Cushing's Disease Whole Exome Sequencing Study

Eunice Kennedy Shriver National Institute Of Child Health & Human Development

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Abstract

We are currently analyzing whole exome sequencing (WES) data with appropriate follow up to identify important genetic factors associated with Cushing's disease (CD) and related abnormal physical features. The ultimate goal is to identify a genetic variant or variants that cause CD. CD is a condition in which the pituitary gland produces inappropriately high levels of adrenocorticotropic hormone (ACTH). The ACTH stimulates the adrenal gland to produce excess cortisol, leading to clinical disease. CD is caused by ACTH secreting pituitary tumors. CD is a serious condition. It requires surgery to remove the tumor. The tumors sometimes recur in which case radiation or medical therapy is required which is not always successful. CD can cause a wide range of problems due to the high cortisol levels. These include diabetes, fractures, poor growth, and hypertension. CD can be fatal. Whole exome sequencing (WES) is a powerful tool for identifying important genetic variants associated with medical conditions. It is an efficient method of determining the genetic code (sequence) of all the regions in the genome that are translated into protein, the exons. The exons constitute about 1% of DNA, thus sequencing exons provides a large amount of information at a lower cost than sequencing the entire genome. Pediatric aged patients seen at NICHD with a confirmed diagnosis of CD are evaluated for this study. Those who have histopathologically confirmed disease in conjunction with DNA, hormonal documentation of the disease and complete clinical data are potential cases. Analysis comparing variants found in the cases with large control populations has been done. In addition, the data are being examined for copy number variants in the exons to determine if they play a role in Cushing's disease. We have shown the contributions of multiple germline and somatic variants to Cushing disease in a large single cohort. In all these account for 20% of cases. Our investigation of possible genetic predictors of time to recovery of the hypothalamic-pituitary-adrenal axis did not uncover any strong genetic modifiers. We have identified new genetic associations with ectopic posterior pituitary and confirmed previous associations.