Redundant Genetic Instructions in 'Junk DNA' Support Healthy Development
ScienceDaily (July 17, 2010) — Seemingly redundant portions of the fruit fly genome may not be so redundant after all. New findings from a Princeton-led team of researchers suggest that repeated instructional regions in the flies' DNA may contribute to normal development under less-than-ideal growth conditions by making sure that genes are turned on and off at the appropriate times. If similar regions are found in humans, they may hold important clues to understanding developmental disorders.
The research results, published in the July 22 issue of the journal Nature, add to the growing body of evidence that so-called "junk DNA" is anything but rubbish. The term "junk DNA" is commonly used to describe the portion of the genome that doesn't contain genes, which are pieces of DNA that code for the production of proteins and other molecules that have specific functions. The noncoding region is often surprisingly large; in humans, some 98 percent of the genome merits "junk" status. But according to David Stern, a Princeton professor in the Department of Ecology and Evolutionary Biology, scientists increasingly believe "junk DNA" is crucial for turning the information encoded in genes into useful products.
"Over the past 10 to 20 years, research has shown that instructional regions outside the protein-coding region are important for regulating when genes are turned on and off," said Stern, the senior scientist on the paper. "Now we're finding that additional copies of these genetic instructions are important for maintaining stable gene function even in a variable environment, so that genes produce the right output for organisms to develop normally."
Stern, along with Nicolás Frankel, a postdoctoral research fellow at Princeton, and their collaborators focused their attention on instructional regions called enhancers. These regions play an important role in the process by which information encoded in genes is used to direct the synthesis of the proteins that make an organism what it is -- be it a fly, a mouse or a human.
"To interpret and fully understand the genome, we need to think of it from an ecological and evolutionary perspective," Stern said. "Its purpose is to produce a healthy organism in a variable environment, so a good portion of it has evolved to deal with contingencies that organisms will experience in the real world."
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Read more here/Leia mais aqui: Science Daily
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Nature advance online publication 30 May 2010 | doi:10.1038/nature09158; Received 30 December 2009; Accepted 11 May 2010; Published online 30 May 2010
Phenotypic robustness conferred by apparently redundant transcriptional enhancers
- Howard Hughes Medical Institute and Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey 08544, USA
- Department of Biology, Bryn Mawr College, 101 N. Merion Ave, Bryn Mawr, Pennsylvania 19010, USA
- Université de Toulouse and Centre National de la Recherche Scientifique, Centre de Biologie du Développement, UMR5547, Toulouse, F-31062, France
Correspondence to: David L. Stern1 Email: dstern@princeton.edu
Genes include cis-regulatory regions that contain transcriptional enhancers. Recent reports have shown that developmental genes often possess multiple discrete enhancer modules that drive transcription in similar spatio-temporal patterns1, 2, 3, 4: primary enhancers located near the basal promoter and secondary, or ‘shadow’, enhancers located at more remote positions. It has been proposed that the seemingly redundant activity of primary and secondary enhancers contributes to phenotypic robustness1, 5. We tested this hypothesis by generating a deficiency that removes two newly discovered enhancers of shavenbaby (svb, a transcript of the ovolocus), a gene encoding a transcription factor that directs development of Drosophila larval trichomes6. At optimal temperatures for embryonic development, this deficiency causes minor defects in trichome patterning. In embryos that develop at both low and high extreme temperatures, however, absence of these secondary enhancers leads to extensive loss of trichomes. These temperature-dependent defects can be rescued by a transgene carrying a secondary enhancer driving transcription of the svb cDNA. Finally, removal of one copy of wingless, a gene required for normal trichome patterning7, causes a similar loss of trichomes only in flies lacking the secondary enhancers. These results support the hypothesis that secondary enhancers contribute to phenotypic robustness in the face of environmental and genetic variability.
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NOTA CAUSTICANTE DESTE BLOGGER:
Eu li esta parte da entrevista de Stern e fiquei encafifado:
"To interpret and fully understand the genome, we need to think of it from an ecological and evolutionary perspective,.. Its purpose is to produce a healthy organism in a variable environment, so a good portion of it has evolved to deal with contingencies that organisms will experience in the real world."
Traduzindo em graúdos: Para interpretar e entender plenamente o genoma, nós precisamos pensar nele a partir de uma perspectiva ecológica e evolucionária... Seu propósito [Argh, isso é como cometer um assassinato epistêmico contra Darwin que, segundo alguns e outros, eliminou de vez a teleologia da biologia evolutiva. Será???] é produzir um organismo saudável [Argh, agora ele cometeu um holausto epistêmico contra a teoria da evolução através da seleção natural de Darwin cuja proposição de seleção natural é de um mecanismo cego, aleatório e sem nenhuma preocupação de saudabilidade ou não dos seres vivos], em um ambiente variável, assim, uma boa porção do genoma evoluiu [Mas Stern et al não disseram COMO que o genoma evoluiu. Stern só disse: evoluiu, Abracadabra] para lidar [Ué, lidar não requer saber algo com antecedência??? ] com contigências que os organismos irão experimentar no mundo real."
Fui, nem sei por que, pensando: a Lógica Darwiniana 101 não é a maior ideia que toda a humanidade já teve. Traduzindo em miúdos: a seleção natural não é esta Coca-Cola toda, oops, não é assim uma Brastemp em um contexto de justificação teórica.
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