Chromosome Cycle Research Articles

Sex chromosome cycle as a mechanism of stable sex determination.

Recent advances in DNA sequencing technology have enabled the precise decoding of genomes in non-model organisms, providing a basis for unraveling the patterns and mechanisms of sex chromosome evolution. Studies of different species have yielded conflicting results regarding the traditional theory that sex chromosomes evolve from autosomes via the accumulation of deleterious mutations and degeneration of the Y (or W) chromosome. The concept of the 'sex chromosome cycle,' emerging from this context, posits that at any stage of the cycle (i.e., differentiation, degeneration, or loss), sex chromosome turnover can occur while maintaining stable sex determination. Thus, understanding the mechanisms that drive both the persistence and turnover of sex chromosomes at each stage of the cycle is crucial. In this review, we integrate recent findings on the mechanisms underlying maintenance and turnover, with a special focus on several organisms having unique sex chromosomes. Our review suggests that the diversity of sex chromosomes in the maintenance of stable sex determination is underappreciated and emphasizes the need for more research on the sex chromosome cycle.

CCDC58 is a potential biomarker for diagnosis, prognosis, immunity, and genomic heterogeneity in pan-cancer

Coiled-coil domain-containing 58 (CCDC58) is a member of the CCDC protein family. Similar to other members, CCDC58 exhibits potential tumorigenic roles in a variety of malignancies. However, there is no systematic and comprehensive pan-cancer analysis to investigate the diagnosis, prognosis, immune infiltration, and other related functions of CCDC58. We used several online websites and databases, such as TCGA, GTEx, UALCAN, HPA, CancerSEA, BioGRID, GEPIA 2.0, TIMER 2.0, and TISIDB, to extract CCDC58 expression data and clinical data of patients in pan-cancer. Then, the relationship between CCDC58 expression and diagnosis, prognosis, genetic alterations, DNA methylation, genomic heterogeneity, and immune infiltration level were determined. In addition, the biological function of CCDC58 in liver hepatocellular carcinoma (LIHC) was investigated. Pan-cancer analysis results showed that CCDC58 was differentially expressed in most tumors and showed excellent performance in diagnosis and prediction of prognosis. The expression of CCDC58 was highly correlated with genetic alterations, DNA methylation, and genomic heterogeneity in some tumors. In addition, the correlation analysis of CCDC58 with the level of immune infiltration and immune checkpoint marker genes indicated that CCDC58 might affect the composition of the tumor immune microenvironment. Enrichment analysis showed that CCDC58-related genes were mainly linked to mitosis, chromosome, and cell cycle. Finally, biological function experiments demonstrated that CCDC58 plays an important role in tumor cell proliferation and migration. CCDC58 was first identified as a pan-cancer biomarker. It may be used as a potential therapeutic target to improve the prognosis of patients in the future.

The Crk4-Cyc4 complex regulates G2/M transition in Toxoplasma gondii

A versatile division of apicomplexan parasites and a dearth of conserved regulators have hindered the progress of apicomplexan cell cycle studies. While most apicomplexans divide in a multinuclear fashion, Toxoplasma gondii tachyzoites divide in the traditional binary mode. We previously identified five Toxoplasma CDK-related kinases (Crk). Here, we investigated TgCrk4 and its cyclin partner TgCyc4. We demonstrated that TgCrk4 regulates conventional G2 phase processes, such as repression of chromosome rereplication and centrosome reduplication, and acts upstream of the spindle assembly checkpoint. The spatial TgCyc4 dynamics supported the TgCrk4–TgCyc4 complex role in the coordination of chromosome and centrosome cycles. We also identified a dominant TgCrk4–TgCyc4 complex interactor, TgiRD1 protein, related to DNA replication licensing factor CDT1 but played no role in licensing DNA replication in the G1 phase. Our results showed that TgiRD1 also plays a role in controlling chromosome and centrosome reduplication. Global phosphoproteome analyses identified TgCrk4 substrates, including TgORC4, TgCdc20, TgGCP2, and TgPP2ACA. Importantly, the phylogenetic and structural studies suggest the Crk4–Cyc4 complex is limited to a minor group of the binary dividing apicomplexans.

A clinical predictive model for live birth in women of advanced age undergoing PGT cycles.

