1
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Woodruff ED, Kircher BK, Armfield BA, Levy JK, Bloch JI, Cohn MJ. Domestic cat embryos reveal unique transcriptomes of developing incisor, canine, and premolar teeth. J Exp Zool B Mol Dev Evol 2022; 338:516-531. [PMID: 35816012 DOI: 10.1002/jez.b.23168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 04/26/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
Division of the dentition into morphologically distinct classes of teeth (incisors, canines, premolars, and molars) and the acquisition of tribosphenic molars facilitated precise occlusion between the teeth early in mammal evolution. Despite the evolutionary and ecological importance of distinct classes of teeth with unique cusp, crest, and basin morphologies, relatively little is known about the genetic basis for the development of different tooth classes within the embryo. Here we investigated genetic differences between developing deciduous incisor, canine, and premolar teeth in the domestic cat (Felis catus), which we propose to be a new model for tooth development. We examined differences in both developmental timing and crown morphology between the three tooth classes. Using RNA sequencing of early bell stage tooth germs, we showed that each of the three deciduous tooth classes possess a unique transcriptional profile. Three notable groups of genes emerged from our differential expression analysis; genes involved in the extracellular matrix (ECM), Wnt pathway signaling, and members of multiple homeobox gene families (Lhx, Dlx, Alx, and Nkx). Our results suggest that ECM genes may play a previously under-appreciated role in shaping the surface of the tooth crown during development. Differential regulation of these genes likely underlies differences in tooth crown shape and size, although subtle temporal differences in development between the tooth germs could also be responsible. This study provides foundational data for future experiments to examine the function of these candidate genes in tooth development to directly test their potential effects on crown morphology.
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Affiliation(s)
- Emily D Woodruff
- Department of Biology, University of Florida, Gainesville, Florida, USA
- Department of Natural History, Florida Museum of Natural History, University of Florida, Gainesville, Florida, USA
| | - Bonnie K Kircher
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Brooke A Armfield
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, USA
| | - Julie K Levy
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA
| | - Jonathan I Bloch
- Department of Biology, University of Florida, Gainesville, Florida, USA
- Department of Natural History, Florida Museum of Natural History, University of Florida, Gainesville, Florida, USA
| | - Martin J Cohn
- Department of Biology, University of Florida, Gainesville, Florida, USA
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, USA
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2
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Griffing AH, Gamble T, Cohn MJ, Sanger TJ. Convergent developmental patterns underlie the repeated evolution of adhesive toe pads among lizards. Biol J Linn Soc Lond 2022; 135:518-532. [PMID: 35185322 PMCID: PMC8842688 DOI: 10.1093/biolinnean/blab164] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 11/24/2021] [Accepted: 11/25/2021] [Indexed: 01/07/2023]
Abstract
How developmental modifications produce key innovations, which subsequently allow for rapid diversification of a clade into new adaptive zones, has received much attention. However, few studies have used a robust comparative framework to investigate the influence of evolutionary and developmental constraints on the origin of key innovations, such as the adhesive toe pad of lizards. Adhesive toe pads evolved independently at least 16 times in lizards, allowing us to examine whether the patterns observed are general evolutionary phenomena or unique, lineage-specific events. We performed a high-resolution comparison of plantar scale development in 14 lizard species in Anolis and geckos, encompassing five independent origins of toe pads (one in Anolis, four in geckos). Despite substantial evolutionary divergence between Anolis and geckos, we find that these clades have undergone similar developmental modifications to generate their adhesive toe pads. Relative to the ancestral plantar scale development, in which scale ridges form synchronously along the digit, both padded geckos and Anolis exhibit scansor formation in a distal-to-proximal direction. Both clades have undergone developmental repatterning and, following their origin, modifications in toe pad morphology occurred through relatively minor developmental modifications, suggesting that developmental constraints governed the diversification of the adhesive toe pad in lizards.
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Affiliation(s)
- Aaron H Griffing
- Department of Biological Sciences, Marquette University, PO Box 1881, Milwaukee, WI 53201, USA,Corresponding author. E-mail:
| | - Tony Gamble
- Department of Biological Sciences, Marquette University, PO Box 1881, Milwaukee, WI 53201, USA,Milwaukee Public Museum, 800 W. Wells St., Milwaukee, WI 53233, USA,Bell Museum of Natural History, University of Minnesota, 2088 Larpenteur Ave. W., St. Paul, MN 55113, USA
| | - Martin J Cohn
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Thomas J Sanger
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, Gainesville, FL 32610, USA,Department of Biology, Loyola University Chicago, 1032 W. Sheridan Rd, Chicago, IL 60660, USA
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3
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Armfield BA, Cohn MJ. Single cell transcriptomic analysis of external genitalia reveals complex and sexually dimorphic cell populations in the early genital tubercle. Dev Biol 2021; 477:145-154. [PMID: 34033822 DOI: 10.1016/j.ydbio.2021.05.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 05/13/2021] [Accepted: 05/17/2021] [Indexed: 11/27/2022]
Abstract
External genital organs are among the most recognizable sexually dimorphic characters. The penis and clitoris develop from the embryonic genital tubercle, an outgrowth at the anterior margin of the cloaca that undergoes an extensive period of development in male and female embryos prior to the onset of sexual differentiation. In mice, differentiation into the penis and clitoris begins around embryonic day (E)15.5. Current knowledge of cell types that comprise the genital tubercle is limited to a few studies that have fate mapped derivatives of endoderm, mesoderm, and ectoderm. Here we use single cell transcriptomics to characterize the cell populations in the genital tubercles of male and female mouse embryos at E14.5, approximately 24 h before the onset of sexual differentiation, and we present the first comprehensive atlas of single-cell gene expression during external genital development. Clustering analyses and annotation using marker genes shows 19 distinct cell populations in E14.5 genital tubercles. Mapping of cell clusters to anatomical locations using in situ gene expression patterns revealed granularity of cellular specializations and positional identities. Although E14.5 precedes sexually dimorphic morphogenesis of the genital tubercle, comparative analysis of males and females identified sexual dimorphisms at the single cell level, including male-specific cell clusters with transcriptional signatures of smooth muscle and bone progenitors, both of which are known to be sexually dimorphic in adult genitalia, as well as immune cells. These results provide a new resource for classification of external genital cell types based on gene expression profiles and reveal sex-specific cellular specializations in the early genital tubercle.
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Affiliation(s)
- Brooke A Armfield
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, Gainesville, FL, 32610, USA.
| | - Martin J Cohn
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, Gainesville, FL, 32610, USA; Department of Biology, University of Florida, Gainesville, FL, 32611, USA.
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4
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Woodruff ED, Gutierrez GC, Van Otterloo E, Williams T, Cohn MJ. Anomalous incisor morphology indicates tissue-specific roles for Tfap2a and Tfap2b in tooth development. Dev Biol 2021; 472:67-74. [PMID: 33460639 PMCID: PMC8018193 DOI: 10.1016/j.ydbio.2020.12.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 12/17/2020] [Accepted: 12/21/2020] [Indexed: 01/13/2023]
Abstract
Mice possess two types of teeth that differ in their cusp patterns; incisors have one cusp and molars have multiple cusps. The patterning of these two types of teeth relies on fine-tuning of the reciprocal molecular signaling between dental epithelial and mesenchymal tissues during embryonic development. The AP-2 transcription factors, particularly Tfap2a and Tfap2b, are essential components of such epithelial-mesenchymal signaling interactions that coordinate craniofacial development in mice and other vertebrates, but little is known about their roles in the regulation of tooth development and shape. Here we demonstrate that incisors and molars differ in their temporal and spatial expression of Tfap2a and Tfap2b. At the bud stage, Tfap2a is expressed in both the epithelium and mesenchyme of the incisors and molars, but Tfap2b expression is restricted to the molar mesenchyme, only later appearing in the incisor epithelium. Tissue-specific deletions show that loss of the epithelial domain of Tfap2a and Tfap2b affects the number and spatial arrangement of the incisors, notably resulting in duplicated lower incisors. In contrast, deletion of these two genes in the mesenchymal domain has little effect on tooth development. Collectively these results implicate epithelial expression of Tfap2a and Tfap2b in regulating the extent of the dental lamina associated with patterning the incisors and suggest that these genes contribute to morphological differences between anterior (incisor) and posterior (molar) teeth within the mammalian dentition.
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Affiliation(s)
- Emily D Woodruff
- Department of Biology, University of Florida, Gainesville, FL, USA.
| | | | - Eric Van Otterloo
- Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Denver, CO, USA
| | - Trevor Williams
- Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Denver, CO, USA
| | - Martin J Cohn
- Department of Biology, University of Florida, Gainesville, FL, USA; Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA.
