex chromosomes in some species and on autosomes in other species.  In this talk, I will describe genomic organization and expression of key sex-determining genes between American Alligators and Emus.  Alligators exhibit temperature-dependent sex determination and Emus are genotypically sex-determined.  Despite this difference, similar expression data have been reported for a series of sex-determining genes in both species.  These similarities and differences speak to the evolutionary history of sex-determining mechanisms and avian sex chromosomes.

9 Ettore Olmo
Istituto di Biologia e Genetica
Facolta di Scienze
Universita Politecnica delle Marche
Via Brecce Bianche
60131 Ancona Italia

The research interests of E. Olmo regard the cytogenetics and molecular evolution of some groups of lower vertebrates (especially reptiles, amphibians and fishes from Antarctica) and of bivalve molluscs. In particular he has studied the role of the variability of chromosome morphology in the evolution of the different lineages of reptiles; the presence of the highly repetitive DNA families in lower vertebrates and molluscs and its role in centromere structure and function; the evolution of genome size and composition in reptiles and amphibians and the nucleotypic influence that the variability of these parameters could have on cell morphology and physiology and through them on the process of environmental adaptation.

Chris Organ

10 NIH Postdoctoral Fellow
Department of Organismic and Evolutionary Biology
Harvard University
26 Oxford St.
Cambridge, MA 02138

My colleagues and I use an integrative approach to study genome evolution that combines genetics, paleohistology, and comparative methods adapted by Mark Pagel and Andrew Meade at the University of Reading into an innovative bayesian framework to produce phylogenetically informed statistical models. I am also pursuing related, but independent research, on the evolution of the osteogenic bmp2 gene in reptiles. Bone morphogenetic proteins (BMPs) are a subgroup of proteins contained within the transforming growth factor beta (TGF-ß) superfamily. They are highly conserved in vertebrates and act as regulators of bone formation, maintenance, and repair and have been a critical linchpin integrating paleontology, development, and genetics to address various questions, including digit identity in birds and their evolution from non-avian dinosaurs.

15 Christopher Schneider
Assistant Professor
Department of Biology
Boston University
5 Cummington St.
Boston, MA 02215

I am primarily interested in the evolutionary process and geographic context of population divergence and species formation.  In particular, I am interested in the degree to which local adaptation drives divergence and speciation.  I have approached these questions through broad scale comparative analyses of various species, geographic and niche modeling, and common population genetic approaches.  I am now exploiting information from the Anolis carolinensis genome project to examine, in detail, the ecological and population genetics of Anolis marmoratus, a highly polymorphic species complex from the Caribbean island of Guadeloupe.  Genomic data provide a variety of resources with which to examine population structure, gene flow and the history of population divergence.  In addition, fine scale analyses exploiting genomic resources have the potential to identify loci under selection and candidate genes for divergent characters.  I will speak about the power of multi-locus sequence analyses in the context of population divergence and speciation and also about the prospects for exploiting genomic resources in studies of speciation.

13 Dieldrich Bermudez
Graduate Student
University of Florida
528 Bartram Hall
Box 118525
Gainesville, FL 32611

Thyroid hormones are known to have a cooperative role in gonadal development and function. There is a growing body of work demonstrating that thyroid hormones play a crucial role in the development of Sertoli and Leydig cells in the testis. Thyroid hormones at proper levels are necessary for ovulation and severe hypothyroidism can cause ovarian atrophy and amenorrhea. Thyroid receptors are found in various parts of the ovary such as granulosa cells, oocytes and cumulus cells of the follicle, and corpora lutea, indicating that thyroid hormones can play a role in various cells of the ovary. The mechanisms of action are still not well understood. In many vertebrate species, including humans, thyroid disorders are more frequent in the female population. In addition, studies have shown that neoplastic thyroids have a higher number of estrogen receptors (ER) compared to normal tissue, suggesting a relationship between the sex of an individual and susceptibility to thyroid abnormalities. Recently, it has been shown that thyroid hormone concentrations parallel sex steroid patterns in American alligators. We investigated the mechanism of communication between the thyroid and gonad axis of the American alligator. Previous studies have demonstrated a one directional endocrine pathway from the thyroid to the gonad. We describe a possible new avenue of communication from the gonad to thyroid via the estrogen receptor located on alligator thyroid follicles. Through the use of genetic markers for thyroid and gonadal physiology, we describe a novel mechanism of communication between these organs.

12 Robert Thomson
Graduate Student
Section of Evolution and Ecology
University of California
One Shields Ave.
Davis, CA 95616

My research focus is broadly centered on the systematics of rapid radiations. How do we delimit species and infer topology in clades that have radiated quickly and where incongruity among gene trees is strong? What, and how much, data is necessary to reliably infer species level topologies when rapid radiations are present in the tree? How can we collect this data in non-model organisms and what are our prospects for doing so? I am empirically focused, but also employ bioinformatic and simulation approaches in order to inform my empirical work. My organismal focus is on amphibians and reptiles, and I do much of my work on turtles. Turtles are an ancient clade that constitutes a major conservation concern. This clade provides several examples of rapid radiations that have traditionally defied systematic progress and serve as good systems for the questions I am interested in. Finally, the increasing availability of genomic tools in this clade is beginning to make it feasible to gather sufficient data to answer questions that have traditionally defied progress using morphological and single or few gene analyses. I have developed a large panel of nuclear sequence markers for turtles and am currently examining their utility across the turtle tree of life. These markers will be employed in an effort to understand species boundaries in map turtles (genus Graptemys), a rapid radiation of turtles in the southeastern United States; and, in collaboration with my advisor and several colleagues, a large scale multiple marker phylogeny of all turtle species.

14 Nicole Valenzuela
Assistant Professor
Department of Ecology, Evolution and Organismal Biology
Iowa State University
239 Bessey Hall
Ames, IA 50011

I am an evolutionary ecologist interested in the evolution of the molecular pathways underlying the development of the sexual phenotype. I investigate proximate and ultimate processes that explain the evolution of sex determining mechanisms in vertebrates, especially turtles. My research program focuses on deciphering the developmental modus operandi of alternative sex-determining systems from an evolutionary genomic perspective, and their ecological context, in a multidisciplinary effort to understanding their evolution. My research group studies thermal ecology in the wild and in the laboratory across turtle species to gain a comprehensive view of the effects of temperature on gene expression, sex determination and differentiation, development, and fitness. Additionally, we are exploring the nature, extent and significance of the divergence of sex determining mechanisms across species, as a critical step to understand the evolution of their developmental hierarchies and related traits, and how conserved phenotypic outcomes result from divergent gene regulatory networks. This divergence entails regulatory changes reflected in varying patterns of gene expression within and among sex determining mechanisms (TSD: temperature-dependent, and GSD: genotypic), the molecular evolution of the network elements and their syntenic groups, the potential co-option of conserved elements as master thermal switches that bestow thermal-sensitivity to vertebrate sexual differentiation, and the retention in GSD species of relic or preexisting thermal sensitivity in gene expression which may be co-optable during TSD evolution. These and our other eco-genomic approaches will provide an integrative view to understand the ecological significance of TSD and GSD and the challenges posed by global climate change.