Ana Redondo Palacios

Polyketide Synthase Genes from Marine Dinoflagellates

Rapidly developing techniques for manipulating the pathways of polyketide biosynthesis at the genomic level have created the demand for new pathways with novel biosynthetic capability. Polyketides derived from dinoflagellates are among the most complex and unique structures identified thus far, yet no studies of the biosynthesis of dinoflagellate-derived polyketides at the genomic level have been reported. Nine strains representing 7 different species of dinoflagellates were screened for the presence of type I and type II polyketide synthases (PKSs) by polymerase chain reaction (PCR) and reverse transcriptase PCR. Seven of the 9 strains yielded products that were homologous with known and putative type I PKSs. Unexpectedly, a PKS gene was amplified from cultures of the dinoflagellate Gymnodinium catenatum, a saxitoxin producer, which is not known to produce a polyketide. In each case the presence of a PKS gene was correlated with the presence of bacteria in the cultures as identified by amplification of the bacterial 16S ribosomal RNA gene. However, amplification from polyadenylated RNA, the lack of PKS expression in light-deprived cultures, residual phylogenetic signals, resistance to methylation-sensitive restriction enzymes, and the lack of hybridization to bacterial isolates support a dinoflagellate origin for most of these genes.

Giant asymptomatic aortic root aneurysm

An asymptomatic 35-year-old male with a family history of right ventricular dysplasia was found to have an 11-cm ascending aortic aneurysm and moderate aortic insufficiency with a bicuspid aortic valve on a routine screening transthoracic echocardiogram (Figure 1). A chest computed tomography scan showed that the aneurysm was limited to the aortic root and ascending aorta, was just beneath the sternum, and appeared to compress the superior vena cava and right atrium (Figure 2). The patient had no physical features of Marfan syndrome or any other connective tissue disease. At the time of surgery, the right axillary artery and femoral vein were cannulated and cardiopulmonary bypass was established prior to opening the sternum. The aneurysm occupied the entire mediastinum (Figure 3). The aortic valve was bicuspid and the annulus measured 30mm in diameter (Figure 4). The patient underwent a root replacement with a #29 mechanical composite graft (Medtronic, Inc., Minneapolis, MN), during a 95-min cross clamp period and 115min of cardiopulmonary bypass. The patient tolerated the procedure well and had an uncomplicated postoperative course. The aortic pathology showed myxoid medial degeneration, fibrosis, and chronic inflammation without evidence of connective tissue disorders. The patient and his family were referred for genetic testing.