Early Stem Cell Differentiation Research Articles

Electrical stimulation of titanium to promote stem cell orientation, elongation and osteogenesis

Electrical stimulation of cells allows exogenous electric signals as stimuli to manipulate cell growth, preferential orientation and bone remodelling. In this study, commercially pure titanium discs were utilised in combination with a custom-built bioreactor to investigate the cellular responses of human mesenchymal stem cells via in-vitro functional assays. Finite element analysis revealed the homogeneous delivery of electric field in the bioreactor chamber with no detection of current density fluctuation in the proposed model. The custom-built bioreactor with capacitive stimulation delivery system features long-term stimulation with homogeneous electric field, biocompatible, sterilisable, scalable design and cost-effective in the manufacturing process. Using a continuous stimulation regime of 100 and 200 mV/mm on cp Ti discs, viability tests revealed up to an approximately 5-fold increase of cell proliferation rate as compared to non-stimulated controls. The human mesenchymal stem cells showed more elongated and differentiated morphology under this regime, with evidence of nuclear elongation and cytoskeletal orientation perpendicular to the direction of electric field. The continuous stimulation did not cause pH fluctuations and hydrogen peroxide production caused by Faradic reactions, signifying the suitability for long-term toxic free stimulation as opposed to the commonly used direct stimulation regime. An approximate of 4-fold increase in alkaline phosphatase production and approximately 9-fold increase of calcium deposition were observed on 200 mV/mm exposed samples relative to non-stimulated controls. It is worth noting that early stem cell differentiation and matrix production were observed under the said electric field even without the presence of chemical inductive growth factors. Statement of significanceThis manuscript presents a study on combining pure titanium (primarily preferred as medical implant materials) and electrical stimulation in a purpose-built bioreactor with capacitive stimulation delivery system. A continuous capacitive stimulation regime on titanium disc has resulted in enhanced stem cell orientation, nuclei elongation, proliferation and differentiation as compared to non-stimulated controls. We believe that this manuscript creates a paradigm for future studies on the evolution of healthcare treatments in the area of targeted therapy on implantable and wearable medical devices through tailored innovative electrical stimulation approach, thereby influencing therapeutic conductive and electroactive biomaterials research prospects and development.

Uncovering the RNA-binding protein landscape in the pluripotency network of human embryonic stem cells.

Embryonic stem cell (ESC) self-renewal and cell fate decisions are driven by a broad array of molecular signals. While transcriptional regulators have been extensively studied in human ESCs (hESCs), the extent to which RNA-binding proteins (RBPs) contribute to human pluripotency remains unclear. Here, we carry out a proteome-wide screen and identify 810 proteins that bind RNA in hESCs. We reveal that RBPs are preferentially expressed in hESCs and dynamically regulated during early stem cell differentiation. Notably, many RBPs are affected by knockdown of OCT4, a master regulator of pluripotency, several dozen of which are directly targeted by this factor. Using cross-linking and immunoprecipitation (CLIP-seq), we find that the pluripotency-associated STAT3 and OCT4 transcription factors interact with RNA in hESCs and confirm the binding of STAT3 to the conserved NORAD long-noncoding RNA. Our findings indicate that RBPs have a more widespread role in human pluripotency than previously appreciated.

ALDH1 Cancer Stem Cell Marker as a Prognostic Factor in Triple-Negative Breast Cancer

Breast cancer is the most common cancer with an increasing incidence in Asia. About 20% of all breast cancers are triple-negative breast cancers (TNBCs). BCSC is a subset of tumor cells that has stem cell-like characteristics, such as a high capacity for self-renewal and tumor initiation, which implies that BCSC may cause aggressiveness of TNBC. ALDH1 has a role in early stem cell differentiation through its function in the oxidation of retinol to retinoic acid, proposed to be a strong candidate for breast cancer stem cells. Various studies have shown that ALDH1 is one of the markers of CSC that can be used as a prognosis indicator because it can be a biological marker for poor prognostic factors in TNBC. This study assessed the prognostic survival rate with a retrospective cohort method in TNBC patients. A total of 54 of 55 patients treated at RSCM were tested for the expression of ALDH1 through an immunohistochemistry assay of breast cancer tissue using ALDH1 staining. Survival analysis was done to obtain the prognostic data of ALDH1. Positive ALDH1 expression was obtained at 38.89% in TNBC patients. One-year survival and three years of survival in TNBC patients with positive ALDH1 expression were 42.9% and 33.3%, respectively. In this study, ALDH1 can be used as a poor survival prognostic factor with HR 2.636 and p value 0.013. The conclusion of this study is that ALDH1 can be used as a poor prognostic factor in TNBC patients although it cannot be an independent prognostic factor.