The trend of delaying childbirth has resulted in a growing number of advanced-aged women who are opting for preimplantation genetic testing (PGT) to screen for monogenic diseases or structural chromosomal rearrangements (PGT-M and PGT-SR). This increase in demand necessitates the development of a clinical predictive model for live birth outcomes in these women. Therefore, the objective of this study is to construct a comprehensive predictive model that assesses the likelihood of achieving a successful live birth in advanced-aged women undergoing PGT-M and PGT-SR treatments. A retrospective cohort study of 37-45-year-old women undergoing preimplantation genetic testing for monogenic disease or structural chromosomal rearrangement cycles from 2010 to 2021 was conducted at a university hospital reproductive centre. The purpose was to develop a clinical predictive model for live birth in these women. The main outcome studied was the cumulative live birth rate in the first or subsequent cycles. Developing a decision tree enabled a comprehensive study of clinical parameters and expected outcomes. The analysis included 158 women undergoing 753 preimplantation genetic testing cycles. The cumulative live birth rate was 37.342% (59/158). Decision tree analysis revealed that women aged ≤ 40.1 or women > 40.1 with one or more top-quality transferable embryos in their first cycle had the best chance for a live baby (56% and 41%, respectively). Those older than 40.1 without top-quality embryos and seven or fewer dominant follicles had no live births. A Kaplan-Meier curve showed that for autosomal dominant diseases, there was a negligible increase in live birth rate after three cycles, compared to six cycles in autosomal recessive inheritance. In older women, the chance of delivering after repeated cycles is higher in those with at least one top-quality unaffected embryo in their first preimplantation genetic testing cycle. Additional preimplantation genetic testing cycles after three in carriers of an autosomal dominant disorder and six in those with an autosomal recessive disorder should be considered prudently.

A compendium of chromatin contact maps reflecting regulation by chromatin remodelers in budding yeast

We herein employ in situ Hi-C with an auxin-inducible degron (AID) system to examine the effect of chromatin remodeling on 3D genome organization in yeast. Eight selected ATP-dependent chromatin remodelers representing various subfamilies contribute to 3D genome organization differently. Among the studied remodelers, the temporary depletions of Chd1p, Swr1p, and Sth1p (a catalytic subunit of the Remodeling the Structure of Chromatin [RSC] complex) cause the most significant defects in intra-chromosomal contacts, and the regulatory roles of these three remodelers in 3D genome organization differ depending on the chromosomal context and cell cycle stage. Furthermore, even though Chd1p and Isw1p are known to share functional similarities/redundancies, their depletions lead to distinct effects on 3D structures. The RSC and cohesin complexes also differentially modulate 3D genome organization within chromosome arm regions, whereas RSC appears to support the function of cohesin in centromeric clustering at G2 phase. Our work suggests that the ATP-dependent chromatin remodelers control the 3D genome organization of yeast through their chromatin-remodeling activities.

Geometric principles underlying the proliferation of a model cell system

Many bacteria can form wall-deficient variants, or L-forms, that divide by a simple mechanism that does not require the FtsZ-based cell division machinery. Here, we use microfluidic systems to probe the growth, chromosome cycle and division mechanism of Bacillus subtilis L-forms. We find that forcing cells into a narrow linear configuration greatly improves the efficiency of cell growth and chromosome segregation. This reinforces the view that L-form division is driven by an excess accumulation of surface area over volume. Cell geometry also plays a dominant role in controlling the relative positions and movement of segregating chromosomes. Furthermore, the presence of the nucleoid appears to influence division both via a cell volume effect and by nucleoid occlusion, even in the absence of FtsZ. Our results emphasise the importance of geometric effects for a range of crucial cell functions, and are of relevance for efforts to develop artificial or minimal cell systems.

Developmental Programming: Sheep Granulosa and Theca Cell-Specific Transcriptional Regulation by Prenatal Testosterone.

