Caenorhabditis elegans unc-49 locus encodes multiple subunits of a heteromultimeric GABA receptor

Journal ArticleIonotropic GABA receptors generally require the products of three subunit genes. By contrast, the GABA receptor needed for locomotion in Caenorhabditis elegans requires only the unc-49 gene. We cloned unc-49 and demonstrated that it possesses an unusual overlapping gene structure

The Magnitude of Global Marine Species Diversity

Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century

“Getting Under the Hood” of Neuronal Signaling in

Caenorhabditis elegans is a powerful model to study the neural and biochemical basis of behavior. It combines a small, completely mapped nervous system, powerful genetic tools, and a transparent cuticle, allowing Ca ++ imaging without the need for dissection. However, these approaches remain one step removed from direct pharmacological and physiological characterization of individual neurons. Much can still be learned by “getting under the hood” or breaching the cuticle and directly studying the neurons. For example, we recently combined electrophysiology, Ca ++ imaging, and pharmacological analysis on partially dissected ASH nociceptors showing that serotonin (5-HT) potentiates depolarization by inhibiting Ca ++ influx. This study challenges the tacit assumption that Ca ++ transient amplitudes and depolarization strength are positively correlated and has validated a new paradigm for interpreting Ca ++ signals. Bypassing the cuticle was critical for the success of these experiments, not only for performing electrical recordings but also for the acute and reversible application of drugs. By contrast, drug soaking or mutating genes can produce long-term effects and compensatory changes, potentially confounding interpretations significantly. Therefore, direct studies of the physiological response of individual neurons should remain a critical objective, to provide key molecular insights complementing global Ca ++ imaging neural network studies

The composition of the GABA receptor at the Caenorhabditis elegans neuromuscular junction

1. The unc-49 gene of the nematode Caenorhabditis elegans encodes three γ-aminobutyric acid type A (GABA(A)) receptor subunits. Two of these, UNC-49B and UNC-49C, are expressed at high abundance and co-localize at the neuromuscular junction. 2. The UNC-49B subunit is sufficient to form a GABA(A) receptor in vitro and in vivo. Furthermore, all loss-of-function unc-49 alleles lack functional UNC-49B. No mutations specifically inactivate UNC-49C. Thus, UNC-49C appears to be dispensable for receptor function; however, UNC-49C has been conserved among different nematode species, suggesting it plays a necessary role. 3. To ascertain whether UNC-49C is part of the GABA(A) receptor in vivo, we performed patch-clamp electrophysiology on C. elegans muscle cells. Sensitivity to GABA, and to the antagonists picrotoxin and pregnenolone sulfate, matched the UNC-49B/C heteromer rather than the UNC-49B homomer, for both exogenous and synaptically-released GABA. 4. The synaptic localization of UNC-49C requires the presence of UNC-49B, indicative of a physical association between the two subunits in vivo. Thus, the in vivo receptor is an UNC-49B/C heteromer. 5. UNC-49C plays a negative modulatory role. Using the rapid ligand-exchange technique in vitro, we determined that UNC-49C causes accelerated receptor desensitization. Previously, UNC-49C was shown to reduce single-channel conductance in UNC-49B/C heteromers. Thus, the function of UNC-49B is to provide GABA responsiveness and localization to synapses, while the function of UNC-49C is to negatively modulate receptor function and precisely shape inhibitory postsynaptic currents

Staphylococcus aureus Genotyping Using Novel Real-Time PCR Formats

One approach to microbial genotyping is to make use of sets of single-nucleotide polymorphisms (SNPs) in combination with binary markers. Here we report the modification and automation of a SNP-plus-binary-marker-based approach to the genotyping of Staphylococcus aureus and its application to 391 S. aureus isolates from southeast Queensland, Australia. The SNPs used were arcC210, tpi243, arcC162, gmk318, pta294, tpi36, tpi241, and pta383. These provide a Simpson's index of diversity (D) of 0.95 with respect to the S. aureus multilocus sequence typing database and define 61 genotypes and the major clonal complexes. The binary markers used were pvl, cna, sdrE, pT181, and pUB110. Two novel real-time PCR formats for interrogating these markers were compared. One of these makes use of “light upon extension” (LUX) primers and biplexed reactions, while the other is a streamlined modification of kinetic PCR using SYBR green. The latter format proved to be more robust. In addition, automated methods for DNA template preparation, reaction setup, and data analysis were developed. A single SNP-based method for ST-93 (Queensland clone) identification was also devised. The genotyping revealed the numerical importance of the “South West Pacific” and “Queensland” community-acquired methicillin-resistant S. aureus (MRSA) clones and the clonal complex 239 “Aus-1/Aus-2” hospital-associated MRSA. There was a strong association between the community-acquired clones and pvl