Perennial water ice identified in the south polar cap of Mars

The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2 km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap.     

C. elegans ORFeome version 1.1: experimental verification of the genome annotation and resource for proteome-scale protein expression

To verify the genome annotation and to create a resource to functionally characterize the proteome, we attempted to Gateway-clone all predicted protein-encoding open reading frames (ORFs), or the 'ORFeome,' of Caenorhabditis elegans. We successfully cloned approximately 12,000 ORFs (ORFeome 1.1), of which roughly 4,000 correspond to genes that are untouched by any cDNA or expressed-sequence tag (EST). More than 50% of predicted genes needed corrections in their intron-exon structures. Notably, approximately 11,000 C. elegans proteins can now be expressed under many conditions and characterized using various high-throughput strategies, including large-scale interactome mapping. We suggest that similar ORFeome projects will be valuable for other organisms, including humans.     

Genetic mechanisms and constraints governing the evolution of correlated traits in drosophilid flies

Some morphological traits differ greatly between related species, but it is not clear whether diversity evolves through changes in the same genes and whether similar, independent (that is, convergent) changes occur by the same mechanism. Pigmentation in fruitflies presents an attractive opportunity to explore these issues because pigmentation patterns are diverse, similar patterns have arisen in independent clades, and numerous genes governing their formation have been identified in Drosophila melanogaster. Here we show that both evolutionary diversification and convergence can be due to evolution at the same locus, by comparing abdominal pigmentation and trichome patterns and the expression of Bric-à-brac2 (Bab2), which regulates both traits in D. melanogaster, in 13 species representing the major clades of the subfamily Drosophilinae. Modifications of Bab2 expression are frequently correlated with diverse pigmentation and trichome patterns that evolved independently in multiple lineages. In a few species, Bab2 expression is not correlated with changes in pigmentation but is correlated with a conserved pattern of trichomes, indicating that this locus can be circumvented to evolve new patterns when a correlated trait is under different constraints.     

Network modeling links breast cancer susceptibility and centrosome dysfunction

Many cancer-associated genes remain to be identified to clarify the underlying molecular mechanisms of cancer susceptibility and progression. Better understanding is also required of how mutations in cancer genes affect their products in the context of complex cellular networks. Here we have used a network modeling strategy to identify genes potentially associated with higher risk of breast cancer. Starting with four known genes encoding tumor suppressors of breast cancer, we combined gene expression profiling with functional genomic and proteomic (or 'omic') data from various species to generate a network containing 118 genes linked by 866 potential functional associations. This network shows higher connectivity than expected by chance, suggesting that its components function in biologically related pathways. One of the components of the network is HMMR, encoding a centrosome subunit, for which we demonstrate previously unknown functional associations with the breast cancer-associated gene BRCA1. Two case-control studies of incident breast cancer indicate that the HMMR locus is associated with higher risk of breast cancer in humans. Our network modeling strategy should be useful for the discovery of additional cancer-associated genes.     

Mutations in LRP2, which encodes the multiligand receptor megalin, cause Donnai-Barrow and facio-oculo-acoustico-renal syndromes

Donnai-Barrow syndrome is associated with agenesis of the corpus callosum, congenital diaphragmatic hernia, facial dysmorphology, ocular anomalies, sensorineural hearing loss and developmental delay. By studying multiplex families, we mapped this disorder to chromosome 2q23.3-31.1 and identified LRP2 mutations in six families with Donnai-Barrow syndrome and one family with facio-oculo-acoustico-renal syndrome. LRP2 encodes megalin, a multiligand uptake receptor that regulates levels of diverse circulating compounds. This work implicates a pathway with potential pharmacological therapeutic targets.     

Cycling or not cycling: cell cycle regulatory molecules and adult neurogenesis

The adult brain most probably reaches its highest degree of plasticity with the lifelong generation and integration of new neurons in the hippocampus and olfactory system. Neural precursor cells (NPCs) residing both in the subgranular zone of the dentate gyrus and in the subventricular zone of the lateral ventricles continuously generate neurons that populate the dentate gyrus and the olfactory bulb, respectively. The regulation of NPC proliferation in the adult brain has been widely investigated in the past few years. Yet, the intrinsic cell cycle machinery underlying NPC proliferation remains largely unexplored. In this review, we discuss the cell cycle components that are involved in the regulation of NPC proliferation in both neurogenic areas of the adult brain.