Prenatal testosterone (T)-treated sheep, similar to polycystic ovarian syndrome women, manifest reduced cyclicity, functional hyperandrogenism, and polycystic ovary (PCO) morphology. The PCO morphology results from increased follicular recruitment and persistence of antral follicles, a consequence of reduced follicular growth and atresia, and is driven by cell-specific gene expression changes that are poorly understood. Therefore, using RNA sequencing, cell-specific transcriptional changes were assessed in laser capture microdissection isolated antral follicular granulosa and theca cells from age 21 months control and prenatal T-treated (100 mg intramuscular twice weekly from gestational day 30 to 90; term: 147 days) sheep. In controls, 3494 genes were differentially expressed between cell types with cell signaling, proliferation, extracellular matrix, immune, and tissue development genes enriched in theca; and mitochondrial, chromosomal, RNA, fatty acid, and cell cycle process genes enriched in granulosa cells. Prenatal T treatment 1) increased gene expression of transforming growth factor β receptor 1 and exosome component 9, and decreased BCL6 corepressor like 1, BCL9 like, and MAPK interacting serine/threonine kinase 2 in both cells, 2) induced differential expression of 92 genes that included increased mitochondrial, ribosome biogenesis, ribonucleoprotein, and ubiquitin, and decreased cell development and extracellular matrix-related pathways in granulosa cells, and 3) induced differential expression of 56 genes that included increased noncoding RNA processing, ribosome biogenesis, and mitochondrial matrix, and decreased transcription factor pathways in theca cells. These data indicate that follicular function is affected by genes involved in transforming growth factor signaling, extracellular matrix, mitochondria, epigenetics, and apoptosis both in a common as well as a cell-specific manner and suggest possible mechanistic pathways for prenatal T treatment-induced PCO morphology in sheep.

ORCA/LRWD1 Regulates Homologous Recombination at ALT-Telomeres by Modulating Heterochromatin Organization.

SummaryTelomeres are maintained by telomerase or in a subset of cancer cells by a homologous recombination (HR)-based mechanism, Alternative Lengthening of Telomeres (ALT). The mechanisms regulating telomere-homeostasis in ALT cells remain unclear. We report that a replication initiator protein, Origin Recognition Complex-Associated (ORCA/LRWD1), by localizing at the ALT-telomeres, modulates HR activity. ORCA's localization to the ALT-telomeres is facilitated by its interaction to SUMOylated shelterin components. The loss of ORCA in ALT-positive cells elevates the levels of two mediators of HR, RPA and RAD51, and consistent with this, we observe increased ALT-associated promyelocytic leukemia body formation and telomere sister chromatid exchange. ORCA binds to RPA and modulates the association of RPA to telomeres. Finally, the loss of ORCA causes global chromatin decondensation, including at the telomeres. Our results demonstrate that ORCA acts as an inhibitor of HR by modulating RPA binding to ssDNA and inducing chromatin compaction.

Do steviol glycosides affect the oxidative and genotoxicity parameters in BALB/c mice?

This study was performed with 40 (20 males, 20 females) BALB/c mice divided into 4 experimental groups and a control group, each consisting of 8 mice (4 males, 4 females). Experimental groups were administered 470, 620, 940, and 1880 mg/kg doses of steviol glycosides, orally, for 4 weeks. The total antioxidants and the oxidant status, paraoxonase-1 enzyme activity, high density lipoprotein-cholesterol, and low-density lipoprotein-cholesterol levels were analyzed from blood samples. The chromosomal aberrations and cell cycle activities were examined from bone marrow samples. Plasma lipid parameters were not affected by the dose of steviol glycosides, however, the total antioxidants, oxidant status, and paraoxonase-1 enzyme activity were found to be negatively correlated with the doses. A positive correlation was found between the total oxidant status and the dose (r = 0.65) and between the mitotic index and the dose (r = 0.74). The dose of steviol glycosides also increased the percentage of the abnormal cells and the CA/cell dose in a dependent manner (r = 0.74 and 0.76, respectively). The study findings concluded that steviol glycosides slightly increased the oxidative damage, cell cycle activity, and chromosomal aberration frequency. However, we did not evaluate the potential of steviol glycosides as genotoxic and mitogenic agents, and, therefore, further investigations are required. CAS number: 58543–16-1

Retrospective analysis of meiotic segregation pattern and interchromosomal effects in blastocysts from inversion preimplantation genetic testing cycles

