Cheryll Tickle | |
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Born | Cheryll Anne Tickle 18 January 1945 [1] |
Alma mater |
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Awards | EMBO Member (2001) |
Scientific career | |
Fields | Developmental biology |
Institutions | |
Thesis | Quantitative studies on the positioning of cells in aggregates (1970) |
Doctoral advisor | Adam S. G. Curtis |
Website | researchportal |
Cheryll Anne Tickle (born 18 January 1945) CBE FRS FRSE FMedSci [2] [3] is a British scientist, known for her work in developmental biology and specifically for her research into the process by which vertebrate limbs develop ab ovo . She is an emeritus professor at the University of Bath. [4]
Tickle was educated at the University of Cambridge graduating with a masters degree in 1967, and received her PhD from the University of Glasgow in 1970. [5] [6]
Tickle worked as a postdoctoral researcher at Yale University, as a lecturer and reader at the Middlesex Hospital Medical School, and (after Middlesex merged with it in 1987) a reader and professor at University College London. She then moved to the University of Dundee in 1998, where she became Foulerton Professor of the Royal Society in 2000, and moved again to the University of Bath in 2007, retaining the Foulerton Professor title. [7] [8]
Tickle's research in developmental biology investigates how single cells, the fertilised egg, gives rise to a new individual during embryogenesis. [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22]
As Tickle was nearing the end of her undergraduate career at the University of Cambridge, the concept of sorting-out was on the rise. Sorting-out or cell sorting is the phenomenon where cultured cells are disaggregated and then re-aggregated with the purpose of observing the reestablishment of the spatial organization of cell structures within a cell. [23]
Following the completion of her PhD in 1970, Tickle was given a NATO fellowship where she completed a postdoc in the United States working with John Philip Trinkaus at Yale University on cell sorting in fish embryos. After two years, Tickle moved back to London where she worked with Lewis Wolpert, who had been her PhD supervisor. At this time, she decided that she was going to focus on the effects of positional or pattern information on the sorting out process of cells during the limb development of chicken embryos. Tickle’s hypothesis was that if cells of the embryonic limb were to be given distinct characteristics in a random arrangement the cells would arrange themselves into a generated pattern or “sort out”. [23]
In 1969, a scientist named John Saunders established that the apical ectodermal ridge (AER)--a transparent rim along limb buds—plays an important role in the development or outgrowth of a limb along with the zone of polarizing activity(ZPA). Using these findings, Tickle focused her research on how the ZPA controlled the development of the limb, specifically along the anterior and posterior axis of a developing limb as this axis is controlled by the signaling of the ZPA. [23]
It was at this time that Wolpert suggested that the ZPA produced morphogen to create a concentration gradient so that cells at varying positions along the limb bud would be exposed to different concentrations ultimately providing them with the information necessary to develop into the appropriate number of digits. In other words, he believed that the distance from the polarizing region would lead to the formation of different digits during limb development. Tickle’s experiments in his lab on embryonic chicken wings did find that the type of digit that developed did depend on its distance from the polarizing region. Cells closest to the polarizing region on the posterior side of the limb would come in contact with higher concentrations of morphogen to then form a chicken digit 4, whereas the cells furthest from the polarizing region on the anterior side of the limb would experience much lower concentrations and therefore develop the chicken digit 2. These results were important in the field of developmental biology at this time, as it suggested that this model would be a definitive way of understanding how the polarizing region or ZPA worked. [23]
In 1976, Bruce Alberts, an American biochemist, brought the concept of using beads to further their research in the development of limbs. Together, they came up with the idea to soak the beads in extracts made from the polarizing region and then position them along the anterior margin of a developing chicken limb. There was also little known about what other chemicals were utilized during development, so the beads were soaked in many other substances thought to be significant, including insulin which was suggested to lead to duplication of limbs in ducks. In the early 1980’s, Tickle’s lab identified retinoic acid as a chemical that could mimic the signaling of the polarizing region by using carriers soaked in the retinoic acid. [23]
By 1990, it was discovered that homologs of many developmentally important genes in vertebrates were found in Drosophila melanogaster and multiple scientists cloned chick homologs of these genes. Cheryll Tickle worked alongside Eddy De Robertis and Denis Duboule to look at Hox gene expression in developing limbs to relate it to chicken wing patterns. They found that if a limb was duplicated with retinoic acid, the pattern of Hox gene expression would also be copied. [23]
Tickle also worked with Gail Martin and Lee Niswander in 1994 to find that fibroblast growth factors (FGF) are what is used by the apical ectodermal ridge for signaling. They also discovered that bone morphogenetic proteins (BMP) were involved in the polarizing region signaling. To test this, Tickle utilized the bead technology introduced by Bruce Alberts by using particular beads to apply various chemicals to developing limbs. When the ACR was removed and FGF soaked beads were substituted within a chick wing bud, it was found to be able to promote proper chicken wing development. This was a significant finding that led to further discovery of this concept within mice by Gail Martin on a more complex scale. A student in Tickle’s lab found that the placement of a bead soaked with FGF for only a few hours could induce the development of a new limb where one would not naturally form. It was concluded that FGF signaling must be turned off following the completion of limb development or else the organism risks additional digit formation and other abnormalities taking place. [23]
Tickle was elected a Fellow of the Royal Society (FRS) in 1998, a Fellow of the Royal Society of Edinburgh (FRSE) in 2000, a Fellow of the Academy of Medical Sciences (FMedSci) in 2001, and a member of the European Molecular Biology Organisation in 2001. In 2004 the University of St. Andrews awarded her an honorary doctorate. In 2005 she was named a Commander of The Most Excellent Order of the British Empire (CBE). [24] She also serves as a governor of the Caledonian Research Foundation. [25] Her nomination for the Royal Society reads:
Distinguished for her contribution to developmental biology. She demonstrated a quantitative relationship between the signal from the polarizing region in the embryo limb and the pattern digits, and that a similar signal was present in mammals. She discovered that local application of retinoic acid can mimic the signal from the polarizing region. Both these signals were shown to control homeobox gene expression. She has now shown that the signal from the apical ridge which is essential for limb development is a fibroblast growth factor. Her work is characterized by outstanding experimental skill, design and interpretation. [3]
Tickle married John Gray in 1979. [1]
Sonic hedgehog protein (SHH) is encoded for by the SHH gene. The protein is named after the character Sonic the Hedgehog.
