Cloning, mapping, and tissue distribution of a human homologue of the mouse jerky gene product

Regulation of Alpha-Secretase ADAM10 In vitro and In vivo: Genetic, Epigenetic, and Protein-Based Mechanisms

ADAM10 (A Disintegrin and Metalloproteinase 10) has been identified as the major physiological alpha-secretase in neurons, responsible for cleaving APP in a non-amyloidogenic manner. This cleavage results in the production of a neuroprotective APP-derived fragment, APPs-alpha, and an attenuated production of neurotoxic A-beta peptides. An increase in ADAM10 activity shifts the balance of APP processing toward APPs-alpha and protects the brain from amyloid deposition and disease. Thus, increasing ADAM10 activity has been proposed an attractive target for the treatment of neurodegenerative diseases and it appears to be timely to investigate the physiological mechanisms regulating ADAM10 expression. Therefore, in this article, we will (1) review reports on the physiological regulation of ADAM10 at the transcriptional level, by epigenetic factors, miRNAs and/or protein interactions, (2) describe conditions, which change ADAM10 expression in vitro and in vivo, (3) report how neuronal ADAM10 expression may be regulated in humans, and (4) discuss how this knowledge on the physiological and pathophysiological regulation of ADAM10 may help to preserve or restore brain function.

Convergent domestication of pogo-like transposases into centromere-binding proteins in fission yeast and mammals

The mammalian centromere-associated protein B (CENP-B) shares significant sequence similarity with 3 proteins in fission yeast (Abp1, Cbh1, and Cbh2) that also bind centromeres and have essential function for chromosome segregation and centromeric heterochromatin formation. Each of these proteins displays extensive sequence similarity with pogo-like transposases, which have been previously identified in the genomes of various insects and vertebrates, in the protozoan Entamoeba and in plants. Based on this distribution, it has been proposed that the mammalian and fission yeast centromeric proteins are derived from "domesticated" pogo-like transposons. Here we took advantage of the vast amount of sequence information that has become recently available for a wide range of fungal and animal species to investigate the origin of the mammalian CENP-B and yeast CENP-B-like genes. A highly conserved ortholog of CENP-B was detected in 31 species of mammals, including opossum and platypus, but was absent from all nonmammalian species represented in the databases. Similarly, no ortholog of the fission yeast centromeric proteins was identified in any of the various fungal genomes currently available. In contrast, we discovered a plethora of novel pogo-like transposons in diverse invertebrates and vertebrates and in several filamentous fungi. Phylogenetic analysis revealed that the mammalian and fission yeast CENP-B proteins fall into 2 distinct monophyletic clades, each of which includes a different set of pogo-like transposons. These results are most parsimoniously explained by independent domestication events of pogo-like transposases into centromeric proteins in the mammalian and fission yeast lineages, a case of "convergent domestication." These findings highlight the propensity of transposases to give rise to new host proteins and the potential of transposons as sources of genetic innovation.

Turning junk into gold: domestication of transposable elements and the creation of new genes in eukaryotes

Autonomous transposable elements, generally considered as junk and selfish, encode transposition proteins that can bind, copy, break, join or degrade nucleic acids as well as process or interact with other proteins. Such a repertoire of activities might be of interest for the host cell. There is indeed substantial evidence that mobile DNA can serve as a dynamic reservoir for new cellular functions. Transposable element genes encoding transposase, integrase, reverse transcriptase as well as structural and envelope proteins have been repeatedly recruited by their host during evolution in most eukaryotic lineages. Such domesticated sequences protect us against infections, are necessary for our reproduction, allow the replication of our chromosomes and control cell proliferation and death; others are essential for plant development. Many new candidates for domesticated sequences have been revealed by sequencing projects. Their functional analysis will uncover new aspects of evolutionary alchemy, the turning of junk into gold within genomes.

Identification and characterization of cvHsp. A novel human small stress protein selectively expressed in cardiovascular and insulin-sensitive tissues

Starting with computational tools that search for tissue-selective expression of assembled expressed sequenced tags, we have identified by focusing on heart libraries a novel small stress protein of 170 amino acids that we named cvHsp. cvHsp was found as being computationally selectively and highly (0.3% of the total RNA) expressed in human heart. The cvHsp gene mapped to 1p36.23-p34.3 between markers D1S434 and D1S507. The expression of cvHsp was analyzed with RNA dot, Northern blots, or reverse transcription-polymerase chain reaction: expression was high in heart, medium in skeletal muscle, and low in aorta or adipose tissues. In the heart of rat models of cardiac pathologies, cvHsp mRNA expression was either unchanged (spontaneous hypertension), up-regulated (right ventricular hypertrophy induced by monocrotaline treatment), or down-regulated (left ventricular hypertrophy following aortic banding). In obese Zucker rats, cvHsp mRNA was increased in skeletal muscle, brown, and white adipose tissues but remained unchanged in the heart. Western blot analysis using antipeptide polyclonal antibodies revealed two specific bands at 23 and 25 kDa for cvHsp in human heart. cvHsp interacted in both yeast two-hybrid and immunoprecipitation experiments with alpha-filamin or actin-binding protein 280. Within cvHsp, amino acid residues 56-119 were shown to be important for its specific interaction with the C-terminal tail of alpha-filamin.

JH8, a gene highly homologous to the mouse jerky gene, maps to the region for childhood absence epilepsy on 8q24

Insertional inactivation of the jerky gene in transgenic mice resulted epileptic seizures, suggesting that the jerky gene was responsible for mouse epilepsy. To isolate a human homologue of the jerky gene, we screened an Expressed Sequence Tag (EST) database using the cDNA sequence of the mouse jerky gene and identified several EST clones which contained homologous sequences to mouse jerky gene. Using a clone which showed highest homology as a probe, we isolated cDNA clones from a human fetal brain cDNA library. Sequence analysis of these clones named JH8 (jerky homologue of Human on chromosome 8) indicated that it encoded a putative protein with 520 amino acid residues. The JH8 gene has 77% identity to the mouse jerky gene at the DNA level, and its protein has 76% identity and 84% similarity to the mouse protein at the amino acid level. Northern blot analysis showed that the JH8 gene is expressed ubiquitously with a major transcript of about 9.5 kb in size. Fluorescence in situ Hybridization (FISH) analysis and radiation hybrid panel mapping revealed that the JH8 gene was located on chromosome band 8q24.3 in a region that was syntenic to mouse chromosome 15, the mapping site of the mouse jerky gene. Childhood Absence Epilepsy (CAE), one type of Idiopathic Generalized Epilepsy (IGE), has been mapped to chromosome 8q24.3 by linkage analysis. These results suggest that JH8 is a strong candidate gene for CAE.