Chapter 5 Answers to Select Review Questions

1.  What are the three ground-breaking technologies developed to reprogram cells?

Cell fusion, somatic cell nuclear transfer and induced pluripotency

3.  How does leprosy bacterium enhance its infectivity success?

The leprosy bacterium reprograms Schwann cells into a progenitor/stem-like state migrate which then secrete immunomodulatory factors that further drive and exacerbate leprosy spread through the promotion of bacteria laden macrophage release.

4.  Give an example of naturally occurring cell fusion.

Mature muscle cells are syncytia of fused mononuclear myocytes resulting from successive cell fusion.

9.  What role does epigenetics play in cellular reprogramming?

Epigenetics promotes changes in gene expression and ultimately cellular phenotypes. 

14.  List at least five species cloned since 1952.

Five species cloned since 1952 include frogs, sheep, mice, pigs and cats.

18.  What discovery in flies did Walter Gehring and colleagues at the University of Basel make in 1987 that set the stage for studies on the regulation and manipulation of cell and body plan fate?

It was the discovery of the Drosophila melanogaster transcription factor Antennapedia and its ability to transform antennae into legs when overexpressed in developing fly embryos that shed light on the possibilities of transcription factor-based cell fate and modification.

21.  What are the key factors involved in pluripotency induction?

Oct 2/4, Sox2, c-Myc and Klf4

24.  What is the major drawback of using retroviruses and lentiviruses to introduce the key factors required for pluripotency into cells?

The application of retroviral- or lentiviral-based systems for introducing key transcription factors to induce pluripotency in somatic cells has one major drawback:  transgenes, which are defined as a gene or genetic material transferred from one organism to another, are stably incorporated into the genome of the host cell.  The existence of these transgene integrants poses several disadvantages, the most critical of which is the possibility, however remote, that transgene integration may either activate a proto-oncogene or inactivate (repress or silence) a tumor suppressor locus.  This could result in a tumorigenic phenotype and as such is not safe in regards to cell-based therapy. 

28.  How would one make mRNA transfection less immunogenic?

mRNA can be made less immunogenic by replacing the synthetic nucleic acid bases pseudouridine with uridine and cytidine with 5-methylcytidine to convert the mRNA sequences into those less resembling that of a virus.

33.  List at least two differences between iPS and ES cells.

Differences between iPS and ES cells include their global patterns of gene expression and capacities to differentiate into terminal lineages.

35.  How was the pluripotency of mouse embryonic fibroblast-derived iPS cells definitively proven?

Mouse embryonic fibroblast-derived iPS cells were demonstrated to give rise to adult chimeras and transmit through the germline.