To determine factors affecting unbalanced chromosomal rearrangement originating from parental inversion and interchromosomal effect occurrence in blastocysts from inversion carriers. Retrospective study. University-affiliated center. Couples with one partner carrying inversion underwent preimplantation genetic testing for chromosomal structural rearrangement cycles. Not applicable. Unbalanced rearrangement embryo rate, normal embryo rate, interchromosomal effect. Preimplantation genetic testing was performed for 576 blastocysts from 57 paracentric (PAI) and 94 pericentric (PEI) inversion carriers. The percentage of normal/balanced blastocysts was significantly higher in PAI than PEI carriers (70.4% vs. 57.5%). Logistic regression indicated the inverted segment size ratio was a statistically significant risk factor for abnormality from parental inversion in both PEI and PAI. The optimal cutoff values to predict unbalanced rearrangement risk were 35.7% and 57%. In PAI, rates of abnormality from parental inversion were 0% and 12.1% in the <35.7% and ≥35.7% groups, respectively, with no gender difference. For PEI, the rates of abnormality from parental inversion were 7.9% and 33.1% in the <57% and ≥57% groups, respectively. In the ≥57% group, the rate of unbalanced rearrangement was significantly higher from paternal than maternal inversion (43.3% vs. 23.6%). In inversion carriers, 21,208 chromosomes were examined, and 187 (0.88%) malsegregations were identified from structurally normal chromosomes. In controls, 56,488 chromosomes were assessed, and 497 (0.88%) aneuploidies were identified, indicating no significant difference. The risk of unbalanced rearrangement is affected by the ratio of inverted segment size in both PAI and PEI carriers and is associated with gender.

Concurrent processes set E. coli cell division

A cell can divide only upon completion of chromosome segregation; otherwise, its daughters would lose genetic material. However, we do not know whether the partitioning of chromosomes is the key event for the decision to divide. We show how key trends in single-cell data reject the classic idea of replication-segregation as the rate-limiting process for cell division. Instead, the data agree with a model where two concurrent processes (setting replication initiation and interdivision time) set cell division on competing time scales. During each cell cycle, division is set by the slowest process (an "AND" gate). The concept of transitions between cell cycle stages as decisional processes integrating multiple inputs instead of cascading from orchestrated steps can affect the way we think of the cell cycle in general.

In praise of mealybugs

The fascinating chromosomal cycle leading to facultative heterochromatization in the mealybugs has been a challenging system for mechanistic understanding of the phenomenon of genomic imprinting and epigenetics. The elegant cytological dissection of the various processes reported in the literature is equally fascinating for the researchers of current molecular age. Presently, a two way approach is being pursued; continued efforts of utilizing elegant cytology, in combination with the molecular probes to decipher molecular correlates on one hand and on the other, the de novo biochemical/molecular analysis for the identification of the molecular players using genomic tools. The hope is to uncover novel players in genomic imprinting and epigenetic regulation in the mealybug system which shows differential regulation of the entire genome, with 50% of its genome being transcriptionally inactivated in a parental-origin-specific and sex specific manner. In addition to being a model for epigenetic regulation, the mealybugs are being utilized for the analysis of radiation resistance as well as metabolic interactions between the microbiome and the host. The overview presented here is an attempt to bring out some of the work carried out in these directions. We also discuss the areas that remain poorly explored in this system, such as the role/involvement of noncoding RNA in male-specific inactivation and the molecular dissection of heterochromatin, the cytological manifestation of the inactive state of genes and chromosome.

Controlling centriole numbers: Geminin family members as master regulators of centriole amplification and multiciliogenesis.

To ensure that the genetic material is accurately passed down to daughter cells during mitosis, dividing cells must duplicate their chromosomes and centrosomes once and only once per cell cycle. The same key steps-licensing, duplication, and segregation-control both the chromosome and the centrosome cycle, which must occur in concert to safeguard genome integrity. Aberrations in genome content or centrosome numbers lead to genomic instability and are linked to tumorigenesis. Such aberrations, however, can also be part of the normal life cycle of specific cell types. Multiciliated cells best exemplify the deviation from a normal centrosome cycle. They are post-mitotic cells which massively amplify their centrioles, bypassing the rule for once-per-cell-cycle centriole duplication. Hundreds of centrioles dock to the apical cell surface and generate motile cilia, whose concerted movement ensures fluid flow across epithelia. The early steps that control the generation of multiciliated cells have lately started to be elucidated. Geminin and the vertebrate-specific GemC1 and McIdas are distantly related coiled-coil proteins, initially identified as cell cycle regulators associated with the chromosome cycle. Geminin is required to ensure once-per-cell-cycle genome replication, while McIdas and GemC1 bind to Geminin and are implicated in DNA replication control. Recent findings highlight Geminin family members as early regulators of multiciliogenesis. GemC1 and McIdas specify the multiciliate cell fate by forming complexes with the E2F4/5 transcription factors to switch on a gene expression program leading to centriole amplification and cilia formation. Positive and negative interactions among Geminin family members may link cell cycle control to centriole amplification and multiciliogenesis, acting close to the point of transition from proliferation to differentiation. We review key steps of centrosome duplication and amplification, present the role of Geminin family members in the centrosome and chromosome cycle, and discuss links with disease.