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5
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Stadler HS, Peters CA, Sturm RM, Baker LA, Best CJM, Bird VY, Geller F, Hoshizaki DK, Knudsen TB, Norton JM, Romao RLP, Cohn MJ. Meeting report on the NIDDK/AUA Workshop on Congenital Anomalies of External Genitalia: challenges and opportunities for translational research. J Pediatr Urol 2020; 16:791-804. [PMID: 33097421 PMCID: PMC7885182 DOI: 10.1016/j.jpurol.2020.09.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 09/10/2020] [Accepted: 09/13/2020] [Indexed: 01/02/2023]
Abstract
Congenital anomalies of the external genitalia (CAEG) are a prevalent and serious public health concern with lifelong impacts on the urinary function, sexual health, fertility, tumor development, and psychosocial wellbeing of affected individuals. Complications of treatment are frequent, and data reflecting long-term outcomes in adulthood are limited. To identify a path forward to improve treatments and realize the possibility of preventing CAEG, the National Institute of Diabetes and Digestive and Kidney Diseases and the American Urological Association convened researchers from a range of disciplines to coordinate research efforts to fully understand the different etiologies of these common conditions, subsequent variation in clinical phenotypes, and best practices for long term surgical success. Meeting participants concluded that a central data hub for clinical evaluations, including collection of DNA samples from patients and their parents, and short interviews to determine familial penetrance (small pedigrees), would accelerate research in this field. Such a centralized datahub will advance efforts to develop detailed multi-dimensional phenotyping and will enable access to genome sequence analyses and associated metadata to define the genetic bases for these conditions. Inclusion of tissue samples and integration of clinical studies with basic research using human cells and animal models will advance efforts to identify the developmental mechanisms that are disrupted during development and will add cellular and molecular granularity to phenotyping CAEG. While the discussion focuses heavily on hypospadias, this can be seen as a potential template for other conditions in the realm of CAEG, including cryptorchidism or the exstrophy-epispadias complex. Taken together with long-term clinical follow-up, these data could inform surgical choices and improve likelihood for long-term success.
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Affiliation(s)
- H Scott Stadler
- Department of Skeletal Biology, Shriners Hospital for Children, 3101 SW Sam Jackson Park Road, Portland, OR, Oregon Health & Science University, Department of Orthopaedics and Rehabilitation, Portland, 97239, OR, USA.
| | - Craig A Peters
- Department of Urology, University of Texas Southwestern, 5323 Harry Hines Blvd., Dallas, 75390-9110, TX, USA; Pediatric Urology, Children's Health System Texas, University of Texas Southwestern, Dallas, 75390, TX, USA.
| | - Renea M Sturm
- Department of Urology, Division of Pediatric Urology, University of California Los Angeles, 200 Medical Plaza #170, Los Angeles, 90095, CA, USA
| | - Linda A Baker
- Department of Urology, University of Texas Southwestern, 5323 Harry Hines Blvd., Dallas, 75390-9110, TX, USA
| | - Carolyn J M Best
- American Urological Association, 1000 Corporate Boulevard, Linthicum, 21090, MD, USA
| | - Victoria Y Bird
- Department of Urology, University of Florida, Gainesville, 32610, FL, USA; National Medical Association and Research Group, 5745 SW 75th Street, #507, Gainesville, 32608, FL, USA
| | - Frank Geller
- Department of Epidemiology Research, Statens Serum Institut, 5 Artillerivej, Copenhagen S, DK-2300, Denmark
| | - Deborah K Hoshizaki
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 6707 Democracy Boulevard, Bethesda, 20892, MD, USA
| | - Thomas B Knudsen
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Research Triangle Park, 27711, NC, USA
| | - Jenna M Norton
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 6707 Democracy Boulevard, Bethesda, 20892, MD, USA
| | - Rodrigo L P Romao
- Departments of Surgery and Urology, IWK Health Centre, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Martin J Cohn
- Department of Molecular Genetics and Microbiology, Department of Biology, And UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, 32610, FL, USA.
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6
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Gredler ML, Patterson SE, Seifert AW, Cohn MJ. Foxa1 and Foxa2 orchestrate development of the urethral tube and division of the embryonic cloaca through an autoregulatory loop with Shh. Dev Biol 2020; 465:23-30. [PMID: 32645357 DOI: 10.1016/j.ydbio.2020.06.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 06/23/2020] [Accepted: 06/24/2020] [Indexed: 01/04/2023]
Abstract
Congenital anomalies of external genitalia affect approximately 1 in 125 live male births. Development of the genital tubercle, the precursor of the penis and clitoris, is regulated by the urethral plate epithelium, an endodermal signaling center. Signaling activity of the urethral plate is mediated by Sonic hedgehog (SHH), which coordinates outgrowth and patterning of the genital tubercle by controlling cell cycle kinetics and expression of downstream genes. The mechanisms that govern Shh transcription in urethral plate cells are largely unknown. Here we show that deletion of Foxa1 and Foxa2 results in persistent cloaca, an incomplete separation of urinary, genital, and anorectal tracts, and severe hypospadias, a failure of urethral tubulogenesis. Loss of Foxa2 and only one copy of Foxa1 results in urethral fistula, an additional opening of the penile urethra. Foxa1/a2 participate in an autoregulatory feedback loop with Shh, in which FOXA1 and FOXA2 positively regulate transcription of Shh in the urethra, and SHH feeds back to negatively regulate Foxa1 and Foxa2 expression. These findings reveal novel roles for Foxa genes in development of the urethral tube and in division of the embryonic cloaca.
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Affiliation(s)
- Marissa L Gredler
- Department of Biology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL, 32611, USA; Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL, 32611, USA
| | - Sara E Patterson
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL, 32611, USA
| | - Ashley W Seifert
- Department of Biology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL, 32611, USA
| | - Martin J Cohn
- Department of Biology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL, 32611, USA; Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL, 32611, USA.
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7
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Abstract
Cephalopod mollusks evolved numerous anatomical novelties, including arms and tentacles, but little is known about the developmental mechanisms underlying cephalopod limb evolution. Here we show that all three axes of cuttlefish limbs are patterned by the same signaling networks that act in vertebrates and arthropods, although they evolved limbs independently. In cuttlefish limb buds, Hedgehog is expressed anteriorly. Posterior transplantation of Hedgehog-expressing cells induced mirror-image limb duplications. Bmp and Wnt signals, which establish dorsoventral polarity in vertebrate and arthropod limbs, are similarly polarized in cuttlefish. Inhibition of Bmp2/4 dorsally caused ectopic expression of Notum, which marks the ventral sucker field, and ectopic sucker development. Cuttlefish also show proximodistal regionalization of Hth, Exd, Dll, Dac, Sp8/9, and Wnt expression, which delineates arm and tentacle sucker fields. These results suggest that cephalopod limbs evolved by parallel activation of a genetic program for appendage development that was present in the bilaterian common ancestor.
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Affiliation(s)
- Oscar A Tarazona
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, United States.,Department of Biology, UF Genetics Institute, University of Florida, Gainesville, United States
| | - Davys H Lopez
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, United States
| | - Leslie A Slota
- Department of Biology, UF Genetics Institute, University of Florida, Gainesville, United States
| | - Martin J Cohn
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, United States.,Department of Biology, UF Genetics Institute, University of Florida, Gainesville, United States
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8
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Gonçalves O, Freitas R, Ferreira P, Araújo M, Zhang G, Mazan S, Cohn MJ, Castro LFC, Wilson JM. Molecular ontogeny of the stomach in the catshark Scyliorhinus canicula. Sci Rep 2019; 9:586. [PMID: 30679499 PMCID: PMC6346038 DOI: 10.1038/s41598-018-36413-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 11/21/2018] [Indexed: 01/27/2023] Open
Abstract
The origin of extracellular digestion in metazoans was accompanied by structural and physiological alterations of the gut. These adaptations culminated in the differentiation of a novel digestive structure in jawed vertebrates, the stomach. Specific endoderm/mesenchyme signalling is required for stomach differentiation, involving the growth and transcription factors: 1) Shh and Bmp4, required for stomach outgrowth; 2) Barx1, Sfrps and Sox2, required for gastric epithelium development and 3) Cdx1 and Cdx2, involved in intestinal versus gastric identity. Thus, modulation of endoderm/mesenchyme signalling emerges as a plausible mechanism linked to the origin of the stomach. In order to gain insight into the ancient mechanisms capable of generating this structure in jawed vertebrates, we characterised the development of the gut in the catshark Scyliorhinus canicula. As chondrichthyans, these animals retained plesiomorphic features of jawed vertebrates, including a well-differentiated stomach. We identified a clear molecular regionalization of their embryonic gut, characterised by the expression of barx1 and sox2 in the prospective stomach region and expression of cdx1 and cdx2 in the prospective intestine. Furthermore, we show that gastric gland development occurs close to hatching, accompanied by the onset of gastric proton pump activity. Our findings favour a scenario in which the developmental mechanisms involved in the origin of the stomach were present in the common ancestor of chondrichthyans and osteichthyans.
