During evolution, there has been a trend to reduce both the number of teeth and the location where they are found within the oral cavity. In mammals, the formation of teeth is restricted to a horseshoe band of odontogenic tissue, creating a single dental arch on the top and bottom of the jaw. Additional teeth and structures containing dental tissue, such as odontogenic tumors or cysts, can appear as pathologies. These tooth-like structures can be associated with the normal dentition, appearing within the dental arch, or in nondental areas. The etiology of these pathologies is not well elucidated. Reawakening of the potential to form teeth in different parts of the oral cavity could explain the origin of dental pathologies outside the dental arch, thus such pathologies are a consequence of our evolutionary history. In this review, we look at the changing pattern of tooth formation within the oral cavity during vertebrate evolution, the potential to form additional tooth-like structures in mammals, and discuss how this knowledge shapes our understanding of dental pathologies in humans.
- MeSH
- biologická evoluce * MeSH
- lidé MeSH
- obratlovci růst a vývoj MeSH
- odontogeneze * MeSH
- savci anatomie a histologie růst a vývoj MeSH
- ústa růst a vývoj MeSH
- zuby patologie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
The apparent evolvability of the vertebrate head skeleton has allowed a diverse array of shapes, sizes, and compositions of the head in order to better adapt species to their environments. This encompasses feeding, breathing, sensing, and communicating: the head skeleton somehow participated in the evolution of all these critical processes for the last 500 million years. Through evolution, present head diversity was made possible via developmental modifications to the first head skeletal genetic program. Understanding the development of the vertebrate common ancestor's head skeleton is thus an important step in identifying how different lineages have respectively achieved their many innovations in the head. To this end, cyclostomes (jawless vertebrates) are extremely useful, having diverged from jawed vertebrates approximately 400 million years ago, at the deepest node within living vertebrates. From this ancestral vantage point (that is, the node connecting cyclostomes and gnathostomes) we can best identify the earliest major differences in development between vertebrate classes, and start to address how these might translate onto morphology. In this review we survey what is currently known about the cell biology and gene expression during head development in modern vertebrates, allowing us to better characterize the developmental genetics driving head skeleton formation in the most recent common ancestor of all living vertebrates. By pairing this vertebrate composite with information from fossil chordates, we can also deduce how gene regulatory modules might have been arranged in the ancestral vertebrate head. Together, we can immediately begin to understand which aspects of head skeletal development are the most conserved, and which are divergent, informing us as to when the first differences appear during development, and thus which pathways or cell types might be involved in generating lineage specific shape and structure.
- MeSH
- biologická evoluce * MeSH
- genetická variace * MeSH
- hlava růst a vývoj MeSH
- lebka růst a vývoj MeSH
- obratlovci genetika růst a vývoj MeSH
- zkameněliny MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Extant bilaterally symmetrical animals usually show asymmetry in the arrangement of their inner organs. However, the exaggerated left-right (LR) asymmetry in amphioxus represents a true peculiarity among them. The amphioxus larva shows completely disparate fates of left and right body sides, so that organs associated with pharynx are either positioned exclusively on the left or on the right side. Moreover, segmented paraxial structures such as muscle blocks and their neuronal innervation show offset arrangement between the sides making it difficult to propose any explanation or adaptivity to larval and adult life. First LR asymmetries can be traced back to an early embryonic period when morphological asymmetries are preceded by molecular asymmetries driven by the action of the Nodal signaling pathway. This review sums up recent advances in understanding LR asymmetry specification in amphioxus and proposes upstream events that may regulate asymmetric Nodal signaling. These events include the presence of the vertebrate-like LR organizer and a cilia-driven fluid flow that may be involved in the breaking of bilateral symmetry. The upstream pathways comprising the ion flux, Delta/Notch, Wnt/β-catenin and Wnt/PCP are hypothesized to regulate both formation of the LR organizer and expression of the downstream Nodal signaling pathway genes. These suggestions are in line with what we know from vertebrate and ambulacrarian LR axis specification and are directly testable by experimental manipulations. Thanks to the phylogenetic position of amphioxus, the proposed mechanisms may be helpful in understanding the evolution of LR axis specification across deuterostomes.
- MeSH
- kopinatci embryologie genetika růst a vývoj MeSH
- molekulární evoluce MeSH
- obratlovci embryologie genetika růst a vývoj MeSH
- rozvržení tělního plánu genetika MeSH
- signální transdukce genetika MeSH
- vývojová regulace genové exprese * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
The amphioxus (lancelet) was first described by Pallas in 1774 and incorrectly assigned to mollusks. Since then, amphioxus attracted generations of zoologists. It took however almost one hundred years until Alexander Kowalevsky recognized that the larval stages of amphioxus had much in common with vertebrate embryos. Widely studied around 1900 as the 'elementary vertebrate', amphioxus as a model went out of fashion with the decline of comparative anatomy. Due to the scarcity of taxa at the invertebrate-to-vertebrate transition, amphioxus nevertheless remained the species with a privileged position in animal phylogeny. Its resurrection as the popular model of evolutionary developmental biology came with the advent of modern molecular biology and genomics. In the 1990s amphioxus developmental control genes were identified and characterized at a fast pace with the hope that such studies could provide novel insight into an important evolutionary transition: the origin of vertebrates. Indeed, amphioxus was found to be vertebrate-like but much simpler. Its body resembles that of the vertebrate, but it lacks most of the complexities associated with typical vertebrate organs. Its genome is only 1/6 of the human genome and it has not undergone the whole genome duplications that occurred in the vertebrate lineage. For all of these reasons, amphioxus became widely regarded as a useful proxy for the primitive ancestor of all vertebrates. A persistent problem interpreting amphioxus in the phylogenetic context is the difficulty to distinguish ancestral features, and those that are secondarily derived. There is no doubt that an integrative approach combining information from various disciplines is needed in order to help resolve such issues. Anatomy and comparative morphology has always been strong since the dawn of amphioxus research. Recent developments such as the availability of genomic sequences for three Branchiostoma species, established laboratory cultures of amphioxus that can be spawned at the investigator's will, or techniques allowing transgenesis and gene knockouts represent a major leap for studies on how the genotype generates a phenotype. These advances also enable the smooth transition of amphioxus from the model system of a distinguished past into the one with a very bright future.
