Metakaryotic stem cell nuclei use pangenomic dsRNA/DNA intermediates in genome replication and segregation.

Bell shaped nuclei of metakaryotic cells double their DNA content during and after symmetric and asymmetric amitotic fissions rather than in the separate, pre-mitotic S-phase of eukaryotic cells. A parsimonious hypothesis was tested that the two anti-parallel strands of each chromatid DNA helix were first segregated as ssDNA-containing complexes into sister nuclei then copied to recreate a dsDNA genome. Metakaryotic nuclei that were treated during amitosis with RNase A and stained with acridine orange or fluorescent antibody to ssDNA revealed large amounts of ssDNA. Without RNase treatment metakaryotic nuclei in amitosis stained strongly with an antibody complex specific to dsRNA/DNA. Images of amitotic figures co-stained with dsRNA/DNA antibody and DAPI indicated that the entire interphase dsDNA genome (B-form helices) was transformed into two dsRNA/DNA genomes (A-form helices) that were segregated in the daughter cell nuclei then retransformed into dsDNA. As this process segregates DNA strands of opposite polarity in sister cells it hypothetically offers a sequential switching mechanism within the diverging stem cell lineages of development.

Human fetal/tumor metakaryotic stem cells: pangenomic homologous pairing and telomeric end-joining of chromatids.

Metakaryotic cells and syncytia with large, hollow, bell-shaped nuclei demonstrate symmetrical and asymmetrical amitotic nuclear fissions in microanatomical positions and numbers expected of stem cell lineages in tissues of all three primordial germ layers and their derived tumors. Using fluorescence in situ hybridization, mononuclear metakaryotic interphase cells have been found with only 23 centromeric and 23 telomeric staining regions. Syncytial bell-shaped nuclei found approximately during weeks 5-12 of human gestation display 23 centromeric and either 23 or 46 telomeric staining regions. These images suggest that (1) homologous chromatids pair at centromeres and telomeres, (2) all paired telomeres join end-to-end with other paired telomeres in all mononuclear and some syncytial metakaryotic cells, and (3) telomere junctions may open and close during the syncytial phase of development. Twenty-three telomeric joining figures could be accounted by 23 rings of one chromatid pair each, a single pangenomic ring of 23 joined chromatid pairs, or any of many possible sets of oligo-chromatid pair rings. As telomeric end-joining may affect peri-telomeric gene expression, a programmed sequence of telomeric end-joining associations in metakaryotic stem cells could guide developmental arboration and errors in, or interruptions of, this program could contribute to carcinogenesis.

Metakaryotic stem cell lineages in organogenesis of humans and other metazoans.

A non-eukaryotic, metakaryotic cell with large, open mouthed, bell shaped nuclei represents an important stem cell lineage in fetal/juvenile organogenesis in humans and rodents. each human bell shaped nucleus contains the diploid human DNA genome as tested by quantitative Feulgen DNA cytometry and fluorescent in situ hybridization with human pan-telomeric, pan-centromeric and chromosome specific probes. From weeks approximately 5-12 of human gestation the bell shaped nuclei are found in organ anlagen enclosed in sarcomeric tubular syncytia. Within syncytia bell shaped nuclear number increases binomially up to 16 or 32 nuclei; clusters of syncytia are regularly dispersed in organ anlagen. Syncytial bell shaped nuclei demonstrate two forms of symmetrical amitoses, facing or "kissing" bells and "stacking" bells resembling separation of two paper cups. Remarkably, DNA increase and nuclear fission occur coordinately. Importantly, syncytial bell shaped nuclei undergo asymmetrical amitoses creating organ specific ensembles of up to eight distinct closed nuclear forms, a characteristic required of a stem cell lineage. Closed nuclei emerging from bell shaped nuclei are eukaryotic as demonstrated by their subsequent increases by extra-syncytial mitoses populating the parenchyma of growing anlagen. From 9-14 weeks syncytia fragment forming single cells with bell shaped nuclei that continue to display both symmetrical and asymmetrical amitoses. These forms persist in the juvenile period and are specifically observed in bases of colonic crypts. Metakaryotic forms are found in organogenesis of humans, rats, mice and the plant Arabidopsis indicating an evolutionary origin prior to the divergence of plants and animals.