Session 4 – Moderated by Ryan Kerney

Maria Antonietta Tosches (Online)


Cell Type Profiling in Salamanders Identifies Innovations in Vertebrate Forebrain Evolution

The evolution of advanced cognition in vertebrates is associated with two independent innovations in the forebrain: the six-layered neocortex in mammals and the dorsal ventricular ridge (DVR) in sauropsids (reptiles and birds). How these novelties arose in vertebrate ancestors remains unclear. To reconstruct forebrain evolution in tetrapods, we took advantage of the phylogenetic position and of the simple brain architecture of salamanders. Using single-cell RNA sequencing, we built a cell-type atlas of the telencephalon of Pleurodeles waltl. Moreover, we used bioinformatic approaches to compare these cell-type data to similar datasets from other vertebrate species. This analysis reveals the series of innovations that resulted in the emergence of the sauropsid DVR, and the mammalian six-layered neocortex. General implications on the value of salamanders in evolutionary studies will be discussed.

Takuji Sugiura

15.30 – 15.50

Do Non-Canonical Protein Secretion Mechanisms Contribute to Regeneration Signaling?

Cell-cell communication is essential for biological phenomena. Extracellular signaling molecules, for example, growth factors and cell surface proteins, are one of the substances of intercellular communication. During organ regeneration, signaling molecules are involved in critical cellular events such as cell migration, proliferation, differentiation, patterning and size control. Previously, we identified a molecule, Axolotl MARCKS Like Protein (AxMLP) as an extracellular factor that can initiate initial proliferative response in the axolotl (Ambystoma mexicanum) appendage regeneration (Sugiura, T., et al., Nature 2016). Importantly, we found that AxMLP was expressed in the wound epidermis (WE) that is an essential tissue to promote the process of appendage regeneration in salamanders (Tornier G. 1906. Arch. fur Entwmech). AxMLP was released into extracellular space in vitro. This was surprising, as MARCKS family proteins had been described to be intracellular proteins (El Amri, M., et al., J Biomed Sci. 2018). In the current study, we focus on the mechanisms of AxMLP secretion. Our preliminary results suggest that:

1. AxMLP is not secreted via the canonical protein secretion pathway

2. Extracellular vesicles containing AxMLP can induce proliferation of cultured myotubes

3. Membrane association of AxMLP is related to its secretion

4. Pharmacological screening identify promising molecules that regulate AxMLP secretion

5. MLP reporter transgenic axolotl allows us to investigate MLP secretion in vivo. Taken together with our previous study, these results imply that MLP released extracellularly from the WE via a non-canonical protein secretion pathway initiates proliferative response to the cells underneath the WE and contributes to forming the blastema.

Mehmet Anıl Oguz

15.50 – 16.10

Salamander Species in Turkey: Their Populations and Biology

Aim: Turkey has high amphibian variation as a consequence of its geographic and climatic diversity. Every salamander species in Turkey belong to Salamandridae family. The aim is to present and introduce the populations and biology of salamander species in Turkey with the photos in their own habitats.

Material and Methods: As a result of vast number of fieldwork and excursions conducted throughout many years, I have photographed as well as researched salamander species in Turkey. Due to they are mostly nocturnal and they hide under the stones in rainy seasons in the day, I have found them at night or under the stones in the day.

Results: Turkey currently has sixteen salamander species. These species are: Salamandra infraimmaculata (Turkish Fire Salamander), Mertensiella caucasica (Caucasian Salamander), Lyciasalamandra antalyana (Antalya Salamander), L. atifi (Atıf’s Lycian Salamander), L. billae (Bille’s Lycian Salamander), L. flavimembris (Marmaris Salamander), L. luschani (Luschan’s Lycian Salamander), L. fazilae (Fazıla’s Lycian Salamander), Neurergus crocatus (Urmia Newt), Neurergus strauchii (Anatolian/Strauch’s Spotted Newt), Lissotriton vulgaris (The Smooth Newt), Ommatotriton vittatus (Southern Banded Newt), Ommatotriton ophryticus (North-Eastern Banded Newt), Ommatotriton nesterovi (North-Western Banded Newt), Triturus ivanbureschi (Balkan-Anatolian Crested Newt), Triturus anatolicus (Anatolian Crested Newt). The taxonomic status of salamander species in Turkey changes continuously due to their genetic variations. Hence, the taxonomic status should always be followed.

Conclusions: Turkey hosts many salamander species, resulted by its climate and geography. In addition, to the existing phenotypes, their phenotypes show lots of variety among the populations because of the mutations. Salamander species are mostly used as model organism in regeneration and neuroscience researches. Salamanders in Turkey have been understudied in the field of regeneration and neuroscience areas so far. Hence, they have a great potential to discover novel field of medicine, biology and pharmacology.

Anita Dittrich

16.10- 16.25

Metabolic Adaptations During Cardiac Regeneration in the Axolotl

Aim: Illuminate the interplay of metabolic processes in the heart and capacity for cardiac regeneration by assaying metabolism during different time points of cardiac regeneration. The axolotl represents a unique animal model to this end, as the vertebrate most closely related to humans known to be capable of true intrinsic cardiac regeneration. Metabolism has been proven to play a key role in regenerative processes. In adult and neonatal mice as well as zebrafish, studies have shown that specific metabolic adaptations are favorable to heart regeneration, although the exact mechanisms involved remain unclear.

Materials/methods: In this ongoing study, we use a cryoinjury to model myocardial infarction and investigate the metabolic profile accompanying different stages of regeneration – from initial injury response, transient scar formation and finally regeneration and maturation into new fully functioning myocardium. To this end, we are utilizing echocardiography, respirometry, metabolite analysis in blood and cardiac tissue, quantitative histology as well as autoradiography with radiolabeled FDG (glucose analog) and acetate (correlates with OXPHOS in heart) tracers to gather a detailed picture of metabolic processes in vivo that underlie a successful regenerative response.

Results: Preliminary results indicate a global increase in oxygen consumption during the instigation of the regenerative response, and a general up-regulation of cardiac metabolism in response to injury, the details of which will be highly informative in understanding how specific pathways may support or inhibit regenerative processes. Further data analysis is currently ongoing. A temperature based experiment in which animals were housed at different temperatures (10, 20 and 30 ̊C), shows key adaptations in metabolism including oxygen consumption and blood glucose, ketone and lactate; accompanied by inhibition of regenerative ability at colder temperatures and indications of increased regeneration rate at warmer temperatures.

Conclusion: cardiac regeneration in the axolotl is associated with distinct adaptations in systemic and local cardiac metabolic processes.