Historical Significance
That genetic mutations in HRAS cause Costello syndrome was first reported in 2005. These mutations, along with mutations that cause cardiofaciocutaneous syndrome, found soon after, surprised geneticists and changed how genetic syndromes can be grouped. Before this, geneticists looked for new mutations in genes with mutations that caused syndromes similar to the unknown syndrome. For example, researchers looked at and around the most common Noonan syndrome mutation, PTPN11, but did not find anything related to Costello syndrome or cardiofaciocutaneous syndrome syndrome. The first mutation that is now identified as one of the Costello syndrome alleles was found unexpectedly when Japanese researchers used the DNA of children with Costello syndrome as a control, looking for another Noonan gene
Geneticists realized that the syndromes they were grouping together clinically according to their signs and symptoms were related in a way they had never realized: the mutations that cause Costello syndrome, Noonan syndrome and cardiofaciocutaneous syndromes are linked by their cellular function, not by being on or close to a gene with a known mutation. The cellular function that links them is a common signalling pathway that brings information from outside the cell to the nucleus. This pathway is called the Ras-MAP-kinase signal transduction pathway (Ras-MAPK Pathway).
Read more about this topic: Costello Syndrome
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