Dr. Tjitske Kleefstra

Dr. Tjitske Kleefstra

I am a Clinical Geneticist working at the Department of Human Genetics, Radboud University Nijmegen Medical Centre. Prior to my training in this specialism, I finished MSc in both Medicine and Medical Biology.

I have always been driven by searching for causes of medical disorders, in particular for genetic causes of intellectual disability (ID).  During my PhD studies I came across a female with ID who had a particular chromosome disorder: a seemingly balanced translocation (two chromosome parts were exchanged) between chromosomes 9 and X.

To take a long story short, we found that the translocation breakpoint on chromosome 9 was disrupting the EHMT1 gene. Since this patient that carried the translocation had striking clinical similarities to the patients with 9q34 deletions, we thought that it was this gene that might cause the majority of symptoms seen in ‘9q subtelomere deletion syndrome’.

We set up a DNA test for this EHMT1 gene and indeed found disturbances of only this gene (so not additional genes in 9q34) in several patients. Thereby we confirmed that this gene is the ‘major’ gene within the 9q34 deletion syndrome. Since this finding, the EHMT1 gene is a major focus of my research and of that of my colleagues who perform further studies within our department. I follow up the patients known in our centre and collect data form others that are from outside the Netherlands to study the further aspects and clinical presentation of this syndrome. This work has now officially led to assign the 9q34 deletion syndrome the name ‘Kleefstra Syndrome’ in the Online Mendelian Inheritance of Man (OMIM) database. Further studies at our department are more fundamental and aimed to identify the biological pathways that are affected by the EHMT1 gene. Only by exploring these pathways, one might at some point consider possible means to interrupt, replace or restore biological functions and someday perhaps even develop medication.

I am very thankful to all the families that participate in my research. I have great respect for the care of their own children and the responsibility they take to contribute to the general knowledge of this disorder.
I hope that I and my colleagues can continue to study the disorder of your children and find many more answers to the questions we all have.

Tjitske Kleefstra, 2010.


A video of Dr. Kleefstra describing Kleefstra syndrome was published by Frambu (Norway’s largest centre of excellence for rare disordered) on the video sharing site Vimeo:

Page updated: 14-05-2017