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Affiliation(s)
- Odete Gonçalves
- CIIMAR - Interdisciplinary Centre of Marine and Environmental Research, Univ. Porto, Porto, Portugal.,Institute of Biomedical Sciences Abel Salazar (ICBAS), Univ. Porto, Porto, Portugal
| | - Renata Freitas
- I3S- Institute for Innovation and Health Research, Univ. Porto, Porto, Portugal. .,IBMC- Institute for Molecular and Cell Biology, Univ. Porto, Porto, Portugal.
| | - Patrícia Ferreira
- CIIMAR - Interdisciplinary Centre of Marine and Environmental Research, Univ. Porto, Porto, Portugal.,Institute of Biomedical Sciences Abel Salazar (ICBAS), Univ. Porto, Porto, Portugal
| | - Mafalda Araújo
- I3S- Institute for Innovation and Health Research, Univ. Porto, Porto, Portugal.,IBMC- Institute for Molecular and Cell Biology, Univ. Porto, Porto, Portugal
| | - GuangJun Zhang
- Department of Comparative Pathobiology, Purdue Univ., Lafayette, USA.,Purdue Institute for Integrative Neuroscience, Purdue Univ., Lafayette, USA.,Purdue Univ. Center for Cancer, Purdue Univ., Lafayette, USA.,Purdue Institute for Inflammation, Immunology and Infectious Diseases, Purdue Univ., Lafayette, USA
| | - Sylvie Mazan
- CNRS, Sorbonne Universités, UPMC Univ. Paris, Observatoire Océanologique, Banyuls, France
| | - Martin J Cohn
- Howard Hughes Medical Institute, UF Genetics Institute, Univ. Florida, Florida, USA.,Department of Biology, UF Genetics Institute, Univ. Florida, Florida, USA.,Department of Molecular Genetics and Microbiology, UF Genetics Institute, Univ. Florida, Florida, USA
| | - L Filipe C Castro
- CIIMAR - Interdisciplinary Centre of Marine and Environmental Research, Univ. Porto, Porto, Portugal. .,Department of Biology, Faculty of Sciences, Univ. Porto, Porto, Portugal.
| | - Jonathan M Wilson
- CIIMAR - Interdisciplinary Centre of Marine and Environmental Research, Univ. Porto, Porto, Portugal. .,Department of Biology, Wilfrid Laurier Univ., Waterloo, Canada.
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Filowitz GL, Rajakumar R, O’Shaughnessy KL, Cohn MJ. Cartilaginous Fishes Provide Insights into the Origin, Diversification, and Sexually Dimorphic Expression of Vertebrate Estrogen Receptor Genes. Mol Biol Evol 2018; 35:2695-2701. [DOI: 10.1093/molbev/msy165] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Grant L Filowitz
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, Gainesville, FL
| | - Rajendhran Rajakumar
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, Gainesville, FL
| | - Katherine L O’Shaughnessy
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, Gainesville, FL
| | - Martin J Cohn
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, Gainesville, FL
- Department of Biology, University of Florida, Gainesville, FL
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10
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Leal F, Cohn MJ. Developmental, genetic, and genomic insights into the evolutionary loss of limbs in snakes. Genesis 2017; 56. [DOI: 10.1002/dvg.23077] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 09/29/2017] [Accepted: 10/06/2017] [Indexed: 12/31/2022]
Affiliation(s)
- Francisca Leal
- Howard Hughes Medical Institute, UF Genetics Institute, University of Florida; Gainesville FL 32610
- Department of Biology; University of Florida; Gainesville FL 32610
| | - Martin J. Cohn
- Department of Biology; University of Florida; Gainesville FL 32610
- Department of Molecular Genetics and Microbiology; University of Florida; Gainesville FL 32610
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11
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Aires R, Jurberg AD, Leal F, Nóvoa A, Cohn MJ, Mallo M. Oct4 Is a Key Regulator of Vertebrate Trunk Length Diversity. Dev Cell 2016; 38:262-74. [DOI: 10.1016/j.devcel.2016.06.021] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 05/19/2016] [Accepted: 06/15/2016] [Indexed: 01/13/2023]
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Armfield BA, Seifert AW, Zheng Z, Merton EM, Rock JR, Lopez MC, Baker HV, Cohn MJ. Molecular Characterization of the Genital Organizer: Gene Expression Profile of the Mouse Urethral Plate Epithelium. J Urol 2016; 196:1295-302. [PMID: 27173853 DOI: 10.1016/j.juro.2016.04.091] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/22/2016] [Indexed: 01/09/2023]
Abstract
PURPOSE Lower urinary tract malformations are among the most common congenital anomalies in humans. Molecular genetic studies of mouse external genital development have begun to identify mechanisms that pattern the genital tubercle and orchestrate urethral tubulogenesis. The urethral plate epithelium is an endodermal signaling region that has an essential role in external genital development. However, little is known about the molecular identity of this cell population or the genes that regulate its activity. MATERIALS AND METHODS We used microarray analysis to characterize differences in gene expression between urethral plate epithelium and surrounding tissue in mouse genital tubercles. In situ hybridizations were performed to map gene expression patterns and ToppCluster (https://toppcluster.cchmc.org/) was used to analyze gene associations. RESULTS A total of 84 genes were enriched at least 20-fold in urethral plate epithelium relative to surrounding tissue. The majority of these genes were expressed throughout the urethral plate in males and females at embryonic day 12.5 when the urethral plate is known to signal. Functional analysis using ToppCluster revealed genetic pathways with known functions in other organ systems but unknown roles in external genital development. Additionally, a 3-dimensional molecular atlas of genes enriched in urethral plate epithelium was generated and deposited at the GUDMAP (GenitoUrinary Development Molecular Anatomy Project) website (http://gudmap.org/). CONCLUSIONS We identified dozens of genes previously unknown to be expressed in urethral plate epithelium at a crucial developmental period. It provides a novel panel of genes for analysis in animal models and in humans with external genital anomalies.
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Affiliation(s)
- Brooke A Armfield
- Department of Molecular Genetics and Microbiology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida
| | - Ashley W Seifert
- Department of Biology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida
| | - Zhengui Zheng
- Department of Molecular Genetics and Microbiology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida
| | - Emily M Merton
- Department of Molecular Genetics and Microbiology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida
| | - Jason R Rock
- Department of Molecular Genetics and Microbiology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida
| | - Maria-Cecilia Lopez
- Department of Molecular Genetics and Microbiology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida
| | - Henry V Baker
- Department of Molecular Genetics and Microbiology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida
| | - Martin J Cohn
- Department of Molecular Genetics and Microbiology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida; Department of Biology, University of Florida Genetics Institute, University of Florida, Gainesville, Florida; Howard Hughes Medical Institute, University of Florida Genetics Institute, University of Florida, Gainesville, Florida.
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Sharma PP, Tarazona OA, Lopez DH, Schwager EE, Cohn MJ, Wheeler WC, Extavour CG. A conserved genetic mechanism specifies deutocerebral appendage identity in insects and arachnids. Proc Biol Sci 2016; 282:20150698. [PMID: 25948691 DOI: 10.1098/rspb.2015.0698] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The segmental architecture of the arthropod head is one of the most controversial topics in the evolutionary developmental biology of arthropods. The deutocerebral (second) segment of the head is putatively homologous across Arthropoda, as inferred from the segmental distribution of the tripartite brain and the absence of Hox gene expression of this anterior-most, appendage-bearing segment. While this homology statement implies a putative common mechanism for differentiation of deutocerebral appendages across arthropods, experimental data for deutocerebral appendage fate specification are limited to winged insects. Mandibulates (hexapods, crustaceans and myriapods) bear a characteristic pair of antennae on the deutocerebral segment, whereas chelicerates (e.g. spiders, scorpions, harvestmen) bear the eponymous chelicerae. In such hexapods as the fruit fly, Drosophila melanogaster, and the cricket, Gryllus bimaculatus, cephalic appendages are differentiated from the thoracic appendages (legs) by the activity of the appendage patterning gene homothorax (hth). Here we show that embryonic RNA interference against hth in the harvestman Phalangium opilio results in homeonotic chelicera-to-leg transformations, and also in some cases pedipalp-to-leg transformations. In more strongly affected embryos, adjacent appendages undergo fusion and/or truncation, and legs display proximal defects, suggesting conservation of additional functions of hth in patterning the antero-posterior and proximo-distal appendage axes. Expression signal of anterior Hox genes labial, proboscipedia and Deformed is diminished, but not absent, in hth RNAi embryos, consistent with results previously obtained with the insect G. bimaculatus. Our results substantiate a deep homology across arthropods of the mechanism whereby cephalic appendages are differentiated from locomotory appendages.
