The science of a rare disease

Mapping the genetics of a new rare syndrome

‘What’s that black thing on his brain?’

The time from the initial question asked, almost innocently, by my husband during what was expected to be a fairly routine ultrasound scan in the 34th week of my second pregnancy to the subsequent clinical finding of ‘a large fluid-filled cavity is present in the left cerebral hemisphere’ is both crystal clear and hazy. Often the actual moment in which your life is irrevocably changed is fleeting. But the fear, and shock are deeply seared into your being, the trauma so surprising as to still not feel truly real. Memories that you might revisit often, or try your hardest to bury, but that will always be there, as much part of you now as your name.

When a large porencephalic cyst was found on our baby boy’s brain, a cyst that hadn’t been there at the 20 week scan, no one could really explain why it was there now. Eventually it was decided it was likely ‘just one of those things’ that happens sometimes. But surely even these things that ‘just happen’ must have happened for a reason? 18 months later we had our answer, our son had an ultrarare mutation in the COL4A2 gene, and was ‘heterozygous for a pathogenic c.1856G>A mutation in exon 25 of the COL4A2 gene.’ But what did that even mean?

Key words & definitions

First a note on nomenclature, genes are always in italics and proteins are not (in humans).

• Genetics - the scientific study of genes and heredity.

• Genes – a gene is a segment of DNA that contains the instructions for building one or more of the molecules that help our body to work, it is estimated that humans have around 20,000 genes *1

• Genetic mutation - a genetic mutation occurs when there is a change in the sequence of your DNA. If the DNA sequence is in the wrong place, isn’t complete or is damaged you might experience symptoms of a genetic condition.

• Genetic conditions – Genetic conditions are also often referred to as genetic disorders, diseases, or syndromes, however these do describe different functions, listed below *2

• A disease is a pathophysiological response to internal or external factors.

• A disorder is a disruption to regular bodily structure and function.

• A syndrome is a collection of signs and symptoms associated with a specific healthrelated cause.

• Phenotype - In genetics the phenotype is the set of observable characteristics or traits of an organism

• Exons - an exon is a coding region of a gene that contains the information required to encode a protein.

• Transcription factors – In molecular biology a transcription factor is a protein that controls the rate of transcription of genetic information from DNA

Doug Gould grew up on a farm in Consort, a rural farming town with around 600 inhabitants in Eastern Alberta, Canada, before moving to Edmonton to attend the University of Alberta. He thought he might become a teacher, like both his father and grandmother before him, when the decision to take a genetics course changed everything. “I took a genetic course for the first time and was just kind of blown away, that was the first time that there was a real spark there, I took a real interest in it. And so I did a specialization in genetics for my undergraduate degree”

(Some Canadian Universities offer BSc Specialization degrees which provide a more focused education in one area of study).

That summer instead of returning to the farm as he usually did he volunteered in a research lab, where he heard that there was going to be a new Medical Genetics department opening there that year.

“And again, there was just sort of this light switch moment and I realized that my interest in science was underpinning this wider interest in human biology and medicine.” After graduating he went on to join this new department to begin work on his PhD. From there he moved to the Jackson Laboratory in Maine as a postdoctoral fellow, where he worked on using mutagenesis in mice to develop new genetic models of glaucoma (glaucoma is a fairly common eye condition where the optic nerve, which connects the eye to the brain, becomes damaged).

In molecular biology the use of mutagenesis is an important tool where mutations are induced randomly across the genome to help identify genets that contribute to a particular disease or phonotype (observable physical properties). This approach is then used to understand the normal function of the unmutated version of the gene. It was during the process of studying their findings that Doug observed and began to map something unexpected, mutations in the gene encoding type IV collagen alpha 1 (COL4A1). He still remembers the moment when the realisation hit him that “this thing you’ve been observing is potentially bigger and more important than you perhaps initially believed it to be… I was using a phenotype to map the gene. The way you do this is you figure out what part of a chromosome the mutation must be on and you look at what genes are in there, then you sequence them. I narrowed the chromosomal interval to a region that contained three or four genes, and two of them are these little transcription factors with very few exons. And then there was type IV collagen alpha 1 and collagen type alpha 2 (COL4A1 and COL4A2) which sit beside each other on the chromosome. And they’re enormous. Or they seemed enormous compared to a three exon transcription factor… and at the time I honestly had zero interest in studying collagens. They just seemed so boring, they are just a scaffold, and the real action, the real biology happens in cells, not in these scaffolds. I was naïve.”

What they were observing in the mice was striking, because they didn’t only have defects in the development of their eyes, they also had lots of other defects, and most notably intercranial cerebral hemorrhages. Following the realisation that in fact a fault, or mutation in the COL4A1 or COL4A2 genes had the potential to be hugely important, and whilst still working in The Jackson Laboratory, Doug shared his findings with a colleague who specialized in brain pathology. On reviewing the brain sections of the mutagenized mice they identified that the cavities they had developed on their brains were very similar to porencephalic cysts found in human brains. After searching through all the published medical science papers on porencephalic cysts he could find to try to understand how this might tie into his research and findings into COL4A1 and COL4A2 he found a paper which documented an ultra-rare familial case of porencephaly. He reached out to the authors and suggested they test for mutations in the families’ gene, and ‘sure enough, they found these mutations.’ Doug presented his groundbreaking findings in the first paper to publish human mutations in COL4A1; Mutations in

COl4A1 Cause Perinatal Cerebral Haemorrhage and Porencephaly by Gould et al. in the journal Science in May 2005.

But porencephaly was not, Doug recalls, ‘the end of the story.’ As COL4A1 and COL4A2 proteins are found in all organs the ways in which an individual can be affected by the mutation are numerous.

