292 Ophthalmic Surgery, Lasers & Imaging Retina | Healio.com/OSLIRetina Practical Retina Incorporating current trials and technology into clinical practice Genetic Testing for Retina Specialists by Edward H. Wood, MD; and Kimberly A. Drenser, MD, PhD In December 2017, the U.S. Food and Drug Administration approved Lux- terna (voretigene neparvovec-rzyl; Spark Therapeutics, Philadelphia, PA) as a new gene therapy to treat children and adult patients with RPE65 mu- tations resulting in vision loss. The availability of this landmark treat- ment has brought attention to the need for genetic testing by retina specialists. For this column, Kimberly Drenser, MD, PhD, and Ed- ward H. Wood, MD, from William Beaumont Hospital in Royal Oak, MI, provide us with an overview of this important topic. They will begin with a historical perspec- tive, dating back to 1953 during the days of Watson and Crick. They will then review genetic sequencing, pro- vide an overview of the importance of genetic testing in retina, and conclude with American Academy of Ophthal- mology guidelines for genetic testing. We are grateful to Drs. Drenser and Wood for generously sharing their ex- tensive knowledge on this topic with our community. Given the numerous gene therapies currently in clinical trials, I anticipate that genetic testing will be routinely offered to our pa- tients in our practices. Therefore, this piece will likely be of interest to many of us in the retina community. When Watson and Crick published their seminal Nature paper 1 in 1953 proposing the double-helix, they simultaneously pre- dicted the field of genetic sequencing en- tirely: “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copy- ing mechanism for the genetic material.” Since this time, the scientific progress made within genomics has been remark- able. Sixty-five years later, we are now able to sequence an individual’s entire genome and have begun to treat disease-causing mutations with gene therapy and gene ed- iting tools. But, how do we bridge the gap between genetic testing performed within specialized academic research institutions and biotechnology companies, and genetic testing performed within routine vitreoret- inal clinical practice? A BRIEF HISTORY OF GENETIC SEQUENCING The discovery of DNA 1 in 1953 and the development of the central dogma 2 (DNA makes RNA, RNA makes protein) in 1970 marks a paradigm shift. The discovery of DNA cleav- ing enzymes, type 2 restriction enzymes, 2,3 in 1970 followed by the ability to clone DNA via molecules called plasmids 4 (1973) allowed for targeted DNA cutting, isolation, and map- ping, thus setting the stage for genetic sequencing. Frederic Sanger’s development of “chain termination” method of se- quencing 5 at Oxford (1977) and polymerase chain reaction (PCR) by Kary Mullis (1985) 6 revolutionized genetic sequenc- ing. Sanger sequencing was used by the Human Genome Proj- ect 7 (1990-2003) and Craig Venter’s group at Celera 8 to map the first human genome and remains the gold-standard meth- odology (with error rates less than 1%). However, Sanger sequencing is slow and requires large DNA fragments to be cloned, which contributed to the Human Genome Project costing $2.7 billion. 9 These disadvantages inspired scientists to create a second generation of genetic sequencing methods. Next-generation sequencing (NGS) methods allow sequencing of huge numbers of samples at one time, so called “massively parallel sequencing.” This improvement makes it possible to sequence an individual’s entire genome (with the “genome” consisting of 3x10 9 bases) in “whole genome sequencing” Edward H. Wood Kimberly A. Drenser doi: 10.3928/23258160-20180501-01 Seenu M. Hariprasad Practical Retina Co-Editor