were done to demonstrate that the central nervous system of holothurians, the socalled radial nerve cords, could also regenerate (San Miguel et al. 2009). Results
showed that following transection, nerve fibers could re-grow and bridge the injury
gap forming a new scar-free nerve cord in about a month time. A process of
neurogenesis was also documented that produced new neurons within the regenerated cord. Ongoing experiments are aimed at characterizing the genes associated
with this regeneration process.
Genomics
The laboratory began to study the molecular basis of intestinal regeneration in the
late 1990s. Initially the work was done on a gene-by-gene strategy, where the
selected genes were either candidate genes, such as Hox genes (Méndez et al.
2000) or genes identified by differential display techniques comparing regenerating and normal intestines (Roig-López et al. 2001). In this way, several genes of
interest were characterized in the holothurian and were shown to be overexpressed
during intestinal regeneration. Among these were serum amyloid A (Santiago et al.
2000) and ependymin (Suarez-Castillo et al. 2004).
With the advent of high throughput molecular analyses, the number of genes
associated with intestinal regeneration was multiplied. First, three cDNA libraries
were prepared from normal and regenerating intestines and over 5,000 EST
(Expressed Sequence Tags) were identified (Rojas-Cartagena et al. 2007). These
ESTs represent sequences of mRNAs (and therefore gene sequences) that were
expressed in the tissues at the time of dissection. This was the first attempt to
obtain large genomic information from a holothurian. These ESTs sequences were
then probed in a custom-made microarray in order to determine which genes were
differentially expressed during the regeneration process (Ortiz-Pineda et al. 2009).
As mentioned earlier, a large number of genes (*73 %) were found to be differentially expressed at P \ 0.05 probability. At more stringent conditions
(P \ .001) the percentage was still highly significant (*40 %). These studies have
identified holothurian genes possibly associated with wound healing, cell proliferation, differentiation, morphological plasticity, cell survival, stress response,
immune challenge, and neoplastic transformation. Among those that have been
described are cytoskeletal genes, such as actins, and developmental genes, such as
Wnt and Hox genes that show interesting expression profiles during regeneration.
More recently large-scale 454 pyrosequencing techniques have been applied to
study regenerative processes and have identified over 2,000,000 ESTs that cluster
into *80,000 contigs (Mashanov et al. in prep.). The tissue used for these analyses
was the radial nerve cord of normal and regenerating animals following the
transection of their cord. Thus, when the data are fully analyzed, the expectation is
to obtain a large percent of the transcriptome of normal and regeneration radial
nerve cords.
452
S. M. Williams et al.
showed that following transection, nerve fibers could re-grow and bridge the injury
gap forming a new scar-free nerve cord in about a month time. A process of
neurogenesis was also documented that produced new neurons within the regenerated cord. Ongoing experiments are aimed at characterizing the genes associated
with this regeneration process.
Genomics
The laboratory began to study the molecular basis of intestinal regeneration in the
late 1990s. Initially the work was done on a gene-by-gene strategy, where the
selected genes were either candidate genes, such as Hox genes (Méndez et al.
2000) or genes identified by differential display techniques comparing regenerating and normal intestines (Roig-López et al. 2001). In this way, several genes of
interest were characterized in the holothurian and were shown to be overexpressed
during intestinal regeneration. Among these were serum amyloid A (Santiago et al.
2000) and ependymin (Suarez-Castillo et al. 2004).
With the advent of high throughput molecular analyses, the number of genes
associated with intestinal regeneration was multiplied. First, three cDNA libraries
were prepared from normal and regenerating intestines and over 5,000 EST
(Expressed Sequence Tags) were identified (Rojas-Cartagena et al. 2007). These
ESTs represent sequences of mRNAs (and therefore gene sequences) that were
expressed in the tissues at the time of dissection. This was the first attempt to
obtain large genomic information from a holothurian. These ESTs sequences were
then probed in a custom-made microarray in order to determine which genes were
differentially expressed during the regeneration process (Ortiz-Pineda et al. 2009).
As mentioned earlier, a large number of genes (*73 %) were found to be differentially expressed at P \ 0.05 probability. At more stringent conditions
(P \ .001) the percentage was still highly significant (*40 %). These studies have
identified holothurian genes possibly associated with wound healing, cell proliferation, differentiation, morphological plasticity, cell survival, stress response,
immune challenge, and neoplastic transformation. Among those that have been
described are cytoskeletal genes, such as actins, and developmental genes, such as
Wnt and Hox genes that show interesting expression profiles during regeneration.
More recently large-scale 454 pyrosequencing techniques have been applied to
study regenerative processes and have identified over 2,000,000 ESTs that cluster
into *80,000 contigs (Mashanov et al. in prep.). The tissue used for these analyses
was the radial nerve cord of normal and regenerating animals following the
transection of their cord. Thus, when the data are fully analyzed, the expectation is
to obtain a large percent of the transcriptome of normal and regeneration radial
nerve cords.
452
S. M. Williams et al.