MicroRNAs (miRNAs), which are non-coding RNAs 18–25 nt in length, regulate a variety of biological processes, including vertebrate development. To identify new species of miRNA and to simultaneously obtain a comprehensive quantitative profile of small RNA expression in mouse embryos, we used the massively parallel signature sequencing technology that potentially identifies virtually all of the small RNAs in a sample. This approach allowed us to detect a total of 390 miRNAs, including 195 known miRNAs covering ∼80% of previously registered mouse miRNAs as well as 195 new miRNAs, which are so far unknown in mouse. Some of these miRNAs showed temporal expression profiles during prenatal development (E9.5, E10.5 and E11.5). Several miRNAs were positioned in polycistron clusters, including one particular large transcription unit consisting of 16 known and 23 new miRNAs. Our results indicate existence of a significant number of new miRNAs expressed at specific stages of mammalian embryonic development and which were not detected by earlier methods.
A range of bacteria have been shown to contain collagen-like sequences that form triple-helical structures. Some of these proteins have been shown to form triple-helical motifs that are stable around body temperature without the inclusion of hydroxyproline or other secondary modifications to the protein sequence. This makes these collagen-like proteins particularly suitable for recombinant production as only a single gene product and no additional enzyme needs to be expressed. In the present study, we have examined the cytotoxicity and immunogenicity of the collagen-like domain from Streptococcus pyogenes Scl2 protein. These data show that the purified, recombinant collagen-like protein is not cytotoxic to fibroblasts and does not illicit an immune response in SJL/J and Arc mice. The freeze dried protein can be stabilised by glutaraldehyde cross-linking giving a material that is stable at >37°C and which supports cell attachment while not causing loss of viability. These data suggest that bacterial collagen-like proteins, which can be modified to include specific functional domains, could be a useful material for medical applications and as a scaffold for tissue engineering.
Over 30 key leaders in the field participated in a 1-day workshop entitled 'Recent Advances and Opportunities in the Development and Use of Humanized Immune System Mouse Models' to discuss the benefits and limitations of using human fetal tissue versus non-fetal tissue sources to generate mice with a humanized immune system. This Comment summarizes the workshop discussions, including highlights of some of the key advances made through the use of humanized mice in improving the understanding of immune system function and developing novel therapeutics for the treatment of infectious, immunological and allergic diseases, as well as current challenges in the production, characterization and utilization of these animal models.
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