MRPL53, a New Candidate Gene for Orofacial Clefting, Identified Using an eQTL Approach

A valuable approach to understand how individual and population genetic differences can predispose to disease is to assess the impact of genetic variants on cellular functions (e.g., gene expression) of cell and tissue types related to pathological states. To understand the genetic basis of nonsyndromic cleft lip with or without cleft palate (NSCL/P) susceptibility, a complex and highly prevalent congenital malformation, we searched for genetic variants with a regulatory role in a disease-related tissue, the lip muscle (orbicularis oris muscle [OOM]), of affected individuals. From 46 OOM samples, which are frequently discarded during routine corrective surgeries on patients with orofacial clefts, we derived mesenchymal stem cells and correlated the individual genetic variants with gene expression from these cultured cells. Through this strategy, we detected significant cis-eQTLs (i.e., DNA variants affecting gene expression) and selected a few candidates to conduct an association study in a large Brazilian cohort (624 patients and 668 controls). This resulted in the discovery of a novel susceptibility locus for NSCL/P, rs1063588, the best eQTL for the MRPL53 gene, where evidence for association was mostly driven by the Native American ancestry component of our Brazilian sample. MRPL53 (2p13.1) encodes a 39S protein subunit of mitochondrial ribosomes and interacts with MYC, a transcription factor required for normal facial morphogenesis. Our study illustrates not only the importance of sampling admixed populations but also the relevance of measuring the functional effects of genetic variants over gene expression to dissect the complexity of disease phenotypes.

Doppler hemodynamic characteristics of four widely used aortic valve prostheses

Fifty-one patients with normofunctioning aortic prosthetic heart valves were evaluated by Doppler-Echocardiography to determine type-related flow characteristics. The four mechanical valves tested were: Starr-Edwards (1200-1260 aortic), Bjork-Shiley (60 degrees-60 degrees cc aortic), Medtronic-Hall (aortic) and St. Jude Medical (aortic). The most significant dynamic indexes were calculated: Peak (PG) and Mean (MG) Gradient across the valve, Cardiac Index (CI) or Cardiac Output (CO), Regurgitant Jets, Effective Orifice Area (EOA), Spectral Diagram Systolic Trend (SDST) and PVRT (time required to reach peak velocity during systole)/LVET (left ventricular ejection time) Ratio. Patients with Doppler assessed prosthetic dysfunction were dropped out of the study group. As expected, significant reverse correlation (-0.70) was found when transvalvular pressure gradients were compared with valve size. Significant direct correlation (0.82) was found when EOA was compared with valve size, thus suggesting the high reliability of the continuity equation in the assessment of the real orifice area. The Starr-Edwards valve, when compared with the other prostheses of the same size, showed the highest calculated transvalvular gradient; the St. Jude Medical showed the lowest. On the other hand, the Starr-Edwards valve was not commonly associated with regurgitation, while the St. Jude valve was usually moderately incompetent. Those hemodynamic differences should guide the selection of the ideal prosthetic valve for elective surgical indications. Doppler measurements provided noninvasive information similar to that given by cardiac catheterisation, which was reproducible and specific for valve function. According to this high sensitivity and specificity and to the absolute innocuity of the procedure, Doppler-Echocardiography should be considered the elective technique for long-term follow-up in patients with aortic prosthetic heart valves.