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Regional expression of CFTR in developing human respiratory tissues
E F Tizzano1, H O'Brodovich, D Chitayat
1Department of Genetics, Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Cystic fibrosis (CF) transmembrane conductance regulator (CFTR) mRNA is found in fetal lungs but decreases after birth. CFTR expression in submucosal glands appears postnatally, offering insights into CF lung disease pathogenesis.
Area of Science:
- Pulmonary Medicine
- Developmental Biology
- Molecular Genetics
Background:
- Morbidity and mortality in cystic fibrosis (CF) are primarily linked to respiratory complications.
- Understanding CFTR gene expression during lung development is crucial for deciphering CF pathogenesis.
Purpose of the Study:
- To investigate the localization and levels of CFTR mRNA in human fetal, newborn, and infant respiratory tissues.
- To correlate CFTR expression patterns with lung development and the onset of CF-related pathology.
Main Methods:
- In situ hybridization was employed to analyze CFTR mRNA distribution.
- Respiratory tissues from different developmental stages (fetal, newborn, infant) were examined.
Main Results:
- CFTR transcript was detected in fetal lung epithelium, decreasing in later developmental stages and primarily localized to small airway epithelium postnatally.
- Expression in tracheal and large bronchial epithelia showed differential patterns.
- CFTR was absent in fetal submucosal glands but appeared gradually after birth.
Conclusions:
- The dynamic CFTR expression pattern during lung development may reflect the transition from a fluid-secreting to an absorbing organ.
- The late appearance of CFTR in submucosal glands contrasts with early CF lung pathology (hyperplasia), suggesting complex regulatory factors.
- Further research into factors influencing CFTR expression and its relationship with fetal lung development is needed for CF therapeutic strategies.
Abstract:
Morbidity and mortality in cystic fibrosis (CF) patients is strongly related to their respiratory disease. We have analyzed, by means of in situ hybridization, the localization and levels of CFTR mRNA in fetal, newborn, and infant respiratory tissues. Measurable levels of CFTR transcript are present in the fetal primordial epithelium of the pseudoglandular stage lung. During the following stages of lung development, CFTR expression decreases in cells of the future alveolar spaces and is gradually limited to the epithelium of the small airways. After birth, expression decreases in the small airways and is not detected in alveolar epithelia. In trachea and large bronchi, a differential pattern of expression is also observed. No CFTR expression is found in fetal submucosal glands during fetal development, but appears gradually in the newborn period. Since CFTR codes for a secretory Cl- channel, these data probably reflect the changes that occur in the lung transition from a fluid-secreting to an absorbing organ. The pattern of expression seems paradoxical in view of the clinical-pathological manifestations of CF. Although CFTR is expressed in the normal fetus and lung development is influenced by the amount of fetal lung liquid, newborns affected with CF have normal lungs. In addition, the earliest pathologic change described in CF lungs in hyperplasia of the submucosal glands, yet expression in these structures is seen only after birth. An improved understanding of the factors that alter the expected relationship between CFTR expression and pathologic lesions in the fetal lung may provide important insights into the pathogenesis and potential treatment of lung disease in CF patients.