Developmental, behavioral, and physiological phenotype of cloned mice

Defective chromatin architectures in embryonic stem cells derived from somatic cell nuclear transfer impair their differentiation potentials

Nuclear transfer embryonic stem cells (ntESCs) hold enormous promise for individual-specific regenerative medicine. However, the chromatin states of ntESCs remain poorly characterized. In this study, we employed ATAC-seq and Hi-C techniques to explore the chromatin accessibility and three-dimensional (3D) genome organization of ntESCs. The results show that the chromatin accessibility and genome structures of somatic cells are re-arranged to ESC-like states overall in ntESCs, including compartments, topologically associating domains (TADs) and chromatin loops. However, compared to fertilized ESCs (fESCs), ntESCs show some abnormal openness and structures that have not been reprogrammed completely, which impair the differentiation potential of ntESCs. The histone modification H3K9me3 may be involved in abnormal structures in ntESCs, including incorrect compartment switches and incomplete TAD rebuilding. Moreover, ntESCs and iPSCs show high similarity in 3D genome structures, while a few differences are detected due to different somatic cell origins and reprogramming mechanisms. Through systematic analyses, our study provides a global view of chromatin accessibility and 3D genome organization in ntESCs, which can further facilitate the understanding of the similarities and differences between ntESCs and fESCs.

Abnormal gene expression in regular and aggregated somatic cell nuclear transfer placentas

Background

Placental defects in somatic cell nuclear transfer (SCNT) are a major cause of complications during pregnancy. One of the most critical factors for the success of SCNT is the successful epigenetic reprogramming of donor cells. Recently, it was reported that the placental weight in mice cloned with the aggregated SCNT method was significantly reduced. Here, we examine the profile of abnormal gene expression using microarray technology in both regular SCNT and aggregated SCNT placentas as well as in vivo fertilization placentas. One SCNT embryo was aggregated with two 2 to 4 -cell stage tetraploid embryos from B6D2F1 mice (C57BL/6 × DBA/2).

Results

In SCNT placentas, 206 (1.6%) of the 12,816 genes probed were either up-regulated or down-regulated by more than two-fold. However, 52 genes (0.4%) showed differential expression in aggregated SCNT placentas compared to that in controls. In comparison of both types of SCNT placentas with the controls, 33 (92%) out of 36 genes were found to be up-regulated (>2-fold) in SCNT placentas. Among 36 genes, 13 (36%) genes were up-regulated in the aggregated SCNT placentas. Eighty-five genes were down-regulated in SCNT placentas compared with the controls. However, only 9 (about 10.5%) genes were down-regulated in the aggregated SCNT placentas. Of the 34 genes known as imprinted genes, expression was lower in SCNT placentas than that in the controls. Thus, these genes may be the cause of placentomegaly in mice produced post SCNT.

Conclusions

These results suggest that placentomegaly in the SCNT placentas was probably caused by abnormal expression of multiple genes. Taken together, these results suggest that abnormal gene expression in cloned placentas was reduced in a genome-wide manner using the aggregation method with tetraploid embryos.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-017-0355-4) contains supplementary material, which is available to authorized users.

Learning, memory and exploratory similarities in genetically identical cloned dogs

Somatic cell nuclear transfer allows generation of genetically identical animals using donor cells derived from animals with particular traits. To date, few studies have investigated whether or not these cloned dogs will show identical behavior patterns. To address this question, learning, memory and exploratory patterns were examined using six cloned dogs with identical nuclear genomes. The variance of total incorrect choice number in the Y-maze test among cloned dogs was significantly lower than that of the control dogs. There was also a significant decrease in variance in the level of exploratory activity in the open fields test compared to age-matched control dogs. These results indicate that cloned dogs show similar cognitive and exploratory patterns, suggesting that these behavioral phenotypes are related to the genotypes of the individuals.

Application of iPS in assisted reproductive technology: sperm from somatic cells?

