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Saving an Endangered Species: iPSC Technology to the Rescue?!

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Review of “Flexible adaptation of male germ cells from female iPSCs of endangered Tokudaia osimensis” from Science Advances by Stuart P. Atkinson

The severely endangered Ryukyu spiny rat (Tokudaia osimensis) is a species of rodent in the family Muridae and displays some fascinating characteristics. The karyotype of this creature presents with an odd diploid number (2n = 25) due to the loss of the Y chromosome and with it, the master sex-determining gene SRY (sex-determining region Y) [1]. 

To discover the sex determination mechanism of this endangered species, researchers from the laboratory of Arata Honda (University of Miyazaki and RIKEN, Japan) employed induced pluripotent stem cell (iPSC) technology to generate, maintain, and study naïve state iPSCs. While this new Science Advances study aimed to apply rat iPSCs to uncover specific points related to evolution, epigenetic regulation, sex determination, and gametogenesis, Honda et al. may have also revealed an exciting new means to save an endangered species [2]!

Following in the footsteps of endangered species such as the orangutan, drill, northern white rhinoceros, and the snow leopard [3-5], the authors of this new study generated iPSC employing PiggyBac (PB) transposase vectors encoding mouse reprogramming factors and tail-tip fibroblasts from a live female animal. To maintain naïve pluripotency and the ability to form teratomas in vivo, the study employed typical N2B27 2iL medium with an added requirement for the SB590885 B-Raf inhibitor. 

Encouragingly, the generated rat iPSCs also contributed to interspecific chimeras (employing mice as the host and recipient for embryo transplantation) including the female germ line in the adult. However, analysis of the male adults also indicated a restricted contribution to the male germ line, demonstrating the potential for the production of both eggs and sperm from a single iPSC source, irrespective of sex.

The generation of iPSCs from the endangered species Tokudaia osimensis demonstrates the high sexual plasticity of the cells of this (karyotypically!) unusual animal, which may be enough to save this endangered species from total extinction. Indeed, the authors suggest that derivation and banking of naïve state iPSCs from endangered species may represent a viable strategy for species conservation. Moving forward with Tokudaia osimensis iPSCs, future studies will hopefully highlight what controls sexual plasticity in this species and uncover mechanisms of sex determination without a Y chromosome.

For all the future updates into iPSC generation and the conservation of endangered species, keep the Stem Cells Portal, bookmarked and only a mouse-click away!

References

  1. Kuroiwa A, Ishiguchi Y, Yamada F, et al. The process of a Y-loss event in an XO/XO mammal, the Ryukyu spiny rat. Chromosoma 2010;119:519-526.
  2. Honda A, Choijookhuu N, Izu H, et al. Flexible adaptation of male germ cells from female iPSCs of endangered Tokudaia osimensis. Science advances 2017;3:e1602179.
  3. Ben-Nun IF, Montague SC, Houck ML, et al. Induced pluripotent stem cells from highly endangered species. Nat Methods 2011;8:829-831.
  4. Ramaswamy K, Yik WY, Wang XM, et al. Derivation of induced pluripotent stem cells from orangutan skin fibroblasts. BMC research notes 2015;8:577.
  5. Verma R, Holland MK, Temple-Smith P, et al. Inducing pluripotency in somatic cells from the snow leopard (Panthera uncia), an endangered felid. Theriogenology 2012;77:220-228, 228 e221-222.