Single cell gene expression analysis of pluripotent stem cells

Leukemia-initiating HSCs in chronic lymphocytic leukemia reveal clonal leukemogenesis and differential drug sensitivity

The existence of "leukemia-initiating cells" (LICs) in chronic lymphocytic leukemia (CLL) remains controversial due to the difficulty in isolating and identifying the tumor-initiating cells. Here, we demonstrate a microchannel electroporation (MEP) microarray that injects RNA-detecting probes into single live cells, allowing the imaging and characterization of heterogeneous LICs by intracellular RNA expression. Using limited-cell FACS sequencing (LC-FACSeq), we can detect and monitor rare live LICs during leukemogenesis and characterize their differential drug sensitivity. Disease-associated mutation accumulation in developing B lymphoid but not myeloid lineage in CLL patient hematopoietic stem cells (CLL-HSCs), and development of independent clonal CLL-like cells in murine patient-derived xenograft models, suggests the existence of CLL LICs. Furthermore, we identify differential protein ubiquitination and unfolding response signatures in GATA2^high CLL-HSCs that exhibit increased sensitivity to lenalidomide and resistance to fludarabine compared to GATA2^lowCLL-HSCs. These results highlight the existence of therapeutically targetable disease precursors in CLL.

Comparison of 2, 5, and 20 % O2 on the development of post-thaw human embryos

PURPOSE

The objective of this study is to investigate the effect of 2, 5, and 20 % O2 on post-thaw day 3 human embryo culture until blastocyst stage.

METHODS

One hundred fifty-five day 3 human embryos were used. One hundred twenty out of 155 embryos were recovered after thawing. Surviving embryos were distributed into 2, 5, or 20 % O2 groups and cultured for 2.5 days. At the end of culture, blastocyst formation was assessed, and then, embryos were collected for RT-qPCR or immunofluorescence analysis.

RESULTS

Using visible blastocoel to define blastocyst formation, 58.7 % (27/46) of surviving day 3 embryos formed blastocyst at 2 % O2, 63.6 % (28/44) at 5 % O2, and 66.7 % (20/30) at 20 % O2. The difference in blastocyst formation rates was not significant. Average blastocyst cell number was 119.44 ± 11.64 at 2 % O2, 142.55 ± 22.47 at 5 % O2, and 97.29 ± 14.87 at 20 % O2. Average apoptotic rate was 4.7 % ± 0.4 % for blastocyst formed at 2 % O2, 3.5 % ± 0.7 % at 5 % O2, and 5.8 % ± 1.1 % at 20 % O2. Apoptosis rate was significantly lower for blastocysts formed at 5 % O2 (p < 0.05). Compared with gene expression levels at 5 % O2, which were arbitrarily set as "1," 20 % O2 is associated with significantly higher expression of BAX (2.14 ± 0.47), G6PD (2.92 ± 1.06), MnSOD (2.87 ± 0.88), and HSP70.1 (8.68 ± 4.19). For all genes tested, no significant differences were found between 2 and 5 % O2.

CONCLUSION

The result suggests that development of cryopreserved human embryos from day 3 to blastocyst stage benefits from culture at 5 % O2.

A simple and effective method for the isolation of inner cell mass samples from human blastocysts for gene expression analysis

The isolation of pure inner cell mass (ICM) and trophectoderm (TE) cells from a single human blastocyst is necessary to obtain accurate gene expression patterns of these cells, which will aid in the understanding of the primary steps of embryo differentiation. However, previously developed pure ICM isolation methods are either time-consuming or alter the normal gene expression patterns of these cells. Here, we demonstrate a simple and effective method of ICM samples isolation from human blastocysts. In total, 35 human blastocysts of all stages with expanded and good morphology were incubated in calcium/magnesium-free HEPES medium for 5 min before micromanipulation. With the aid of a laser, a biopsy pipette was inserted directly into the blastocoel for the suction-based removal of ICM samples. The ICM samples were obtained through simple mechanical pulling force or laser assistance, and each isolation process required 3-4 min. The isolated ICM and TE fractions were subjected to single-cell real-time quantitative RT-PCR to evaluate keratin 18 (KRT18) expression. Finally, 33 paired ICM and TE samples were verified using gene expression analysis. KRT18 was readily detectable in all TE cells but absent in 30 ICM counterparts, indicating a pure ICM isolation rate of 90.9% (30/33). The relative KRT18 expression of three TE samples compared with their three contaminated ICM counterparts was 19-fold (P < 0.001), indicating that the contamination was very weak. These results demonstrate that our ICM isolation method is simple and effective.