The lung miRNA expression profile is highly conserved among mammalian species. miRNAs are involved in homeostasis and lung development, inflammation and viral infections, and many pulmonary diseases such as cancer and chronic obstructive pulmonary disease. Knowledge on the role of miRNAs in lung development is still limited and based mainly on data from animal models. Among quantification techniques used to study miRNAs, quantitative real time PCR is one of the most specific, sensitive and fast. Due to the small size of miRNA, a new qPCR method was developed to provide better specificity and sensitivity. This method includes two steps: stem-loop reverse transcription and qPCR. In the first step, a stem-loop RT primer is hybridized to a miRNA molecule and pulsed RT is initiated. In the second step, the RT product is amplified with a specific forward primer and a universal reverse primer. RT and qPCR efficiencies are subjected to variation due to several factors including the amount and quality of starting materials. To take into account these variations, normalization is performed using endogenous control genes. It has been reported that it is better to normalize target RNA levels with control genes belonging to the same RNA class. Therefore, for normalization of miRNA levels, the endogenous control genes would belong to the small non-coding RNA family, such as snRNA and snoRNA. Several candidate snRNAs and snoRNAs were tested across different tissues and experimental conditions to determine suitable endogenous controls. However, no such analysis has yet been performed in the changing PD325901 customer reviews developing mouse lung. snoRNAs are constitutively and abundantly expressed molecules found within the nucleolus where they are involved in chemical modification of various classes of RNAs. For this study, we selected five snoRNAs that were already tested across different adult mouse tissues for stability. We already demonstrated that the expression profile of many genes varies according to sex and developmental stage. Expression of several miRNAs was also shown to vary according to sex and developmental age in the developing lung. Let-7 is highly conserved across animal species. Some studies report the important role of Let-7 in the development of Caenorhabditis elegans, Drosophila, and some mammals. Let-7 genes are expressed in the mouse developing lung and are among the highly expressed miRNAs in the adult mouse lung. They were shown to exert anti- and pro-inflammatory actions in respiratory diseases, and to act as tumor suppressor in lung cancer. In order to find endogenous control genes to study miRNA expression in the developing mouse lung of both sexes, expression stability of five putative snoRNA endogenous control genes was studied. The results are presented here. Calculation was performed separately for each developmental stage, and with all the time points together.