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Affiliation(s)
- Prashant P Sharma
- Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA
| | - Oscar A Tarazona
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Davys H Lopez
- Department of Biology, University of Florida, Gainesville, FL 32611, USA Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Evelyn E Schwager
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Martin J Cohn
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Ward C Wheeler
- Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA
| | - Cassandra G Extavour
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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Sanger TJ, Gredler ML, Cohn MJ. Resurrecting embryos of the tuatara, Sphenodon punctatus, to resolve vertebrate phallus evolution. Biol Lett 2015; 11:20150694. [PMID: 26510679 PMCID: PMC4650183 DOI: 10.1098/rsbl.2015.0694] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 09/30/2015] [Indexed: 11/12/2022] Open
Abstract
The breadth of anatomical and functional diversity among amniote external genitalia has led to uncertainty about the evolutionary origins of the phallus. In several lineages, including the tuatara, Sphenodon punctatus, adults lack an intromittent phallus, raising the possibility that the amniote ancestor lacked external genitalia and reproduced using cloacal apposition. Accordingly, a phallus may have evolved multiple times in amniotes. However, similarities in development across amniote external genitalia suggest that the phallus may have a single evolutionary origin. To resolve the evolutionary history of amniote genitalia, we performed three-dimensional reconstruction of Victorian era tuatara embryos to look for embryological evidence of external genital initiation. Despite the absence of an intromittent phallus in adult tuataras, our observations show that tuatara embryos develop genital anlagen. This illustrates that there is a conserved developmental stage of external genital development among all amniotes and suggests a single evolutionary origin of amniote external genitalia.
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Affiliation(s)
- Thomas J Sanger
- Department of Molecular Genetics and Microbiology, University of Florida, PO Box 103610, Gainesville, FL 32610, USA
| | - Marissa L Gredler
- Department of Biology, University of Florida, PO Box 103610, Gainesville, FL 32610, USA
| | - Martin J Cohn
- Department of Molecular Genetics and Microbiology, University of Florida, PO Box 103610, Gainesville, FL 32610, USA Department of Biology, University of Florida, PO Box 103610, Gainesville, FL 32610, USA Howard Hughes Medical Institute, University of Florida, PO Box 103610, Gainesville, FL 32610, USA
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15
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Abstract
Congenital anomalies frequently occur in organs that undergo tubulogenesis. Hypospadias is a urethral tube defect defined by mislocalized, oversized, or multiple openings of the penile urethra. Deletion of Fgfr2 or its ligand Fgf10 results in severe hypospadias in mice, in which the entire urethral plate is open along the ventral side of the penis. In the genital tubercle, the embryonic precursor of the penis and clitoris, Fgfr2 is expressed in two epithelial populations: the endodermally derived urethral epithelium and the ectodermally derived surface epithelium. Here, we investigate the tissue-specific roles of Fgfr2 in external genital development by generating conditional deletions of Fgfr2 in each of these cell types. Conditional deletion of Fgfr2 results in two distinct phenotypes: endodermal Fgfr2 deletion causes mild hypospadias and inhibits maturation of a complex urethral epithelium, whereas loss of ectodermal Fgfr2 results in severe hypospadias and absence of the ventral prepuce. Although these cell type-specific mutants exhibit distinctive genital anomalies, cellular analysis reveals that Fgfr2 regulates epithelial maturation and cell cycle progression in the urethral endoderm and in the surface ectoderm. The unexpected finding that ectodermal deletion of Fgfr2 results in the most severe hypospadias highlights a major role for Fgfr2 in the developing genital surface epithelium, where epithelial maturation is required for maintenance of a closed urethral tube. These results demonstrate that urethral tubulogenesis, prepuce morphogenesis, and sexually dimorphic patterning of the lower urethra are controlled by discrete regions of Fgfr2 activity.
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Affiliation(s)
- Marissa L Gredler
- Department of Biology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL 32611, USA
| | - Ashley W Seifert
- Department of Biology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL 32611, USA
| | - Martin J Cohn
- Department of Biology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, FL 32611, USA Howard Hughes Medical Institute, Department of Molecular Genetics and Microbiology, University of Florida, PO Box 103610, Gainesville, FL 32611, USA
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16
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Georgas KM, Armstrong J, Keast JR, Larkins CE, McHugh KM, Southard-Smith EM, Cohn MJ, Batourina E, Dan H, Schneider K, Buehler DP, Wiese CB, Brennan J, Davies JA, Harding SD, Baldock RA, Little MH, Vezina CM, Mendelsohn C. An illustrated anatomical ontology of the developing mouse lower urogenital tract. Development 2015; 142:1893-908. [PMID: 25968320 DOI: 10.1242/dev.117903] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 04/01/2015] [Indexed: 01/10/2023]
Abstract
Malformation of the urogenital tract represents a considerable paediatric burden, with many defects affecting the lower urinary tract (LUT), genital tubercle and associated structures. Understanding the molecular basis of such defects frequently draws on murine models. However, human anatomical terms do not always superimpose on the mouse, and the lack of accurate and standardised nomenclature is hampering the utility of such animal models. We previously developed an anatomical ontology for the murine urogenital system. Here, we present a comprehensive update of this ontology pertaining to mouse LUT, genital tubercle and associated reproductive structures (E10.5 to adult). Ontology changes were based on recently published insights into the cellular and gross anatomy of these structures, and on new analyses of epithelial cell types present in the pelvic urethra and regions of the bladder. Ontology changes include new structures, tissue layers and cell types within the LUT, external genitalia and lower reproductive structures. Representative illustrations, detailed text descriptions and molecular markers that selectively label muscle, nerves/ganglia and epithelia of the lower urogenital system are also presented. The revised ontology will be an important tool for researchers studying urogenital development/malformation in mouse models and will improve our capacity to appropriately interpret these with respect to the human situation.
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Affiliation(s)
- Kylie M Georgas
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Jane Armstrong
- Center for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Janet R Keast
- Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Christine E Larkins
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - Kirk M McHugh
- Centre for Molecular and Human Genetics, The Research Institute at Nationwide Children's Hospital and Division of Anatomy, The Ohio State University, Columbus, OH 43205/10, USA
| | - E Michelle Southard-Smith
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Martin J Cohn
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA Department of Biology, Genetics Institute, University of Florida, Gainesville, FL 32610, USA Howard Hughes Medical Institute, University of Florida, Gainesville, FL 32610, USA
| | | | - Hanbin Dan
- Columbia University, Department of Urology, New York, NY 10032, USA
| | - Kerry Schneider
- Columbia University, Department of Urology, New York, NY 10032, USA
| | - Dennis P Buehler
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Carrie B Wiese
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Jane Brennan
- Center for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Jamie A Davies
- Center for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Simon D Harding
- MRC Human Genetics Unit, MRC IGMM, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Richard A Baldock
- MRC Human Genetics Unit, MRC IGMM, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Melissa H Little
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Chad M Vezina
- University of Wisconsin-Madison, School of Veterinary Medicine, Madison, WI 53706, USA
| | - Cathy Mendelsohn
- Columbia University, Department of Urology, New York, NY 10032, USA
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O'Shaughnessy KL, Dahn RD, Cohn MJ. Molecular development of chondrichthyan claspers and the evolution of copulatory organs. Nat Commun 2015; 6:6698. [PMID: 25868783 PMCID: PMC4403318 DOI: 10.1038/ncomms7698] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 02/19/2015] [Indexed: 11/09/2022] Open
Abstract
The earliest known vertebrate copulatory organs are claspers, paired penis-like structures that are associated with evolution of internal fertilization and viviparity in Devonian placoderms. Today, only male chondrichthyans possess claspers, which extend from posterior pelvic fins and function as intromittent organs. Here we report that clasper development from pelvic fins of male skates is controlled by hormonal regulation of the Sonic hedgehog (Shh) pathway. We show that Shh signalling is necessary for male clasper development and is sufficient to induce clasper cartilages in females. Androgen receptor (AR) controls the male-specific pattern of Shh in pelvic fins by regulation of Hand2. We identify an androgen response element (ARE) in the Hand2 locus and present biochemical evidence that AR can directly bind the Hand2 ARE. Together, our results suggest that the genetic circuit for appendage development evolved an androgen regulatory input, which prolonged signalling activity and drove clasper skeletogenesis in male fins. Claspers are copulatory organs found in male cartilaginous fishes. Here, the authors show that androgen receptor signalling maintains the Shh pathway to promote clasper development in male skates and suggest the importance of hormonal regulation in the evolution of male copulatory organs.
