Evolution of CFTR protein distribution in lung tissue from normal and CF human fetuses

Abstract

In order to determine whether or not CFTR protein distribution differs between the airways of fetuses with Cystic Fibrosis (CF) from the airways of normal fetuses we studied the distribution pattern of the CFTR protein in lung. Cases of normal and CF human fetuses as well as cases of normal neonates were examinated. Our aim was to establish whether CFTR expression during pregnancy could be correlated with the maturation of the airways, and to compare normal and CF samples. We hypothesized that any difference between normal and CF fetal lung in CFTR protein expression could be related to a functional change appearing in early development even if no morphological differences could be detected at the light microscopic level. The distribution of CFTR protein progressively increased from 10 weeks of gestation (WG) to mid-gestation, but thereafter decreased until term. The CFTR protein was first detected in the cytoplasm of undifferentiated epithelial cells. Before mid-gestation, the immunostaining was strongly positive in bronchi, in sub-mucosal glands, and in lung parenchyma. Then, it became localized to the apical zone of the epithelial cells. This pattern correlated with differentiation during the second half of gestation. The main difference observed between normal and CF fetuses was a 3-week delay in detectability of the CFTR protein expression in the latter until 15 weeks of gestation. These results support the hypothesis of an early functional change. Abnormal fetal lung CFTR protein regulation could give rise to a predisposition to the post-natal inflammatory changes of the airways that characterize CF disease.

Transcription factors and miRNAs that regulate fetal to adultCFTRexpression change are new targets for cystic fibrosis

“…In the lung, CFTR transcripts can be detected early during embryo development (12th week of pregnancy) and their level progressively increases up to the 24th week of pregnancy. Thereafter, CFTR expression in the airways decreases and is repressed until after birth and remains very low during adult life [10][11][12][13][14]. The changes in CFTR protein expression in human fetuses are consistent with CFTR mRNA temporal pattern [14].…”

Cystic Fibrosis Transmembrane Conductance Regulator Protein (CFTR) Expression in the Developing Human Brain

“…or low expression of CFTR in some parts of the brain, such as the cortex, hippocampus or hypothalamus, may be due to a delay in the appearance of the protein, as previously observed in other tissues (Marcorelles et al 2007;2012). In all structures, CFTR labeling in the CF case was only diffuse and cytoplasmic.…”

“…Negative controls were obtained by omission of the primary antibody or the use of other antibodies of known reactivity such as VEGF (Sentilhes et al 2010) or ARX, a transcription factor widely expressed in the developing brain and giving only nuclear labeling. In addition, the specificity of our CFTR labeling was carefully checked using different anti-CFTR antibodies (MAB3480 from Chemicon, Temecula, CA; MAB25031 and MAB1660 from R&D Systems, Abington, UK) and by testing them in parallel on lung, kidney and vas deferens sections (positive controls) and on heart and thymus sections (negative controls) (Todd-Turla et al 1996;Devuyst et al 1996;Marcorelles et al 2007;2012).…”

“…In addition, several studies have reported the expression of CFTR very early during development in immature cells of the same organs as in adulthood, suggesting a previously unsuspected role for CFTR during development (Harris et al 1991;Tizzano et al 1993). These characteristics have predominantly been documented in the main systems affected in CF, particularly the respiratory tract, the intestine and the male reproductive system (Harris et al 1991;Tizzano et al 1993;Marcorelles et al 2007;2012). However, in the absence of clear genotype-phenotype correlations in CF, the developmental pattern of expression of CFTR has not been documented in organs that are not the major targets of the disease.…”

“…However, in the absence of clear genotype-phenotype correlations in CF, the developmental pattern of expression of CFTR has not been documented in organs that are not the major targets of the disease. As both peripheral and central neurological symptoms have sometimes been reported in patients with CF (Cavalier and Gambetti 1981;Cochran et al 1991;El-Salem et al 2010), we decided to investigate the expression of CFTR in the developing human CNS using immunohistochemistry and searched for, as previously described in the lung and male reproductive system (Marcorelles et al 2007;2012), possible differences in the expression and/or localization of the protein in deceased fetal and neonatal subjects with CF at different gestational ages.…”