A Gata6-Wnt pathway required for epithelial stem cell development and airway regeneration

Epithelial organs, including the lung, are known to possess regenerative abilities through activation of endogenous stem cell populations, but the molecular pathways regulating stem cell expansion and regeneration are not well understood. Here we show that Gata6 regulates the temporal appearance and number of bronchioalveolar stem cells (BASCs) in the lung, its absence in Gata6-null lung epithelium leading to the precocious appearance of BASCs and concurrent loss in epithelial differentiation. This expansion of BASCs was the result of a pronounced increase in canonical Wnt signaling in lung epithelium upon loss of Gata6. Expression of the noncanonical Wnt receptor Fzd2 was downregulated in Gata6 mutants and increased Fzd2 or decreased beta-catenin expression rescued, in part, the lung epithelial defects in Gata6 mutants. During lung epithelial regeneration, canonical Wnt signaling was activated in the niche containing BASCs and forced activation of Wnt signaling led to a large increase in BASC numbers. Moreover, Gata6 was required for proper lung epithelial regeneration, and postnatal loss of Gata6 led to increased BASC expansion and decreased differentiation. Together, these data demonstrate that Gata6-regulated Wnt signaling controls the balance between progenitor expansion and epithelial differentiation required for both lung development and regeneration.     

Chemical studies on the silver staining of nucleoli

The uptake of Ag-ions by isolated nucleoli of rat liver cells was studied. Nucleolar proteins separated by electrophoresis were examined for selective silver-staining. A mechanism for preferential Ag-staining of the nucleoli is discussed.     

Neuropsychology: pitch discrimination in the early blind

Do blind people develop superior abilities in auditory perception to compensate for their lack of vision? They are known to be better than sighted people at orientating themselves by sound, but it is not clear whether this enhanced awareness extends to other auditory domains, such as listening to music or to voices. Here we show that blind people are better than sighted controls at judging the direction of pitch change between sounds, even when the speed of change is ten times faster than that perceived by the controls--but only if they became blind at an early age. The younger the onset of blindness, the better is the performance, which is in line with cerebral plasticity being optimal during the early years.     

Chemical studies on the silver staining of nucleoli

Summary The uptake of Ag-ions by isolated nucleoli of rat liver cells was studied. Nucleolar proteins separated by electrophoresis were examined for selective silver-staining. A mechanism for a preferential Ag-staining of the nucleoli is discussed.We thank Mrs L. Schwinn for her valuable technical assistance, and Mrs K. Jain for presenting us DNA. We would like to thank the Department of Biology V for making possible the measurements with the atomic absorption spectrophotometer. This work was supported by the Deutsche Forschungsgemeinschaft.