While snakes and lizards belong to a number of scaly, they have apparent aspect: snakes have no limbs.
Scientists have studied the genetic changes that led to this difference, and analyzed the degradation in the eyes of some subterranean animals, informs Rus.Media.
“Our work consisted of studying the genomes of several vertebrate species, including identification of genomic regions that have changed just in the underground snakes or mammals, while remaining unchanged in other species that have lost limbs or have normal eyes”, – says the head of the research group Gusson ROSTO Juliana (Juliana Gusson Roscito). It studies the Institute of molecular cell biology and genetics max Planck in Dresden (Germany) published in the journal Nature Communications.
According to scientists, the mammals with degraded visual system, apparently, is isolated from the genomes of certain genes, usually those associated with the formation of the lens and fotoreceptori cells in the eyes. Most likely, this process was gradual, and, in the end, these genes completely lost the ability to encode proteins. However, according to Rosso, this did not happen with snakes that have not lost the genes associated with the formation of the limbs.
“To be more precise, our research, which sequentual the genome of the snake, really revealed the loss of one gene, but only one. Therefore, the approach we chose was to study genes and elements that regulate their expression,” she adds.
Gene expression – whether “active” gene or not depends on regulatory elements that are located outside the gene. They basically pass or block the information within the gene, which is transcribed into RNA and then transferred to generate the protein. This process is controlled by CIS-regulatory elements (cis-regulatory elements, CRE) sequences of nucleotides in DNA located near the genes they regulate. These CRE can significantly change the functionality of the genome with the genes that they block or activate.
“Regulatory element can activate or repress gene expression in a particular part of the body such as the extremities, while the other regulatory element can activate or repress the expression of the same gene in another part of the body. If the gene is lost, it ceases expressvisa in both places and often can have a negative effect on the formation of the body. However, if you lose just one of the regulatory elements, the expression may disappear in one part, while remaining in another,” explains Rosso.
However, to accurately determine the CRE is quite difficult. All genes follow a certain structural scheme, with the base pairs at each end of the gene, so they are easy to differentiate. CRE must be determined indirectly, usually by comparing DNA sequences from different species. That’s what made a team of scientists: they compared the genomes of snakes with the genes of various reptiles and vertebrates that have limbs. According to experts, as the “genomic sequences for reptiles with well developed limbs small,” they are on their own and for the first time sequenced the genome of the Argentine black and white tag (Salvator merianae).
Using this genome as an example, the team examined the genomes and of several other types: two snakes (boa and Python), the other three reptiles, three birds, alligator, three turtles, 14 species of mammals and fish squad alicantina (Coelacanthiformes). Having five thousand possible candidates for regulatory elements in the DNA of these species, the team studied the genomes of several species of snakes. They managed to narrow the search to a set of CRE, the mutation of which could lead to the disappearance of the limbs of these reptiles.
ROSTO notes, found that CRE is just one of the regulatory elements for one of the several genes that control the formation of limbs. In their work, scientists have greatly expanded this set by showing that some other elements responsible for the regulation of many genes, mutated into snakes.