A novel approach to identify regulated long non‐coding RNAs in selected pathways

We have developed a highly sensitive RT‐qPCR‐based workflow that quantifies the expression of lncRNAs in a RNA sample. The workflow utilizes a novel reagent that enables streamlined genomic DNA removal, cDNA synthesis and multi‐target pre‐amplification and allows for reliable quantification of as little as 25 pg of RNA (single cell equivalent). This reagent can be used together with pre‐designed qPCR array panels that contain lncRNA targets identified as being involved in specific biological/pathophysiological pathways through perturbation experiments, guilt‐by‐association experiments or literature mining. We demonstrate the utility of this workflow by identifying seven lncRNAs that are regulated in early stem cell differentiation using the NTera2 model system. Two lncRNAs are suppressed and five lncRNAs are induced during the differentiation process and may play a role in the maintenance of the pluripotent state or in stem cell differentiation respectively. Two of the lncRNAs have been previously reported to be involved in stem cell differentiation; the other five lncRNAs appear to be a new finding. We believe that this workflow represents a powerful discovery tool to identify lncRNAs involved in biological/pathophysiological pathways and can promote new insights in lncRNA research.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

DNA methylation is dispensable for changes in global chromatin architecture but required for chromocentre formation in early stem cell differentiation.

Epiblast stem cells (EpiSCs), which are pluripotent cells isolated from early post-implantation mouse embryos (E5.5), show both similarities and differences compared to mouse embryonic stem cells (mESCs), isolated earlier from the inner cell mass (ICM) of the E3.5 embryo. Previously, we have observed that while chromatin is very dispersed in E3.5 ICM, compact chromatin domains and chromocentres appear in E5.5 epiblasts after embryo implantation. Given that the observed chromatin re-organization in E5.5 epiblasts coincides with an increase in DNA methylation, in this study, we aimed to examine the role of DNA methylation in chromatin re-organization during the in vitro conversion of ESCs to EpiSCs. The requirement for DNA methylation was determined by converting both wild-type and DNA methylation-deficient ESCs to EpiSCs, followed by structural analysis with electron spectroscopic imaging (ESI). We show that the chromatin re-organization which occurs in vivo can be re-capitulated in vitro during the ESC to EpiSC conversion. Indeed, after 7days in EpiSC media, compact chromatin domains begin to appear throughout the nuclear volume, creating a chromatin organization similar to E5 epiblasts and embryo-derived EpiSCs. Our data demonstrate that DNA methylation is dispensable for this global chromatin re-organization but required for the compaction of pericentromeric chromatin into chromocentres.

The circular SiZer, inferred persistence of shape parameters and application to early stem cell differentiation

We generalize the SiZer of Chaudhuri and Marron (J. Amer. Statist. Assoc. 94 (1999) 807-823, Ann. Statist. 28 (2000) 408-428) for the detection of shape parameters of densities on the real line to the case of circular data. It turns out that only the wrapped Gaussian kernel gives a symmetric, strongly Lipschitz semi-group satisfying "circular" causality, that is, not introducing possibly artificial modes with increasing levels of smoothing. Some notable differences between Euclidean and circular scale space theory are highlighted. Based on this, we provide an asymptotic theory to make inference about the persistence of shape features. The resulting circular mode persistence diagram is applied to the analysis of early mechanically-induced differentiation in adult human stem cells from their actin-myosin filament structure. As a consequence, the circular SiZer based on the wrapped Gaussian kernel (WiZer) allows the verification at a controlled error level of the observation reported by Zemel et al. (Nat. Phys. 6 (2010) 468-473): Within early stem cell differentiation, polarizations of stem cells exhibit preferred directions in three different micro-environments.

