Welcome back from holidays! Spending some weeks on an island is a pleasant way to relax and maybe it is a good feeling as well for induced pluripotent stem cells (iPSCs), because they like to grow in clusters of cells mimicking "islands".

But what are iPSCs? iPSCs are generated from somatic cells that have the ability to self-renew and differentiate along different cell-lineages (Menon et al, 2016). Takahashi and Yamanaka (Takahashi et al, 2007) proved the capability to reprogram human somatic cells to iPSCs through the over-expression of a combination of a small set of embryonic transcription factors: these four genes, Klf4, Sox2, c-Myc and Oct4 are known as "Yamanaka factors". It has been described an Oct4-only reprogramming as well, demonstrating that a single transcription factor, Oct4, combined with a small molecule cocktail may be sufficient to reprogram human somatic cells to iPSCs (Zhu et al, 2010).

iPSCs are a good tool to study pluripotency, reprogramming and disease, they are a source of autologous stem cells (avoiding the problem of tissue rejection) via a simple derivation process, and, in addition, there are not ethical/legal issues involved. One disadvantage is that, although both iPSCs and embryonic stem cells have a similar profile of expression of pluripotency markers, it is not yet clear if they have molecular and functional equivalence (Hochedlinger and Jaenisch, 2015). Protein profiles of iPSC and embryonic stem cells including subcellular protein distribution could help to find the answer.

Anna Martinez Casals