The nematode Caenorhabditis elegans is a powerful model system to study contemporary biological problems. This system would be even more useful if we had mutations in all the genes of this multicellular metazoan. The combined efforts of the C. elegans Deletion Mutant Consortium and individuals within the worm community are moving us ever closer to this goal. At present, of the 20,377 protein-coding genes in this organism, 6764 genes with associated molecular lesions are either deletions or null mutations (WormBase WS220). Our three laboratories have contributed the majority of mutated genes, 6841 mutations in 6013 genes. The principal method we used to detect deletion mutations in the nematode utilizes polymerase chain reaction (PCR). More recently, we have used array comparative genome hybridization (aCGH) to detect deletions across the entire coding part of the genome and massively parallel short-read sequencing to identify nonsense, splicing, and missense defects in open reading frames. As deletion strains can be frozen and then thawed when needed, these strains will be an enduring community resource. Our combined molecular screening strategies have improved the overall throughput of our gene-knockout facilities and have broadened the types of mutations that we and others can identify. These multiple strategies should enable us to eventually identify a mutation in every gene in this multicellular organism. This knowledge will usher in a new age of metazoan genetics in which the contribution to any biological process can be assessed for all genes.

In multicellular organisms, the surface barrier is essential for maintaining the internal environment. In mammals, the barrier is the stratum corneum. Fatty acid transport protein 4 (FATP4) is a key factor involved in forming the stratum corneum barrier. Mice lacking Fatp4 display early neonatal lethality with features such as tight, thick, and shiny skin, and a defective skin barrier. These symptoms are strikingly similar to those of a human skin disease called restrictive dermopathy. FATP4 is a member of the FATP family that possesses acyl-CoA synthetase activity for very long chain fatty acids. How Fatp4 contributes to skin barrier function, however, remains to be elucidated. In the present study, we characterized two Caenorhabditis elegans genes, acs-20 and acs-22, that are homologous to mammalian FATPs. Animals with mutant acs-20 exhibited defects in the cuticle barrier, which normally prevents the penetration of small molecules. acs-20 mutant animals also exhibited abnormalities in the cuticle structure, but not in epidermal cell fate or cell integrity. The acs-22 mutants rarely showed a barrier defect, whereas acs-20;acs-22 double mutants had severely disrupted barrier function. Moreover, the barrier defects of acs-20 and acs-20;acs-22 mutants were rescued by acs-20, acs-22, or human Fatp4 transgenes. We further demonstrated that the incorporation of exogenous very long chain fatty acids into sphingomyelin was reduced in acs-20 and acs-22 mutants. These findings indicate that C. elegans Fatp4 homologue(s) have a crucial role in the surface barrier function and this model might be useful for studying the fundamental molecular mechanisms underlying human skin barrier and relevant diseases.

In eukaryotes, different subcellular organelles have distinct cholesterol concentrations, which is thought to be critical for biological functions. Oxysterol-binding protein-related proteins (ORPs) have been assumed to mediate nonvesicular cholesterol trafficking in cells; however, their in vivo functions and therefore the biological significance of cholesterol in each organelle are not fully understood. Here, by generating deletion mutants of ORPs in Caenorhabditis elegans, we show that ORPs are required for the formation and function of multivesicular bodies (MVBs). In an RNAi enhancer screen using obr quadruple mutants (obr-1; -2; -3; -4), we found that MVB–related genes show strong genetic interactions with the obr genes. In obr quadruple mutants, late endosomes/lysosomes are enlarged and membrane protein degradation is retarded, although endocytosed soluble proteins are normally delivered to lysosomes and degraded. We also found that the cholesterol content of late endosomes/lysosomes is reduced in the mutants. In wild-type worms, cholesterol restriction induces the formation of enlarged late endosomes/lysosomes, as observed in obr quadruple mutants, and increases embryonic lethality upon knockdown of MVB–related genes. Finally, we show that knockdown of ORP1L, a mammalian ORP family member, induces the formation of enlarged MVBs in HeLa cells. Our in vivo findings suggest that the proper cholesterol level of late endosomes/lysosomes generated by ORPs is required for normal MVB formation and MVB–mediated membrane protein degradation.