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Affiliation(s)
- Katherine L O'Shaughnessy
- Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, Florida 32610, USA
| | | | - Martin J Cohn
- 1] Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, Florida 32610, USA [2] Howard Hughes Medical Institute and Department of Biology, University of Florida, PO Box 103610, Gainesville, Florida 32610, USA
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18
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Abstract
Genital malformations occur at a high frequency in humans, affecting ~1:250 live births. The molecular mechanisms of external genital development are beginning to be identified; however, the origin of cells that give rise to external genitalia is unknown. Here we use cell lineage analysis to show that the genital tubercle, the precursor of the penis and clitoris, arises from two populations of progenitor cells that originate at the lateral edges of the embryo, at the level of the posterior hindlimb buds and anterior tail. During body wall closure, the left and right external genital progenitor pools are brought together at the ventral midline, where they form the paired genital swellings that give rise to the genital tubercle. Unexpectedly, the left and right external genital progenitor pools form two lineage-restricted compartments in the phallus. Together with previous lineage studies of limb buds, our results indicate that, at the pelvic level, the early lateral mesoderm is regionalized from medial to lateral into dorsal limb, ventral limb, and external genital progenitor fields. These findings have implications for the evolutionary diversification of external genitalia and for the association between external genital defects and disruption of body wall closure, as seen in the epispadias-extrophy complex.
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Affiliation(s)
- Ana M Herrera
- Department of Molecular Genetics and Microbiology, Howard Hughes Medical Institute, UF Genetics Institute, University of Florida, P.O. Box 103610, Gainesville, FL 32610, USA
| | - Martin J Cohn
- 1] Department of Molecular Genetics and Microbiology, Howard Hughes Medical Institute, UF Genetics Institute, University of Florida, P.O. Box 103610, Gainesville, FL 32610, USA [2] Department of Biology, Howard Hughes Medical Institute, UF Genetics Institute, University of Florida, P.O. Box 103610, Gainesville, FL 32610, USA
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19
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Herrera AM, Brennan PL, Cohn MJ. Development of Avian External Genitalia: Interspecific Differences and Sexual Differentiation of the Male and Female Phallus. Sex Dev 2014; 9:43-52. [DOI: 10.1159/000364927] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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20
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Gredler ML, Seifert AW, Cohn MJ. Morphogenesis and Patterning of the Phallus and Cloaca in the American Alligator, Alligator mississippiensis. Sex Dev 2014; 9:53-67. [DOI: 10.1159/000364817] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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21
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22
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23
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Gredler ML, Sanger TJ, Cohn MJ. Development of the Cloaca, Hemipenes, and Hemiclitores in the Green Anole, Anolis carolinensis. Sex Dev 2014; 9:21-33. [DOI: 10.1159/000363757] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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24
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Gredler ML, Larkins CE, Leal F, Lewis AK, Herrera AM, Perriton CL, Sanger TJ, Cohn MJ. Evolution of External Genitalia: Insights from Reptilian Development. Sex Dev 2014; 8:311-26. [DOI: 10.1159/000365771] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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25
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Abstract
Over the past decade, the genetics of external genital development have begun to be understood. Male and female external genitalia develop from the genital tubercle. The early tubercle has a superficial resemblance to the limb bud, but an important distinction is that the limb consists of only mesoderm and ectoderm, whereas the genital tubercle also has an endodermal component, the urethral epithelium. Urethral epithelium, which expresses Sonic hedgehog, acts as a signaling region that controls outgrowth and pattern formation, and ultimately differentiates into the urethral tube. While there are intriguing parallels between limb and genital development, recent studies have identified some key differences, including the role of Fgf signaling. Our understanding of the mechanisms of genital development still lags far behind the limb, and major questions remain to be answered, including the molecular nature of the signals that initiate genital budding, sustain outgrowth, induce tissue polarity and orchestrate urethral tubulogenesis.
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Affiliation(s)
- Martin J Cohn
- Howard Hughes Medical Institute, Department of Molecular Genetics and Microbiology, Department of Biology, University of Florida, Gainesville, Florida, USA.
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26
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Seifert AW, Zheng Z, Ormerod BK, Cohn MJ. Sonic hedgehog controls growth of external genitalia by regulating cell cycle kinetics. Nat Commun 2010; 1:23. [PMID: 20975695 PMCID: PMC2964453 DOI: 10.1038/ncomms1020] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 04/28/2010] [Indexed: 02/07/2023] Open
Abstract
The faithful positioning and growth of cells during
embryonic development is essential. In this study Seifert et al. demonstrate that
inactivation of Sonic Hedgehog during development of the genital tubercle results in a
prolonged G1 phase and a slower rate of growth. During embryonic development, cells are instructed which position to occupy, they interpret
these cues as differentiation programmes, and expand these patterns by growth. Sonic
hedgehog (Shh) specifies positional identity in many organs; however, its role in growth is
not well understood. In this study, we show that inactivation of Shh in external
genitalia extends the cell cycle from 8.5 to 14.4 h, and genital growth is reduced by ∼75%.
Transient Shh signalling establishes pattern in the genital tubercle; however,
transcriptional levels of G1 cell cycle regulators are reduced. Consequently, G1 length is
extended, leading to fewer progenitor cells entering S-phase. Cell cycle genes responded
similarly to Shh inactivation in genitalia and limbs, suggesting that Shh may regulate
growth by similar mechanisms in different organ systems. The finding that Shh regulates cell
number by controlling the length of specific cell cycle phases identifies a novel mechanism
by which Shh elaborates pattern during appendage development.
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Affiliation(s)
- Ashley W Seifert
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
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27
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Seifert AW, Bouldin CM, Choi KS, Harfe BD, Cohn MJ. Multiphasic and tissue-specific roles of sonic hedgehog in cloacal septation and external genitalia development. Development 2009; 136:3949-57. [PMID: 19906862 DOI: 10.1242/dev.042291] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Malformations of the external genitalia are among the most common congenital anomalies in humans. The urogenital and anorectal sinuses develop from the embryonic cloaca, and the penis and clitoris develop from the genital tubercle. Within the genital tubercle, the endodermally derived urethral epithelium functions as an organizer and expresses sonic hedgehog (Shh). Shh knockout mice lack external genitalia and have a persistent cloaca. This identified an early requirement for Shh, but precluded analysis of its later role in the genital tubercle. We conducted temporally controlled deletions of Shh and report that Shh is required continuously through the onset of sexual differentiation. Shh function is divisible into two temporal phases; an anogenital phase, during which Shh regulates outgrowth and patterning of the genital tubercle and septation of the cloaca, and a later external genital phase, during which Shh regulates urethral tube closure. Disruption of Shh function during the anogenital phase causes coordinated anorectal and genitourinary malformations, whereas inactivation during the external genital phase causes hypospadias. Shh directs cloacal septation by promoting cell proliferation in adjacent urorectal septum mesenchyme. Additionally, conditional inactivation of smoothened in the genital ectoderm and cloacal/urethral endoderm shows that the ectoderm is a direct target of Shh and is required for urethral tube closure, highlighting a novel role for genital ectoderm in urethragenesis. Identification of the stages during which disruption of Shh results in either isolated or coordinated malformations of anorectal and external genital organs provides a new tool for investigating the etiology of anogenital malformations in humans.
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Affiliation(s)
- Ashley W Seifert
- Department of Biology, University of Florida, Cancer/Genetics Research Complex, PO Box 103610, Gainesville, FL 32610-3610, USA
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28
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Seifert AW, Yamaguchi T, Cohn MJ. Functional and phylogenetic analysis shows that Fgf8 is a marker of genital induction in mammals but is not required for external genital development. Development 2009; 136:2643-51. [PMID: 19592577 DOI: 10.1242/dev.036830] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
In mammalian embryos, male and female external genitalia develop from the genital tubercle. Outgrowth of the genital tubercle is maintained by the urethral epithelium, and it has been reported that Fgf8 mediates this activity. To test directly whether Fgf8 is required for external genital development, we conditionally removed Fgf8 from the cloacal/urethral epithelium. Surprisingly, Fgf8 is not necessary for initiation, outgrowth or normal patterning of the external genitalia. In early genital tubercles, we found no redundant Fgf expression in the urethral epithelium, which contrasts with the situation in the apical ectodermal ridge (AER) of the limb. Analysis of Fgf8 pathway activity showed that four putative targets are either absent from early genital tubercles or are not regulated by Fgf8. We therefore examined the distribution of Fgf8 protein and report that, although it is present in the AER, Fgf8 is undetectable in the genital tubercle. Thus, Fgf8 is transcribed, but the signaling pathway is not activated during normal genital development. A phylogenetic survey of amniotes revealed Fgf8 expression in genital tubercles of eutherian and metatherian mammals, but not turtles or alligators, indicating that Fgf8 expression is neither a required nor a conserved feature of amniote external genital development. The results indicate that Fgf8 expression is an early readout of the genital initiation signal rather than the signal itself. We propose that induction of external genitalia involves an epithelial-epithelial interaction at the cloacal membrane, and suggest that the cloacal ectoderm may be the source of the genital initiation signal.
