Conservation of the Caenorhabditis elegans cuticle collagen gene col-12 in Caenorhabditis briggsae

Neuron cell type-specific SNAP-25 expression driven by multiple regulatory elements in the nematode Caenorhabditis elegans

In order to characterize the mechanisms regulating neuronal expression of the nematode SNAP-25 gene, we identified the SNAP-25 genes of Caenorhabditis elegans and Caenorhabditis briggsae. Comparative sequence analysis and reporter assays revealed two putative 5' regulatory elements, P1 and P2, and four elements, I1h, I1m, I2h, and I2m, in the first intron. Nuclear extracts contained activities that bound the P2 and I1h elements. Different elements were required for SNAP-25 expression in different neuronal subsets; P1 was required in DA and DD motor neurons, and I1m and I2m were required in DB and DA neurons, respectively. P2 was active in amphid and phasmid neurons, I1h in pharyngeal neurons, and I2h in touch receptor neurons. The I2h element contained a putative binding site for transcription factor UNC-86. Both UNC-86 and MEC-3 were required for I2h activity in the mechanosensory neurons: in these neurons, GFP expression driven by I2h was abolished in animals bearing either an unc-86 null or a mec-3 null mutation, or an unc-86 mutation that leads to defective interaction with MEC-3. Deletion of the MEC-3 binding site also abolished the GFP expression. Gel mobility-shift assay results suggest that transcriptional regulation of SNAP-25 may involve multiple transcription factors.

Genome changes and gene expression in human solid tumors

Genome-wide analysis techniques such as chromosome painting, comparative genomic hybridization, representational difference analysis, restriction landmark genome scanning and high-throughput analysis of LOH are now accelerating high-resolution genome aberration localization in human tumors. These techniques are complemented by procedures for detection of differentially expressed genes such as differential display, nucleic acid subtraction, serial analysis of gene expression and expression microarray analysis. These efforts are enabled by work from the human genome program in physical map development, cDNA library production/sequencing and in genome sequencing. This review covers several commonly used large-scale genome and gene expression analysis techniques, outlines genomic approaches to gene discovery and summarizes information that has come from large-scale analyses of human solid tumors.

Conservation and novelty in the evolution of cell adhesion and extracellular matrix genes

New proteins and modules have been invented throughout evolution. Gene "birth dates" in Caenorhabditis elegans range from the origins of cellular life through adaptation to a soil habitat. Possibly half are "metazoan" genes, having arisen sometime between the yeast-metazoan and nematode-chordate separations. These include basement membrane and cell adhesion molecules implicated in tissue organization. By contrast, epithelial surfaces facing the environment have specialized components invented within the nematode lineage. Moreover, interstitial matrices were likely elaborated within the vertebrate lineage. A strategy for concerted evolution of new gene families, as well as conservation of adaptive genes, may underlie the differences between heterochromatin and euchromatin.

Identification and characterization of a serine hydroxymethyltransferase isoform in Caenorhabditis briggsae

In the nematode Caenorhabditis elegans, the maternal effect lethal gene mel-32 encodes a serine hydroxymethyltransferase isoform. Since interspecies DNA comparison is a valuable tool for identifying sequences that have been conserved because of their functional importance or role in regulating gene activity, mel-32(SHMT) genomic DNA from C. elegans was used to screen a genomic library from the closely related nematode Caenorhabditis briggsae. The C. briggsae genomic clone identified fully rescues the Mel-32 phenotype in C. elegans, indicating functional and regulatory conservation. Computer analysis reveals that CbMEL-32(SHMT) is 92% identical (97% similar) to CeMEL-32(SHMT) at the amino acid level over the entire length of the protein (484 amino acids), whereas the coding DNA is 82.5% identical (over 1455 nucleotides). Several highly conserved non-coding regions upstream and downstream of the mel-32(SHMT) gene reveal potential regulatory sites that may bind trans-acting protein factors.