TRIM28-Regulated Transposon Repression Is Required for Human Germline Competency and Not Primed or Naive Human Pluripotency.

Transition from primed to naive pluripotency is associated with dynamic changes in transposable element (TE) expression and demethylation of imprinting control regions (ICRs). In mouse, ICR methylation and TE expression are each regulated by TRIM28; however, the role of TRIM28 in humans is less clear. Here, we show that a null mutation in TRIM28 causes significant alterations in TE expression in both the naive and primed states of human pluripotency, and phenotypically this has limited effects on self-renewal, instead causing a loss of germline competency. Furthermore, we discovered that TRIM28 regulates paternal ICR methylation and chromatin accessibility in the primed state, with no effects on maternal ICRs. Taken together, our study shows that abnormal TE expression is tolerated by self-renewing human pluripotent cells, whereas germline competency is not

An integration-free, virus-free rhesus macaque induced pluripotent stem cell line (riPSC89) from embryonic fibroblasts

We generated a rhesus macaque induced pluripotent stem cell (riPSC) line, riPSC89, from rhesus embryonic fibroblasts (REFs). Fibroblasts were expanded from the skin of a rhesus macaque embryo at embryonic day 47. REFs and riPSCs had a normal male (42, XY) karyotype. The riPSC89 line was positive for markers of self-renewal including OCT4, NANOG, TRA-1-81 and SSEA4. Pluripotency was demonstrated through the generation of teratomas using transplantation into immunocompromised mice. The riPSC89 line may be a useful non-human primate resource to uncover developmental origins of disease, or used as a basic model to understand lineage specification in the primate embryo

An integration-free, virus-free rhesus macaque induced pluripotent stem cell line (riPSC90) from embryonic fibroblasts

The rhesus macaque induced pluripotent stem cell (riPSC) line, UCLAi090-A (riPSC90), was generated from rhesus embryonic fibroblast (REF) cells called REF90. REF90 cells and the riPSC90 line were authenticated by short tandem repeat analysis and had a normal male (42, XY) karyotype. The riPSC90 line expressed markers of self-renewal including OCT4, NANOG, TRA-1-81 and SSEA4, and generated teratomas after transplantation into immunocompromised mice. riPSC90 could be used in parallel with riPSC89, which was derived from REFs cultured from a different rhesus macaque embryo (Sosa et al. 2016)

An integration-free, virus-free rhesus macaque induced pluripotent stem cell line (riPSC89) from embryonic fibroblasts

We generated a rhesus macaque induced pluripotent stem cell (riPSC) line, riPSC89, from rhesus embryonic fibroblasts (REFs). Fibroblasts were expanded from the skin of a rhesus macaque embryo at embryonic day 47. REFs and riPSCs had a normal male (42, XY) karyotype. The riPSC89 line was positive for markers of self-renewal including OCT4, NANOG, TRA-1-81 and SSEA4. Pluripotency was demonstrated through the generation of teratomas using transplantation into immunocompromised mice. The riPSC89 line may be a useful non-human primate resource to uncover developmental origins of disease, or used as a basic model to understand lineage specification in the primate embryo

The Sm protein methyltransferase PRMT5 is not required for primordial germ cell specification in mice

PRMT5 is a type II protein arginine methyltransferase with roles in stem cell biology, reprograming, cancer and neurogenesis. During embryogenesis in the mouse, it was hypothesized that PRMT5 functions with the master germline determinant BLIMP1 to promote primordial germ cell (PGC) specification. Using a Blimp1-Cre germline conditional knockout, we discovered that Prmt5 has no major role in murine germline specification, or the first global epigenetic reprograming event involving depletion of cytosine methylation from DNA and histone H3 lysine 9 dimethylation from chromatin. Instead, we discovered that PRMT5 functions at the conclusion of PGC reprograming I to promote proliferation, survival and expression of the gonadal germline program as marked by MVH. We show that PRMT5 regulates gene expression by promoting methylation of the Sm spliceosomal proteins and significantly altering the spliced repertoire of RNAs in mammalian embryonic cells and primordial cells