Segmentation in biology is the division of some animal and plant body plans into a linear series of repetitive segments that may or may not be interconnected to each other. This article focuses on the segmentation of animal body plans, specifically using the examples of the taxa Arthropoda, Chordata, and Annelida. These three groups form segments by using a "growth zone" to direct and define the segments. While all three have a generally segmented body plan and use a growth zone, they use different mechanisms for generating this patterning. Even within these groups, different organisms have different mechanisms for segmenting the body. Segmentation of the body plan is important for allowing free movement and development of certain body parts. It also allows for regeneration in specific individuals.
Somitogenesis is the process by which somites form. Somites are bilaterally paired blocks of paraxial mesoderm that form along the anterior-posterior axis of the developing embryo in segmented animals. In vertebrates, somites give rise to skeletal muscle, cartilage, tendons, endothelium, and dermis.
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The apical ectodermal ridge (AER) is a structure that forms from the ectodermal cells at the distal end of each limb bud and acts as a major signaling center to ensure proper development of a limb. After the limb bud induces AER formation, the AER and limb mesenchyme—including the zone of polarizing activity (ZPA)—continue to communicate with each other to direct further limb development.
Limb development in vertebrates is an area of active research in both developmental and evolutionary biology, with much of the latter work focused on the transition from fin to limb.
The limb bud is a structure formed early in vertebrate limb development. As a result of interactions between the ectoderm and underlying mesoderm, formation occurs roughly around the fourth week of development. In the development of the human embryo the upper limb bud appears in the third week and the lower limb bud appears four days later.
T-box refers to a group of transcription factors involved in embryonic limb and heart development. Every T-box protein has a relatively large DNA-binding domain, generally comprising about a third of the entire protein that is both necessary and sufficient for sequence-specific DNA binding. All members of the T-box gene family bind to the "T-box", a DNA consensus sequence of TCACACCT.
T-box transcription factor TBX5, is a protein that in humans is encoded by the TBX5 gene. Abnormalities in the TBX5 gene can result in altered limb development, Holt-Oram syndrome, Tetra-amelia syndrome, and cardiac and skeletal problems.
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Gail Roberta Martin is an American biologist. She is professor emerita in the Department of Anatomy, University of California, San Francisco. She is known for her pioneering work on the isolation of pluripotent stem cells from normal embryos, for which she coined the term ‘embryonic stem cells’. She is also widely recognized for her work on the function of Fibroblast Growth Factors (FGFs) and their negative regulators in vertebrate organogenesis. She and her colleagues also made valuable contributions to gene targeting technology.
The zone of polarizing activity (ZPA) is an area of mesenchyme that contains signals which instruct the developing limb bud to form along the anterior/posterior axis. Limb bud is undifferentiated mesenchyme enclosed by an ectoderm covering. Eventually, the limb bud develops into bones, tendons, muscles and joints. Limb bud development relies not only on the ZPA, but also many different genes, signals, and a unique region of ectoderm called the apical ectodermal ridge (AER). Research by Saunders and Gasseling in 1948 identified the AER and its subsequent involvement in proximal distal outgrowth. Twenty years later, the same group did transplantation studies in chick limb bud and identified the ZPA. It wasn't until 1993 that Todt and Fallon showed that the AER and ZPA are dependent on each other.
Diplopodia is a congenital anomaly in tetrapods that involves duplication of elements of the foot on the hind limb. It comes from the Greek roots diplo = "double" and pod = "foot". Diplopodia is often found in conjunction with other structural abnormalities and can be lethal. It is more extreme than polydactyly, the presence of extra digits.
The order Chiroptera, comprising all bats, has evolved the unique mammalian adaptation of flight. Bat wings are modified tetrapod forelimbs. Because bats are mammals, the skeletal structures in their wings are morphologically homologous to the skeletal components found in other tetrapod forelimbs. Through adaptive evolution these structures in bats have undergone many morphological changes, such as webbed digits, elongation of the forelimb, and reduction in bone thickness. Recently, there have been comparative studies of mouse and bat forelimb development to understand the genetic basis of morphological evolution. Consequently, the bat wing is a valuable evo-devo model for studying the evolution of vertebrate limb diversity.
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Clifford James Tabin is chairman of the Department of Genetics at Harvard Medical School.
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T-box transcription factor Tbx4 is a transcription factor that belongs to T-box gene family that is involved in the regulation of embryonic developmental processes. The transcription factor is encoded by the TBX4 gene located on human chromosome 17. Tbx4 is known mostly for its role in the development of the hindlimb, but it also plays a critical role in the formation of the umbilicus. Tbx4 has been shown to be expressed in the allantois, hindlimb, lung and proctodeum.
John W. Saunders Jr. was an American scientist whose research in the field of developmental biology and zoology played an integral part in helping to understand how various vertebrate limbs develop. Saunders researched the vertebrate limb and studied the apical ectodermal ridge (AER). This research was critical in recognizing growth factors that are secreted from the AER and are important in assisting the pattern of developing vertebrate limbs.