Let’s Chat About … Genetics and Inherited Retinal Disease

 In Blog

You or your loved one just received a clinical diagnosis of Leber congenital amaurosis (LCA), a rare inherited retinal disorder caused by a mutated gene. The disease causes severe vision loss at birth and affects the peripheral rod cells that allow night vision and the central cone cells  responsible for fine detail and color vision. What now?

The next most important step is to get a genetic test for a confirmed genetic diagnosis to clarify the underlying genetic explanation of the disease. Finding the specific gene causing the defect is critical for moving forward with research and treatment.

Genetic counselors like Emily Place help navigate the complex world of gene mutations, genetic testing, and genetic diagnoses. She is among the more than 4,700 certified genetic counselors nationwide, and she specializes in counseling families living with inherited retinal diseases (IRDs). 

Place, a Licensed Genetic Counselor and Research Study Coordinator at Massachusetts Eye and Ear (MEE), discussed her role in the ever-evolving world of genetics in our March webinar episode: “Let’s Chat About…the ins and outs of genetic testing.” Sofia Sees Hope Director of Marketing and Communications Elissa Bass moderated the monthly series, which you can watch here

Place began her work at MEE’s Ocular Genomics Institute (OGI) in 2011, about the same time the first clinical trials were underway for a vision-improving gene therapy. Six years later, researchers identified, and regulators approved LUXTURNA®, the first gene therapy treatment for an inherited disease, and specifically for LCA2-RPE65, one of the more than 25 gene mutations associated with LCA.

Before OGI, Place worked as a pediatric genetic counselor at Children’s Hospital of Philadelphia, the same place researchers and Spark Therapeutics developed that RPE65 gene therapy.

She earned a Bachelor of Arts in Biology from the University of St. Thomas and her master’s degree in Human Genetics from New York’s Sarah Lawrence College, which in 1969 established the first graduate degree program in genetic counseling. With ever-expanding genetic studies, the profession dramatically increased with more than 50 programs now in the United States.

Basic Genetics

The Human Genome Project (HGP) began in 1990 as an international, collaborative quest to map and understand all the genes of human beings and their roles in health and disease. The project, completed in 2003, revealed there are probably about 20,500 human genes, referred to collectively as our genome, according to the National Human Genome Research Institute.

Scientists have since identified more than 30,000 genes in our body and more genetic causes of inherited conditions, and more research remains to be done to better understand the causes of inherited conditions and to identify more genes.

“Genes are instructions or blueprints that tell us how to grow and function,” Place said.

This genetic information is organized in our chromosomes and can be found in every cell of our body. 

More than 200 genes have been identified as playing a specific role to help retina function.

“These inherited retinal conditions can arise because of a genetic variation or change within a gene that we know is important for retinal function and, what we really mean here, is that this genetic change is changing the genetic code in some sort of way that is causing the gene not to function properly within the retinal cells.”

With a few exceptions, she said, a general eye exam will not reveal the underlying genetic explanation for retinal disease.

“That’s where genetic testing is necessary to rule in or identify which one of these 200-plus genes could be the underlying explanation and thus, more definitively rule in an inherited condition and provide a more definitive specific genetic diagnosis.”

The most common pattern for inherited retinal diseases to occur is a recessively inherited condition, the result of inheriting a genetic variation in two copies of the gene, one of those copies inherited from mom and one from dad.

“In these recessive conditions, generally, there may be no family history of anybody else in the family with similar conditions, and that’s because individuals can be carriers, and they may carry one copy of a variation and one copy of their gene, but they have another that can compensate. 

“Carriers can be asymptomatic and run through multiple generations and not even know that they’re carriers, and it isn’t until two carriers meet that there’s even a chance for both of them to pass on the genetic change.”

Specific Genetic Identification Versus No Clear Explanation

Counselors help in multiple ways as a family or patient is working toward a genetic diagnosis. Place can begin counseling families before testing, gleaning family history details, reviewing complexities of different inheritance patterns, and looking into what can and cannot be learned from testing.

“It’s also exploring with patients and families whether this is the right time for genetic testing. Is this something that the individual is ready to move forward with or is it something that maybe should be discussed or pursued a later time?”

Counselors can work with families after testing, reviewing the result, whether it be that the testing identified a specific gene or that no clear explanation was found, which happens 30 percent of the time, Place said. 

No clear explanation could mean a negative result or an inconclusive result. A negative result can mean no genetic variations were identified. An inconclusive one could be that variants were identified within one to two genes, and the lab does not currently have enough data to classify those variants as disease-causing, but they also cannot be ruled out as not disease causing, she said.

“Sometimes additional testing of other family members may be helpful in resolving the significance of those variants, or that it’s going to take some time and more genetic knowledge is needed to better classify those variants.”

Working with a counselor also helps sort out next steps to take, including the possibility of periodically checking back with your genetic counselor to see if more recent research has updated results or new testing options.

“A True Privilege” To Create Relationships

Long-term relationships can develop between counselors and families after testing. If the test identified a specific gene, they discuss the result, assess the risk of other family members having the mutation, coordinate whether they should get tested, and maintain communications going forward about potential genetic-related treatments and therapies. 

Place said it may not be the case with every counselor, but long-term relationships with families are the norm in her work.

“I think every clinic and counselor’s experience will be a bit different. I have the true pleasure of working within an IRD clinic where we’ve had long-term relations with the families, and I get to see families back over the course of their visits with us, and so it is a true privilege to be able to create these longer relationships with families.”

Her approach to testing is that a patient diagnosed with any type of IRD should undergo a full IRD panel testing so as not to miss a particular gene. 

She also said it’s important for the patients and families to have back-and-forth relationships with their ophthalmologists.

“It’s definitely a two-way relationship, continuing to stay engaged with your providers, but your provider also thinking about being on top of the different testing options that are available.”

Getting Genetically Tested

A person needs a doctor’s order to be genetically tested. Diagnostic testing is done on a patient’s blood or saliva sample at a clinically certified lab that analyzes a specific set of genes identified to be the cause of retinal condition.

Whether you are living in a rural area or a city, you can find genetic counselors and information about testing through the National Society of Genetic Counselors (NSGC) or local genetic providers through the American College of Medical Genetics and Genomics (ACMG).

ACMG is a place to locate a Medical Geneticist (MD/physician), as well as medical genetics clinics. The search ‘Find a Genetic Service’ can be used to locate a genetic professional.

Search engines in both organizations bring up regional options by entering your zip code. Counselors can meet in-person with patients or, depending on the clinic, via telehealth, by phone, video conferencing, and other virtual methods.

Testing resources also can be found through medical or clinical genetics’ departments in your hospital system.

Also, Sofia Sees Hope has donated more than $140,000 to fund free genetic testing for individuals with inherited retinal disease through the My Retina Tracker® program, launched and managed by the Foundation Fighting Blindness. The program is an open access, no-cost genetic testing program for individuals with a clinical diagnosis of an IRD.

“So much has changed in terms of access to genetic testing for inherited retinal diseases over the last several years, and it’s more available to patients than it ever has been in the past. I would say this is really a good time to work toward getting a genetic diagnosis – getting genetic testing if you haven’t had it or re-engaging with your providers if you’ve had testing years ago without a positive result and discuss updated testing options. 

“There are resources out there and available, so there are plenty of individuals like me that are available to help facilitate testing or get you in touch with the right counselor or medical geneticist to help facilitate testing for you.”