“ATF6 Promotes Early Stem Cell Development”

Stem cells have scant and simplified organelles. The endoplasmic reticulum (ER) is the organelle of protein assembly, protein folding and protein maturation. The Unfolded Protein Response (UPR) is the regulatory mechanism that supports ER function and homeostasis. We identified significant expansion of the ER and the UPR regulators, IRE1, PERK, and ATF6, during early human embryonic stem cell development. Interestingly, the ATF6 pathway, but not the IRE1 or PERK pathways, was found to be strongly activated during early differentiation. Over‐expression of the transcriptional activator bZIP domain of ATF6 led to a dramatic increase of ER in hESCs. By contrast, pharmacologic inhibition of ATF6 cleavage by S1P reduced ER growth. We obtained similar findings using induced pluripotent stem cells (iPSCs), generated from achromatopsia patients that carry the loss‐of‐function R342C mutation in ATF6. In mutant ATF6 iPS cells, growth of the ER was significantly impaired during early stem cell differentiation when compared to wild‐type ATF6 iPS cells. Last, we found that ATF6 expression enhanced the acquisition of germ layer (ectoderm, mesoderm, endoderm) markers while ATF6 inhibition impaired acquisition of differentiation markers. We further identified that ATF6 expression can be stimulated by the FGF2 signaling cascade during these early differentiation steps. In summary, we identify a novel function for ATF6 in stem cells to promote ER expansion coupled with differentiation. Our findings suggest defects in stem cell differentiation may contribute to the early pathologies seen in human patients bearing loss‐of‐function ATF6 mutations.

Expression of stem cell biomarker aldehyde dehydrogenase 1 (ALDH1) in canine mammary tumor

The study was conducted to investigate the immunohistochemical expression of a stem cell biomarker, ALDH1 in CMTs. ALDH1 is a cytosolic enzyme responsible for oxidizing intracellular aldehydes leading to the oxidation of retinol to retinoic acid, a key step involved in early stem cell differentiation. It was noticed that the cells expressing this marker possess ability to self renew. In present investigation, we assessed the expression of ALDH1 by immunohistochemistry on paraffin embedded tissue sections from 31 confirmed clinical cases of canine mammary tumors (CMT). The results of immunohistochemistry were analyzed semiquantitatively by calculating percentage score and staining intensity using light microscope and comparing it with the histological types. ALDH1 expression was detected in 26 (83%) of CMTs and it was observed in benign lesions, invasive cells and cells undergoing epithelial to mesenchymal transition (EMT). The high expression patterns of ALDH1 in various histological types of CMT indicated poor prognosis.

Mixed Phenotype Acute Leukemia (MPAL) Has a High Frequency of Mutations in Epigenetic Regulatory Genes: Results from Whole Exome Sequencing

Introduction: Mixed phenotype acute leukemia (MPAL) is a relatively rare and difficult to treat leukemia with features of at least two cell lineages (typically myeloid combined with B-ALL or T-ALL). Early abnormalities in hematopoiesis appear to result in specific types of bone marrow disorders and leukemias. Epigenetic changes, such as aberrant DNA methylation facilitated by mutated DNA methyltransferases, have been implicated in the pathogenesis of many hematopoietic disorders. A recent study of adult patients with T-ALL/myeloid mixed phenotype acute leukemia demonstrated a 50% mutation frequency in the DNMT3A gene (Kern et al., ASH 2012). Interestingly, a Dnmt3a-null mouse model in our lab develops both myeloid and lymphoid malignancies. We hypothesize that epigenetic genes are an important regulator of early stem cell differentiation and that mutations in these genes may cause abnormal stem cell differentiation resulting in the ambiguous phenomenon of mixed phenotype acute leukemia.Methods: We analyzed DNA from a total of 19 MPAL samples (12 T/myeloid, 6 B/myeloid, and 1 B-ALL/T-ALL), with an age range of 20-74 years old. Pathology and flow cytometry records were reviewed by a hematopathologist to ensure that all samples met WHO 2008 criteria for MPAL prior to analysis. Five of the samples were cytogenetically normal, 7 had complex karyotypes or other high risk features, 3 had intermediate risk cytogenetic abnormalities, 1 was Philadelphia chromosome positive, 2 had MLL rearrangement and 2 samples did not have cytogenetic data available. Exome capture array was performed with Nimblegen and sequencing runs were performed in paired-end mode using the Illumina HiSeq 2500 platform for next generation sequencing. Samples achieved >96% of the targeted exome bases covered to a depth of 20x or greater. Results were mapped to Human Reference Genome, common SNPs were eliminated and mutations were identified with variant allele frequency >0.05 (most were >0.2). Over 500 previously reported genes with mutations in leukemias and other cancers were assessed.Results: Twelve of the 19 samples (63%) had mutations in epigenetic regulatory genes. The most commonly mutated gene was DNMT3A with 6 patients (32%); 3 of these patients had T/myeloid subtype, 2 of these patients had B/myeloid subtype and 1 patient and B-ALL/T-ALL subtype. Other mutations in epigenetic regulatory genes were found in EZH2 (3 patients, 16%), IDH1 (2 patients, 11%), IDH2 (3 patients, 16%, all T/myeloid), TET1 (3 patients, 16%, all T/myeloid), and TET3 (3 patients, 16%). Interestingly, DNMT3A was co-mutated with TP53 in 5 patients, IDH2 in 3 patients, NRAS in 2 patients, TET3 in 1 patient, and NOTCH1 in 1 patient. Mutations were also frequently found in PRPF40B (6 patients, 32%), TP53 (5 patients, 26%), BRAF (4 patients, 21%), NOTCH1 (4 patients, 21%). Other genes found to be mutated at a lower frequency were RUNX1, GATA2, JAK2, KRAS, NRAS, SIRPA, LRP1B, and NF1.Conclusions: Identifying abnormalities in epigenetic regulators may provide additional understanding of the pathogenesis of these rare and difficult to treat disorders. Adults with AML and DNMT3A mutations have demonstrated worse clinical outcomes (Ley et al., 2010), suggesting that standard chemotherapy may not be sufficient to treat malignancies which arise from hematopoietic stem cells. This understanding may guide future decisions regarding the necessity of personalized genetic testing at the time of diagnosis, the appropriateness of stem cell transplantation as well as providing prognostic information and future therapeutic targets for these patients. DisclosuresNo relevant conflicts of interest to declare.

