Cell Biology

Pluripotent stem cells such as induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs) form teratomas when transplanted into immunodeficient mice. As teratomas contain all three germ layers (endoderm, mesoderm, ectoderm), teratoma formation assay is widely used as an index of pluripotency (Evans and Kaufman, 1981; Hentze et al., 2009; Gropp et al., 2012). On the other hand, teratoma-forming tumorigenicity also represents a major risk factor impeding potential clinical applications of pluripotent stem cells (Miura et al., 2009; Okano et al., 2013). Recently, we reported that iPSCs derived from naked mole-rat lack teratoma-forming tumorigenicity when engrafted into the testes of non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice due to an ES cell-expressed Ras (ERAS) and Alternative reading frame (ARF)-dependent tumor-suppression mechanism specific to this species (Miyawaki et al., 2016). Here, we describe a method for transplanting pluripotent stem cells into the testes of NOD/SCID mice to generate teratomas for assessing the pluripotency and tumorigenicity.

Cuscuta spp. are widespread obligate holoparasitic plants with a broad host spectrum. Rootless Cuscuta penetrates host stems with so called haustoria to form a direct connection to the host vascular tissue (Dawson et al., 1994; Lanini and Kogan, 2005; Kaiser et al., 2015). This connection allows a steady uptake of water, assimilates and essential nutrients from the host plant and therefore enables Cuscuta growth and proliferation. To quantify the parasites’ ability to grow on potential host plants one can use the quantitative growth assay (Hegenauer et al., 2016) described herein, which exclusively utilizes fresh weight measurement as readout.