Genomic instability of human embryonic stem cell lines using different passaging culture methods.

BACKGROUND: Human embryonic stem cells exhibit genomic instability that can be related to culture duration or to the passaging methods used for cell dissociation. In order to study the impact of cell dissociation techniques on human embryonic stem cells genomic instability, we cultured H1 and H9 human embryonic stem cells lines using mechanical/manual or enzymatic/collagenase-IV dissociation methods. Genomic instability was evaluated at early (p60) passages by using oligonucleotide based array-comparative genomic hybridization 105 K with a mean resolution of 50 Kb. RESULTS: DNA variations were mainly located on subtelomeric and pericentromeric regions with sizes <100 Kb. In this study, 9 recurrent genomic variations were acquired during culture including the well known duplication 20q11.21. When comparing cell dissociation methods, we found no significant differences between DNA variations number and size, DNA gain or DNA loss frequencies, homozygous loss frequencies and no significant difference on the content of genes involved in development, cell cycle tumorigenesis and syndrome disease. In addition, we have never found any malignant tissue in 4 different teratoma representative of the two independent stem cell lines. CONCLUSIONS: These results show that the occurrence of genomic instability in human embryonic stem cells is similar using mechanical or collagenase IV-based enzymatic cell culture dissociation methods. All the observed genomic variations have no impact on the development of malignancy.

Multiplex Genome-Edited T-cell Manufacturing Platform for "Off-the-Shelf" Adoptive T-cell Immunotherapies.

Adoptive immunotherapy using autologous T cells endowed with chimeric antigen receptors (CAR) has emerged as a powerful means of treating cancer. However, a limitation of this approach is that autologous CAR T cells must be generated on a custom-made basis. Here we show that electroporation of transcription activator-like effector nuclease (TALEN) mRNA allows highly efficient multiplex gene editing in primary human T cells. We use this TALEN-mediated editing approach to develop a process for the large-scale manufacturing of T cells deficient in expression of both their αß T-cell receptor (TCR) and CD52, a protein targeted by alemtuzumab, a chemotherapeutic agent. Functionally, T cells manufactured with this process do not mediate graft-versus-host reactions and are rendered resistant to destruction by alemtuzumab. These characteristics enable the administration of alemtuzumab concurrently or prior to engineered T cells, supporting their engraftment. Furthermore, endowing the TALEN-engineered cells with a CD19 CAR led to efficient destruction of CD19(+) tumor targets even in the presence of the chemotherapeutic agent. These results demonstrate the applicability of TALEN-mediated genome editing to a scalable process, which enables the manufacturing of third-party CAR T-cell immunotherapies against arbitrary targets. As such, CAR T-cell immunotherapies can therefore be used in an "off-the-shelf" manner akin to other biologic immunopharmaceuticals

Recurrent 70.8 Mb 4q22.2q32.3 duplication due to ovarian germinal mosaicism.

A mosaicism is defined by the presence of two or more populations of cells with different genotypes in one individual. Chromosomal germinal mosaicism occurs in germ cells before the onset of meiosis. Previously, few studies have described germinal mosaicism. In this study, we report on two siblings who carried identical pure and direct interstitial 4q22.2q32.3 duplication. Procedure investigations included complete clinical description, conventional cytogenetic analysis, fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH) array experiments and microsatellite study searching for parental origin of the duplication. Microarray CGH and further FISH experiments with BAC clones showed the same 70.8 Mb direct duplication, dup(4)(q22.2q32.3). Molecular studies of the 4q duplication were consistent with maternal origin associated with mitotic or meiotic rearrangements. This structural chromosomal aberration was associated in both cases with increased nuchal translucency, growth retardation and dysmorphy. Cardiopathy and lung malformations were only evident in the first case. These clinical manifestations are similar to those previously reported in previous studies involving pure 4q trisomy of the same region, except for thumb and renal abnormalities that were not obvious in the presented cases. The amplified region included genes involved in neurological development (NEUROG2, MAB21L2, PCDH10/18 and GRIA2). The recurrent 4q duplication in these siblings is consistent with a maternal ovarian germinal mosaicism. This is the first description of germinal mosaicism for a large chromosomal duplication and highlights that genetic counselling for apparently de novo chromosome aberration should be undertaken with care.

Human embryonic stem cells reveal recurrent genomic instability at 20q11.21.

By analyzing five human embryonic stem (hES) cell lines over long-term culture, we identified a recurrent genomic instability in the human genome. An amplification of 2.5-4.6 Mb at 20q11.21, encompassing approximately 23 genes in common, was detected in four cell lines of different origins. This amplification, which has been associated with oncogenic transformation, may provide a selective advantage to hES cells in culture.