Dr. Douglas Gould from the Department of Ophthalmology and Anatomy at the Institute for Human Genetics, School of Medicine, University of California, San Francisco, USA, began his presentation titled “Establishing Foundations for Translational Interventions” by thanking the Association for the invitation before diving straight into the core of his talk.

During his conference, Dr. Gould explored the future of treatments and potential cures for conditions related to Type IV Collagen. He encouraged everyone to imagine where we want to be in 20 years and to outline a clear path to achieve those goals. His presentation focused on three fundamental questions:

• What is Type IV Collagen and what does it do?
• Who will be treated?
• How will they be treated?

These questions guided the discussion, providing a clear and strategic vision for the future of research and clinical applications in this field.

What is Type IV Collagen and what does it do?

Type IV Collagen is one of the many proteins in the large collagen family, which includes 28 different variants found in both humans and mice. These proteins are virtually everywhere, present in all basal membranes of animals. However, their exact functions are still largely unknown. Type IV Collagen has a triple-helix structure essential for its function, though it’s not yet clear how it performs its tasks.

In 1990, Carl Tryggvason discovered the first human mutations in Type IV Collagen, specifically in the COL4A5 gene, which is linked to Alport Syndrome, a disease that primarily affects the kidneys. This highlighted the importance of Type IV Collagen in kidney function. Collagen IV Alpha-1 and Alpha-2 (CLO4A1 and COL4A2) are found throughout the body, and their functions are not yet fully understood.

Collagen is produced in the endoplasmic reticulum, transported through the Golgi apparatus, and then secreted into the basal membrane, where it forms flexible structures. These structures influence cells in ways that are not yet fully clear; they might have multiple, still unknown functions. While researchers are beginning to understand the consequences of collagen mutations or deficiencies, the exact mechanisms by which these proteins operate remain a mystery. So, while it’s easy to say what Type IV Collagen is, understanding what it does is much more complex and requires further research to develop treatments based on its functioning mechanisms.

Who will be treated?

In early 2004, a significant moment in scientific research emerged in Italy. One Saturday, while working in the lab, Dr. Gould came across an article by Alberto Aguglia and Peter Heutink about a family in southern Italy where three generations had inherited porencephaly, a rare condition. Since Dr. Gould and his team had been studying mutations in mice related to this condition for about a year, they reached out to Dr. Heutink, suspecting they knew the mutated gene in that family. Genetic sequencing confirmed a mutation in one of the conserved glycine residues. The following year, they identified other families with porencephaly who had similar mutations.

Realizing that the pathology was not confined to the eye or brain, they examined retinal vasculature and discovered an abnormal pattern of vessels. They also studied the kidneys, given the connection to Alport syndrome, and using electron microscopy on a wild-type mouse, they noted that the glomerular basement membrane was thinner, with focal variations in thickness, and exhibited significant albuminuria.

In collaboration with Dr. Tournier Lasserve, Dr. Gould’s team studied a family with multifocal cerebrovascular disease, characterized by recurrent haemorrhages, retinal haemorrhages, vascular tortuosity, and hematuria. They identified a mutation in a conserved glycine residue within the collagen triple helix domain. A year later, a landmark paper by Dr. Plaisier and Pierre Ronco confirmed that this was a multisystemic disease.

How will they be treated?

During his presentation, Dr. Gould explored potential treatment methods for conditions related to Type IV Collagen. Building on the phenotypes discussed by Dr. Tournier Lasserve, which were caused by glycine missense mutations, he emphasized that these did not represent the entire clinical picture. Additionally, Gould mentioned other phenotypes observed in mice that have not been documented in humans, such as skeletal development issues. He also highlighted age-related cerebrovascular dysfunction in mutant mice, noting that while the function was normal at three months, it deteriorated by twelve months, with decreased myogenic tone and compromised neurovascular coupling. These findings suggested that not all phenotypes are congenital and may develop over time.

Dr. Gould also discussed genome-wide association studies on small vessel diseases, highlighting the strong association of Collagen IV Alpha-2 with these conditions. He explained that although these studies focus on common variants, the relevance of Collagen IV Alpha-2 suggests a broader role beyond rare mutations. He cited research indicating a potential link between collagen levels and cerebrovascular health, and studies on mouse models with mutations in conserved binding elements showing signs of cerebrovascular disease. Gould emphasized the importance of further investigating the biological functions of collagen, especially regarding mutations in non-coding regions, to better understand the pathogenesis of related diseases.

Understanding the factors contributing to the variability of disease expression is crucial for developing effective treatments. Environmental factors, such as physical exercise and the use of certain medications like anticoagulants, can influence the severity of the disease. For example, studies on mice have shown how delivery methods and physical activity can affect intracerebral hematoma. Genetic factors, such as genetic mosaicism and genetic modifiers, also play a significant role, with the timing and extent of mutations affecting disease severity. Genetic mosaicism, where an unaffected parent carries the mutation and has an affected child, underscores the importance of considering the timing and extent of mutation onset. Additionally, genetic background can influence disease expression, as demonstrated by experiments where different genetic backgrounds either mitigated or worsened phenotypes in mice with the same mutation.

Dr. Gould’s research also focuses on the variable expressivity of different alleles. By studying a series of mutant mice with various mutations, they discovered that the position of the mutation within the gene affects the severity of intracellular protein accumulation and the severity of the disease. Promoting the secretion of Collagen IV heterotrimers could be a potential therapeutic strategy. They tested this hypothesis using a chemical chaperone, 4-phenylbutyric acid (4-PBA), which promotes protein folding and secretion. Treatment with 4-PBA improved collagen secretion in mutant mice, reducing intracellular accumulation and improving cerebral hematoma outcomes. However, this approach might not benefit all tissues, as evidenced by a case where a mutation caused severe skeletal myopathy despite improved secretion and mild cerebral hematoma.

In summary, Collagen IV Alpha-1 and Alpha-2 are crucial proteins for the structural integrity of various tissues, but their precise functions are still largely unknown. Mutations in these proteins cause a multisystem disorder with a wide range of phenotypes. Environmental and genetic factors significantly influence disease severity, and understanding these factors is essential for developing effective treatments. Promoting the secretion of mutant Collagen IV proteins with chemical chaperones shows promise as a therapeutic strategy, although with variable effects on different tissues. The future of treatment for conditions related to Type IV Collagen will require a comprehensive understanding of these proteins’ functions and the factors influencing disease variability.