Publications by authors named "Igor Schneider"

Article Synopsis
  • The genomes of lungfishes, particularly the recently sequenced African and South American species, provide insights into the evolutionary transition from fish to tetrapods during the Devonian period.
  • The Lepidosiren genome is the largest animal genome sequenced to date, about 91 Gb, and features significant genome expansion due to active transposable elements, growing rapidly over the past 100 million years.
  • The study finds that while lungfish chromosomes retain features of their ancient tetrapod ancestors, the loss of limb-like appendages in some species is likely linked to the deletion of specific enhancers associated with limb development.
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Based on embryology and comparative genomics, recent studies reveal that genetic pathways and gene regulatory elements responsible for the invasion of land by tetrapod ancestors are deeply conserved in fish.

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Salamanders, frog tadpoles and diverse lizards have the remarkable ability to regenerate tails. Palaeontological data suggest that this capacity is plesiomorphic, yet when the developmental and genetic architecture of tail regeneration arose is poorly understood. Here, we show morphological and molecular hallmarks of tetrapod tail regeneration in the West African lungfish , a living representative of the sister group of tetrapods.

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Article Synopsis
  • Regeneration varies widely among species, with a key feature being the formation of a blastema, which contains progenitor cells necessary for tissue regrowth.
  • Researchers discovered that the expression of vwde (von Willebrand factor D and EGF domains) is consistently found in blastemas of highly regenerative species like axolotls and lungfish.
  • vwde is essential for successful regeneration, acting as a significant growth factor in the blastema, highlighting the importance of using evolutionary perspectives to uncover fundamental genetic elements involved in regeneration.
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It is known that the West African lungfish (Protopterus annectens) harbours multiple myoglobin (Mb) genes that are differentially expressed in various tissues and that the Mbs differ in their abilities to confer tolerance towards hypoxia. Here, we show that other lungfish species (Protopterus dolloi, Protopterus aethiopicus and Lepidosiren paradoxa) display a similar diversity of Mb genes and have orthologous Mb genes. To investigate the functional diversification of these genes, we studied the structures, O binding properties and nitrite reductase enzymatic activities of recombinantly expressed P.

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Salamanders and lungfishes are the only sarcopterygians (lobe-finned vertebrates) capable of paired appendage regeneration, regardless of the amputation level. Among actinopterygians (ray-finned fishes), regeneration after amputation at the fin endoskeleton has only been demonstrated in polypterid fishes (Cladistia). Whether this ability evolved independently in sarcopterygians and actinopterygians or has a common origin remains unknown.

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Globins are a classical model system for the studies of protein evolution and function. Recent studies have shown that - besides the well-known haemoglobin and myoglobin - additional globin-types occur in vertebrates that serve different functions. Globin E (GbE) was originally identified as an eye-specific protein of birds that is distantly related to myoglobin.

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Limb development in salamanders is unique among tetrapods in significant ways. Not only can salamanders regenerate lost limbs repeatedly and throughout their lives, but also the preaxial zeugopodial element and digits form before the postaxial ones and, hence, with a reversed polarity compared to all other tetrapods. Moreover, in salamanders with free-swimming larval stages, as exemplified by the axolotl (Ambystoma mexicanum), each digit buds independently, instead of undergoing a paddle stage.

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Despite their evolutionary, developmental and functional importance, the origin of vertebrate paired appendages remains uncertain. In mice, a single enhancer termed ZRS is solely responsible for Shh expression in limbs. Here, zebrafish and mouse transgenic assays trace the functional equivalence of ZRS across the gnathostome phylogeny.

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Wnt proteins regulate diverse biological responses by initiating two general outcomes: β-catenin-dependent transcription and β-catenin-independent activation of signaling cascades, the latter including modulation of calcium and regulation of cytoskeletal dynamics (Planar Cell Polarity, PCP). It has been difficult to elucidate the mechanisms by which Wnt signals are directed to effect one or the other outcome due to shared signaling proteins between the β-catenin-dependent and -independent pathways, such as the Dishevelled binding protein Naked. While all Naked paralogs contain a putative calcium-binding domain, the EF-Hand, Drosophila Naked does not bind calcium.

