Regulation of Cementoblast Gene Expression by Inorganic Phosphate In Vitro

Examination of mutant and knockout phenotypes with altered phosphate/pyrophosphate distribution has demonstrated that cementum, the mineralized tissue that sheathes the tooth root, is very sensitive to local levels of phosphate and pyrophosphate. The aim of this study was to examine the potential regulation of cementoblast cell behavior by inorganic phosphate (P i ). Immortalized murine cementoblasts were treated with P i in vitro , and effects on gene expression (by quantitative real-time reverse-transcriptase polymerase chain reaction [RT-PCR]) and cell proliferation (by hemacytometer count) were observed. Dose-response (0.1–10 mM) and time-course (1–48 hours) assays were performed, as well as studies including the Na-P i uptake inhibitor phosphonoformic acid. Real-time RT-PCR indicated regulation by phosphate of several genes associated with differentiation/mineralization. A dose of 5 mM P i upregulated genes including the SIBLING family genes osteopontin ( Opn , >300% of control) and dentin matrix protein-1 ( Dmp-1 , >3,000% of control). Another SIBLING family member, bone sialoprotein ( Bsp ), was downregulated, as were osteocalcin ( Ocn ) and type I collagen ( Col1 ). Time-course experiments indicated that these genes responded within 6–24 hours. Time-course experiments also indicated rapid regulation (by 6 hours) of genes concerned with phosphate/pyrophosphate homeostasis, including the mouse progressive ankylosis gene ( Ank ), plasma cell membrane glycoprotein-1 ( Pc-1 ), tissue nonspecific alkaline phosphatase ( Tnap ), and the Pit1 Na-P i cotransporter. Phosphate effects on cementoblasts were further shown to be uptake-dependent and proliferation-independent. These data suggest regulation by phosphate of multiple genes in cementoblasts in vitro . During formation, phosphate and pyrophosphate may be important regulators of cementoblast functions including maturation and regulation of matrix mineralization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48015/1/223_2005_Article_184.pd

KIAA1462, A Coronary Artery Disease Associated Gene, Is a Candidate Gene for Late Onset Alzheimer Disease in APOE Carriers

Alzheimer disease (AD) is a devastating neurodegenerative disease affecting more than five million Americans. In this study, we have used updated genetic linkage data from chromosome 10 in combination with expression data from serial analysis of gene expression to choose a new set of thirteen candidate genes for genetic analysis in late onset Alzheimer disease (LOAD). Results in this study identify the KIAA1462 locus as a candidate locus for LOAD in APOE4 carriers. Two genes exist at this locus, KIAA1462, a gene associated with coronary artery disease, and “rokimi”, encoding an untranslated spliced RNA The genetic architecture at this locus suggests that the gene product important in this association is either “rokimi”, or a different isoform of KIAA1462 than the isoform that is important in cardiovascular disease. Expression data suggests that isoform f of KIAA1462 is a more attractive candidate for association with LOAD in APOE4 carriers than “rokimi” which had no detectable expression in brain