Infertility is an emotionally charged problem, and it is a condition of increasing incidence. In addition, in 40% to 60% of all infertile couples, it was the male who had a problem that led to infertility. Among the male fertility problems, non-obstructive azoospermia (NOA) (caused by testis failure or impaired spermatogenesis) is the most prevalent. Despite enormous clinical and experimental efforts, treatment of this disorder--assistant reproduction technique (ART) with donor spermatozoa remains controversial. We present the hypothesis that induced pluripotent stem (iPS) cell derived spermatozoa can be a potential source for male gametes for patients with NOA; we support this with the following three evidence: the first is the generation of viable, live-born, fertile mature organism from iPS cells; the second is the successful induced differentiation of male gametes from pluripotent cells in vitro; and the last is the wide use of intracytoplasmic sperm injection (ICSI) in human assisted reproduction. If the hiPS derived spermatozoa prove practical in the generation offspring with ICSI, this method might be able to grant a new chance for NOA patients to have their genetic children with fewer emotional, ethical and legislative problems. To ensure the safety of the technology itself and the production of healthy offspring, further investigations are needed. We also suggest several laboratory and clinical approaches for testing our hypothesis.

Human procreation in unchartered territory: new twists in ethical discussions

Since their validation in mammals, there have been profound ethical discussions on the possible applications of somatic cell nuclear transfer, human embryonic stem cells and induced pluripotent stem cells to reproductive medicine. This has been the case whether these technologies were considered as direct (i.e. when procreation is the ultimate goal) or indirect applications. In most countries, the majority of these approaches have been either stringently regulated, or regulation has been strongly and consensually suggested. However, this is not necessarily the case for possibilities such as same-sex chimaeras or the direct differentiation of gametes from somatic cells, skipping a pluripotent cell intermediate. The author suggests that the field of reproductive medicine should be more proactive in discussing both current and emerging developments with possible implications for human reproduction, even those reaching beyond current paradigms.

Effect of in vitro maturation of mouse oocytes on the health and lifespan of adult offspring

BACKGROUND

In vitro maturation of oocytes can, in some circumstances, provide an alternative approach to gonadotrophin-induced maturation in clinical settings. However, the consequences of these protocols on the long-term health of offspring are unknown. Here, the long-term health status and lifespans of offspring produced by in vitro maturation of mouse oocytes was compared with that of oocytes induced to mature in vivo using gonadotrophin treatment.

METHODS

Mouse oocytes were matured in vitro using both an established optimized system and in the absence of amino acids to produce a suboptimal condition for maturation. Oocytes induced to mature in vivo with gonadotrophins constituted the control group. All metaphase II oocytes were fertilized in vitro and transferred at the 2-cell stage to the oviducts of pseudo-pregnant foster mothers for development to term. Offspring were subjected to a wide variety of physiological and behavioral tests for the first year of life and natural lifespan determined.

RESULTS

There was no difference among the groups in lifespan or in most of the physiological and behavioral analyses. However, the pulse rate and cardiac output were slightly, but significantly, reduced in the optimized in vitro matured group compared with the in vivo matured group (P = 0.0119 and P = 0.0197, respectively). Surprisingly, these decreases were largely abrogated in the in vitro group matured without amino acids.

CONCLUSIONS

Evidence presented here using a mouse model suggests that the in vitro maturation of oocytes has minimal effects on the long-term health of offspring. However, a finding of slight reductions in pulse rate and cardiac output may focus future clinical attention.

Derivation of embryonic stem cells for therapy: new technologies

Embryonic stem cells are currently derived from the inner cell mass of human blastocysts, generated from spare embryos donated for research. To overcome ethical concerns raised by destruction of the embryo, two groups of workers have attempted to derive these cells from isolated blastomeres of 8- to 10-cell stage embryos using the embryo biopsy method akin to that used in preimplantation diagnosis. This paper briefly discusses these two techniques in relation to the routine derivation of stem cells from blastocysts. Some embryological aspects of using the inner cell mass of blastocysts in preference to early embryonic cells are presented. The paper also considers some pitfalls in therapeutic cloning, especially in non-human primates, since legislation to allow this procedure for stem cell research is currently being passed in Australia.