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Limbs with digits evolved as sarcopterygian fish transitioned to a terrestrial life, giving rise to modern tetrapods. Since the Devonian, most of the sarcopterygian fish diversity became extinct, with the only surviving representatives being two coelacanth and six lungfish species. As the sister group of tetrapods, sarcopterygian fish constitute the ideal models to address questions regarding the transition of vertebrates from water to land.

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The pelvic fins of male South American lungfish, Lepidosiren paradoxa, are adorned with a distinctive array of filaments, which grow and become highly vascularized during the breeding season. The resemblance between these pelvic fin filaments (PFFs) and external gills of other vertebrates suggested that this gill-like structure was used for physiological gas exchange. It has been proposed that the unique pelvic fin of male L.

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Salamanders are the only living tetrapods capable of fully regenerating limbs. The discovery of salamander lineage-specific genes (LSGs) expressed during limb regeneration suggests that this capacity is a salamander novelty. Conversely, recent paleontological evidence supports a deeper evolutionary origin, before the occurrence of salamanders in the fossil record.

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To connect human biology to fish biomedical models, we sequenced the genome of spotted gar (Lepisosteus oculatus), whose lineage diverged from teleosts before teleost genome duplication (TGD). The slowly evolving gar genome has conserved in content and size many entire chromosomes from bony vertebrate ancestors. Gar bridges teleosts to tetrapods by illuminating the evolution of immunity, mineralization and development (mediated, for example, by Hox, ParaHox and microRNA genes).

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Extreme novelties in the shape and size of paired fins are exemplified by extinct and extant cartilaginous and bony fishes. Pectoral fins of skates and rays, such as the little skate (Batoid, Leucoraja erinacea), show a strikingly unique morphology where the pectoral fin extends anteriorly to ultimately fuse with the head. This results in a morphology that essentially surrounds the body and is associated with the evolution of novel swimming mechanisms in the group.

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The fossil record is a unique repository of information on major morphological transitions. Increasingly, developmental, embryological, and functional genomic approaches have also conspired to reveal evolutionary trajectory of phenotypic shifts. Here, we use the vertebrate appendage to demonstrate how these disciplines can mutually reinforce each other to facilitate the generation and testing of hypotheses of morphological evolution.

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There is no obvious morphological counterpart of the autopod (wrist/ankle and digits) in living fishes. Comparative molecular data may provide insight into understanding both the homology of elements and the evolutionary developmental mechanisms behind the fin to limb transition. In mouse limbs the autopod is built by a "late" phase of Hoxd and Hoxa gene expression, orchestrated by a set of enhancers located at the 5' end of each cluster.

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The discovery of a living coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae.

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More than three centuries ago natural philosophers, and later anatomists, recognized a fundamental organization to the skeleton of tetrapod limbs. Composed of three segments, stylopod, zeugopod, and autopod, this pattern has served as the basis for a remarkably broad adaptive radiation from wings and flippers to hands and digging organs. A central area of inquiry has been tracing the origins of the elements of this Bauplan in the fins of diverse fish.

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Our limbs evolved from fish fins as vertebrates colonized aquatic shallows and land. If we understood the genetics underlying this transition, could we build a limb on a fish? In this issue of Developmental Cell, Freitas et al. (2012) show that boosting Hoxd13 expression can bring zebrafish one step closer to terra firma.

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The evolutionary transition of the fins of fish into tetrapod limbs involved genetic changes to developmental systems that resulted in novel skeletal patterns and functions. Approaches to understanding this issue have entailed the search for antecedents of limb structure in fossils, genes, and embryos. Comparative genetic analyses have produced ambiguous results: although studies of posterior Hox genes from homology group 13 (Hoxa-13 and Hoxd-13) reveal similarities in gene expression between the distal segments of fins and limbs, this functional homology has not been supported by genomic comparisons of the activity of their cis-regulatory elements, namely the Hoxd Global Control Region.

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