Spastin, a new AAA protein, is altered in the most frequent form of autosomal dominant spastic paraplegia

Autosomal dominant hereditary spastic paraplegia (AD-HSP) is a genetically heterogeneous neurodegenerative disorder characterized by progressive spasticity of the lower limbs. Among the four loci causing AD-HSP identified so far, the SPG4 locus at chromosome 2p2-1p22 has been shown to account for 40-50% of all AD-HSP families. Using a positional cloning strategy based on obtaining sequence of the entire SPG4 interval, we identified a candidate gene encoding a new member of the AAA protein family, which we named spastin. Sequence analysis of this gene in seven SPG4-linked pedigrees revealed several DNA modifications, including missense, nonsense and splice-site mutations. Both SPG4 and its mouse orthologue were shown to be expressed early and ubiquitously in fetal and adult tissues. The sequence homologies and putative subcellular localization of spastin suggest that this ATPase is involved in the assembly or function of nuclear protein complexes.     

The prolactin releasing peptides: RF-amide peptides

Although dopamine is considered the major hypothalamic controller of prolactin release from the anterior pituitary gland, there is evidence that a yet to be discovered prolactin releasing factor (PRF) also exists in brain. Recently, two peptides were isolated, products of the same prohormone, that were reported to have significant prolactin-releasing activity. These peptides, called prolactin releasing peptides, are not accepted by all investigators to be in fact PRFs. Instead, it appears that their widespread distribution in brain and the presence of receptors for the peptides in sites unrelated to neuroendocrine function are the basis for a variety of central nervous system action including activation of the autonomic nervous system. Thus, these peptides may not be PRFs, but instead neuroactive agents that are involved in many brain circuits with divergent functions.     

Old radiocarbon ages in the southwest Pacific Ocean during the last glacial period and deglaciation

Marine radiocarbon (14C) dates are widely used for dating oceanic events and as tracers of ocean circulation, essential components for understanding ocean-climate interactions. Past ocean ventilation rates have been determined by the difference between radiocarbon ages of deep-water and surface-water reservoirs, but the apparent age of surface waters (currently approximately 400 years in the tropics and approximately 1,200 years in Antarctic waters) might not be constant through time, as has been assumed in radiocarbon chronologies and palaeoclimate studies. Here we present independent estimates of surface-water and deep-water reservoir ages in the New Zealand region since the last glacial period, using volcanic ejecta (tephras) deposited in both marine and terrestrial sediments as stratigraphic markers. Compared to present-day values, surface-reservoir ages from 11,900 14C years ago were twice as large (800 years) and during glacial times were five times as large (2,000 years), contradicting the assumption of constant surface age. Furthermore, the ages of glacial deep-water reservoirs were much older (3,000-5,000 years). The increase in surface-to-deep water age differences in the glacial Southern Ocean suggests that there was decreased ocean ventilation during this period.     

The DNA sequence and analysis of human chromosome 14

Chromosome 14 is one of five acrocentric chromosomes in the human genome. These chromosomes are characterized by a heterochromatic short arm that contains essentially ribosomal RNA genes, and a euchromatic long arm in which most, if not all, of the protein-coding genes are located. The finished sequence of human chromosome 14 comprises 87,410,661 base pairs, representing 100% of its euchromatic portion, in a single continuous segment covering the entire long arm with no gaps. Two loci of crucial importance for the immune system, as well as more than 60 disease genes, have been localized so far on chromosome 14. We identified 1,050 genes and gene fragments, and 393 pseudogenes. On the basis of comparisons with other vertebrate genomes, we estimate that more than 96% of the chromosome 14 genes have been annotated. From an analysis of the CpG island occurrences, we estimate that 70% of these annotated genes are complete at their 5' end.     

