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

Purpose. GAPDH, beta -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, beta -actin and HPRT in special situations may come under temporary regulatory control, but that 1 8S rRNA may be more likely to remain constitutive. However, little is known about the quantitative expression of these genes in fibroblasts and in par ticular 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, beta -actin. HPRT, and 18S rRNA gene expression were analyz ed in the rabbit sclera from 1 day to 8 weeks postnatally by real-time, com parative PCR. Results. Real-time PCR analysis showed that the expression levels of GAPDH, beta -actin, and HPRT were higher in the first postnatal week and then dec lined. However, from 2 to 8 weeks, the mRNA levels of these three genes und erwent significant variations (P<0.01) in their levels of expression. In co ntrast, the expression level of 18S rRNA showed no significant variation (P <greater than or equal to>0.5) over this time period. Conclusions. The present study shows that GAPDH, beta -actin and HPRT gene were differentially expressed in early postnatal scleral development. It al so suggests that these gene products could be implicated in the development al process and have a crucial role in the early postnatal period. This stud y demonstrates that 18S rRNA may be preferable to normalize genes of intere st in studies of early development.