Scitech | Discovering Trisomy 21

The life and works of Jérôme Lejeune

On September 5, a crowd gathered in Redpath Hall at McGill despite the chilly weather. Some came out of curiosity, some out of respect, and some to remember. Whatever the reason, people had gathered at an exhibit for the man who is arguably the father of modern genetics, Dr. Jérôme Lejeune.

The exhibition was organized by various people who hoped to share Lejeune’s fascinating life work with the rest of the Montreal community. It started with an introduction by Marc Chabati, a graduate student at McGill, and was followed by a lecture about Lejeune’s life by Dr. Mark Basik, a McGill researcher who studies the genomics of breast and colon cancer.

After attending and training at the Paris Institute of Medicine, Jérôme Lejeune decided to become a surgeon. However, he was unfortunately (or fortunately) unable to pass the exam – a turn of events that led him down a different path.

After abandoning the field of surgery, Lejeune delved into the broad world of medical research. Lejeune joined the lab of Dr. Raymond Turpin, where he began research into the cause of Down syndrome.

Down syndrome is a relatively rare genetic disorder occurring one in approximately 1,000 births worldwide. The disease is characterized by mental disabilities and various physical conditions. In Lejeune’s time, Down’s was believed to be caused by an infectious pathogen, resulting in the ostracism of those affected by the disease.

Lejeune and Turpin first tried to identify the key observable differences between those with and without Down’s during embryonic formation. They found that permanent characteristics, such as palm lines and fingerprints, were different between the two groups. What was even more surprising was that these differences developed during the first two months of pregnancy – suggesting a genetic link to the cause of Down’s.

Lejeune believed that a disability with many anomalies could not be formed by a single gene, and in 1957 he started karyotyping (counting the number of chromosomes in) children with Down syndrome. In 1958, he was able to show children with Down syndrome had one extra chromosome – a condition that was later named Trisomy 21. The scientific community first took this discovery with skepticism because it was still believed at the time that Down’s was caused by an infection. As a result, Lejeune travelled the world spreading news about his discovery.

This was the first time a chromosomal abnormality was linked to a disease, marking the beginning of a new field called cytogenetics. It was due to this discovery that Lejeune is sometimes termed as ‘the father of modern genetics.’

Lejeune enjoyed research, but his primary concern as a pediatrician was his patients, whom he cared for deeply; he claimed that he knew 2,000 of his patients by their first names. After discovering the cause of Down syndrome, he actively tried to find a cure. He proposed pinpointing the overexpressed genes on chromosome 21 or shutting off the whole chromosome, but both approaches required technologies (such as gene sequencing) that were not available at the time.

While Lejeune was searching for a cure, the discovery of the cause of Down syndrome had a big and unexpected side effect – the rate of abortion rose to 90 to 95 per cent for embryos diagnosed with Down’s. This upset Lejeune, and while France was in the process of legalizing abortion, he became a pro-life activist; his motto being “Hate the disease, Love the patient.”

When asked if his pro-life stance was due to him being a devout Catholic, Lejeune replied, “If the Pope were to legalize abortion, then I would leave Catholicism immediately,” emphasizing that his views were based on purely scientific and humanistic reasons.

When Basik was asked what he hoped people would learn from Lejeune’s story, he replied, “I hope they see that science is bigger than just data and that human beings are much more than scientific data [and see them in the way] Lejeune saw it and love it the way he did.” In the end, whether or not you share Lejeune’s views, one cannot doubt his great compassion, love for his patients, and of course his vital contributions to the field of genetics.


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