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Presents research which showed that the T-box genes Tbx4 and Tbx5 are regulators of limb outgrowth in chicks. Genes associated with fibroblast growth factor (FGF), bone morphogenic protein (BMP), and Wnt; Role of Pitx1 genes in embryonic development; Control of limb identity by Tbx4 and Tbx5.

Discusses the cloning of a chick gene, Radical fringe (R-fng) that is homologous to the Drosophila fng gene. The demonstration that R-fng plays an important role in vertebrate limb outgrowth; The direction of formation and positioning at the dorsoventral limb boundary; Evolutionary conservation of developmental programs.

Reports on distinct Wnt pathways regulating apical ectodermal ridge (AER) formation and dorsoventral polarity in the chick limb bud. The ability of the genes Beta-catenin and Lef1 to mimic the effect of Wnt3a functions in AER formation through the Beta-catenin/LEF1 pathway.

CpG islands (CGIs) are primarily promoter-associated genomic regions and are mostly unmethylated within highly methylated mammalian genomes. The mechanisms by which CGIs are protected from de novo methylation remain elusive. Here we show that insertion of CpG-free DNA into targeted CGIs induces de novo methylation of the entire CGI in human pluripotent stem cells (PSCs). The methylation status is stably maintained even after CpG-free DNA removal, extensive passaging, and differentiation. By targeting the DNA mismatch repair gene MLH1 CGI, we could generate a PSC model of a cancer-related epimutation. Furthermore, we successfully corrected aberrant imprinting in induced PSCs derived from an Angelman syndrome patient. Our results provide insights into how CpG-free DNA induces de novo CGI methylation and broaden the application of targeted epigenome editing for a better understanding of human development and disease. [ABSTRACT FROM AUTHOR]

Nodal, a member of the TGF-β superfamily, plays an important role in vertebrate and invertebrate early development. The biochemical study of Nodal and its signaling pathway has been a challenge, mainly because of difficulties in producing the protein in sufficient quantities. We have developed a library of stable, chemically refoldable Nodal/BMP2 chimeric ligands (NB2 library). Three chimeras, named NB250, NB260, and NB264, show Nodal-like signaling properties including dependence on the co-receptor Cripto and activation of the Smad2 pathway. NB250, like Nodal, alters heart looping during the establishment of embryonic left-right asymmetry, and both NB250 and NB260, as well as Nodal, induce chondrogenic differentiation of human adipose-derived stem cells. This Nodal-induced differentiation is shown to be more efficient than BPM2-induced differentiation. Interestingly, the crystal structure of NB250 shows a backbone scaffold similar to that of BMP2. Our results show that these chimeric ligands may have therapeutic implications in cartilage injuries. [ABSTRACT FROM AUTHOR]

Summary: The IκB kinase (IKK) activity is critical for processing IκB inhibitory proteins and activating the NF-κB signaling, which is involved in a series of physiological and developmental steps in vertebrates [1–4]. The IKK activity resides in two catalytic subunits, IKK1 and IKK2, and two regulatory subunits, NEMO and ELKS [5–8]. IKK2 is the major cytokine-responsive IκB kinase [9–11] because depletion of IKK1 does not interfere with the IKK activity [12–14]. In fact, IKK1−/− mice display morphological abnormalities that are independent of its kinase activity and NF-κB activation [12–14]. Hence, using zebrafish (Danio rerio) as a model, we examined the evolutionary role of IKK1 in modulating NF-κB. Ikk1−/− zebrafish embryos present head and tail malformations and, surprisingly, show upregulation of NF-κB-responsive genes and increased NF-κB-dependent apoptosis. Overexpression of ikk1 leads to midline structure defects that resemble NF-κB blockage in vivo [1]. Zebrafish Ikk1 forms complexes with NEMO that represses NF-κB in vertebrate cells. Indeed, truncation of its NEMO binding domain (NBD) restores NF-κB-dependent transcriptional activity and, consequently, the ikk1-overexpressing phenotype. Here, we report that Ikk1 negatively regulates NF-κB by sequestering NEMO from active IKK complexes, indicating that IKK1 can function as a repressor of NF-κB. [Copyright &y& Elsevier]

Summary Aging is the major risk factor for many human diseases. In vitro studies have demonstrated that cellular reprogramming to pluripotency reverses cellular age, but alteration of the aging process through reprogramming has not been directly demonstrated in vivo. Here, we report that partial reprogramming by short-term cyclic expression of Oct4 , Sox2 , Klf4 , and c-Myc (OSKM) ameliorates cellular and physiological hallmarks of aging and prolongs lifespan in a mouse model of premature aging. Similarly, expression of OSKM in vivo improves recovery from metabolic disease and muscle injury in older wild-type mice. The amelioration of age-associated phenotypes by epigenetic remodeling during cellular reprogramming highlights the role of epigenetic dysregulation as a driver of mammalian aging. Establishing in vivo platforms to modulate age-associated epigenetic marks may provide further insights into the biology of aging. [ABSTRACT FROM AUTHOR]