Monitoring the DNA Topoisomerase II Checkpoint in Saccharomyces cerevisiae.

Topoisomerase II activity is crucial to maintain genome stability through the removal of catenanes in the DNA formed during DNA replication and scaffolding the mitotic chromosome. Perturbed Topo II activity causes defects in chromosome segregation due to persistent catenations and aberrant DNA condensation during mitosis. Recently, novel top2 alleles in the yeast Saccharomyces cerevisiae revealed a checkpoint control which responds to perturbed Topo II activity. Described in this chapter are protocols for assaying the phenotypes seen in top2 mutants on a cell biological basis in live cells: activation of the Topo II checkpoint using spindle morphology, chromosome condensation using fluorescently labeled chromosomal loci and cell cycle progression by flow cytometry. Further characterization of this novel checkpoint is warranted so that we can further our understanding of the cell cycle, genomic stability, and the possibility of identifying novel drug targets.

FISH-based mitotic and meiotic diakinesis karyotypes of Morus notabilis reveal a chromosomal fusion-fission cycle between mitotic and meiotic phases

Mulberry (Morus spp.), in family Moraceae, is a plant with important economic value. Many polyploid levels of mulberry have been determined. In the present study, the fluorescence in situ hybridization (FISH) technique was applied in Morus notabilis, using four single-copy sequences, telomere repeats, and 5S and 25S rDNAs as probes. All the mitotic chromosomes were clearly identified and grouped into seven pairs of homologous chromosomes. Three dot chromosome pairs were distinguished by the FISH patterns of the 25S rDNA probe and a simple sequence repeat (SSR2524). According to the FISH signals, chromosome length and morphology, detailed meiotic diakinesis karyotype was constructed. Interestingly, only six bivalent chromosomes were observed in diakinesis cells. The 25S rDNA probe was used to illustrate chromosome alterations. The results indicated that mitotic chromosomes 5 and 7 fused into diakinesis chromosome 5 during the meiotic phase. In mitotic cells, the fused chromosome 5 broke into chromosomes 5 and 7. A chromosomal fusion-fission cycle between the meiotic and mitotic phases in the same individual is reported here for the first time. This finding will contribute to the understanding of karyotype evolution in plants.

Abstract 506: The role of Nek2 in hepatocellular carcinoma

Abstract Cancer is a disease of aging. Among different types of cancer, liver cancer is one of the most prevalent cancers over the world and particularly affects people in some East Asia countries such as Korea, Japan and China. The NIMA-related kinase 2 (Nek2), which regulates centrosome cohesion, is a potential player in carcinogenesis. Our evidence showed Nek2 mRNA and protein levels are overexpressed in liver cancer cells and promotes HCC cell growth. Since Nek2 is pertinent to centrosome, we speculated that it might take part in centrosome regulation. To study the effect of Nek2 in chromosomal instability, centrosome splitting and cell cycle, a stable isoform Nek2A overexpression inducible system was generated in different Hepatocellular Carcinoma cell lines for investigations through immunofluorescent staining and cell-cytometry. For the study of centrosome, we observed that higher proportion of cells with centrosome splitting occurred in the Nek2A overexpressing cells in both HepG2 and SMMC-7721 inducible cell lines. Moreover, cell cycle analysis showed an increased content of DNA when Nek2A is overexpressed, suggesting that Nek2A induces more aneuploidy cells. To conclude, overexpression of Nek2 exacerbates chromosomal instability. Dysregulation of centrosome may be the key for understanding of regulatory mechanism of chromosomal instability by Nek2. Citation Format: Chan Shing Ho Vincent. The role of Nek2 in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 506. doi:10.1158/1538-7445.AM2017-506

Germline-specific labeling of the somatic chromosomes by protein phosphatase 2A and histone H3S28 phosphorylation in Acricotopus lucidus

