Can RNA Splicing Errors Cause Disease?



before computers and digital cameras movies were edited by hand editors would get rows of raw film and physically cut and paste the scenes together this process was called splicing but what does this old editing technique have to do with human disease it runs in the family chances are you've heard this phrase before today we know that the biological details from our bodies I passed out for my parents this includes physical traits like your hair color or height but also your susceptibility to certain kinds of disease all this information is encoded in your DNA DNA is made up of four nucleotide bases a G C and T and spell out the information in the cell needs to carry out the functions of life these are organized into units called genes now every cell in your body contains workers called ribosomes ribosomes build proteins and each protein carries out a specific task in the cell however ribosomes need instructions every time they put together a protein inside every cell there's a nucleus and inside every nucleus there's a copy of your DNA think of the nucleus as a media center it produces tutorials that teach ribosomes how to build proteins and right now we need to build a protein to strengthen the walls of the nucleus we'll call it protein X imagine your DNA is a strip of film from here to here is one gene inside this gene is the whole tutorial for building protein X but how do we make the tutorial first the nucleus copies this gene this copy is called RNA and can be read by the ribosome the original DNA stays in the nucleus and is preserved for future reference but the tutorial is not ready yet because the footage is scattered around the gene part of it is here another part is here another part is here these frames of footage are called exons the filmstrip also contains frames that aren't part of the video these sequences are called introns and will not be in the final tutorial one of their purposes is to provide instructions on how and where to edit the film this is the spliceosome think of it as a film editor it follows directions in the introns cuts them out and pastes the exons together this entire process is known as splicing now we have a coherent tutorial video that can be related to the ribosomes splicing is crucial to the correct construction of proteins unfortunately mistakes can occur as a result of mutations mutations are variations from the nucleotide sequences in our original DNA we used to think only mutations and the movie frames themselves caused disease but now we know that mutations that affect the splicing process can also cause disease back to protein X if there are no mutations in the film protein X will look like this and fit perfectly into the structure but let's say there's a mutation in the film frames this might cause protein X to have a little hole in it like this when it slots in it leaves a gap in the wall and you get a slightly weaker structure now let's say there's a splicing mutation a mutation and the instructional frames this will cause the organization of the video to be altered some scenes might be missing others might be cut short and others may include unnecessary segments of film this will have a much bigger effect on how protein X is built the finished protein might have an entire region missing like this keep in mind that this is happening in many cells at once so imagine the kinds of damage that splicing mutations can do so why is splicing important experts estimate that one third of all heritable disease involves an error in splicing still we don't have a detailed understanding of how exactly splicing goes wrong part of the problem is that each person has about 3 million unique differences in their DNA so it's hard to tell which ones caused disease today researchers are using computers and statistics to comb through mountains of mutations and model their effects on splicing we hope to find patterns that tell us how splicing is directed eventually doctors may be able to come up with personalized treatments by studying the mutations that affect how our genetic tutorials are edited

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