ABSTRACT
Temporal colinearity in mouse HoxD is dependent on repressive activity of sequences within the 5' end of the complex. We show that a 5-kb DNA fragment from this region represses transgenes when combined in mouse as well as in Drosophila melanogaster. Moreover, repressive activity in Drosophila depends on some members of the Polycomb-group (PcG) genes, for example, extra sex combs. We also showed direct association of these factors with the repressive fragment, both in transgenic flies and in the context of the native mouse HoxD complex. These results suggest that the global repressive region of the HoxD complex functions in two very different species and that some PcG genes are involved in establishing the early repressive state of the HoxD complex, thus contributing to temporal colinearity.
Subject(s)
Body Patterning/genetics , Gene Expression Regulation, Developmental , Genes, Homeobox , Repressor Proteins/genetics , Repressor Proteins/physiology , Animals , Animals, Genetically Modified , Drosophila/embryology , Drosophila/genetics , Embryo, Mammalian , Embryo, Nonmammalian , Mice , Mice, Inbred C57BL , NIH 3T3 Cells , Polycomb Repressive Complex 2 , Polycomb-Group Proteins , Regulatory Sequences, Nucleic Acid/genetics , Repressor Proteins/metabolism , TransgenesABSTRACT
Expression of Hox genes is tightly regulated in spatial and temporal domains. Evx2 is located next to Hoxd13 within 8 kb on the opposite DNA strand. Early in development, the pattern of Hoxd13 expression resembles that of Evx2 in limb and genital buds. After 10 dpc, however, Evx2 begins to be expressed in CNS as well. We analyzed the region responsible for these differences using ES cell techniques, and found that the intergenic region between Evx2 and Hoxd13 behaves as a boundary element that functions differentially in space and time, specifically in the development of limbs, genital bud, and brain. This boundary element comprises a large sequence spanning several kilobases that can be divided into at least two units: a constitutive boundary element, which blocks transcription regulatory influences from the chromosomal environment, and a regulatory element, which controls the function of the constitutive boundary element in time and space.
Subject(s)
DNA, Intergenic , Enhancer Elements, Genetic , Gene Expression Regulation, Developmental , Homeodomain Proteins/genetics , Promoter Regions, Genetic , Transcription Factors/genetics , Animals , Chickens , DNA Methylation , Embryo, Mammalian/anatomy & histology , Embryo, Mammalian/physiology , Female , Gene Expression Profiling , Genotype , Homeodomain Proteins/metabolism , Mice , Mice, Transgenic , NIH 3T3 Cells , Pregnancy , Transcription Factors/metabolism , TransgenesABSTRACT
A clear understanding of cell fate regulation during differentiation is key in successfully using stem cells for therapeutic applications. Here, we report that mild electrical stimulation strongly influences embryonic stem cells to assume a neuronal fate. Although the resulting neuronal cells showed no sign of specific terminal differentiation in culture, they showed potential to differentiate into various types of neurons in vivo, and, in adult mice, contributed to the injured spinal cord as neuronal cells. Induction of calcium ion influx is significant in this differentiation system. This phenomenon opens up possibilities for understanding novel mechanisms underlying cellular differentiation and early development, and, perhaps more importantly, suggests possibilities for treatments in medical contexts.
