Localization of the human GM-CSF receptor gene to the X-Y pseudoautosomal region

Mammalian sex chromosomes share a small terminal region of homologous DNA sequences, which pair and recombine during male meiosis. Alleles in this region can be exchanged between X and Y chromosomes and are therefore inherited as if autosomal. Genes from this so-called pseudoautosomal region (PAR) are present in two doses in both males and females, and escape inactivation of the X chromosome in females. Indirect evidence suggests that there must be several pseudoautosomal genes, and several candidates have been proposed. Until now, the only gene that has been unequivocally located in the PAR is MIC2, which encodes a cell-surface antigen of unknown function. We now report the localization of a gene of known function to this region--the gene for the receptor of the haemopoietic regulator, granulocyte-macrophage colony stimulating factor. The chromosomal localization of this gene may be important in understanding the generation of M2 acute myeloid leukaemia.     

Increasing dominance of large lianas in Amazonian forests

Ecological orthodoxy suggests that old-growth forests should be close to dynamic equilibrium, but this view has been challenged by recent findings that neotropical forests are accumulating carbon and biomass, possibly in response to the increasing atmospheric concentrations of carbon dioxide. However, it is unclear whether the recent increase in tree biomass has been accompanied by a shift in community composition. Such changes could reduce or enhance the carbon storage potential of old-growth forests in the long term. Here we show that non-fragmented Amazon forests are experiencing a concerted increase in the density, basal area and mean size of woody climbing plants (lianas). Over the last two decades of the twentieth century the dominance of large lianas relative to trees has increased by 1.7-4.6% a year. Lianas enhance tree mortality and suppress tree growth, so their rapid increase implies that the tropical terrestrial carbon sink may shut down sooner than current models suggest. Predictions of future tropical carbon fluxes will need to account for the changing composition and dynamics of supposedly undisturbed forests.     

Annexin II light chain regulates sensory neuron-specific sodium channel expression

The tetrodotoxin-resistant sodium channel Na(V)1.8/SNS is expressed exclusively in sensory neurons and appears to have an important role in pain pathways. Unlike other sodium channels, Na(V)1.8 is poorly expressed in cell lines even in the presence of accessory beta-subunits. Here we identify annexin II light chain (p11) as a regulatory factor that facilitates the expression of Na(V)1.8. p11 binds directly to the amino terminus of Na(V)1.8 and promotes the translocation of Na(V)1.8 to the plasma membrane, producing functional channels. The endogenous Na(V)1.8 current in sensory neurons is inhibited by antisense downregulation of p11 expression. Because direct association with p11 is required for functional expression of Na(V)1.8, disrupting this interaction may be a useful new approach to downregulating Na(V)1.8 and effecting analgesia.