Single‐cell microinjection has been successfully used to deliver exogenous proteins, cDNA constructs, peptides, drugs and particles into transfection‐challenged cells. With precisely controlled delivery dosage and timing, microinjection has been used in many studies of primary cultured cells, transgenic animal production, in vitro fertilization and RNA inference. This review discusses the advantages and limits of microinjection as a mechanical delivery method and its applications to attached and suspended cells. BioEssays 30:606–610, 2008. © 2008 Wiley Periodicals, Inc.

Microinjection of frog oocytes, a technique whose usefulness for studies on gene expression is already established, may be similarly helpful for the unraveling of several enigmas of cellular metabolism and its organization.

Many principles of eukaryotic DNA replication and its relationship to transcription have been revealed by studying the replication of animal virus chromosomes. Now microinjection of viral DNA into eggs and embryos is providing clues about regulation of chromosomal replication and transcription during early mammalian development.

The creation of transgenic animals has application in the following areas of pharmaceutical and biomedical research: the production of biopharmaceuticals for human use; the production of organs for xenotransplantation; and the generation of animal models for human genetic diseases. Nuclear transfer technology offers a more precise and efficient way of performing genetic modification and creating transgenic animals than the more traditional method of pronuclear microinjection. This paper will review nuclear transfer as ameans of producing transgenic animals; introduce advantages nuclear (...) transfer technology offers in the field of animal transgenesis; and highlight some of the animal welfare issues and ethical concerns raised by the generation and use of transgenic animals in the aforementioned fields of study. Finally, the influence of objectifying language and terminology used to describe transgenic animals will be considered, and the impact of phrases such as “living bioreactor” and “spare part supplier” examined. (shrink)

Mitotic spindles constitute the machinery responsible for equidistribution of the genetic material into each daughter cell during cell division. They are transient and hence quite labile structures, changing their morphology even while performing their function. Biochemical, immunological and genetic analyses of mitotic cells have allowed us to identify a variety of molecules that are recruited to form the spindle at the onset of mitosis. Evaluation of the roles of these molecules in both the formation and in the dynamics of spindle (...) microtubules should be important for understanding the molecular basis of mitosis and its regulation. We have recently identified a novel mitosis‐specific microtubule‐associated protein (MAP) using a monoclonal antibody probe raised against the mitotic spindles isolated from cultured mammalian cells. This 95/105 kDa antigen represents a unique component of the spindle distinct from any of the other MAPs reported so far. Antibody microinjection resulted in mitotic inhibition in a stage‐specific and dosedependent manner, indicating that the protein is an essential spindle component. (shrink)

Nucleoli are the sites of ribosome biogenesis. Transcription of the ribosomal RNA genes as well as processing and initial packaging of their transcripts with ribosomal and non‐ribosomal proteins all occur within the nucleolus in an ordered manner and under defined topological conditions. Components of the nucleolus have been localized by immunocytochemistry and their functional aspects investigated by microinjection of antibodies directed against the enzyme responsible for rDNA transcription, RNA polymerase I. The role of nascent transcripts in postmitotic formation of (...) nucleoli will be discussed. (shrink)

The bulk of the DNA in eukaryotic chromatin behaves as if it is topologically relaxed; however, a subfraction can be shown to be under suercoil tension. Endonuclease S1 cuts at specific hypersentive sites in chromatin (in the promoter regions of active genes) and this enzyme cuts in the same region in supercoiled plasmids, but not in relaxed or linearized molecules. A subfraction of the minichromosomes formed after SV40 infection or microinjection of plasmid DNA into oocytes contains supercoil tension and (...) this subfraction is thought to play an important role in transcription. (shrink)

Going back to the late 1970s and early 1980s, we trace the Xenopus oocyte microinjection experiments that led to the emergence of the concept of “modulator”. The finding that the modulator could transactivate transcription from far upstream and in either orientation suggested that a new genetic element, different from the classical prokaryotic promoter sequences, had been discovered. This particular enhancer transactivates transcription of the sea urchin early (α) histone H2A gene which is regulated in early sea urchin development. We (...) summarise the data from sea urchin microinjection experiments that confirm and extend the results obtained with Xenopus oocytes. We conclude that the H2A enhancer is bipartite, is located approx. 100 bp upstream of the TATAAATA box in the H2A gene of two sea urchin species and enhances transcription when placed at a position far upstream or far downstream of the gene unless an insulator intervenes between enhancer and promoter. Evidence from microinjection experiments with sea urchin embryos suggests that the developmental control of H2A expression resides not with the enhancer, which is constitutively active, but with a striking chromatin structure with two positioned nucleosomes near the 3′ end of the gene. Within this structure, there is an insulator element. BioEssays 24:850–857, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

The acoel worm Symsagittifera roscoffensis, an early offshoot of the Bilateria and the only well‐studied marine acoel that lives in a photosymbiotic relationship, exhibits a centralized nervous system, brain regeneration, and a wide repertoire of complex behaviors such as circatidal rhythmicity, photo/geotaxis, and social interactions. While this animal can be collected by the thousands and is studied historically, significant progress is made over the last decade to develop it as an emerging marine model. The authors here present the feasibility of (...) culturing it in the laboratory and describe the progress made on different areas, including genomic and tissue architectures, highlighting the associated challenges. In light of these developments, and on the ability to access abundant synchronized embryos, the authors put forward S. roscoffensis as a marine system to revisit questions in the areas of photosymbiosis, regeneration, chronobiology, and the study of complex behaviors from a molecular and evolutionary perspective. (shrink)