U.S. Department of Health and Human Services

Laboratory of Cellular and Developmental Biology

Jurrien Dean, M.D., Chief

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Photo showing polytene chromosomes of Drosophila salivary glandsHighly replicated polytene chromosomes of the Drosophila salivary glands stained with DAPI (blue) and antibodies directed against gypsy insulator proteins Su(Hw) (green) and Mod(mdg4)2.2 (red).Enlarge
Photo showing epifluorescent whole-mount staining of third instar larval imaginal discEpifluorescent whole-mount staining of third instar larval imaginal disc to visualize insulator bodies using anti-CP190 antibodies (green) and DAPI (blue).Enlarge
A working model of the relationship between chromatin looping and transcription activation in the β-globin locusIn erythroid cells, the β-globin LCR and gene are occupied by the Ldb1/LMO2/TAL1/GATA-1 complex, and Ldb1 dimerization is the basis of loop formation (Song, et al., Molecular Cell, 2007; Deng et al., Cell, 2012). The locus moves from the nuclear periphery to the interior for robust transcription of the gene in transcription factories (Song et al., Blood, 2010). (A) Looping could be promoted by pol II density and by transcription in a factory. (B) Alternatively, looping might be facilitated by a cell-type specific chromosomal organization that is stabilized by Ldb1 dimerization (reviewed in Krivega and Dean, Current Opinion in Genetics & Development, 2012). Mutational analysis of Ldb1 favors the latter model (I. Krivega and A. Dean, unpublished).Enlarge
Early Mouse DevelopmentMaternal RNA and proteins accumulate during oocyte growth. The zona pellucida that surrounds ovulated eggs (green) is modified following fertilization (red) to prevent polyspermy. Activation of the embryonic genome occurs in the 2-cell embryo and, following the third cell division, embryos compact to form morulae and then blastocysts that implant on the wall of the uterus.Enlarge
Mouse FertilizationFertilization occurs in the ampulla of the oviduct where the fertilizing sperm encounters an ovulated egg. After initial binding to the zona pellucida, the sperm penetrates through the zona matrix to fuse with the egg plasma membrane. The subsequent cortical granule reaction leads to a potent block to polyspermy.Enlarge