“We now know that mutations in COL4A1 and COL4A2 are pleiotropic and genetically complex and lead to a vast spectrum of seemingly unrelated human diseases.”

*3 He secured crucial funding from the Canadian Stroke Network and later moved to the University of California in San Francisco to set up his own lab, The Gould Lab. The central and primary aim of his lab is to continue to research ‘the tissue-specific molecular mechanisms that underlie this multi-system disorder that is caused by mutations in the genes encoding COL4A1 and COL4A2.’

But what does it actually mean if you are told that your loved one has a genetic mutation in COL4A1 or COL4A2 and you receive a genetic report which lists a whole lot of letters and numbers which mean absolutely nothing to the average person? In the identification and mapping of any new mutation or disease it is typically those most severely impacted that are discovered first. Accordingly, a lot of the early genetic testing done was focused on young children with complex disabilities, children who had for example suffered a perinatal stroke. And so this question of ‘what does this even mean’ was a question that many parents asked when they first began to receive an underlying COL4A1 mutation as a diagnosis for their child. Answers were hard to find, and so over the years, and with the ability to connect via social media parents began to link up online, forming support groups and sharing their experiences. Today there are both a US based foundation and a European charity working hard to bring much needed awareness, funding and even recognition to this syndrome. In 2019 the US based support group officially changed the name of the foundation to the Gould Syndrome Foundation, part of a carefully managed campaign to get the National Institute of Health in America to recognise this condition, and to assign it an ICD code (International Classification of Diseases).

In choosing the name Gould Syndrome the foundation carried on the long standing tradition of naming a disease after the person who first identified it, and in this instance who continues to be the main researcher into it. Through being able to engage closely with the patient population the team at Gould Lab have access to the medical histories of a wide range of those individuals with a COL4A1 or COL4A2 mutations, facilitated in large part through the work of the organizations and their linked support groups. And for Doug the experiences of the patients can help to inform the direction and focus of the continued research. As he explains, “the Foundation put together a global registry, where they asked people to self-report and that was really valuable and helped shape what we do. Seizures were not something that we were directly studying, we’re studying things that might lead to seizures, like the permeability of the blood brain barrier for example, but I hadn’t appreciated that seizures were the biggest concern of patients and their families.” This patient led research focus has, at its heart, the ultimate hope that one day those living with it will have access to ‘mechanismbased therapies that can prevent, reduce or delay disease.’

Today, on receiving the clinical finding that you, or your child, has this seemingly incomprehensible diagnosis of a COL4A1 c.2263G>A p.G755R*4 mutation an initial internet search will give you access to something that makes a little more sense. The Gould Syndrome Foundation website explains that ‘Gould Syndrome is a rare, genetic, multi-system disorder. Gould Syndrome is often characterized by abnormal blood vessels in the brain (cerebral vasculature defects), eye development defects (ocular dysgenesis), muscle disease (myopathy), and kidney abnormalities (renal pathology); however, many other aspects of the syndrome including abnormalities

Information and support

For more information about Gould syndrome/ COL4A1 and COL4A2 syndrome visit: The Gould Lab at the University of California , San Franciscohttps://ophthalmology.ucsf.edu/ gouldlab/

Associazione Famiglie COL4A1-A2

APShttps://www.col4a1.net/en/

The Gould syndrome Foundationhttps://gouldsyndromefoundation. org/

Gould Talks – Episode 1 is the first in a planned series of virtual discussions looking at COL4a1/a2 which you can find herehttps://www.youtube.com/@ gouldtalks

For support: The Gould syndrome foundation has both a public Facebook page and a private support group page: https://www.facebook.com/ Col4A1Foundation

There is also a private Facebook support group called the Gould Syndrome Family Support Group (Col4a1/Col4a2) which you can find herehttps://www.facebook.com/ groups/col4a1 almost all basal membranes. For this reason, a mutation in the COL4A1 or COL4A2 gene causes a disorder that can affect any organ.’ And, uniquely, what many families who are struggling to understand this new diagnosis also have access to is Doug, someone whose commitment to, and interest in this rare genetic mutation means he truly is the global expert. And whilst he is always sure to point out that he is not a medical doctor, and that he can’t offer a prognosis, or yet as the number of people with an underlying diagnosis of COL4A1 and COL4A2 grows it is becoming ever more evident that there is a huge breadth and variability in the symptoms experienced. Indeed, Doug explained that the calling card of Gould syndrome seems to be the variability of associated symptoms. Based on the patient data they’ve analysed to date “cerebrovascular disease is the most highly penetrant (so) if you have the mutation, you probably have a cerebrovascular disease… about 30, or 35%, of people with the mutation have some sort of ocular dysgenesis, then there’s skeletal myopathy in maybe 20% of cases, and then some renal involvement in 15%

Today there are in excess of 500 people who have received a diagnosis for COL4A2 mutation, and for each of those diagnosed there will likely be many, many more who won’t. Interestingly, more recently there are a growing number of adults who are receiving a diagnosis, often after a lifetime of poor health, but some because of the wider familial testing done on behalf of a severely impacted child. So whilst the majority are still ‘de novo’, which means that the mutation happened spontaneously and was not inherited, there are increasing numbers of families that are found to have a hereditary mutation, adding more pieces to the bigger picture. And with each new diagnosis, and through the continued research they are doing, Doug and his team are continuing to ‘put the pieces of the puzzle together’ as they continue to map the genetics of a (relatively) new disease.

FOOTNOTES:

*1 - https://www.nigms.nih.gov/education/fact-sheets/Pages/genetics.aspx

* 2 https://www.healthwriterhub.com/disease-disorder-condition-syndrome-whats-the-difference

*3 Welcome - Douglas Gould Lab - UCSF Department of Ophthalmology

*4 Taken from the presentation in Gould Talks, Episode 1, see ‘Information and Support.’