Hox genes from nematodes and RNAi in Brugia malayi

Hox genes are important: playing a central role in the anteroposterior patterning of bodyplans, showing conservation of relative expression pattern and chromosomal order of paralogous groups between phyla, providing the framework for a molecular map of animal body plan evolution and gross morphology. One organism for which this paradigm appears to be inaccurate is in the nematode C. elegans, which has a depauperate Hox cluster compared to other protostomes. The data presented here reveal that Hox genes within the phylum Nematoda are undergoing rapid and dynamic evolution. Hox genes orthologous to those in other protostome phyla have been identified from species representative of a cross-section of the whole of Nematoda, which are definitively absent from C. elegans. This demonstrates loss of multiple Hox genes within the nematode lineage and challenges previously defined Hox signatures for the two major protostome lineages. In addition we observe alternate cis-splicing of the same N-terminal exon to two different C-terminal homeodomains from different Hox orthology groups within the parasitic nematode B. malayi. These findings demonstrate Hox gene loss as an alternative mechanism for the evolution of body plans to gene duplication and changes in coding and regulatory sequences, within the Nematoda. Furthermore the conservation of the simple nematode body plan has not been accompanied by coordinate Hox gene loss through the whole phylum.One problem when working with parasitic species is the lack of molecular genetic techniques available to study gene function directly. A method for studying gene function using the conserved mechanism of RNAi is described and evaluated. The technique successfully results in loss of specific mRNA transcripts from the target organism B. malayi, and allows the observation of resulting phenotypes in culture. This new approach offers the possibility of investigating the roles of developmental genes such as the Hox gene family, or screening for potential novel drug target candidates and should also be applicable to other parasitic helminths

Mangrove ecosystems of Minicoy Island, Lakshadweep

Mangroves play an Important role in coral reef ecosystems. The fringe and basin type mangrove forests act as depositional areas and are effective binders of sediments. This reduces the sediment loads in coastal waters. Trapping and stabilizing sediments is important for adjacent coral reefs because it prevents abrasion and burial of reefs during stormy conditions

Conservation of epigenetic regulation by the MLL3/4 tumour suppressor in planarian pluripotent stem cells

Currently, little is known about the evolution of epigenetic regulation in animal stem cells. Here we demonstrate, using the planarian stem cell system to investigate the role of the COMPASS family of MLL3/4 histone methyltransferases that their function as tumor suppressors in mammalian stem cells is conserved over a long evolutionary distance. To investigate the potential conservation of a genome-wide epigenetic regulatory program in animal stem cells, we assess the effects of Mll3/4 loss of function by performing RNA-seq and ChIP-seq on the G2/M planarian stem cell population, part of which contributes to the formation of outgrowths. We find many oncogenes and tumor suppressors among the affected genes that are likely candidates for mediating MLL3/4 tumor suppression function. Our work demonstrates conservation of an important epigenetic regulatory program in animals and highlights the utility of the planarian model system for studying epigenetic regulation

Zooplankton abundance and distribution at Minicoy lagoon, Lakshadweep

The environmental parameters such as water temperature, salinity, cloud cover wind foree, rainfall and tide that influence the distribution and abundance of zooplankton at two sites in Minicoy lagoon were siudied from August 1994 to July 1995. The northern part of the lagoon with more live corals had better abundance of ooplankton when compared to the southern area, Zooplankton from different lagoon bottoms namely coralline, sandy and seagrass bed did not how significant variation between sites. Copepods, 8mphipods and decapod larvae were the dominant groups

Gtdap-1 and the role of autophagy during planarian regeneration and starvation

Planarians have been established as an ideal model organism for stem cell research and regeneration. Planarian regeneration and homeostasis require an exquisite balancing act between cell death and cell proliferation as new tissues are made (epimorphosis) and existing tissues remodeled (morphallaxis). Some of the genes and mechanisms that control cell proliferation and pattern formation are known. However, studies about cell death during remodeling are few and far between. We have studied the gene Gtdap-1, the planarian ortholog of human death-associated protein-1 or DAP-1. DAP-1 together with DAP-kinase has been identified as a positive mediator of programmed cell death induced by gamma-interferon in HeLa cells. We have found that the gene functions at the interface between autophagy and cell death in the remodeling of the organism that occurs during regeneration and starvation in sexual and asexual races of planarians. Our data suggest that autophagy of existing cells may be essential to fuel the continued proliferation and differentiation of stem cells by providing the necessary energy and building blocks to neoblasts

Коррупция в России как фактор социальной нестабильности

Malacostracans Imd pathway components. (PDF 351 kb

Telomere maintenance and telomerase activity are differentially regulated in asexual and sexual worms

In most sexually reproducing animals, replication and maintenance of telomeres occurs in the germ line and during early development in embryogenesis through the use of telomerase. Somatic cells generally do not maintain telomere sequences, and these cells become senescent in adults as telomeres shorten to a critical length. Some animals reproduce clonally and must therefore require adult somatic mechanisms for maintaining their chromosome ends. Here we study the telomere biology of planarian flatworms with apparently limitless regenerative capacity fueled by a population of highly proliferative adult stem cells. We show that somatic telomere maintenance is different in asexual and sexual animals. Asexual animals maintain telomere length somatically during reproduction by fission or when regeneration is induced by amputation, whereas sexual animals only achieve telomere elongation through sexual reproduction. We demonstrate that this difference is reflected in the expression and alternate splicing of the protein subunit of the telomerase enzyme. Asexual adult planarian stem cells appear to maintain telomere length over evolutionary timescales without passage through a germ-line stage. The adaptations we observe demonstrate indefinite somatic telomerase activity in proliferating stem cells during regeneration or reproduction by fission, and establish planarians as a pertinent model for studying telomere structure, function, and maintenance

A Dual Platform Approach to Transcript Discovery for the Planarian Schmidtea Mediterranea to Establish RNAseq for Stem Cell and Regeneration Biology

The use of planarians as a model system is expanding and the mechanisms that control planarian regeneration are being elucidated. The planarian Schmidtea mediterranea in particular has become a species of choice. Currently the planarian research community has access to this whole genome sequencing project and over 70,000 expressed sequence tags. However, the establishment of massively parallel sequencing technologies has provided the opportunity to define genetic content, and in particular transcriptomes, in unprecedented detail. Here we apply this approach to the planarian model system. We have sequenced, mapped and assembled 581,365 long and 507,719,814 short reads from RNA of intact and mixed stages of the first 7 days of planarian regeneration. We used an iterative mapping approach to identify and define de novo splice sites with short reads and increase confidence in our transcript predictions. We more than double the number of transcripts currently defined by publicly available ESTs, resulting in a collection of 25,053 transcripts described by combining platforms. We also demonstrate the utility of this collection for an RNAseq approach to identify potential transcripts that are enriched in neoblast stem cells and their progeny by comparing transcriptome wide expression levels between irradiated and intact planarians. Our experiments have defined an extensive planarian transcriptome that can be used as a template for RNAseq and can also help to annotate the S. mediterranea genome. We anticipate that suites of other 'omic approaches will also be facilitated by building on this comprehensive data set including RNAseq across many planarian regenerative stages, scenarios, tissues and phenotypes generated by RNAi