One of the most common chromosomal deletions in humans happens on chromosome 22. It’s known as 22q and affects as many as one in 2,000 live births. People with the deletion can present with a wide variety of traits. Some have heart defects. Others have defects in the palate, while still others have developmental delays. But in 2005, Donna McDonald-McGinn, director of the 22Q and You Center at the Children’s Hospital of Philadelphia and clinical professor at the University of Pennsylvania, noticed some patients had rare, atypical clinical features such as limb differences and rectal malformations. Now, in a recent publication in GIM, she and an international team of scientists reveal variants in a gene called CDC45 on the non-deleted chromosome are responsible for the unusual traits. The 22q deletion had unmasked the effects of the CDC45 variants. On this month’s GenePod podcast, Dr. McDonald-McGinn and host Cynthia Graber chat about how this unmasking phenomenon may be responsible for other conditions as well.

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https://www.nature.com/articles/s41436-019-0645-4