Dawn of the death of a technology….

Microarrays have fascinated me due to their highly parallel and miniaturized approach and the time, money and labour it saves during analyses. Microarrays have had many research applications including gene expression analysis and typing specific sequence variations in the human genome. But an interesting report in nature published 4 years before, says microarray could be a dying technology.

With the advent of novel sequencing technologies, faster, more reliable and cost effective sequences could be obtained in a fraction of the time compared to traditional sequencing methodologies. Thus researchers prefer to sequencing in some specific areas of life sciences research where microarrays have dominated. For example, certain limitations of microarray technology in analysis of genetic links to diseases has turned heads towards the targeted sequencing of certain regions of the genome rather than whole genome typing.

Several microarray companies are experiencing decline which some analysts think may be due to preference of sequencing in gene expression analysis over microarrays. Thus microarray manufacturers are focusing on more improved and cost effective designs which may provide better survival of this technology. And also creation of arrays known as ”capture arrays’ that specifically isolate targeted locations of the genome for sequencing have opened up new application of microarray technology. This joint venture of sequencing and array is more economical and enables effective utilization of resources.

Source : http://www.nature.com/news/2008/081015/full/455847a.html

Trypanosoma control via paratransgenesis

African sleeping sickness or African Trypanosomiasis is a disease caused by the trypanosoma parasite which is biologically transmitted by the tsetse fly (Glossina sp.). The insect is essential for the completion of the parasite’s life cycle. Individuals with the disease exhibit symptoms in two stages. First stage being the haemolymphatic phase and the second stage being the neurological phase. The disease is known as the sleeping sickness due to the second phase which includes symptoms such as confusion, lack of coordination and disrupted sleep cycle.

Sodalis glossinidius is a gram-negative endosymbiotic bacteria living in the alimentary canal of the tsetse fly. These bacteria help the tsetse fly to acquire nutrients that are not synthesized by the fly or not present in their diet. The striking feature of S. glossinidius is that it is one of the few endosymbiotic bacteria that could be cultured and modified genetically.

A group of scientists from Belgium have utilized this feature to genetically modify the endosymbiote to express proteins that can control the sleeping sickness parasite. This is known as paratransgenesis. A transgene is introduced into S. glossinidius where the gene products interfere with the development of the pathogen inside the tsetse host and at the same time preserving host and the symbiote’s viability and fitness.

Nanobodies® (Nbs) are the smallest known antigen binding fragments that target specific antigenic epitopes that are less efficiently targeted by antibodies. Nbs have several superior properties such as small size and stability and therefore are perfect candidates to be used in paratransgenesis. A trypanosome surface glycoprotein specific Nb_An33 Nanobody® was used for targeting the trypanosoma parasite.

Expression plasmids were constructed using the Nbs gene (Nb_An33) with a lac promoter and two genes for the secretion signal for extracellular release of Nb_An33 Nanobody®. The Nb_An33 secreting strains exhibited growth comparable to the wild type. Expressed Nanobody concentrations were determined using ELISA. Binding ability of the extracellularly expressed Nb_An33 with trypanasoma parasite was determined using flow cytometry and fluorescence microscopy.

These results indicate that S. glossinidius could be manipulated to be a paratransgenic organism and the use of Nbs effectors in biological control of  other vector borne diseases.

Source : Microbial cell factories

Interference becomes a good thing now!!!

First discovered in the nematode Caenorhabditis elegans RNAi or interference RNA technology has since been a hot area of research in the field of molecular biology. Introduction of RNA into cells that satisfy certain requirements can interfere with expression of specific genes in certain biological systems. The exogenously injected RNA can hybridize with the endogenously produced mRNA transcript provided that sequence complementarity is present.  Andrew Fire and Craig C. Mello shared the Nobel Prize in Physiology or Medicine for their work on RNA interference in the nematode worm C. elegans, which they published in 1998.

The paper that they published is given here