Considering Unknown Unknowns: Reconstruction of Nonconfoundable Causal Relations in Biological Networks

Our current understanding of cellular networks is rather incomplete. We over look important but so far unknown genes and mechanisms in the pathways. Moreover, we often only have a partial account of the molecular interactions and modifications of the known players. When analyzing the cell, we look through narrow windows leaving potentially important events in blind spots. Network reconstruction is naturally confined to what we have observed. Little is known on how the incompleteness of our observations confounds our interpretation of the available data. Here we ask which features of a network can be confounded by incomplete observations and which cannot. In the context of nested effects models, we show that in the presence of missing observations or hidden factors a reliable reconstruction of the full network is not feasible. Nevertheless, we can show that certain characteristics of signaling networks like the existence of cross-talk between certain branches of the network can be inferred in a nonconfoundable way. We derive a test for inferring such nonconfoundable characteristics of signaling networks. Next, we introduce a new data structure to represent partially reconstructed signaling networks. Finally, we evaluate our method both on simulated data and in the context of a study on early stem cell differentiation in mice.

O52. Immunoexpression of putative cancer stem cell markers in oral epithelial dysplasia and squamous cell carcinoma

Introduction: In recent years there has been mounting evidence for the presence of cancer stem cells. Aldh1, NGFR, CD44, Lgr5, and CD24 have been reported as representative cancer stem cell markers in a variety of solid cancers. Although these markers appear to be promising markers for isolation and characterisation of cancer stem cells, little is known about their immunohistochemical expression in oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC). Here, we evaluate the expression of these markers in normal oral mucosa (NOR), OED, and OSCC.Methods: Specimens consisting of 18 NOR, 24 mild dysplasia (MD), 11 severe dysplasia (SD) and 49 OSCC were stained using standard immunohistochemistry methods to determine the expression of Aldh1, NGFR, CD44, Lgr5, and CD24.Results: Immunohistochemical analysis showed cytoplasmic localization of Aldh1 and membranous expression of NGFR and CD44, while Lgr5 and CD24 showed both cytoplasmic and membranous immunoreactivity. In this study, all markers were localized at the basal third of epithelium which is known to harbor stem cells of normal mucosa. The expression of Aldh1, Lgr5, CD24 and CD44 increased in parallel with the severity of OED. Significantly higher staining of Aldh1, Lgr5 and CD24 was noted in SD samples compared with samples of MD (p < 0.05). Likewise there was a significant increase in Aldh1, Lgr5, CD24, and CD44 in OSCC compared to NOR and MD (p < 0.05). No significant difference between histopathologic groups was found regarding NGFR expression. Additionally, Aldh1 was positively correlated with Lgr5 (r = 0.19, p < 0.05), CD24 (r = 0.3, p < 0.05) and CD44 (r = 0.2, p < 0.05). Similarly, CD24 was positively correlated with CD44 (r = 0.36, p < 0.05) and Lgr5 (r = 0.35, p < 0.05).Discussion: Increasing levels of Aldh1 (an enzyme involved in the oxidation of retinal to retinoic acid in early stem cell differentiation), Lgr5 (a target gene activated by Wnt-signaling) and CD24 (mucin-like adhesion molecule linked with shortened patient survival and lymph node metastasis) were found in OSCC and SD lesions compared to MD. These results suggest that the characteristic expression of these markers may be of diagnostic and prognostic value for OED and should be investigated further as markers of cancer progression.

