Evolution may be front-end loaded (Introduction)

by David Turell , Wednesday, August 19, 2015, 00:23 (3384 days ago)

This massive study of genes in 48 species suggests that suppression of genes advances diversity:-http://phys.org/news/2015-08-nature-tinkerer-inventor.html-The Krüppel-like factor and specificity protein (KLF/SP) genes are found across many species, ranging from single cell organisms to humans. This gene family has been conserved during evolution, because it plays a vital role in regulating the expression of other genes. Understanding the evolutionary history of the KLF/SP gene family may shed light on major events in animal evolution and perhaps help discern some of the molecular mechanisms associated with certain human diseases, including many cancers. -By closely examining the genomes of 48 species, biologists from the University of Miami (UM) College of Arts & Sciences have revealed the timing and mechanisms underlying the expansion and diversification of the KLF/SP gene family, which is known to regulate the maintenance of stem cells. Their study shows that, while the origin of the KLF/SP gene family predates the origins of animals well over 600 million years ago, the expansion of the gene family and increasing cell type diversity in animals happened concurrently.-"Our study paints a picture of nature innovating largely through sharing the functional bits of genes—tinkering with molecular genetic material that already exists," said William E. Browne, assistant professor of Biology at UM's College of Arts & Sciences and principal investigator of the study.-***-KLF/SP genes belong to an important class of genes, called transcription factors, which either turn on or turn off the expression of other genes. The findings show a clear increase in repressor domains (domains that turn off the expression of other genes) as the KLF/SP gene family has expanded. This expansion mirrors increases in cell type diversity among animals and demonstrates that the transition from single-cell life to multicellular life occurred largely by "tinkering" with existing genes.-"This is interesting because it supports the idea that the appearance of new types of cells in a lineage of organisms as they evolve may be, more commonly, a consequence of turning off genes in unique temporal and spatial combinations," Browne said. "Large numbers of unique cell types are required to support the development of complex tissues and organs."-The original article conclusion:-Our analysis across 48 eukaryotic genomes illuminates the origin and evolutionary
history of the KLF/SP gene family. We also identify and characterize associated transactivation/repression domains, including LCRs, enabling us to develop models of KLF/SP domain co-occurrence evolution. By extending our domain search to include entire proteomes we find evidence for a complex intersection of domain shuffling, gene duplication, and de novo domain evolution as the primary mechanisms for the diversification of the KLF/SP gene family across the Metazoa. Our results uncover a pattern of an increased frequency of repressive domain connectivity repertoires (P-rich LCRs, SID, R2/R3, and PVDLS domains) in the KLF/SP gene family among metazoans suggesting a role in mediating diverse transcriptional repression
activity. Our phylogenetic results further suggest the expansion of the KLF/SP gene family mirrors increased cell type diversity during metazoan lineage diversification. The expansion and diversification of the KLF/SP gene family within the Metazoa may thus reflect the accumulation of differential transcriptional repression strategies associated with the development of extensive repertoires of cell types required to support complex tissues.- http://gbe.oxfordjournals.org/content/early/2015/07/30/gbe.evv141.full.pdf+html