Differentiation of mucous neck cells into parietal cells: a new concept of mitochondrial biogenesis

Abstract

Parietal cells of the gastric fundic mucosa are small and contain only a few tiny mitochondria when they begin to differentiate from mucous neck cells. The canalicular ATPase activity characteristic of mature parietal cells is discrete in these young cells, whereas areas of very high activity are apparent in the Golgi complex, reticulum, nuclear envelope, mitochondrial wall, and plasma membrane. Close relations and contacts occur between mitochondria and these organelles, and the size and number of mitochondria increase progressively. These relations, as well as mitochondrial ATPase activity (a true differentiation marker), cease once the mitochondria become as numerous and large as those of a mature parietal cell. Our observations suggest that a secondary form of mitochondrial biogenesis, involving the massive participation of other organelles and independent of the classical mechanisms inherent in mitosis, occurs in parietal cells at the beginning of G1 phase during the 6 days of their maturation.

Serial blockface SEM suggests that stem cells may participate in adult notochord growth in an invertebrate chordate, the Bahamas lancelet

“…The larger mitochondrial volume per cell in zone c might be correlated with a more advanced state of differentiation, as proposed for mammalian gut cells [ 23 ] and/or might reflect the higher energy needs or the muscular lamellar cells in more mature parts of the notochord. The mitochondria in the zone c lamellar cells have two additional features of unknown significance: first is their general tendency to occur in dorsal and ventral groups in the cytoplasm, and second is their occasional aggregation along the plasma membrane on either the anterior ( c5 ) or the posterior ( c14 ) side of the cell.…”