UC San Diego

C-fos and fra-2, both transcription factors under the control of PKGII, were seen in previous experiments to have significantly decreased mRNA transcript levels in PKGII -/- mice compared with wild type litter mates (Rangaswami 2010). Osteoblasts derived from PKGII -/- mice have impaired cGMP-dependent Src and Erk activation, steps along a PKGII signaling pathway (Rangaswami 2010). These findings, as well as the fact that PKGII -/- suffer from dwarfism with severe endochondral ossification defects, all suggest that PKGII has an integral part in proper bone development and function (Pfeiffer 1996). RNA was extracted from the tibial diaphysis of PKG -/- mice and wild type or heterozygous litter mates of three age groups : seven, eleven, and twenty-eight day-old mice, and used to analyze by reverse transcription/quantitative real-time polymerase chain reaction (RT-PCR) five genes of interest, all pertaining to osteoblast or osteoclast proliferation and function. Relative mRNA levels of the genes of interest were calculated via 2-[Delta]Ct method, where [Delta]Ct represents the difference in threshold cycle values between the gene of interest and the housekeeping reference gene, Gapdh. Out of the five genes of interest, and in all the age groups examined, only osteoprotegerin (OPG) in the seven and eleven day-old mice showed a significant difference in relative mRNA levels between wild-type and knock-out mice. OPG is produced by (pre)osteoblasts and negatively regulates osteoclast differentiation. The up-regulation of OPG in PKGII -/- mice suggests a novel role for PKGII in the regulation of osteoclast differentiation, and warrants further study