Lsh Participates in DNA Methylation and Silencing of Stem Cell Genes

Transcriptional control of stem cell genes is a critical step in differentiation of embryonic stem cells and in reprogramming of somatic cells into stem cells. Here we report that Lsh, a regulator of repressive chromatin at retrotransposons, also plays an important role in silencing of stem cell-specific genes such as Oct4. We found that CpG methylation is gained during in vitro differentiation of several stem cell-specific genes (in 11 of 12 promoter regions) and thus appears to be a common epigenetic mark. Lsh depletion prevents complete silencing of stem cell gene expression and moreover promotes the maintenance of stem cell characteristics in culture. Lsh is required for establishment of DNA methylation patterns at stem cell genes during differentiation, in part by regulating access of Dnmt3b to its genomic targets. Our results indicate that Lsh is involved in the control of stem cell genes and suggest that Lsh is an important epigenetic modulator during early stem cell differentiation.

Moving Forward in Human Mammary Stem Cell Biology and Breast Cancer Prognostication Using ALDH1

In this issue of Cell Stem Cell, the seminal work of Ginestier et al. (2007) elegantly demonstrates that aldehyde dehydrogenase 1 (ALDH1) facilitates the identification and isolation of normal and malignant human mammary stem cells in vitro, in vivo, and in situ in fixed tissues.

Stem cell factor/c-Kit interactions regulate human islet-epithelial cluster proliferation and differentiation

Stem cell factor (SCF), a progenitor cell growth factor, binds to and activates the c-Kit receptor tyrosine kinase, which is critical for early stem cell differentiation in haematopoiesis and gametogenesis. Nothing is known regarding these interactions during islet development in the human fetal pancreas. The present study was to investigate whether an increase in c-Kit receptor activity in isolated human fetal islet-epithelial clusters, by giving exogenous SCF, would promote β-cell development. In the intact fetal pancreas, SCF and c-Kit were observed co-localizing with cytokeratin 19 in both ductal and newly forming islet cells. Islet cells isolated from 14 to 16 weeks fetal pancreata were cultured with SCF (50 ng/ml) or vehicle for 48 h. We observed an increase in the number of c-Kit-, pancreatic and duodenal homeobox gene 1- (PDX-1-), insulin- and glucagon-expressing cells in the SCF-treated group (PDX-1 and insulin, p < 0.05). PDX-1 and c-Kit mRNA levels were also up-regulated in the SCF group (PDX-1, p < 0.05), with no change in preproinsulin or proglucagon gene expression. Co-localization of insulin with PDX-1 or c-Kit was observed frequently in SCF-treated cultures. A significantly ( p < 0.05) greater proliferative capacity of islet-epithelial clusters was found in the SCF group in parallel with increased ( p < 0.02) phosphorylation of Akt in a phosphatidylinositol-3 kinase (PI3K)-dependent manner. Our results demonstrate that SCF/c-Kit interactions are likely to be involved in mediating islet cell differentiation and proliferation during human fetal pancreatic development, and that phosphorylated Akt may have a role downstream of SCF/c-Kit signaling.

