ABSTRACT
L1CAMs are immunoglobulin cell adhesion molecules that function in nervous system development and function. Besides being associated with autism and schizophrenia spectrum disorders, impaired L1CAM function also underlies the X-linked L1 syndrome, which encompasses a group of neurological conditions, including spastic paraplegia and congenital hydrocephalus. Studies on vertebrate and invertebrate L1CAMs established conserved roles that include axon guidance, dendrite morphogenesis, synapse development, and maintenance of neural architecture. We previously identified a genetic interaction between the Caenorhabditis elegans L1CAM encoded by the sax-7 gene and RAB-3, a GTPase that functions in synaptic neurotransmission; rab-3; sax-7 mutant animals exhibit synthetic locomotion abnormalities and neuronal dysfunction. Here, we show that this synergism also occurs when loss of SAX-7 is combined with mutants of other genes encoding key players of the synaptic vesicle (SV) cycle. In contrast, sax-7 does not interact with genes that function in synaptogenesis. These findings suggest a postdevelopmental role for sax-7 in the regulation of synaptic activity. To assess this possibility, we conducted electrophysiological recordings and ultrastructural analyses at neuromuscular junctions; these analyses did not reveal obvious synaptic abnormalities. Lastly, based on a forward genetic screen for suppressors of the rab-3; sax-7 synthetic phenotypes, we determined that mutants in the ERK Mitogen-activated Protein Kinase (MAPK) pathway can suppress the rab-3; sax-7 locomotion defects. Moreover, we established that Erk signaling acts in a subset of cholinergic neurons in the head to promote coordinated locomotion. In combination, these results suggest a modulatory role for Erk MAPK in L1CAM-dependent locomotion in C. elegans.
Subject(s)
Caenorhabditis elegans Proteins , Neural Cell Adhesion Molecule L1 , Animals , Caenorhabditis elegans/metabolism , Caenorhabditis elegans Proteins/metabolism , Cholinergic Neurons/metabolism , Locomotion , Mitogen-Activated Protein Kinases/genetics , Mutation , Neural Cell Adhesion Molecule L1/genetics , Neural Cell Adhesion Molecule L1/metabolism , Neural Cell Adhesion Molecules/geneticsABSTRACT
Enzyme immunoassays are currently the most common tests used in the clinical laboratory for the detection of Clostridium difficile toxins; however, significant problems with their performance have recently been described. We prospectively reevaluated the Meridian Premier C. difficile toxin A/B assay with direct comparison to a 2-step algorithm that screened for C. difficile common antigen and compared cytotoxin and real-time polymerase chain reaction (PCR) as confirmatory procedures. The Premier assay lacked sufficient sensitivity, missing 25% of true-positive samples. PCR was the most sensitive method and the only procedure that allowed same day testing and reporting.
