This supplement request pertains to the activities approved under Aim 1 of RO1 AR48147. The central hypothesis of the parent grant is that Hdac3 and Hdac7 are essential components of a multi-protein complex that regulates Runx2 activity. The objective of Aim 1 in this project is to determine if Hdac3 depletion accelerates osteoblast maturation and bone formation in vivo. We have successfully made several mouse lines in which Hdac3 is deleted in a tissue-restricted, osteoblast-directed manner. We have been collecting serum from these mice to measure circulating concentrations of various osteoblast products. A logistical problem we have encountered is that we do not get enough serum from each individual mice to perform all the assays we wish to measure. At best, we can harvest 100-200 ?l of serum from a terminal bleed on a 6 week-old wildtype mouse; however, we get about half of than amount from Hdac3 CKO mice because they are 60-80% smaller than wildtype animals. Most commercial ELISA products require 100-200 ?l of serum per assay, thus we could only run one assay per mouse with our existing equipment. The purpose of this supplement is to buy an instrument (Luminex® with X-Map® technology) that will allow us to simultaneously measure the concentrations of multiple (up to 100) serum markers in as little as 25 ?l of serum. This will allow us to more efficiently assess the effects of osteoblast-specific Hdac3 depletion. This equipment will accelerate the tempo of our scientific research by allowing us to perform multiple assays on a single sample, thereby preventing the need to breed and age additional animals to get enough material for numerous oneanalyte ELISAs. The supplement will stimulate the economy by procuring the equipment package, which includes the Luminex® reader, a computer and monitor, software, plate washer, and plate shaker, for less than $72,000. We will also purchase a one-year service plan to insure that the instrument works properly throughout the funding period, an action that will hopefully save service jobs in the private sector.