Expression Analysis of Twist-1 in Developing and Adult Mouse Organs

Twist-1, a nuclear protein, plays a critical role in bone development. Through its interaction with a partner protein, Runx2, it controls the onset of osteoblast differentiation and thus of mineralization. Recently it has been shown that Twist-1 also plays a role postnatally in tissue homeostasis. Our latest findings of over erupted incisors and ectopic pulpal calcifications in Twist-1 mutant mice raises the question if Twist-1 might be involved in the regulation of mineralization processes and homeostasis in the dental pulp. Objective: The purpose of this study was to gain a better understanding of the precise role of Twist-1 in dental tissues by assessing and comparing its profiles of expression in tooth organs with other hard and soft tissues of developing and adult mice. Methods: Calvaria, brain, femur, kidney, liver, lung and molar organs were obtained from E12 to postnatal Day 60 mice. Tissues were dissected and snap-frozen in liquid nitrogen. Total RNA was then extracted and RT-PCR analysis performed using specific primers for Twist-1 and GAPDH that served as a control for equal RNA loading. Tissues from Twist-1 heterozygote null mutant mice also served as controls. Results: Twist-1 transcripts were present in all tissues studied. Higher expression was evident at embryonic stages when compared to adult time periods. At D60, Twist-1 was present at higher levels in mineralized tissues (molars, calvaria, femur) in contrast to soft tissues. In Twist-1 +/- tissues, expression was significantly reduced. Conclusions: The temporal ad spatial profiles of Twist-1 gene expression suggests a function in both developmental processes as well as in homeostasis of adult tissues. This investigation was supported in part by NIH/NIDCR Training Grant T32-DE015355 to HP and JJ and a grant by the German Academic Exchange Service to KG.