On-microscope staging of live cells reveals changes in the dynamics of transcriptional bursting during differentiation.

Determining the mechanisms by which genes are switched on and off during development is a key aim of current biomedical research. Gene transcription has been widely observed to occur in a discontinuous fashion, with short bursts of activity interspersed with periods of inactivity. It is currently not known if or how this dynamic behaviour changes as mammalian cells differentiate.

Identification of the transcription factor MAZ as a regulator of erythropoiesis.

Erythropoiesis requires a combination of ubiquitous and tissue-specific transcription factors (TFs). Here, through DNA affinity purification followed by mass spectrometry, we have identified the widely expressed protein MAZ (Myc-associated zinc finger) as a TF that binds to the promoter of the erythroid-specific human α-globin gene. Genome-wide mapping in primary human erythroid cells revealed that MAZ also occupies active promoters as well as GATA1-bound enhancer elements of key erythroid genes.

Reactivation of a developmentally silenced embryonic globin gene.

The α- and β-globin loci harbor developmentally expressed genes, which are silenced throughout post-natal life. Reactivation of these genes may offer therapeutic approaches for the hemoglobinopathies, the most common single gene disorders. Here, we address mechanisms regulating the embryonically expressed α-like globin, termed ζ-globin.

Identification and Single-Cell Functional Characterization of an Endodermally Biased Pluripotent Substate in Human Embryonic Stem Cells.

Human embryonic stem cells (hESCs) display substantial heterogeneity in gene expression, implying the existence of discrete substates within the stem cell compartment. To determine whether these substates impact fate decisions of hESCs we used a GFP reporter line to investigate the properties of fractions of putative undifferentiated cells defined by their differential expression of the endoderm transcription factor, GATA6, together with the hESC surface marker, SSEA3. By single-cell cloning, we confirmed that substates characterized by expression of GATA6 and SSEA3 include pluripotent stem cells capable of long-term self-renewal.

Phenotypic and molecular characterization of a serum-free miniature erythroid differentiation system suitable for high-throughput screening and single-cell assays.

In vitro erythroid differentiation systems are used to study the mechanisms underlying normal and abnormal erythropoiesis and to test the effects of various extracellular factors on erythropoiesis. The use of serum or conditioned medium in liquid cultures and the seeding of cultures with heterogeneous peripheral blood mononuclear cells confound the reproducibility of these systems. Newer erythroid differentiation culture systems have overcome some of these limitations by using a fully defined, serum-free medium and initiating cultures using purified CD34 cells.