Background
Retroviruses are efficient tools for delivering heritable genes into the genome of dividing cells. Cell
Biolabs’ pMXs retroviral vector is based on Moloney murine leukemia virus (MMLV). The vector
provides the viral package signal, transcription and processing elements, and MCS for cloning of a target
gene. The viral env gene, produced by the package cell line, encodes the envelop protein, which
determines the viral infectivity range. Transfection into a package cell line produces high-titer,
replication-incompetent viruses.
Induced pluripotent stem (iPS) cells can be generated from various somatic cells by the retrovirusmediated
transfection of four transcription factors, namely Oct3/4, Sox2, c-Myc, and Klf4 (Yamanaka’s
laboratory) or Oct3/4, Sox2, NANOG, and Lin-28 (Thomson’s laboratory). It has been shown that a
combination of all 6 transcription factors (Oct3/4, Sox2, c-Myc, Klf4, NANOG and Lin-28), significantly
increases the efficiency of generating iPS cells from somatic cells. iPS cells are indistinguishable from
ES cells in morphology, proliferation, gene expression, and teratoma formation. Furthermore, when
transplanted into blastocysts, iPS cells can give rise to adult chimeras, which are competent for germline
transmission.