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Comparative evolution and development of the vertebrate spiracular region
Dušek, Martin ; Černý, Robert (advisor) ; Vaškaninová, Valéria (referee)
The area of the first two pharyngeal arches (mandibular and hyoid) represents an evolutionarily very flexible part of the vertebrate head. An example of such flexibility is the spiracular region, comprising the two arches together with the first pharyngeal endodermal pouch (also called spiracular or hyomandibular), which physically seperates them. This pouch is able to break through to the outside creating a small paired opening on the dorsal part of the head behind eyes, termed the spiracle. The spiracle in its typical form can be found in the majority of chondrichthyans and in some basal ray-finned fishes (bichirs, sturgeons and paddlefishes) and serves usually as an additional inhalatory opening for water (in chondrichthyans, when the mouth is occupied) or air (in bichirs, providing the majority of their respiration). This opening apparently has its origins in an ancestral hyomandibular gill slit, which was reduced in size and displaced dorsally by migrating hyoid arch supporting the jaws. In recent tetrapods, including humans, the spiracular cavity corresponds to the cavity of the middle ear, obtaining the function of recieving and transmitting sound waves. This thesis summarizes known important aspects of the spiracular region in terms of morphology, ontogeny and phylogeny of vertebrates.
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Role of transcription factors MEIS in the origin and development of the neural crest
Fábik, Jaroslav
Unique to the vertebrate embryo, neural crest cells represent a multipotent cell population that migrates throughout the body and gives rise to a multitude of different types of cells and tissues. Cranial neural crest cells populate the developing pharyngeal arches and establish skeletogenic condensations that generate the future bones and cartilages of the face and neck. Moreover, these cells send out and receive signals from adjacent tissues of non-neural crest origin, such as the mandibular epithelium and muscle precursor cells. Such reciprocal interactions give rise to organs and structures, for instance, to the tongue. The aim of this work was to elucidate the roles of homeodomain-containing MEIS transcription factors in neural crest cells and in craniofacial development, by using a mouse model with conditional inactivation of Meis2 gene in neural crest cells. We show that transcription factor MEIS2 is expressed in the medial region of the developing mandible and in the developing tongue. Conditional Meis2 inactivation using the Wnt1-Cre2 mouse strain caused mandible and tongue hypoplasia, and ectopic bone formation at the expense of tongue development. These mandibular arch anomalies were accompanied by the loss of Hedgehog signaling in the mandibular epithelium, expanded RUNX2 expression in...
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Role of transcription factors MEIS in the origin and development of the neural crest
Fábik, Jaroslav ; Machoň, Ondřej (advisor) ; Buchtová, Marcela (referee) ; Procházka, Jan (referee)
Unique to the vertebrate embryo, neural crest cells represent a multipotent cell population that migrates throughout the body and gives rise to a multitude of different types of cells and tissues. Cranial neural crest cells populate the developing pharyngeal arches and establish skeletogenic condensations that generate the future bones and cartilages of the face and neck. Moreover, these cells send out and receive signals from adjacent tissues of non-neural crest origin, such as the mandibular epithelium and muscle precursor cells. Such reciprocal interactions give rise to organs and structures, for instance, to the tongue. The aim of this work was to elucidate the roles of homeodomain-containing MEIS transcription factors in neural crest cells and in craniofacial development, by using a mouse model with conditional inactivation of Meis2 gene in neural crest cells. We show that transcription factor MEIS2 is expressed in the medial region of the developing mandible and in the developing tongue. Conditional Meis2 inactivation using the Wnt1-Cre2 mouse strain caused mandible and tongue hypoplasia, and ectopic bone formation at the expense of tongue development. These mandibular arch anomalies were accompanied by the loss of Hedgehog signaling in the mandibular epithelium, expanded RUNX2 expression in...
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The embryonic development of the pharyngeal region in vertebrates
Píchová, Lenka ; Černý, Robert (advisor) ; Minařík, Martin (referee)
The fully-formed pharynx is for adult vertebrates indeed a vital structure. The pharynx provides two main functions - dealing with food and breathing. During embryonic development, pharynx is visible like a series of bulges on the lateral surface of the head. Embryonic development of the pharyngeal region starts with evagination of the endoderm to form the pouches, opposit to that the ectoderm invaginates to form the ectodermal clefts. Pharyngeal arches are formed after fusion of these epithelial layers, and pharynx is thus bordered by ectoderm from the inner, and endoderm from the outer side. Each pharyngeal arch consists of mesenchymal core of mesodermal and neural crest derived cells. All vertebrates develop through the so called phylotypic stage, being represented by the - pharyngula with the present pharyngeal arches. Accordingly, it was generally believed that development of the pharyngeal region is rather conservative in all vertebrates. My comparative analysis of pharyngeal development in different vertebrates species reveals that - only early embryonic formation of pharyngeal arches seems conserved, however, that later in development pharyngeal arches form various and diverse derivatives. Key words: Vertebrates, ectodermal fleft, endodermal pouch, pharyngeal arches, neural crest
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