Abstract
BackgroundThe newt Notophthalmus viridescens possesses the remarkable ability to respond to cardiac damage by formation of new myocardial tissue. Surprisingly little is known about changes in gene activities that occur during the course of regeneration. To begin to decipher the molecular processes, that underlie restoration of functional cardiac tissue, we generated an EST database from regenerating newt hearts and compared the transcriptional profile of selected candidates with genes deregulated during zebrafish heart regeneration.ResultsA cDNA library of 100,000 cDNA clones was generated from newt hearts 14 days after ventricular injury. Sequencing of 11520 cDNA clones resulted in 2894 assembled contigs. BLAST searches revealed 1695 sequences with potential homology to sequences from the NCBI database. BLAST searches to TrEMBL and Swiss-Prot databases assigned 1116 proteins to Gene Ontology terms. We also identified a relatively large set of 174 ORFs, which are likely to be unique for urodele amphibians. Expression analysis of newt-zebrafish homologues confirmed the deregulation of selected genes during heart regeneration. Sequences, BLAST results and GO annotations were visualized in a relational web based database followed by grouping of identified proteins into clusters of GO Terms. Comparison of data from regenerating zebrafish hearts identified biological processes, which were uniformly overrepresented during cardiac regeneration in newt and zebrafish.ConclusionWe concluded that heart regeneration in newts and zebrafish led to the activation of similar sets of genes, which suggests that heart regeneration in both species might follow similar principles. The design of the newly established newt EST database allows identification of molecular pathways important for heart regeneration.
Highlights
The newt Notophthalmus viridescens possesses the remarkable ability to respond to cardiac damage by formation of new myocardial tissue
The quality of our sequence data with respect to read lengths and contig sizes was similar to previous expressed sequence tags (ESTs) sequencing projects focusing on A. mexicanum [14]
Identification of biological pathways activated during zebrafish and newt heart regeneration by GO annotation So far the analysis indicated that our EST dataset is enriched in sequences, which were modulated during newt heart regeneration, and that such sequences were often expressed at different levels during regeneration of zebrafish hearts
Summary
The newt Notophthalmus viridescens possesses the remarkable ability to respond to cardiac damage by formation of new myocardial tissue. Newts are able to regenerate internal organs such as parts of the central nervous system [3] and parts of the ventricles of the heart after amputation or mechanical damage [4,5,6] suggesting that they exhibit a general program that enables regenerative responses This ability distinguishes newts (and teleost fish) from other vertebrates, which have lost (or supress) the capacity for. Newt cardiomyocytes are virtually non-proliferative in undamaged hearts but respond to cardiac injuries by proliferation [4,5,11,12] At present, it is not clear whether proliferating cardiomyocytes arise solely from resting cardiomyocytes, which might undergo partial dedifferentiation or re-programming, or from dedicated cardiac stem cells that are able to replace lost cardiac tissue. The plasticity of newt cardiomyocytes to adopt a different cellular fate is demonstrated by their ability to contribute to skeletal muscle formation in regenerating limbs [13]
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