Regulation of the X Chromosomes in Caenorhabditis elegans

Dosage compensation, which regulates the expression of genes residing on the sex chromosomes, has provided valuable insights into chromatin-based mechanisms of gene regulation.The nematode Caenorhabditis elegans has adopted various strategies to down-regulate and even nearly silence the X chromosomes.This article discusses the different chromatin-based strategies used in somatic tissues and in the germline to modulate gene expression from the C. elegans X chromosomes and compares these strategies to those used by other organisms to cope with similar X-chromosome dosage differences.Outline 1 Sex chromosome imbalance in C. elegans 2 Assessing the X:A ratio 3 The dosage compensation complex (DCC) resembles the condensin complex 4 Recruitment and spreading of the DCC 5 Effects of the DCC: Down-regulation of X-linked genes and the autosomal gene her-1 6 Compensatory up-regulation of X-linked genes 7 Germline development and global repression of the X chromosomes 8 Meiotic silencing of the single X in males 9 Regulation of X-chromosome repression by the MES histone modifiers 10 Paternal X inactivation in early embryos 11