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Congenital heart disease (CHD) is the most common congenital anomaly, with an overall incidence of approximately 1% in the United Kingdom. Exome sequencing in large CHD cohorts has been performed to provide insights into the genetic aetiology of CHD. This includes a study of 1891 probands by our group in collaboration with others, which identified three novel genes—CDK13, PRKD1, and CHD4, in patients with syndromic CHD. PRKD1 encodes a serine/threonine protein kinase, which is important in a variety of fundamental cellular functions. Individuals with a heterozygous mutation in PRKD1 may have facial dysmorphism, ectodermal dysplasia and may have CHDs such as pulmonary stenosis, atrioventricular septal defects, coarctation of the aorta and bicuspid aortic valve. To obtain a greater appreciation for the role that this essential protein kinase plays in cardiogenesis and CHD, we have analysed a Prkd1 transgenic mouse model (Prkd1em1) carrying deletion of exon 2, causing loss of function. High‐resolution episcopic microscopy affords detailed morphological 3D analysis of the developing heart and provides evidence for an essential role of Prkd1 in both normal cardiac development and CHD. We show that homozygous deletion of Prkd1 is associated with complex forms of CHD such as atrioventricular septal defects, and bicuspid aortic and pulmonary valves, and is lethal. Even in heterozygotes, cardiac differences occur. However, given that 97% of Prkd1 heterozygous mice display normal heart development, it is likely that one normal allele is sufficient, with the defects seen most likely to represent sporadic events. Moreover, mRNA and protein expression levels were investigated by RT‐qPCR and western immunoblotting, respectively. A significant reduction in Prkd1 mRNA levels was seen in homozygotes, but not heterozygotes, compared to WT littermates. While a trend towards lower PRKD1 protein expression was seen in the heterozygotes, the difference was only significant in the homozygotes. There was no compensation by the related Prkd2 and Prkd3 at transcript level, as evidenced by RT‐qPCR. Overall, we demonstrate a vital role of Prkd1 in heart development and the aetiology of CHD. [ABSTRACT FROM AUTHOR]

Aims: Polymorphous adenocarcinoma (PAC) usually follows an indolent course, but some cases may show recurrences and high‐grade features. The genetic events associated with recurrences and high‐grade versions are yet to be defined. Our aim was to determine the genetic underpinning of recurrent PACs of the salivary gland and the repertoire of somatic genetic alterations in cases with high‐grade histology. Methods and results: Four PACs from three patients, including one case with matching primary and recurrent tumours, one de‐novo high‐grade PAC, and a PAC that transformed to a high‐grade tumour following multiple recurrences, were subjected to targeted sequencing (Memorial Sloan Kettering Mutation Profiling of Actionable Cancer Targets assay) or whole‐exome sequencing. Both matching primary and recurrent tumours, and the de‐novo high‐grade PAC, harboured clonal PRKD1 E710D hotspot mutations, whereas the PAC that underwent high‐grade transformation upon recurrence, which was wild‐type for PRKD1, harboured a PRKD2 rearrangement. The PACs analysed here also harboured mutations targeting cancer genes such as PIK3CA, SETD2, ARID1A, and NOTCH2. A clonal decomposition analysis of the matching primary and recurrent PACs revealed that a minor subclone from the primary tumour became dominant in the recurrent tumour following a clonal selection evolutionary pattern. Conclusions: Our findings demonstrate that recurrent and high‐grade PACs are underpinned by PRKD1 E710D hotspot mutations or PRKD2 rearrangements, and that recurrences of PACs may stem from the selection of pre‐existing subclones in the primary tumour. [ABSTRACT FROM AUTHOR]