Domes and gland-like structures

Summary

Despite the assumption that metazoan proliferation occurs only by mitosis, there are numerous documented examples of amitosis (reviewed in Fleming, 2016c). This web site explores one of the most recently explored kinds of amitotic cell proliferation. The process described herein could really only have been followed using human endometrial epithelial cells in culture. As shown through the photomicrographs on this site, monolayer cells are recruited to form syncytia containing multiple nuclei that aggregate and become surrounded by giant fused mitochondria in structures called mitonucleons.

Small gas vacuoles form in the mass of chromatin at the center of the mitonucleon resulting in the "optically clear nuclei" (OCN) structure documented in the literature, frequently found associated with cancer. Vesiculated mitochondria separate from, but surrounding, the chromatin develops a large central vacuole so that the chromatin is compressed against the mitonucleon membrane forming a structure that resembles "signet ring cells," so-called because they contain pyknotic nuclei that have been pressured against a cell membrane by a vacuole.

The pressure of the growing vacuole eventually breaches the mitonucleon membrane and the heterochromatin of the pyknotic nuclear aggregate "fades" in a manner characteristic of a process called karyolysis. That fading, and the resulting loss of a typical ovoid nuclear structure extends into karyorrhexis, the fragmentation of chromatin usually associated with cell death. In this instance, DNA fragmentation is reversed, chromatin coalesces and forms multiple nuclei that populate the envelope of the resulting dome. The entire process occurs over a period of 24 to 30 hours. Dozens of anchorage independent cells are formed by amitosis in little more than the time required for the production of two cells by mitosis.