Although changes in nucleotide sequence affecting the composition and the structure of proteins are well known, functional changes resulting from nucleotide substitutions cannot always be inferred from simple analysis of DNA sequence. Because a strong synonymous codon usage bias in the human DRD2 gene, suggesting selection on synonymous positions, was revealed by the relative independence of the G+C content of the third codon positions from the isochoric G+C frequencies, we chose to investigate functional effects of the six known naturally occurring synonymous changes (C132T, G423A, T765C, C939T, C957T, and G1101A) in the human DRD2. We report here that some synonymous mutations in the human DRD2 have functional effects and suggest a novel genetic mechanism. 957T, rather than being 'silent', altered the predicted mRNA folding, led to a decrease in mRNA stability and translation, and dramatically changed dopamine-induced up-regulation of DRD2 expression. 1101A did not show an effect by itself but annulled the above effects of 957T in the compound clone 957T/1101A, demonstrating that combinations of synonymous mutations can have functional consequences drastically different from those of each isolated mutation. C957T was found to be in linkage disequilibrium in a European-American population with the -141C Ins/Del and TaqI 'A' variants, which have been reported to be associated with schizophrenia and alcoholism, respectively. These results call into question some assumptions made about synonymous variation in molecular population genetics and gene-mapping studies of diseases with complex inheritance, and indicate that synonymous variation can have effects of potential pathophysiological and pharmacogenetic importance.

The purpose of this work is to identify and synthesize research produced since the second edition of these Guidelines was published and incorporate new results into revised evidence-based recommendations for the treatment of severe traumatic brain injury in pediatric patients. This document provides an overview of our process, lists the new research added, and includes the revised recommendations. Recommendations are only provided when there is supporting evidence. This update includes 22 recommendations, 9 are new or revised from previous editions. New recommendations on neuroimaging, hyperosmolar therapy, analgesics and sedatives, seizure prophylaxis, temperature control/hypothermia, and nutrition are provided. None are level I, 3 are level II, and 19 are level III. The Clinical Investigators responsible for these Guidelines also created a companion algorithm that supplements the recommendations with expert consensus where evidence is not available and organizes possible interventions into first and second tier utilization. The complete guideline document and supplemental appendices are available electronically (https://doi.org/10.1097/PCC.0000000000001735). The online documents contain summaries and evaluations of all the studies considered, including those from prior editions, and more detailed information on our methodology. New level II and level III evidence-based recommendations and an algorithm provide additional guidance for the development of local protocols to treat pediatric patients with severe traumatic brain injury. Our intention is to identify and institute a sustainable process to update these Guidelines as new evidence becomes available.

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