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Affiliation(s)
- Ashley W Seifert
- Department of Zoology, UF Genetics Institute, University of Florida, Gainesville, FL 32611, USA
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29
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Cohn MJ, Yamaguchi T, Seifert AW. Functional and phylogenetic analysis Fgf8 shows that Fgf8 is not involved in external genital development. Dev Biol 2009. [DOI: 10.1016/j.ydbio.2009.05.419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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30
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Seifert AW, Ormerod BK, Cohn MJ. Sonic hedgehog controls growth of external genitalia by regulating cell cycle kinetics. Dev Biol 2009. [DOI: 10.1016/j.ydbio.2009.05.420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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31
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Choi KS, Cohn MJ, Harfe BD. Identification of nucleus pulposus precursor cells and notochordal remnants in the mouse: implications for disk degeneration and chordoma formation. Dev Dyn 2009; 237:3953-8. [PMID: 19035356 DOI: 10.1002/dvdy.21805] [Citation(s) in RCA: 233] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
A classically identified "notochordal" cell population in the nucleus pulposus is thought to regulate disk homeostasis. However, the embryonic origin of these cells has been under dispute for >60 years. Here we provide the first direct evidence that all cell types in the adult mouse nucleus pulposus are derived from the embryonic notochord. Additionally, rare isolated embryonic notochord cells remained in the vertebral column and resembled "notochordal remnants," which in humans have been proposed to give rise to a rare type of late-onset cancer called chordoma. Previously, this cell type had not been identified in the mouse model system. The development and characterization of a mouse model that can be used to fate map nucleus pulposus precursor cells in any mutant background will be useful for uncovering the cellular and molecular mechanisms of disk degeneration. In addition, the identification of notochordal remnants in mice is the first step towards generating an in vivo model of chordoma.
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Affiliation(s)
- Kyung-Suk Choi
- Department of Molecular Genetics, University of Florida, College of Medicine, Gainesville, Florida 32610, USA
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32
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Reno PL, McCollum MA, Cohn MJ, Meindl RS, Hamrick M, Lovejoy CO. Patterns of correlation and covariation of anthropoid distal forelimb segments correspond to Hoxd expression territories. J Exp Zool 2008; 310:240-58. [DOI: 10.1002/jez.b.21207] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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33
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Freitas R, Zhang G, Cohn MJ. Biphasic Hoxd gene expression in shark paired fins reveals an ancient origin of the distal limb domain. PLoS One 2007; 2:e754. [PMID: 17710153 PMCID: PMC1937022 DOI: 10.1371/journal.pone.0000754] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2007] [Accepted: 07/24/2007] [Indexed: 01/10/2023] Open
Abstract
The evolutionary transition of fins to limbs involved development of a new suite of distal skeletal structures, the digits. During tetrapod limb development, genes at the 5' end of the HoxD cluster are expressed in two spatiotemporally distinct phases. In the first phase, Hoxd9-13 are activated sequentially and form nested domains along the anteroposterior axis of the limb. This initial phase patterns the limb from its proximal limit to the middle of the forearm. Later in development, a second wave of transcription results in 5' HoxD gene expression along the distal end of the limb bud, which regulates formation of digits. Studies of zebrafish fins showed that the second phase of Hox expression does not occur, leading to the idea that the origin of digits was driven by addition of the distal Hox expression domain in the earliest tetrapods. Here we test this hypothesis by investigating Hoxd gene expression during paired fin development in the shark Scyliorhinus canicula, a member of the most basal lineage of jawed vertebrates. We report that at early stages, 5'Hoxd genes are expressed in anteroposteriorly nested patterns, consistent with the initial wave of Hoxd transcription in teleost and tetrapod paired appendages. Unexpectedly, a second phase of expression occurs at later stages of shark fin development, in which Hoxd12 and Hoxd13 are re-expressed along the distal margin of the fin buds. This second phase is similar to that observed in tetrapod limbs. The results indicate that a second, distal phase of Hoxd gene expression is not uniquely associated with tetrapod digit development, but is more likely a plesiomorphic condition present the common ancestor of chondrichthyans and osteichthyans. We propose that a temporal extension, rather than de novo activation, of Hoxd expression in the distal part of the fin may have led to the evolution of digits.
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Affiliation(s)
- Renata Freitas
- Department of Zoology, Cancer/Genetics Research Complex, University of Florida, Gainesville, Florida, United Sates of America
| | - GuangJun Zhang
- Department of Zoology, Cancer/Genetics Research Complex, University of Florida, Gainesville, Florida, United Sates of America
| | - Martin J. Cohn
- Department of Zoology, Cancer/Genetics Research Complex, University of Florida, Gainesville, Florida, United Sates of America
- Department of Anatomy and Cell Biology, Cancer/Genetics Research Complex, University of Florida, Gainesville, Florida, United States of America
- * To whom correspondence should be addressed. E-mail:
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Yong W, Yang Z, Periyasamy S, Chen H, Yucel S, Li W, Lin LY, Wolf IM, Cohn MJ, Baskin LS, Sa Nchez ER, Shou W. Essential role for Co-chaperone Fkbp52 but not Fkbp51 in androgen receptor-mediated signaling and physiology. J Biol Chem 2007; 282:5026-5036. [PMID: 17142810 PMCID: PMC2577319 DOI: 10.1074/jbc.m609360200] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fkbp52 and Fkbp51 are tetratricopeptide repeat proteins found in steroid receptor complexes, and Fkbp51 is an androgen receptor (AR) target gene. Although in vitro studies suggest that Fkbp52 and Fkbp51 regulate hormone binding and/or subcellular trafficking of receptors, the roles of Fkbp52 and Fkbp51 in vivo have not been extensively investigated. Here, we evaluate their physiological roles in Fkbp52-deficient and Fkbp51-deficient mice. Fkbp52-deficient males developed defects in select reproductive organs (e.g. penile hypospadias and prostate dysgenesis but normal testis), pointing to a role for Fkbp52 in AR-mediated signaling and function. Surprisingly, ablation of Fkbp52 did not affect AR hormone binding or nuclear translocation in vivo and in vitro. Molecular studies in mouse embryonic fibroblast cells uncovered that Fkbp52 is critical to AR transcriptional activity. Interestingly, Fkbp51 expression was down-regulated in Fkbp52-deficient males but only in affected tissues, providing further evidence of tissue-specific loss of AR activity and suggesting that Fkbp51 is an AR target gene essential to penile and prostate development. However, Fkbp51-deficient mice were normal, showing no defects in AR-mediated reproductive function. Our work demonstrates that Fkbp52 but not Fkbp51 is essential to AR-mediated signaling and provides evidence for an unprecedented Fkbp52 function, direct control of steroid receptor transcriptional activity.
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Affiliation(s)
- Weidong Yong
- Herman B. Wells Center for Pediatric Research, Section of Pediatric Cardiology, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Zuocheng Yang
- Herman B. Wells Center for Pediatric Research, Section of Pediatric Cardiology, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202; Department of Pediatrics, Third Xiang-Ya Hospital, Central South University, Xiang-Ya School of Medicine, Changsha 410013, China
| | - Sumudra Periyasamy
- Department of Physiology and Pharmacology, College of Medicine, University of Toledo, Toledo, Ohio 43614
| | - Hanying Chen
- Herman B. Wells Center for Pediatric Research, Section of Pediatric Cardiology, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Selcul Yucel
- Department of Urology, University of California School of Medicine, San Francisco, California 94143, and the
| | - Wei Li
- Herman B. Wells Center for Pediatric Research, Section of Pediatric Cardiology, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Leanne Y Lin
- Herman B. Wells Center for Pediatric Research, Section of Pediatric Cardiology, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Irene M Wolf
- Department of Physiology and Pharmacology, College of Medicine, University of Toledo, Toledo, Ohio 43614
| | - Martin J Cohn
- Department of Zoology, University of Florida, Gainesville, Florida 32611
| | - Laurence S Baskin
- Department of Urology, University of California School of Medicine, San Francisco, California 94143, and the
| | - Edwin R Sa Nchez
- Department of Physiology and Pharmacology, College of Medicine, University of Toledo, Toledo, Ohio 43614
| | - Weinian Shou
- Herman B. Wells Center for Pediatric Research, Section of Pediatric Cardiology, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202.
