Wood AJ et al. (2015) Dev Cell "A TAD Closer to Understanding Dosage Compensation."

Wood AJ, Bickmore WA

[Dev Cell, 2015]

Eukaryotic chromosomes are organized into topological domains, but how these are established and maintained is poorly understood. Writing in Nature, Crane et al. (2015) show that a specialized condensin complex enforces the domain boundaries along the C. elegans X chromosome to equalize transcription from the X between males and hermaphrodites.

Reinke V (2007) Nat Genet "Think globally, act locally."

Reinke V

[Nat Genet, 2007]

In the nematode Caenorhabditis elegans, dosage compensation is mediated by a subtle twofold downregulation of both X chromosomes. A new study provides a significant advance in our understanding of how the X is targeted for dosage compensation and how this global regulation is integrated with regulation of the expression of each gene.

Swain A et al. (1998) Nature "Developmental genetics. Too much sex is bad for males."

Lovell-Badge R, Swain A

[Nature, 1998]

Many species rely on chromosome-based systems-such as one X versus two X chromosomes-to trigger the differences between males and females. To do this they must find ways to count the sex chromosomes and to activate the process of dosage compensation, which corrects the imbalance of sex-linked genes. A paper by Carmi, Kopczynski and Meyer on page 168 of this issue brings us closer to understand chromosome counting in the nematode worm Caenorhabditis elegans. The authors have identified an X-linked gene that encodes a protein related to nuclear-hormone receptors. This protein, SEX-1, represses the transcription of xol-1, the pivotal gene involved in both dosage compensation and sex determination.

Carey JF et al. (2009) Curr Biol "Gene regulation: silencing complexes spread out."

Hagstrom KA, Carey JF

[Curr Biol, 2009]

Some protein complexes bind DNA elements and then spread to exert gene regulation over broad domains. The Caenorhabditis elegans dosage compensation complex is one example, and new studies have teased out rules for its recruitment and spreading over X chromosomes.

Ellis RE et al. (2013) Curr Biol "Sex determination: how worms count to two."

Ellis RE, Chen X

[Curr Biol, 2013]

A century ago, Bridges proposed that male genes on the autosomes and female genes on the X chromosome compete to determine sexual identity. New genetic and molecular studies establish Caenorhabditis elegans as the first animal known to use this mechanism.

Dawes HE et al. (1999) Science "Dosage compensation proteins targeted to X chromosomes by a determinant of hermaphrodite fate."

Nusbaum C, Meyer BJ, Dawes HE, Davis TL, Matsubara Lapidus D, Berlin DS

[Science, 1999]

In many organisms, master control genes coordinately regulate sex-specific aspects of development. SDC-2 was shown to induce hermaphrodite sexual differentiation and activate X chromosome dosage compensation in Caenorhabditis elegans. To control these distinct processes, SDC-2 acts as a strong gene-specific repressor and a weaker chromosome-wide repressor. To initiate hermaphrodite development, SDC-2 associates with the promoter of the male sex-determining gene her-1 to repress its transcription. To activate dosage compensation, SDC-2 triggers assembly of a specialized protein complex exclusively on hermaphrodite X chromosomes to reduce gene expression by half. SDC-2 can localize to X chromosomes without other components of the dosage compensation complex, suggesting that SDC-2 targets dosage compensation machinery to X chromosomes.AD - Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3204, USA.FAU - Dawes, H EAU - Dawes HEFAU - Berlin, D SAU - Berlin DSFAU - Lapidus, D MAU - Lapidus DMFAU - Nusbaum, CAU - Nusbaum CFAU - Davis, T LAU - Davis TLFAU - Meyer, B JAU - Meyer BJLA - engSI - GENBANK/AF111934ID - GM30702/GM/NIGMSID - T32 GM07127/GM/NIGMSPT - Journal ArticleCY - UNITED STATESTA - ScienceJID - 0404511RN - 0 (Helminth Proteins)RN - 0 (Repressor Proteins)RN - 0 (Sdc-3 protein)RN - 0 (her-1 protein)SB - IM