BMP9 is produced by hepatocytes and circulates mainly in an active mature form complexed to its prodomain

Bone Morphogenetic Protein 9 (BMP9) has been recently found to be the physiological ligand for the activin receptor-like kinase 1 (ALK1), and to be a major circulating vascular quiescence factor. Moreover, a soluble chimeric ALK1 protein (ALK1-Fc) has recently been developed and showed powerful anti-tumor growth and anti-angiogenic effects. However, not much is known concerning BMP9. This prompted us to investigate the human endogenous sources of this cytokine and to further characterize its circulating form(s) and its function. Analysis of BMP9 expression reveals that BMP9 is produced by hepatocytes and intrahepatic biliary epithelial cells. Gel filtration analysis combined with ELISA and biological assays demonstrate that BMP9 circulates in plasma (1) as an unprocessed inactive form that can be further activated by furin a serine endoprotease, and (2) as a mature and fully active form (composed of the mature form associated with its prodomain). Analysis of BMP9 circulating levels during mouse development demonstrates that BMP9 peaks during the first 3 weeks after birth and then decreases to 2 ng/mL in adulthood. We also show that circulating BMP9 physiologically induces a constitutive Smad1/5/8 phosphorylation in endothelial cells. Taken together, our results argue for the role of BMP9 as a hepatocyte-derived factor, circulating in inactive (40%) and active (60%) forms, the latter constantly activating endothelial cells to maintain them in a resting state.     

Isolation, sequence determination and expression in Escherichia coli of the isopenicillin N synthetase gene from Cephalosporium acremonium

The enzyme isopenicillin N synthetase (IPS) catalyses the oxidative condensation of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (LLD-ACV) to isopenicillin N, which is a central reaction in the pathway to clinically important penicillins and cephalosporins. Here we report the cloning, characterization and expression in Escherichia coli of the gene encoding the IPS protein in Cephalosporium acremonium. The IPS gene was identified by purifying IPS protein, determining the first 23 amino-terminal amino acids, preparing a set of synthetic oligonucleotides encoding a portion of the determined amino-acid sequence, and probing a cosmid genome library with the mixed oligonucleotides. A cosmid hybridizing with the probe was isolated and the IPS gene was localized and sequenced. The IPS gene encodes a polypeptide of relative molecular mass (Mr) 38,416. When this open reading frame was cloned into an E. coli expression vector and inserted into E. coli, the recombinant E. coli produced a new protein co-migrating with authentic IPS as the major protein of the cell (approximately 20% of cell protein). Crude cell extracts condensed LLD-ACV to a penicillinase-sensitive molecule whose antibacterial activity indicated that it was isopenicillin N.     

Variants of ENPP1 are associated with childhood and adult obesity and increase the risk of glucose intolerance and type 2 diabetes

We identified a locus on chromosome 6q16.3-q24.2 (ref. 1) associated with childhood obesity that includes 2.4 Mb common to eight genome scans for type 2 diabetes (T2D) or obesity. Analysis of the gene ENPP1 (also called PC-1), a candidate for insulin resistance, in 6,147 subjects showed association between a three-allele risk haplotype (K121Q, IVS20delT-11 and A-->G+1044TGA; QdelTG) and childhood obesity (odds ratio (OR) = 1.69, P = 0.0006), morbid or moderate obesity in adults (OR = 1.50, P = 0.006 or OR = 1.37, P = 0.02, respectively) and T2D (OR = 1.56, P = 0.00002). The Genotype IBD Sharing Test suggested that this obesity-associated ENPP1 risk haplotype contributes to the observed chromosome 6q linkage with childhood obesity. The haplotype confers a higher risk of glucose intolerance and T2D to obese children and their parents and associates with increased serum levels of soluble ENPP1 protein in children. Expression of a long ENPP1 mRNA isoform, which includes the obesity-associated A-->G+1044TGA SNP, was specific for pancreatic islet beta cells, adipocytes and liver. These findings suggest that several variants of ENPP1 have a primary role in mediating insulin resistance and in the development of both obesity and T2D, suggesting that an underlying molecular mechanism is common to both conditions.