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Zhang G, Cohn MJ. Hagfish and lancelet fibrillar collagens reveal that type II collagen-based cartilage evolved in stem vertebrates. Proc Natl Acad Sci U S A 2006; 103:16829-33. [PMID: 17077149 PMCID: PMC1636540 DOI: 10.1073/pnas.0605630103] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The origin of vertebrates was defined by evolution of a skeleton; however, little is known about the developmental mechanisms responsible for this landmark evolutionary innovation. In jawed vertebrates, cartilage matrix consists predominantly of type II collagen (Col2alpha1), whereas that of jawless fishes has long been thought to be noncollagenous. We recently showed that Col2alpha1 is present in lamprey cartilage, indicating that type II collagen-based cartilage evolved earlier than previously recognized. Here, we investigate the origin of vertebrate cartilage, and we report that hagfishes, the sister group to lampreys, also have Col2alpha1-based cartilage, suggesting its presence in the common ancestor of crown-group vertebrates. We go on to show that lancelets, a sister group to vertebrates, possess an ancestral clade A fibrillar collagen (ColA) gene that is expressed in the notochord. Together, these results suggest that duplication and diversification of ColA genes at the chordate-vertebrate transition may underlie the evolutionary origin of vertebrate skeletal tissues.
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Affiliation(s)
| | - Martin J. Cohn
- *Department of Zoology and
- Department of Anatomy and Cell Biology, University of Florida, P.O. Box 118525, Gainesville, FL 32611
- To whom correspondence should be addressed. E-mail:
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Freitas R, Zhang G, Cohn MJ. Evidence that mechanisms of fin development evolved in the midline of early vertebrates. Nature 2006; 442:1033-7. [PMID: 16878142 DOI: 10.1038/nature04984] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Accepted: 06/19/2006] [Indexed: 11/09/2022]
Abstract
The origin of paired appendages was a major evolutionary innovation for vertebrates, marking the first step towards fin- (and later limb-) driven locomotion. The earliest vertebrate fossils lack paired fins but have well-developed median fins, suggesting that the mechanisms of fin development were assembled first in the midline. Here we show that shark median fin development involves the same genetic programs that operate in paired appendages. Using molecular markers for different cell types, we show that median fins arise predominantly from somitic (paraxial) mesoderm, whereas paired appendages develop from lateral plate mesoderm. Expression of Hoxd and Tbx18 genes, which specify paired limb positions, also delineates the positions of median fins. Proximodistal development of median fins occurs beneath an apical ectodermal ridge, the structure that controls outgrowth of paired appendages. Each median fin bud then acquires an anteroposteriorly-nested pattern of Hoxd expression similar to that which establishes skeletal polarity in limbs. Thus, despite their different embryonic origins, paired and median fins utilize a common suite of developmental mechanisms. We extended our analysis to lampreys, which diverged from the lineage leading to gnathostomes before the origin of paired appendages, and show that their median fins also develop from somites and express orthologous Hox and Tbx genes. Together these results suggest that the molecular mechanisms for fin development originated in somitic mesoderm of early vertebrates, and that the origin of paired appendages was associated with re-deployment of these mechanisms to lateral plate mesoderm.
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Affiliation(s)
- Renata Freitas
- Department of Zoology, University of Florida, PO Box 118525, Gainesville, Florida 32611, USA
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Jun Zhang G, Miyamoto MM, Cohn MJ. Lamprey type II collagen and Sox9 reveal an ancient origin of the vertebrate collagenous skeleton. Dev Biol 2006. [DOI: 10.1016/j.ydbio.2006.04.273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Bouldin CM, Cohn MJ, Harfe BD. Molecular analysis of a polydactylous chicken. Dev Biol 2006. [DOI: 10.1016/j.ydbio.2006.04.191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Thewissen JGM, Cohn MJ, Stevens LS, Bajpai S, Heyning J, Horton WE. Developmental basis for hind-limb loss in dolphins and origin of the cetacean bodyplan. Proc Natl Acad Sci U S A 2006; 103:8414-8. [PMID: 16717186 PMCID: PMC1482506 DOI: 10.1073/pnas.0602920103] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Among mammals, modern cetaceans (whales, dolphins, and porpoises) are unusual in the absence of hind limbs. However, cetacean embryos do initiate hind-limb bud development. In dolphins, the bud arrests and degenerates around the fifth gestational week. Initial limb outgrowth in amniotes is maintained by two signaling centers, the apical ectodermal ridge (AER) and the zone of polarizing activity (ZPA). Our data indicate that the cetacean hind-limb bud forms an AER and that this structure expresses Fgf8 initially, but that neither the AER nor Fgf8 expression is maintained. Moreover, Sonic hedgehog (Shh), which mediates the signaling activity of the ZPA, is absent from the dolphin hind-limb bud. We find that failure to establish a ZPA is associated with the absence of Hand2, an upstream regulator of Shh. Interpreting our results in the context of both the cetacean fossil record and the known functions of Shh suggests that reduction of Shh expression may have occurred approximately 41 million years ago and led to the loss of distal limb elements. The total loss of Shh expression may account for the further loss of hind-limb elements that occurred near the origin of the modern suborders of cetaceans approximately 34 million years ago. Integration of paleontological and developmental data suggests that hind-limb size was reduced by gradually operating microevolutionary changes. Long after locomotor function was totally lost, modulation of developmental control genes eliminated most of the hind-limb skeleton. Hence, macroevolutionary changes in gene expression did not drive the initial reduction in hind-limb size.
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Affiliation(s)
- J G M Thewissen
- Department of Anatomy, Northeastern Ohio Universities College of Medicine, Rootstown, OH 44272, USA.
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Abstract
During vertebrate limb development, Hoxd genes are transcribed in two temporal phases; an early wave controls growth and polarity up to the forearm and a late wave patterns the digits. In this issue of Developmental Cell, Tarchini and Duboule (2006) report that two opposite regulatory modules direct early collinear expression of Hoxd genes.
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Affiliation(s)
- Renata Freitas
- Department of Zoology, University of Florida, P.O. Box 118525, Gainesville, Florida 32611, USA
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Zhang G, Miyamoto MM, Cohn MJ. Lamprey type II collagen and Sox9 reveal an ancient origin of the vertebrate collagenous skeleton. Proc Natl Acad Sci U S A 2006; 103:3180-5. [PMID: 16492784 PMCID: PMC1413883 DOI: 10.1073/pnas.0508313103] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Indexed: 11/18/2022] Open
Abstract
Type II collagen is the major cartilage matrix protein in the jawed vertebrate skeleton. Lampreys and hagfishes, by contrast, are thought to have noncollagenous cartilage. This difference in skeletal structure has led to the hypothesis that the vertebrate common ancestor had a noncollagenous skeleton, with type II collagen becoming the predominant cartilage matrix protein after the divergence of jawless fish from the jawed vertebrates approximately 500 million years ago. Here we report that lampreys have two type II collagen (Col2alpha1) genes that are expressed during development of the cartilaginous skeleton. We also demonstrate that the adult lamprey skeleton is rich in Col2alpha1 protein. Furthermore, we have isolated a lamprey orthologue of Sox9, a direct transcriptional regulator of Col2alpha1 in jawed vertebrates, and show that it is coexpressed with both Col2alpha1 genes during skeletal development. These results reveal that the genetic pathway for chondrogenesis in lampreys and gnathostomes is conserved through the activation of cartilage matrix molecules and suggest that a collagenous skeleton evolved surprisingly early in vertebrate evolution.
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Affiliation(s)
| | | | - Martin J. Cohn
- Departments of Zoology and
- Anatomy and Cell Biology, University of Florida, 223 Bartram Hall, P.O. Box 118525, Gainesville, FL 32611
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Abstract
Vertebrates have evolved electrosensory receptors that detect electrical stimuli on the surface of the skin and transmit them somatotopically to the brain. In chondrichthyans, the electrosensory system is composed of a cephalic network of ampullary organs, known as the ampullae of Lorenzini, that can detect extremely weak electric fields during hunting and navigation. Each ampullary organ consists of a gel-filled epidermal pit containing sensory hair cells, and synaptic connections with primary afferent neurons at the base of the pit that facilitate detection of voltage gradients over large regions of the body. The developmental origin of electroreceptors and the mechanisms that determine their spatial arrangement in the vertebrate head are not well understood. We have analyzed electroreceptor development in the lesser spotted catshark (Scyliorhinus canicula) and show that Sox8 and HNK1, two markers of the neural crest lineage, selectively mark sensory cells in ampullary organs. This represents the first evidence that the neural crest gives rise to electrosensory cells. We also show that pathfinding by cephalic mechanosensory and electrosensory axons follows the expression pattern of EphA4, a well-known guidance cue for axons and neural crest cells in osteichthyans. Expression of EphrinB2, which encodes a ligand for EphA4, marks the positions at which ampullary placodes are initiated in the epidermis, and EphA4 is expressed in surrounding mesenchyme. These results suggest that Eph-Ephrin signaling may establish an early molecular map for neural crest migration, axon guidance and placodal morphogenesis during development of the shark electrosensory system.
