Differential expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), β actin and hypoxanthine phosphoribosyltransferase (HPRT) in postnatal rabbit sclera

Abstract

Purpose. GAPDH, β-actin, HPRT and 18S rRNA are constitutively expressed in all mammalian cells. In accordance with the nature of invariant control, these genes have been used to standardize genes of interest in expression studies. Recent studies have suggested that GAPDH, β-actin and HPRT in special situations may come under temporary regulatory control, but that 18S rRNA may be more likely to remain constitutive. However, little is known about the quantitative expression of these genes in fibroblasts and in particular during early postnatal development, a time of rapid changes in cell metabolism. In this study we have examined the differential expression of these genes in association with scleral development from an early postnatal age up to young adult status. Methods. GAPDH, β-actin, HPRT, and 18S rRNA gene expression were analyzed in the rabbit sclera from 1 day to 8 weeks postnatally by real-time, comparative PCR. Results. Real-time PCR analysis showed that the expression levels of GAPDH, β-actin, and HPRT were higher in the first postnatal week and then declined. However, from 2 to 8 weeks, the mRNA levels of these three genes underwent significant variations (P< 0.01) in their levels of expression. In contrast, the expression level of 18S rRNA showed no significant variation (P ≥ 0.5) over this time period. Conclusions. The present study shows that GAPDH, β actin and HPRT gene were differentially expressed in early post-natal scleral development. It also suggests that these gene products could be implicated in the developmental process and have a crucial role in the early postnatal period. This study demonstrates that 18S rRNA may be preferable to normalize genes of interest in studies of early development.