Background: Transgenic strains of Caenorhabditis elegans are typically generated by injecting DNA into the germline to form multi-copy extrachromosomal arrays. These transgenes are semi-stable and their expression is silenced in the germline. Mos1 transposon or microparticle bombardment methods have been developed to create single-or low-copy chromosomal integrated lines. Here we report an alternative method using ultraviolet trimethylpsoralen (UV/TMP) to generate single/low-copy gene integrations. Results: We successfully integrated low-copy transgenes from extrachromosomal arrays using positive selection based on temperature sensitivity with a vps-45 rescue fragment and negative selection based on benzimidazole sensitivity with a ben-1 rescue fragment. We confirmed that the integrants express transgenes in the germline. Quantitative PCR revealed that strains generated by this method contain single-or low-copy transgenes. Moreover, positive selection marker genes flanked by LoxP sites were excised by Cre recombinase mRNA microinjection, demonstrating Cre-mediated chromosomal excision for the first time in C. elegans. Conclusion: Our UV/TMP integration method, based on familiar extrachromosomal transgenics, provides a useful approach for generating single/low-copy gene integrations.

(58,61). Its concentration in the blood of silkworms was reported to increase during particular stages of metamorphosis, although the physiological role of D-Ser in metamorphosis remains unclear (11). It is also present in the mammalian forebrain, where it persists at high concentrations throughout the life of the animal. DSer is now considered a neuromodulator that binds to the glycinebinding site of the N-methyl-D-Asp (NMDA) receptor, a subtype of the L-glutamate (L-Glu) receptor, and potentiates glutamatergic neurotransmission in the central nervous system (51,60,68). In fact, astroglia-derived D-Ser has been shown to regulate NMDA receptor-dependent long-term potentiation and/or long-term depression, which are basic processes of learning and memory, in the hypothalamic and hippocampal excitatory synapses (25,54). In addition, D-Ser is also found in the cerebellum during the early postnatal period, and it was recently reported that D-Ser derived from the Bergmann glia serves as an endogenous ligand for the ␦2 L-Glu receptor to regulate long-term depression at synapses between parallel fibers and Purkinje cells in the immature cerebellum but not the mature one (31). These lines of evidence suggest the physiological significance of D-Ser in the regulation of higher brain functions through the L-Glu receptors, and indeed, perturbation of D-Ser levels in the central nervous system has now been implicated in the pathophysiology of various neuropsychiatric disorders, including schizophrenia (4, 23, 24, 71), Alzheimer's disease (28, 70), and amyotrophic lateral sclerosis (59).Unlike the tissue-specific expression of D-Ser, substantial amounts of free D-Asp are present in a wide variety of tissues and cells in invertebrates and vertebrates, particularly in the central nervous, neuroendocrine, and endocrine systems. D-Asp is proposed to play an important role in regulating developmental processes, hormone secretion, and steroidogenesis (12,26,35). For instance, it has been reported that in male lizards, intraperitoneally administered D-Asp is taken up rapidly by the testis, which induces a significant increase in testosterone levels and a significant decrease in 17␤-estradiol levels in the testis and plasma (57). Interestingly, a reverse relationship is found between males and females; specifically, in female lizards, exogenous D-Asp induces a significant decrease in testosterone levels in the ovary and plasma, while it enhances follicular production of 17␤-estradiol by upregulating the local aromatase activity (2). Similar findings have also been reported in studies of the green frog (16, 56). These observations suggest that D-Asp is an important regulatory molecule of gonads. In addition, it was recently shown that the amount of D-Asp in human seminal plasma and spermatozoa is significantly reduced in oligoasthenoteratospermic and/or azoospermic donors compared with normospermic donors (14). Moreover, in human female patients undergoing in vitro fertilization, the D-Asp content of the preovulatory follicular fluid ...