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.

Mycelial- to yeast-phase transitions of the dimorphic fungi Blastomyces dermatitidis and Paracoccidioides brasiliensis.

The physiological changes that occur during the mycelial- to yeast-phase transitions induced by a temperature shift from 25 to 37 degrees C of cultures of Blastomyces dermatitidis and Paracoccidioides brasiliensis can be divided into three stages. The triggering event is a heat-related insult induced by the temperature shift which results in partial uncoupling of oxidative phosphorylation and declines in cellular ATP levels, respiration rates, and concentrations of electron transport components (stage 1). The cells then enter a stage in which spontaneous respiration ceases (stage 2), and finally, there is a shift into a recovery phase during which transformation to yeast morphology occurs (stage 3). Cysteine is required during stage 2 for the operation of shunt pathways which permit electron transport to bypass blocked portions of the cytochrome system. The mycelial- to yeast-phase transitions of these two fungi are very similar to that of Histoplasma capsulatum. Therefore, these three dimorphic fungal pathogens have evolved parallel mechanisms to adjust to the temperature shifts which induce these mycelial- to yeast-phase transitions.

Classification of Histoplasma capsulatum isolates by restriction fragment polymorphisms.

Twenty isolates of the dimorphic, pathogenic fungus Histoplasma capsulatum were divided into three classes based on comparisons of restriction enzyme digests of their mitochondrial DNA and rDNA. The majority of isolates, including most North American strains and the African H. capsulatum var. duboisii variants, belong to class 2. Isolates from Central America and South America make up class 3. The attenuated Downs strain is the only member of class 1.