Alexander Hoischen appointed as professor of Genomic Technologies for Immune-Mediated and Infectious Diseases

Geneticist Alexander Hoischen has been appointed as Professor of Genomic Technologies for Immune-Mediated and Infectious Diseases at Radboud university medical center / Radboud University. Hoischen investigates the genetic causes of rare immune disorders. He works on DNA analysis techniques, aims to better understand available data, and maps defects in immune cells.

Hoischen’s expertise lies at the intersection of genetics and immunology, where he studies the DNA of patients with rare immune disorders. When a genetic cause is suspected, Hoischen dives into the DNA, looking for an error. Hoischen: 'I find it rewarding to work on various conditions, for which often little is known. We can really make a difference for the patient. It’s also great that we set up analyses that regularly lead to new tests and diagnoses in the clinic within a year.' 

These patients with immune disorders come to the hospital with many, unusual, or severe infections. A genetic defect can cause part of their immune system to malfunction or become overly active. 'These kinds of rare diseases require academic care, for which we have built a fantastic multidisciplinary team at Radboudumc', says Hoischen. 'We can easily collect immune cells to learn more since they are simply in the blood.' He not only analyzes the DNA of these cells but also conducts follow-up tests in the lab. In 15 to 20% of cases, he finds a genetic cause, gaining a better understanding of the disease. 

Bubble Boy

This often leads to action in a very high percentage of patients, nearly eighty percent. 'Then we know what the prospects are and can think towards therapy', Hoischen explains. 'We use, for example, drugs already registered for other conditions that affect the immune response. It’s also good to end the search for a cause. A genetic basis helps with prevention and family planning, and sometimes in guiding difficult decisions like a stem cell transplantation.' 

A well-known example of Hoischen's work is research on healthy young men who became severely ill from COVID-19. Hoischen and colleagues showed that these men had a mutation in the TLR7 gene, which plays a crucial role in recognizing the coronavirus. This provided treatment leads. Hoischen also found the genetic cause of a rare 'bubble boy' disease, SCID. Some diagnosed patients received a stem cell transplant, and SCID has been included in the national heel prick program since 2021.  

More Complete

The analysis of an individual patient’s entire DNA has been conducted in the clinic since 2008, and the Genetics department is globally leading in this development. Currently, Radboudumc performs 15,000 diagnostic tests per year, mostly using a technique called exome sequencing, which only maps the genes coding for proteins, not the intervening DNA. However, the number of tests using a newer technique, genome sequencing, which maps the entire DNA, is increasing.

Within genome sequencing, there are various developments. 'Initially, we used short reads, reading small pieces of DNA and then puzzling them together. But this leaves gaps in the analysis', Hoischen explains. 'Now we are moving to long read genomes, longer pieces of DNA, making the picture of the genetic material more complete.' Hoischen recently showed that this technique provides a diagnosis in 13% of cases where no genetic cause was previously found. 'I hope that in three years we can perform long read genome sequencing for all patients with rare diseases.'

Career

Alexander Hoischen studied Biology at the Rheinische Friedrich-Wilhelms University in Bonn, where he graduated summa cum laude in 2008 with his thesis, titled: 'Establishment and Application of Array-CGH in Clinical Genetics and Tumor Genetics.' He then started as a postdoc at the Genetics department of Radboudumc, also working at the Institute for Genome Sciences in Seattle. Hoischen currently works in both the Genetics and Internal Medicine departments.

Hoischen is the work-package leader of the European research project Solve-RD and recently received a VICI grant. He is Chief Innovation Officer at the Genetics department, RGL of the Genomics of Rare Undiagnosed Diseases program, and Scientific Director of the Radboudumc Technology Center Genomics. Internationally, he chairs the Scientific Program Committee of the European Society of Human Genetics (ESHG). His appointment as professor began on June 1, 2024, for a five-year term.

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