- MeSH
- genom genetika MeSH
- kopinatci genetika růst a vývoj MeSH
- modely u zvířat * MeSH
- molekulární evoluce MeSH
- obratlovci genetika růst a vývoj MeSH
- vývojová biologie metody MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- úvodní články MeSH
Animal eyes are morphologically diverse. Their assembly, however, always relies on the same basic principle, i.e., photoreceptors located in the vicinity of dark shielding pigment. Cnidaria as the likely sister group to the Bilateria are the earliest branching phylum with a well developed visual system. Here, we show that camera-type eyes of the cubozoan jellyfish, Tripedalia cystophora, use genetic building blocks typical of vertebrate eyes, namely, a ciliary phototransduction cascade and melanogenic pathway. Our findings indicative of parallelism provide an insight into eye evolution. Combined, the available data favor the possibility that vertebrate and cubozoan eyes arose by independent recruitment of orthologous genes during evolution.
- MeSH
- biologické modely MeSH
- Cercopithecus aethiops MeSH
- cilie metabolismus ultrasonografie MeSH
- COS buňky MeSH
- Cubozoa růst a vývoj MeSH
- financování organizované MeSH
- fotoreceptory bezobratlých cytologie metabolismus ultrastruktura MeSH
- krystaliny metabolismus MeSH
- melaniny metabolismus MeSH
- messenger RNA MeSH
- molekulární sekvence - údaje MeSH
- obratlovci růst a vývoj MeSH
- oči cytologie růst a vývoj ultrastruktura MeSH
- oční čočka metabolismus MeSH
- pigmentace MeSH
- regulace genové exprese genetika MeSH
- sekvenční homologie nukleových kyselin MeSH
- transkripční faktor spojený s mikroftalmií genetika metabolismus MeSH
- tyčinkové opsiny metabolismus MeSH
- zrak genetika MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
Acta Universitatis Carolinae. Medica. Monographia ; 1988/125
160 s. : obr., bibliogr.
1. A method for planimetric measurement of areas of standardized dorsoventral projections of embryonal limbs was elaborated. The method permits a quantitative study of the growth of embryonic limbs at early stages of development, since the stage of flat limb bud until the stage at which the external shape of the limb (bending in joint regions and increase in volume) interferes with the simplification of its three-dimensional characteristics to two-dimensional ones of its dorsoventral projection. (Until stage 31-32HH for the chick embryo, see fig. 1 and 2). 2. A method of linear marking was elaborated (fig. 3). The marker proper are India-ink particles suspended in gelatin. Such stained gelatin is spread over a glass carrier (a glass fibre 10-20 microns thick) in the form of a thin film. After drying the fibre is cut in rods of a length desired for the appropriate linear mark. The marks can be introduced into the tissue by a single stab. After the gelatin film had swollen owing to the presence of tissue fluids, it is detached from the carrier surface and the carrier can be removed from the tissue. After the gelatin had been resorbed, a linear mark remains in the tissue. Deformations of the mark line and the scattering of India-ink particles which actually form the mark facilitates the assessment of the growth pattern of the respective marked tissue (see fig. 4-6). 3. During our studies of the differential growth of the wing bud with the method of linear marking the newly coined term "relative tissue shift" had to be specified. That term has been used for designating changes of the mutual position of tissue areas which could not be defined exactly as to their topography within a region or organ (such as the wing bud), showing fluent transitions between one another. If areas with different growth activities occur in the region studied, such areas undergo an uneven increase (differential growth). Thus another factor is added to those operating in the growth process, namely the direction of expansion of the different growing areas of the region studied to one another. The resultant of the mutual ratios of the voluminal growth of the neighbouring tissue areas and the directions of their expansion are the relative tissue shifts in the sense used in our studies.
- MeSH
- abnormality vyvolané léky embryologie MeSH
- adenin analogy a deriváty MeSH
- cévy embryologie růst a vývoj MeSH
- citráty MeSH
- daktinomycin MeSH
- ektoderm MeSH
- končetiny embryologie růst a vývoj MeSH
- křídla zvířecí embryologie MeSH
- kuřecí embryo MeSH
- kyselina citronová MeSH
- mezoderm MeSH
- morfogeneze MeSH
- obratlovci embryologie růst a vývoj MeSH
- teratogeny MeSH
- tkáně embryologie růst a vývoj MeSH
- Check Tag
- kuřecí embryo MeSH
- Konspekt
- Anatomie člověka a srovnávací anatomie
- NLK Obory
- anatomie
- embryologie a teratologie
- cytologie, klinická cytologie
- histologie
- NLK Publikační typ
- studie