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Affiliation(s)
- Renata Freitas
- Department of Zoology, University of Florida, PO Box 118525, Gainesville, FL 32611-8525, USA
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Abstract
Development of external genitalia in mammalian embryos requires tight coordination of a complex series of morphogenetic events involving outgrowth,proximodistal and dorsoventral patterning, and epithelial tubulogenesis. Hypospadias is a congenital defect of the external genitalia that results from failure of urethral tube closure. Although this is the second most common birth defect in humans, affecting one in every 250 children, the molecular mechanisms that regulate morphogenesis of the mammalian urethra are poorly understood. We report that mice lacking the IIIb isoform of fibroblast growth factor receptor 2 (Fgfr2) exhibit severe hypospadias. Urethral signaling regions, as indicated by Shh and Fgf8 expression, are established in Fgfr2-IIIb null mice; however, cell proliferation arrests prematurely and maturation of the urethral epithelium is disrupted. Fgfr2-IIIb-/- mutants fail to maintain the progenitor cell population required for uroepithelial renewal during tubular morphogenesis. In addition, we show that antagonism of the androgen receptor (AR) leads to loss of Fgfr2-IIIb and Fgf10 expression in the urethra, and an associated hypospadias phenotype, suggesting that these genes are downstream targets of AR during external genital development. Genitourinary defects resulting from disruption of AR activity, by either genetic or environmental factors, may therefore involve negative regulation of the Fgfr2 pathway. This represents the first example of how the developing genitourinary system integrates cues from systemically circulating steroid hormones with a locally expressed growth factor pathway.
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Affiliation(s)
- Anita Petiot
- Cancer Research UK, Lincoln's Inn Fields, London WC2A 3PX, UK
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Freitas R, Cohn MJ. Analysis of EphA4 in the lesser spotted catshark identifies a primitive gnathostome expression pattern and reveals co-option during evolution of shark-specific morphology. Dev Genes Evol 2004; 214:466-72. [PMID: 15300436 DOI: 10.1007/s00427-004-0426-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2004] [Accepted: 06/30/2004] [Indexed: 10/26/2022]
Abstract
The Eph family is the largest known group of structurally related receptor tyrosine kinases (RTKs). Each Eph receptor has a specific Ephrin ligand, and these function to define spatial boundaries during development. Analyses of EphA4 in mouse, chick, frog and zebrafish embryos have implicated this gene in a number of developmental processes, including maintenance of segmental boundaries, axon guidance, limb development, neural crest migration and patterning of the ear. In order to determine which components of EphA4 function may be primitive for gnathostomes, we cloned EphA4 from the lesser spotted catshark ( Scyliorhinus canicula) and examined its expression pattern during shark embryonic development. Consistent with the patterns reported for bony fish and tetrapods, we observed segmental expression of EphA4 in the developing hindbrain and later in the pharyngeal arches of shark embryos. EphA4 was also detected during sensory organogenesis, in the developing ear, eye, nasal pits and lateral line. A dynamic pattern of EphA4expression occurs during shark fin development, suggesting an early role in outgrowth and patterning of the fin buds and a later role in tissue differentiation. We also observed several novel domains of EphA4expression that have not been reported in other vertebrates, including external gill buds, dermal denticles, median fins and claspers. While some of these domains may reflect co-option of EphA4expression to novel sites for development of shark-specific characters, others are more likely to be ancestral patterns of expression that were lost in other vertebrate lineages.
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Affiliation(s)
- Renata Freitas
- Department of Zoology, University of Florida, P.O. Box 118525, Gainesville, FL 32611, USA
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Affiliation(s)
- Martin J Cohn
- Department of Zoology, University of Florida, 223 Bartram Hall, Box 11858, Gainesville, FL 32611-8525, USA.
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Abstract
External genital development begins with formation of paired genital swellings, which develop into the genital tubercle. Proximodistal outgrowth and axial patterning of the genital tubercle are coordinated to give rise to the penis or clitoris. The genital tubercle consists of lateral plate mesoderm, surface ectoderm, and endodermal urethral epithelium derived from the urogenital sinus. We have investigated the molecular control of external genital development in the mouse embryo. Previous work has shown that the genital tubercle has polarizing activity, but the precise location of this activity within the tubercle is unknown. We reasoned that if the tubercle itself is patterned by a specialized signaling region, then polarizing activity may be restricted to a subset of cells. Transplantation of urethral epithelium, but not genital mesenchyme, to chick limbs results in mirror-image duplication of the digits. Moreover, when grafted to chick limbs, the urethral plate orchestrates morphogenetic movements normally associated with external genital development. Signaling activity is therefore restricted to urethral plate cells. Before and during normal genital tubercle outgrowth, urethral plate epithelium expresses Sonic hedgehog (Shh). In mice with a targeted deletion of Shh, external genitalia are absent. Genital swellings are initiated, but outgrowth is not maintained. In the absence of Shh signaling, Fgf8, Bmp2, Bmp4, Fgf10, and Wnt5a are downregulated, and apoptosis is enhanced in the genitalia. These results identify the urethral epithelium as a signaling center of the genital tubercle, and demonstrate that Shh from the urethral epithelium is required for outgrowth, patterning, and cell survival in the developing external genitalia.
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Affiliation(s)
- Claire L Perriton
- Division of Zoology, University of Reading, Whiteknights, United Kingdom
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Takahashi T, Holland PWH, Cohn MJ, Shimizu K, Kurokawa M, Hirai H. An orphan PRD class homeobox gene expressed in mouse brain and limb development. Dev Genes Evol 2002; 212:293-7. [PMID: 12111214 DOI: 10.1007/s00427-002-0244-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2001] [Accepted: 03/21/2002] [Indexed: 10/27/2022]
Abstract
We report the cDNA sequence and expression of a mouse homeobox gene, Dmbx1, from the PRD class and comparison to its human orthologue. The gene defines a new homeobox gene family, Dmbx, phylogenetically distinct from the Ptx, Alx, Prx Otx, Gsc, Otp and Pax gene families. The Dmbx1 gene is expressed in the developing mouse diencephalon, midbrain and hindbrain, and has dynamic expression during forelimb and hindlimb development. Unusually for homeobox genes, there is no orthologue in the Drosophila or Caenorhabditis genomes; we argue this reflects secondary loss.
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Affiliation(s)
- Tokiharu Takahashi
- School of Animal and Microbial Science, The University of Reading, Whiteknights, Reading, RG6 6AJ, UK
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Abstract
Explanations of the patterns of vertebrate fin and limb evolution are improving as specific hypotheses based on molecular and developmental data are proposed and tested. Comparative analyses of gene expression patterns and functions in developing limbs, and morphological patterns in embryonic, adult and fossil limbs point to digit specification as a key developmental innovation associated with the origin of tetrapods. Digit development during the fin-to-limb transition involved sustained proximodistal outgrowth and a new phase of Hox gene expression in the distal fin bud. These patterning changes in the distal limb have been explained by the linked concepts of the metapterygial axis and the digital arch. These have been proposed to account for the generation of limb pattern by sequential branching and segmentation of precartilagenous elements along the proximodistal axis of the limb. While these ideas have been very fruitful, they have become increasingly difficult to reconcile with experimental and comparative studies of fin and limb development. Here we argue that limb development does not involve a branching mechanism, and reassess the concept of a metapterygial axis in limb development and evolution.
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Affiliation(s)
- M J Cohn
- Division of Zoology, University of Reading, UK.
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Abstract
The development of jaws was a critical event in vertebrate evolution because it ushered in a transition to a predatory lifestyle, but how this innovation came about has been a mystery. In the embryos of jawed vertebrates (gnathostomes), the jaw cartilage develops from the mandibular arch, where none of the Hox genes is expressed; if these are expressed ectopically, however, jaw development is inhibited. Here I show that in the lamprey, a primitively jawless (agnathan) fish that is a sister group to the gnathostomes, a Hox gene is expressed in the mandibular arch of developing embryos. This finding, together with outgroup comparisons, suggests that loss of Hox expression from the mandibular arch of gnathostomes may have facilitated the evolution of jaws.
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Affiliation(s)
- Martin J Cohn
- Division of Zoology, School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, UK.
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