Abstract:We have isolated a human cDNA encoding a protein, designated DNPI, that shows 82% amino acid identity and 92% similarity to the human brain-specific Na ϩ -dependent inorganic phosphate (Na ϩ /P i ) cotransporter (BNPI), which is localized exclusively to neuron-rich regions. Expression of DNPI mRNA in Xenopus oocytes resulted in a significant increase in Na ϩ -dependent P i transport, indicating that DNPI is a novel Na ϩ /P i cotransporter. Northern blot analysis shows that DNPI mRNA is expressed predominantly in brain, where the highest levels are observed in medulla, substantia nigra, subthalamic nucleus, and thalamus, all of which express BNPI mRNA at low levels. In contrast, DNPI mRNA is expressed at low levels in cerebellum and hippocampus, where BNPI mRNA is expressed at high levels. No hybridizing signal for DNPI mRNA is observed in the glia-rich region of corpus callosum. In other regions examined, both mRNAs are moderately or highly expressed. These results indicate that BNPI and DNPI, which coordinate Na ϩ -dependent P i transport in the neuron-rich regions of the brain, may form a new class within the Na ϩ /P i cotransporter family. Key Words: cDNA cloning-Phosphate transport-Structurally related family-Neuron. J. Neurochem. 74, 2622Neurochem. 74, -2625Neurochem. 74, (2000.Inorganic phosphate (P i ) is essential for various cellular metabolic functions and signal transduction, and its homeostasis in the body is maintained primarily by the kidney (Murer and Biber, 1996). The cells in the proximal tubules of the kidney reabsorb P i in the glomerular filtrate through complex Na ϩ -dependent P i (Na ϩ /P i ) cotransport systems that are driven by the transmembrane electrochemical gradient for Na ϩ . Several cDNAs encoding distinct Na ϩ /P i cotransporters, which are classified into type 1 (NaP i -1-related), type 2 (NaP i -2-related), and type 3 (viral receptor-related) on the basis of molecular structure, have been identified in kidney and some other tissues (Murer and Biber, 1996;Werner et al., 1998). Amino acid comparison of the proteins shows weak overall homology (ϳ20% identity) between these types.A distinct type of the brain-specific Na ϩ /P i cotransporter (BNPI), which has ϳ30% amino acid identity to the type 1 proteins, has been described (Ni et al., 1994(Ni et al., , 1996. Northern blot analysis revealed that BNPI mRNA is expressed predominantly in brain, and in situ hybridization analysis revealed high levels of mRNA expression in certain neuron-rich regions of amygdala, cerebral cortex, and hippocampus. On the other hand, this mRNA was detected at low levels in substantia nigra, subthalamic nuclei, and thalamus, and no hybridization signals were detected in caudate nucleus and hypothalamus, suggesting that additional related proteins may be present in these regions to complement P i transport in brain.Rat pancreatic AR42J cells (Rosewicz et al., 1992) share the feature of pluripotency of the common precursor cells of the pancreas. Treatment of the cells with activin A converts them...

Rupture of intracranial aneurysms (IAs) causes subarachnoid hemorrhage, a devastating condition with high morbidity and mortality. Angiographic and autopsy studies show that IA is a common disorder, with a prevalence of 3%-6%. Although IA has a substantial genetic component, little attention has been given to the genetic determinants. We report here a genomewide linkage study of IA in 104 Japanese affected sib pairs in which positive evidence of linkage on chromosomes 5q22-31 (maximum LOD score [MLS] 2.24), 7q11 (MLS 3.22), and 14q22 (MLS 2.31) were found. The best evidence of linkage is detected at D7S2472, in the vicinity of the elastin gene (ELN), a candidate gene for IA. Fourteen distinct single-nucleotide polymorphisms (SNPs) were identified in ELN, and no obvious allelic association between IA and each SNP was observed. The haplotype between the intron-20/intron-23 polymorphism of ELN is strongly associated with IA (P=3.81x10-6), and homozygous patients are at high risk (P=.002), with an odds ratio of 4.39. These findings suggest that a genetic locus for IA lies within or close to the ELN locus on chromosome 7.

To understand the molecular processes of continuous vasospasm of cerebral arteries after subarachnoid hemorrhage, mRNA differential display and screening of cDNA expression array were performed to identify genes that are differentially expressed in vasospastic arteries of canine two-hemorrhage models. The expression levels of 18 genes were found to be upregulated, and those of two genes to be downregulated. Of these, 12 represent known genes or homologues of genes characterized previously, and the other eight genes are not related to any sequences in the databases. The known genes include five upregulated inflammation-related genes encoding monocyte chemotactic protein-1, cystatin B, inter-alpha-trypsin inhibitor family heavy chain-related protein, serum amyloid A protein, and glycoprotein 130, suggesting that inflammatory reaction may be involved in the development of cerebral vasospasm. The upregulation of three known genes encoding stress-related proteins of vascular endothelial growth factor, BiP protein, and growth-arrest and DNA-damage-inducible protein may be involved in possible cell survival in the damaged arteries. A full-length cDNA for the unknown clone DVS 27, whose expression was most highly upregulated, was isolated from the cerebral artery cDNA library by hybridization. Characterization of these genes should help to clarify the molecular mechanism of continuous cerebral vasospasm after subarachnoid hemorrhage.