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The LexA regulated SOS network is a bacterial response to DNA damage of metabolic or environmental origin. In Clostridium difficile, a nosocomial pathogen causing a range of intestinal diseases, the in-silico deduced LexA network included the core SOS genes involved in the DNA repair and genes involved in various other biological functions that vary among different ribotypes. Here we describe the construction and characterization of a lexA ClosTron mutant in C. difficile R20291 strain. The mutation of lexA caused inhibition of cell division resulting in a filamentous phenotype. The lexA mutant also showed decreased sporulation, a reduction in swimming motility, greater sensitivity to metronidazole, and increased biofilm formation. Changes in the regulation of toxin A, but not toxin B, were observed in the lexA mutant in the presence of sub-inhibitory concentrations of levofloxacin. C. difficile LexA is, therefore, not only a regulator of DNA damage but also controls many biological functions associated with virulence.

Background: Mucopolysaccharidosis (MPS) is a class of hereditary metabolic diseases that demonstrate itself by accumulating incompletely degraded glycosaminoglycans (GAGs). MPS are classified according to the kind(s) of stored GAG(s) and specific genetic/enzymatic defects. Despite the accumulation of the same type of GAG, two MPS diseases, Sanfilippo (MPS III) and Morquio (MPS IV), are further distinguished into subclasses based on different enzymes that are deficient. Although genetic defects in MPS are known, molecular mechanisms of particular MPS types are still incomplete. This work aimed to investigate gene expression patterns in MPS III and MPS IV subtypes to identify dysregulated genes that could indicate unidentified molecular mechanisms of the diseases. Methods: Transcriptomic analyses were conducted to assess gene expression patterns in MPS and control cells. Western blotting and immunohistochemistry determined selected protein levels (products of the most significantly dysregulated genes). Effects of decreased levels of gene expression were investigated using small interferring RNA (siRNA)-mediated gene silencing. Results: Transcriptomic analyses indicated 45 commonly dysregulated genes among all MPS III subtypes and as many as 150 commonly dysregulated genes among both MPS IV subtypes. A few genes revealed particularly high levels of dysregulation, including PFN1, MFAP5, and MMP12. Intriguingly, elevated levels of profilin-1 (product of the PFN1 gene) could be reduced by decreasing GAG levels in genistein-treated MPS III and MPS IV cells, while silencing of PFN1 caused a significant decrease in GAG accumulation in these cells, indicating an interdependent correlation between profilin-1 and GAG levels. Conclusions: A plethora of commonly dysregulated genes were identified in MPS subtypes III and IV. Some of these genes, like PFN1, MFAP5, and MMP12, revealed highly pronounced changes in expression relative to control cells. An interdependent correlation between GAG levels and the expression of the PFN1 gene was identified. Thus, PFN1 could be suggested as a potential new therapeutic target for MPS III and IV.