We report here genome sequences and comparative analyses of three closely related parasitoid wasps: Nasonia vitripennis, N. giraulti, and N. longicornis. Parasitoids are important regulators of arthropod populations, including major agricultural pests and disease vectors, and Nasonia is an emerging genetic model, particularly for evolutionary and developmental genetics. Key findings include the identification of a functional DNA methylation tool kit; hymenopteran-specific genes including diverse venoms; lateral gene transfers among Pox viruses, Wolbachia, and Nasonia; and the rapid evolution of genes involved in nuclear-mitochondrial interactions that are implicated in speciation. Newly developed genome resources advance Nasonia for genetic research, accelerate mapping and cloning of quantitative trait loci, and will ultimately provide tools and knowledge for further increasing the utility of parasitoids as pest insect-control agents.

Regulation of cell volume is essential for every cell and is accomplished by the regulated loss or gain of intracellular ions or other osmolytes. Regulatory volume decrease often involves the parallel activation of potassium and chloride channels. Overexpression of P-glycoprotein leads to volume-activated Cl- currents but its physiological importance for volume regulation is unclear. CIC-2 is a ubiquitously expressed Cl- channel activatable by non-physiologically strong hyperpolarization. We now show that CIC-2 can be activated by extracellular hypotonicity, which suggests that it has a widespread role in volume regulation. Domains necessary for activation by both voltage and volume are localized to the amino terminus. Mutations in an 'essential' region lead to constitutively open channels unresponsive to medium tonicity, whereas deletions in a 'modulating' region produce partially opened channels responsive to both hypo- and hypertonicity. These domains can be transplanted to different regions of the protein without loss of function.

The mechanisms that establish behavioral, cognitive, and neuroanatomical asymmetries are poorly understood. In this study, we analyze the events that regulate development of asymmetric nuclei in the dorsal forebrain. The unilateral parapineal organ has a bilateral origin, and some parapineal precursors migrate across the midline to form this left-sided nucleus. The parapineal subsequently innervates the left habenula, which derives from ventral epithalamic cells adjacent to the parapineal precursors. Ablation of cells in the left ventral epithalamus can reverse laterality in wild-type embryos and impose the direction of CNS asymmetry in embryos in which laterality is usually randomized. Unilateral modulation of Nodal activity by Lefty1 can also impose the direction of CNS laterality in embryos with bilateral expression of Nodal pathway genes. From these data, we propose that laterality is determined by a competitive interaction between the left and right epithalamus and that Nodal signaling biases the outcome of this competition.

belong to the Deg/ENaC super family of ion channels (1). Members of this super gene family form Na ϩ -selective ion channels (P Na /P K , 8 -100) that can be blocked by amiloride (IC 50 , 0.2-20 M). All family members show some common hallmarks including two hydrophobic domains, short intracellular N and C termini, and a large extracellular loop containing conserved cysteines. Channels of this gene family probably form tetramers (2, 3).To date, six different members of the ASIC subfamily have been cloned (ASIC1a, ASIC1b, ASIC2a, ASIC2b, ASIC3, and ASIC4), which are encoded by four genes. ASIC1a and ASIC1b are alternative splice products of the ASIC1 gene (4, 5). Splicing exchanges approximately the first third of the protein, including the first transmembrane domain and the proximal part of the large ectodomain. In contrast, the C-terminal twothirds are identical. We will use the term ASIC1 when we do not refer to a specific splice variant. All ASICs with the exception of ASIC4 (6) are expressed in sensory neurons of the dorsal root ganglion. Proposed functions in sensory neurons include peripheral pain perception (1,7,8) and mechanotransduction (9, 10). Although some evidence suggests that some of the native H ϩ -gated currents in sensory neurons are mediated by heteromeric ASICs (11, 12), part of these currents are probably mediated by homomeric ASIC1 and ASIC3 (8, 11).ASIC1a is expressed in sensory neurons and throughout the brain (13), whereas ASIC1b is specifically expressed in sensory neurons (5). Both subunits are Na ϩ -selective (P Na /P K Ϸ 10 -15), and only ASIC1a has a low Ca 2ϩ permeability (P Na /P Ca Ϸ 15) (4). ASIC1a and ASIC1b form rapidly activating and completely desensitizing ion channels ( act , ϳ10 msec; desens , ϳ1 s) (4). The expression of ASIC1 in small diameter, capsaicinsensitive sensory neurons (5, 11, 14, 15) has led to the proposal that ASIC1a mediates excitation during tissue acidosis, which accompanies inflammation and ischemia. However, complete desensitization of ASIC1 makes it difficult to imagine how this channel can sense H ϩ signals during inflammation and ischemia when the pH persistently falls.Here we show that both ASIC1a and ASIC1b undergo steady-state inactivation. The steady-state inactivation curve for ASIC1b is shifted by 0.25 pH units to more acidic values as compared with ASIC1a, showing that ASIC1b can operate at a more acidic resting pH. pH activation is shifted by 0.7 pH units. Differences in the sensitivity of activation and inactivation by protons are intimately linked, as both are controlled by only two amino acids in the ectodomain. These two amino acids are exchanged by alternative splicing. Moreover, we show that Ca 2ϩ , Mg 2ϩ , and spermine, when applied during the steadystate, shift the steady-state inactivation curves of both ASIC1a and ASIC1b. This leads to a potentiation of the current. Modulation by di-and polyvalent cations may be a means to adapt ASIC1 activity to changes in the extracellular concentration of these ions. Our results show that ASIC1b...

Acid-sensing ion channels (ASICs) are activated by extracellular protons and are involved in neurotransmission in the central nervous system, in pain perception, as well as in mechanotransduction. Six different ASIC subunits have been cloned to date, which are encoded by four genes (ASIC1-ASIC4). Proton-gated currents have been described in isolated neurons from sensory ganglia as well as from central nervous system. However, it is largely unclear which of the cloned ASIC subunits underlie these native proton-gated currents. Recently, a splice variant, ASIC-␤, has been described for ASIC1a. In this variant about one-third of the protein is exchanged at the N terminus. Here we show that ASIC-␤ has a longer N terminus than previously reported, extending the sequence divergence between ASIC1a and this new variant (ASIC1b). We investigated in detail kinetic and selectivity properties of ASIC1b in comparison to ASIC1a. Kinetics is similar for ASIC1b and ASIC1a. Ca 2؉ permeability of ASIC1a is low, whereas ASIC1b is impermeable to Ca 2؉ . Currents through ASIC1a resemble currents, which have been described in sensory and central neurons, whereas the significance of ASIC1b remains to be established. Moreover, we show that a pre-transmembrane 1 domain controls the permeability to divalent cations in ASIC1, contributing to our understanding of the pore structure of these channels.