David B. Guiliano

Guiliano DB et al. (2006) PLoS Genet "Operon conservation and the evolution of trans-splicing in the phylum Nematoda."

Blaxter ML, Guiliano DB

[PLoS Genet, 2006]

The nematode Caenorhabditis elegans is unique among model animals in that many of its genes are cotranscribed as polycistronic pre-mRNAs from operons. The mechanism by which these operonic transcripts are resolved into mature mRNAs includes trans-splicing to a family of SL2-like spliced leader exons. SL2-like spliced leaders are distinct from SL1, the major spliced leader in C. elegans and other nematode species. We surveyed five additional nematode species, representing three of the five major clades of the phylum Nematoda, for the presence of operons and the use of trans-spliced leaders in resolution of polycistronic pre-mRNAs. Conserved operons were found in Pristionchus pacificus, Nippostrongylus brasiliensis, Strongyloides ratti, Brugia malayi, and Ascaris suum. In nematodes closely related to the rhabditine C. elegans, a related family of SL2-like spliced leaders is used for operonic transcript resolution. However, in the tylenchine S. ratti operonic transcripts are resolved using a family of spliced leaders related to SL1. Non-operonic genes in S. ratti may also receive these SL1 variants. In the spirurine nematodes B. malayi and A. suum operonic transcripts are resolved using SL1. Mapping these phenotypes onto the robust molecular phylogeny for the Nematoda suggests that operons evolved before SL2-like spliced leaders, which are an evolutionary invention of the rhabditine lineage.

Guiliano DB et al. (1998) European Worm Meeting "Towards a Physical Map of Brugia malayi New insights into the Biology of Filarial Nematodes"

Blaxter ML, Daub J, Jones SJ, Guiliano DB

[European Worm Meeting, 1998]

Filarial nematodes are one of the most prevalent parasitic organisms worldwide infecting over 120 million people. Previous attempts to find novel vaccine and drug candidates using conventional methods have failed. The WHO and MRC sponsored Brugia malayi genome project is an international collaborative effort between three endemic and four nonendemic laboratories whose primary goals are the identification of thousands of new Brugia genes and their placement on chromosomal maps. To facilitate this, stage specific cDNA and large insert genomic DNA libraries have been constructed and gridded robotically onto high density nylon filters. ESTs Over 14,000 ESTs have been sequenced from stage specific B. malayi cDNA libraries. When grouped by sequence identity these 14,000 ESTs form ~ 5,000 clusters. A consensus sequence for each cluster has been generated from a multiple alignment of the constituent ESTs and this has been used in subsequent database analyses. The EST clusters have allowed the assessment of the productivity of our EST sequencing efforts and identify abundant and stage specific/upregulated genes. A Physical Map The B. malayi physical map will be generated by hybridisation of several thousand Brugia genes identified during the EST sequencing phase of the project and BAC and YAC end probes selected using a sampling without replacement strategy. Generation of high quality genomic libraries has been complicated by AT bias (~70%) of Brugia genomic DNA and the presence of a bacterial endosymbiote which efficiently clones into cosmid and BAC vectors. However we are now entering into the preliminary mapping phase of the project with over two dozen Brugia genes mapped to our BAC filters and the initiation of several walking experiments. Operons? There is currently no information the genomic organisation of any nematodes other the free living Rhabditids Ceanorhabditis elegans and briggsae. One particularly interesting question is whether operon like structures are conserved in other nematode species. A directed approach to identify an operon in Brugia malayi using operons found in C. elegans has failed. To get more information about gene density, organization, and possibility of synteny between Brugia and C. elegan genomes we have undertaken the sequencing of a large piece of Brugia DNA. A single BAC containing the genomic copy of Bm-MIF-1 has been selected and has been sequenced at the Sanger Center.

Guiliano DB et al. (2002) Genome Biol "Conservation of long-range synteny and microsynteny between the genomes of two distantly related nematodes."

Corton CH, Barrell BG, Hall N, Clark LN, Blaxter ML, Jones SJM, Guiliano DB

[Genome Biol, 2002]

Background: Comparisons between the genomes of the closely related nematodes Caenorhabditis elegans and Caenorhabditis briggsae reveal high rates of rearrangement, with a bias towards within-chromosome events. To assess whether this pattern is true of nematodes in general, we have used genome sequence to compare two nematode species that last shared a common ancestor approximately 300 million years ago: the model C. elegans and the filarial parasite Brugia malayi. Results: An 83 kb region flanking the gene from Bm-mif-1 (macrophage migration inhibition factor, a B. malayi homolog of a human cytokine) was sequenced. When compared to the complete genome of C. elegans, evidence for conservation of long-range synteny and microsynteny was found. Potential C. elegans orthologs for 11 of the 12 protein-coding genes predicted in the B. malayi sequence were identified. Ten of these orthologs were located on chromosome I, with eight clustered in a 2.3 Mb region. While several, relatively local, intrachromosomal rearrangements have occurred, the order, composition, and configuration of two gene clusters, each containing three genes, was conserved. Comparison of B. malayi BAC-end genome survey sequence to C. elegans also revealed a bias towards intrachromosome rearrangements. Conclusions: We suggest that intrachromosomal rearrangement is a major force driving chromosomal organization in nematodes, but is constrained by the interdigitation of functional elements

Guiliano DB et al. (2004) Mol Biochem Parasitol "A gene family of cathepsin L-like proteases of filarial nematodes are associated with larval molting and cuticle and eggshell remodeling."

Blaxter ML, Oksov Y, Liu J, Ghedin E, Lustigman S, Guiliano DB, Hong X, McKerrow JH

[Mol Biochem Parasitol, 2004]

Cysteine proteinases are involved in a variety of important biological processes and have been implicated in molting and tissue remodeling in free living and parasitic nematodes. We show that in the lymphatic filarial nematode Brugia pahangi molting of third-stage larvae (L3) to fourth-stage larvae is dependent on the activity of a cathepsin L-like cysteine protease (CPL), which can be detected in the excretory/secretory (ES) products of molting L3. Directed cloning of a cysteine protease gene in B. pahangi and analysis of the expressed sequence tag (EST) and genomic sequences of the closely related human lymphatic filarial nematode Brugia malayi have identified a family of CPLs. One group of these enzymes, Bm-cpl-1, -4, -5 and Bp-cpl-4, is highly expressed in the B. malayi and B. pahangi infective L3 larvae. Immunolocalization indicates that the corresponding enzymes are synthesized and stored in granules of the glandular esophagus of L3 and released during the molting process. Functional analysis of these genes in Brugia and closely related CPL genes identified in the filarial nematode Onchocerca volvulus and the free living model nematode Caenorhabditis elegans indicate that these genes are also involved in cuticle and eggshell remodeling.

igdb

IG (immunoglobulin) and DB (Cys-rich) domains

AVBL

Ventral cord interneuron, synapses onto VB and DB motor neurons; formerly called beta.

AVBR

Ventral cord interneuron, synapses onto VB and DB motor neurons; formerly called beta.

wyEx1199

Caenorhabditis elegans

[Punc-129(DB)::gfp::rab-3::rab-3 3UTR, Podr-1::dsRED]

unc-40 : unc-6

DA and DB dorsal migration defects of are not suppressed by unc-40(ur304).