Additional chromosomes limited to the germline (=Ks) were established as a special form of germline–soma differentiation in the Orthocladiinae, a subfamily of the Chironomidae (Bauer and Beermann in Z Naturforsch 7b: 557–563, 1952). The Ks together with the somatic chromosomes (=Ss) pass through a complex chromosome cycle with elimination at mitosis and a monopolar migration of all Ks. The dissimilar behavior of Ks and Ss in these exceptional mitoses initiated the search for differential chromosome marks in the orthocladiid Acricotopus lucidus. The search, using immunofluorescence, revealed that in metaphases of male gonial mitoses, and both meiotic divisions, the Ss are fully labeled by protein phosphatase 2A (PP2A) and histone H3S28ph, while in metaphases of somatic cells both marks were detected only at the centromeres of the Ss. In another orthocladiid, Psectrocladius obvius, the same labeling pattern of the Ss as in A. lucidus was established for H3S28ph, but not for PP2A, which was localised solely at the centromeres. In Chironomus nuditaris, a species possessing no Ks, PP2A and H3S28ph signals were always restricted to the centromeres. High levels of H3K4me3, a marker of transcriptionally competent chromatin, were detected on the Ss in metaphases I of C. nuditaris, while in both orthocladiids, the Ss in metaphases I were devoid of H3K4me3 signals. This strongly supports an earlier idea of a silencing of the Ss in male meiosis of A. lucidus suggesting the possibility of extending this concept to the Orthocladiinae. The germline–soma differentiation in A. lucidus is not only made apparent by the occurrence of Ks but also by a germline-specific labeling of the Ss by PP2A and H3S28ph.

A cell cycle-controlled redox switch regulates the topoisomerase IV activity.

Topoisomerase IV (topo IV), an essential factor during chromosome segregation, resolves the catenated chromosomes at the end of each replication cycle. How the decatenating activity of the topo IV is regulated during the early stages of the chromosome cycle despite being in continuous association with the chromosome remains poorly understood. Here we report a novel cell cycle-regulated protein in Caulobacter crescentus, NstA (negative switch for topo IV decatenation activity), that inhibits the decatenation activity of the topo IV during early stages of the cell cycle. We demonstrate that in C. crescentus, NstA acts by binding to the ParC DNA-binding subunit of topo IV. Most importantly, we uncover a dynamic oscillation of the intracellular redox state during the cell cycle, which correlates with and controls NstA activity. Thus, we propose that predetermined dynamic intracellular redox fluctuations may act as a global regulatory switch to control cellular development and cell cycle progression and may help retain pathogens in a suitable cell cycle state when encountering redox stress from the host immune response.

Chromosome structure deficiencies in MCPH1 syndrome.

Mutations in the MCPH1 gene result in primary microcephaly in combination with a unique cellular phenotype of defective chromosome condensation. MCPH1 patient cells display premature chromosome condensation in G2 phase of the cell cycle and delayed decondensation in early G1 phase, observable as an increased proportion of cells with prophase-like appearance. MCPH1 deficiency thus appears to uncouple the chromosome cycle from the coordinated series of events that take place during mitosis such as some phases of the centrosome cycle and nuclear envelope breakdown. Here, we provide a further characterization of the effects of MCPH1 loss-of-function on chromosome morphology. In comparison to healthy controls, chromosomes of MCPH1 patients are shorter and display a pronounced coiling of their central chromatid axes. In addition, a substantial fraction of metaphase chromosomes shows apparently unresolved chromatids with twisted appearance. The patient chromosomes also showed signs of defective centromeric cohesion, which become more apparent and pronounced after harsh hypotonic conditions. Taking together, the observed alterations indicate additional so far unknown functions of MCPH1 during chromosome shaping and dynamics.

Chromosomal characteristics at cleavage and blastocyst stages from the same embryos.

To investigate chromosomal characteristics in the same embryos at cleavage and blastocyst stage. Six PGD/PGS cycles were retrospective studied, including five chromosomal translocation PGD cycles and one recurrent abortion PGS cycle. The cleavage embryos were biopsied one blastomere at day 3, followed by blastocyst culture. Trophectoderm cell biopsy was performed when embryos developed into the blastocyst stage. Whole genome amplification and 24-chromosomal analysis by CGH/SNP microarray was performed on each blastomere and trophectoderm cells. After PGD/PGS, only one couple had no euploid embryos to transfer. Five couples delivered a healthy, balanced-karyotype baby. A total of 18 embryos had both blastomere and trophectoderm cell reliable results available. Of the 18 embryos, eleven embryos contained identical chromosomes from cleavage stage to blastocyst stage and six embryos contained almost identical chromosomes . Only one embryo presented opposite chromosomal results for the cleavage and blastocyst stage, with abnormal chromosomes in the blastomere but normal chromosomes in trophectoderm cells. Most embryos maintain chromosomal stability during embryonic development. Compared to cleavage stage, blastocyst stage may provide more reliable aneuploidy results.