Congress Abstracts - Society for Developmental Biology

endothelial cells precedes the mesangial cells in pigs. The cross-talk between these cells might promote the development of the
porcine glomerular tuft.
Program/Abstract # 312
Embryonic origin of cartilaginous elements of the axolotl visceral skeleton
Davidian, Asya (St. Petersburg State Univ, Russian Federation), Epperlein, Hans-Henning; Tanaka, Elly (Technical University
Dresden, Germany); Malashichev, Yegor (St. Petersburg State Univ, Russian Federation)
Traditionally, the cartilaginous viscerocranium of vertebrates is considered as neural crest-derived. However, transplantation of cranial
mesoderm to a position of trunk somites carried out by Stone (1932) had led to the formation of a heterotopic heart anlage and a small
rod-like cartilage, presumably a medial element of the pharyngeal arches. Since then, the embryonic sources of the visceral skeleton
had not been investigated by exact long-term labeling. We performed bilateral homotopic transplantations of neural folds along with
up to 95% of cells of the presumptive neural crest from transgenic embryos into white (d/d) host embryos, or fragments of the GFP+
head lateral plate mesoderm. In these experiments the neural crest-derived GFP+ cells contributed to all elements of the gill arches,
except for basibranchiale 2, whereas the grafting of GFP+ head mesoderm led to a reverse labeling result. The grafting of only the
distal parts of the GFP+ head lateral plate mesoderm resulted in marking the basibranchiale 2 and the heart, implying that both these
structures originate from a common mesodermal region. Co-mapping of the contralateral sides of head mesoderm with differently
colored (GFP+ and Cherry+) transgenic cells showed that basibranchiale 2 develops from a paired anlage, similarly to the heart. If
compared to fish (Kague et al., 2012), in which all branchial elements are of neural crest origin, axolotl demonstrates a deviation, in
which the medio-posterior element of the pharyngeal apparatus consists of mesodermal cells. This might be due to an evolutionary
loss of a part of neural crest derived skeleton in amphibians, in which the head mesoderm replaces neural crest cells in some elements
of the pharyngeal arches.
Program/Abstract # 313
Transgenic axolotls (Ambystoma mexicanum) as an emerging system for the study of organ and tissue embryonic origin.
Malashichev, Yegor, (St. Petersburg State University, Russian Federation)
In the XX century quail-chick chimeras were a most routine tool for mapping the fate of individual cell populations in the avian
embryos and led to important discoveries of the embryonic origin of all major organ types in this model system. Recent decade has
seen a dramatic increase in the interest to the embryonic origin of organs in other organisms, the interest, which was technically
supported mostly with injections of lipophilic dyes, fluorescent dextran conjugates, or retroviruses. A disadvantage of these was the
loss of the marking signal due to cell divisions, or to mark the tissue of interest precisely. Most recently, the lentiviral and other
transgenic marking systems along with transplantation of tissues from the transgenic donor bearing a fluorescent marker to the wt host
became the symbols of a renaissance of the fate mapping of vertebrate embryos, allowing life-long marking. In my talk I present
several examples of use and disuse of these methods from my own experience and the work of others, performed on amphibian and
avian embryos. In particular I will stop on the fate mapping of the neural crest and mesoderm in the anterior trunk and the head,
demonstrating dual embryonic origin of the shoulder girdle (somitic and lateral plate mesoderm), viscerocranium (neural crest, head
paraxial and lateral plate mesoderm), and embryonic kidney (lateral plate vs. somitic and intermediate mesoderm) as well as
endodermal origin of pharyngeal teeth in axolotl. A special reference will be given to dual colour (e.g. GFP+ and Cherry+) multiple
tissue (mesoderm+neural crest or multiple somites) marking techniques. All examples are provided with the discussion of
appropriateness of the methods used and evo-devo speculations.
Program /Abstract # 314
Withdrawn
Program/Abstract # 315
Identification of a novel embryonic signaling peptide essential for mesendoderm migration
Pauli, Andrea; Ma, Jiao; Mitchell, Andrew; Gagnon, James (Harvard, USA); Joung, Keith (Massachusetts General Hospital, USA);
Saghatelian, Alan; Schier, Alexander (Harvard, USA)
Using a combination of computational and genomics approaches, we have identified hundreds of genes encoding un-annotated short
peptides that are expressed during zebrafish embryogenesis. TALEN-induced loss-of-function mutants of one of these genes are
embryonic lethal and have severe cardiovascular defects. This novel developmental regulator encodes a highly conserved secreted
peptide that has been mis-annotated as a non-coding transcript in zebrafish, mouse and human. Detailed characterization of loss- and
gain-of-function phenotypes suggests that this signal regulates mesendodermal cell migration. To uncover the downstream signaling
pathway, we are currently using genetic, biochemical and cell biological approaches to identify the peptide receptor. Our studies
identify a novel migration signal and highlight the potential of genomics approaches for identifying novel developmental signals.
Program/Abstract # 316
Molecular pathogenesis of Joubert Syndrome and related disorders
Caspary, Tamara; Mariani, Laura (Emory University, USA); Higginbotham, Holden (UNC School of Medicine, USA); Fritz, Julie
(Emory University, USA); Anton, Eva (UNC School of Medicine, USA)
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