Optimal Proliferation of a Hematopoietic Progenitor Cell Line Requires Either Costimulation With Stem Cell Factor or Increase of Receptor Expression That Can Be Replaced by Overexpression of Bcl-2

In vitro proliferation of hematopoietic stem cells requires costimulation by multiple regulatory factors whereas expansion of lineage-committed progenitor cells generated by stem cells usually requires only a single factor. The distinct requirement of factors for proliferation coincides with the differential temporal expression of the subunits of cytokine receptors during early stem cell differentiation. In this study, we explored the underlying mechanism of the requirement of costimulation in a hematopoietic progenitor cell line TF-1. We found that granulocyte-macrophage colony-stimulating factor (GM-CSF) optimally activated proliferation of TF-1 cells regardless of the presence or absence of stem cell factor (SCF). However, interleukin-5 (IL-5) alone sustained survival of TF-1 cells and required costimulation of SCF for optimal proliferation. The synergistic effect of SCF was partly due to its anti-apoptosis activity. Overexpression of the IL-5 receptor  subunit (IL5R) in TF-1 cells by genetic selection or retroviral infection also resumed optimal proliferation due to correction of the defect in apoptosis suppression. Exogenous expression of an oncogenic anti-apoptosis protein, Bcl-2, conferred on TF-1 cells an IL-5–dependent phenotype. In summary, our data suggested SCF costimulation is only necessary when the expression level of IL5R is low and apoptosis suppression is defective in the signal transduction of IL-5. Expression of Bcl-2 proteins released the growth restriction of the progenitor cells and may be implicated in leukemia formation.

Optimal Proliferation of a Hematopoietic Progenitor Cell Line Requires Either Costimulation With Stem Cell Factor or Increase of Receptor Expression That Can Be Replaced by Overexpression of Bcl-2

AbstractIn vitro proliferation of hematopoietic stem cells requires costimulation by multiple regulatory factors whereas expansion of lineage-committed progenitor cells generated by stem cells usually requires only a single factor. The distinct requirement of factors for proliferation coincides with the differential temporal expression of the subunits of cytokine receptors during early stem cell differentiation. In this study, we explored the underlying mechanism of the requirement of costimulation in a hematopoietic progenitor cell line TF-1. We found that granulocyte-macrophage colony-stimulating factor (GM-CSF) optimally activated proliferation of TF-1 cells regardless of the presence or absence of stem cell factor (SCF). However, interleukin-5 (IL-5) alone sustained survival of TF-1 cells and required costimulation of SCF for optimal proliferation. The synergistic effect of SCF was partly due to its anti-apoptosis activity. Overexpression of the IL-5 receptor α subunit (IL5Rα) in TF-1 cells by genetic selection or retroviral infection also resumed optimal proliferation due to correction of the defect in apoptosis suppression. Exogenous expression of an oncogenic anti-apoptosis protein, Bcl-2, conferred on TF-1 cells an IL-5–dependent phenotype. In summary, our data suggested SCF costimulation is only necessary when the expression level of IL5Rα is low and apoptosis suppression is defective in the signal transduction of IL-5. Expression of Bcl-2 proteins released the growth restriction of the progenitor cells and may be implicated in leukemia formation.

Prenatal diagnosis of a transient myeloproliferative disorder in trisomy 21

We report the prenatal diagnosis of a transient myeloproliferative disorder suggestive of leukaemia in a fetus with hepatosplenomegaly, hydrops and 47, XY, +21 karyotype. The initial fetal white blood cell count at 26 + 5 weeks' gestation was 190/nl with 70 per cent blast cells. Immunophenotyping of the large blasts revealed surface markers suggestive of an early stem cell differentiation arrest resulting in undifferentiated polyclonal myelopoiesis. The fetal heart tracing showed minimal beat-to-beat variability in the presence of high leukocyte counts. Serial fetal blood sampling showed decreasing blast cells in the peripheral blood and normalization of white blood cell counts. Although there was increasing hydrops, this period was marked by improvement of the fetal heart rate pattern. Finally the fetus developed pancytopenia with increasing hydrops, AV-valvular insufficiency and venous Doppler studies indicative of cardiac decompensation prior to intra-uterine death at 31 + 5 weeks' gestation. Post-mortem examination revealed marked liver and splenic necrosis without evidence of residual leukaemic infiltration in any organ. Fetal hydrops and hepatosplenomegaly may indicate an underlying haematopoietic disorder warranting further investigation. Furthermore, this case indicates that transient abnormal myelopoesis may result in a fulminant clinical picture much like true leukaemia. This may be due to increased vulnerability of the fetus or represent a disease mechanism unique to fetuses with chromosomal abnormalities.