Human cell type diversity, evolution, development, and classification with special reference to cells derived from the neural crest

Abstract

Metazoans are composed of a finite number of recognisable cell types. Similar to the relationship between species and ecosystems, knowledge of cell type diversity contributes to studies of complexity and evolution. However, as with other units of evolution, the cell type often resists definition. This review proposes guidelines for characterising cell types and discusses cell homology and the various developmental pathways by which cell types arise, including germ layers, blastemata (secondary development/neurulation), stem cells, and transdifferentiation. An updated list of cell types is presented for a familiar, albeit overlooked model taxon, adult Homo sapiens, with 411 cell types, including 145 types of neurons, recognised. Two methods for organising these cell types are explored. One is the artificial classification technique, clustering cells using commonly accepted criteria of similarity. The second approach, an empirical method modeled after cladistics, resolves the classification in terms of shared features rather than overall similarity. While the results of each scheme differ, both methods address important questions. The artificial classification provides compelling (and independent) support for the neural crest as the fourth germ layer, while the cladistic approach permits the evaluation of cell type evolution. Using the cladistic approach we observe a correlation between the developmental and evolutionary origin of a cell, suggesting that this method is useful for predicting which cell types share common (multipotential) progenitors. Whereas the current effort is restricted by the availability of phenotypic details for most cell types, the present study demonstrates that a comprehensive cladistic classification is practical, attainable, and warranted. The use of cell types and cell type comparative classification schemes has the potential to offer new and alternative models for therapeutic evaluation.

The statistical geometry of transcriptome divergence in cell-type evolution and cancer

“…T he number of recognizable cell types varies between metazoan lineages by at least two orders of magnitude, from five in the primitive metazoan Trichoplax to at least 500 in humans [1][2][3] . The processes that create this diversity, however, are not well understood.…”

Modularity map of the network of human cell differentiation

“…The process of cell differentiation is then mapped onto a complex network that consists of 873 nodes connected through 977 edges. The nodes in the network represent distinct cell types reported in the literature (1)(2)(3)(4)(5)(6)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) and the edges represent the association between two cell types through a differentiation event.…”

“…Recent advances in the research on stem cell properties and embryonic development have uncovered several steps in the differentiation process (1)(2)(3)(4)(5)(6)(7). Single and multiple sequences of cell differentiation have been identified through in vivo observations of a particular embryo during early stages of development and through pathology studies of miscarriages during late stages of the process.…”

Exposure to Nano-Sized Particles and the Emergence of Contemporary Diseases with a Focus on Epigenetics

“…Hence, the activity of a gene is influenced by the local DNA methylation pattern, the state of histone modifications, the nuclear position of the gene relative to repressive heterochromatin domains, and the architecture of the gene locus. (Vickaryous & Hall, 2006) In any case, epigenetic imprinting associated with the in-and/or activation of genes implies that changes acquired during gametogenesis are not only passed on but also extend into embryonic development. (Jaenisch & Gurdon, 2007) In animal studies it was possible to correlate nano-size particle exposure of a smelter to hypermethylation of sperm-DNA that persisted into the next generation even though the filial generation was no longer exposed to this aerosol.…”