ESPE Abstracts

Carney complex 1 (CNC, OMIM# 160980) is an autosomal-dominantly inherited complex tumor predisposition syndrome associated with skin pigment abnormalities and neoplasms of heart, endocrine glands and other organs. CNC is caused by heterozygous constitutional loss-of-function variants in the PRKAR1A-gene. PRKAR1A codes for the cAMP-dependent protein kinase type I-alpha regulatory subunit, an enzyme that represents an integral part of protein kinase A (PKA) that is involved in inter- and intracellular signaling. We present a case series of four related female individuals (mother and three daughters) carrying the same novel heterozygous intronic PRKAR1A-variant NM_002734.4: c.-7+1del, p.(?). The variant was identified by targeted genetic investigation of the youngest daughter (born 2005) after a diagnosis of an ACTH independent Cushing’s syndrome at the age of 13 in line with bilateral adrenocortical micronodular hyperplasia that was treated successfully by bilateral adrenalectomy. The girl did not show any dermal or other clinical manifestations of CNC. Thorough investigation of the family history revealed that the mother also has a history of Cushing’s syndrome but is otherwise affected rather mildly at the age of 49. The other two daughters (twins born 2002) do not show any manifestations of CNC. Since the identified variant is located at the first exon-intron border an effect on splicing was suspected. RNA from patient’s and control blood samples have been investigated and a set of different transcripts was identified, one of which is exclusively identified in patient’s RNA. Sequencing analyses of this transcript predicted three putative start codons upstream of the native start codon due to a partial intron retention. To further investigate whether the use of any of these start codons might result in translation of an aberrant protein, the transcript was inserted into a pEGFP-N3 expression vector. After transfection of HEK293 cells EGFP-fusion proteins were visualized by fluorescent microscopy and western blot analyses confirmed the presence of the fusion protein with the predicted mass weight. The aberrant transcript was degraded in patient’s blood cells but degradation could be inhibited by with puromycin which blocks nonsense-mediated decay. In summary, functional evidence for the identified non-coding variant to be causative for carney complex in the affected individuals is presented. The rather mild manifestation in the mother and (so far) incomplete penetrance in the family reflects the underlying pathogenic mechanism of the variant generating at least one aberrant PRKAR1A-transcript resulting in a reduction of the functional gene product.