Trisomy 21: discovery published 50 years ago

Today, 16th March 2009, is the 50th anniversary of the publication of Lejeune, Gautier and Turpin’s historic research paper, demonstrating the presence of an extra chromosome in each of the nine children studied. In 1959 the use of the term "Down syndrome" was still some years in the future, and the science of cytogenetics was in its infancy. The actual number of chromosomes present in the typical human cell had not been known for very long.

Almost simultaneously (but just a little later), a similar study was published by Patricia Jacobs and her Scottish colleagues.

It was regarded as a turning point in cytogenetics – the first human condition definitely attributable to aneuploidy (an unusual number of chromosomes).

...... almost a century elapsed between the clinical description of DS and its association with trisomy 21. When Jerome Lejeune associated DS with trisomy 21 in 1959, human cytogenetics was still maturing as a science; thus, Lejeune's discovery represents a landmark in the field.

O'Connor, C. Chromosomal abnormalities: Aneuploidies. Nature Education 1(1), (2008)

Trisomy 21 was the first human condition proven to be caused be aneuploidy (an unusual number of chromosomes), and discoveries about other aneuploidies follows quickly.

This key discovery is important for people with Down syndrome, but has had great benefits for others as well:

Recognition of Trisomy 21 has allowed scientists to look for causes of individual problems – what is genetic in DS, what is not, how intervention might bring benefits to either genetic or non-genetic traits.

Elucidation of other conditions for which genes occur on 21st chromosome has helped develop understanding of Alzheimers disease and leukaemia, for example.
People with DS are known to be at much lower risk of solid tumours than most of us – working out what is protective about chromosome 21 is helping to develop an understanding and therapies for solid tumour cancers.

Prof Jerome Lejeune continued to work in the field of cytogenetics, to great acclaim, until his death in 1994. He expressed great disappointment that his discovery had been used to identify Down syndrome prenatally for the purpose of terminating pregnancies. The search for the cause of Trisomy 21 continues, as does work to ameliorate harmful effects.

World Down Syndrome Day, celebrated internationally on 21st March, will this year focus on the anniversary of Lejuene's discovery.