Highlights d The loss of BIN1 in neurons leads to impaired spatial memory consolidation d Neuronal Bin1 cKO mice have deficits in excitatory synaptic transmission d BIN1 regulates presynaptic vesicular release in hippocampal excitatory synapses d The results highlight a non-redundant role for BIN1 in presynaptic regulation

bStreptococcus mutans is prominently linked to dental caries. Saliva's influence on caries is incompletely understood. Our goal was to identify a salivary protein with anti-S. mutans activity, characterize its genotype, and determine genotypic variants associated with S. mutans activity and reduced caries. An S. mutans affinity column was used to isolate active moieties from saliva obtained from a subject with minimal caries. The bound and eluted protein was identified as lactotransferrin (LTF) by matrixassisted laser desorption ionization-time of flight (MALDI-TOF) analysis and confirmed by Western blotting with LTF antibody. A single nucleotide polymorphism (SNP) that produced a shift from arginine (R) to lysine (K) at amino acid position 47 in the LTF antimicrobial region (rs: 1126478) killed S. mutans in vitro. Saliva from a subject with moderate caries and with the LTF "wild-type" R form at position 47 had no such activity. A pilot genetic study (n ‫؍‬ 30) showed that KK subjects were more likely to have anti-S. mutans activity than RR subjects (P ‫؍‬ 0.001; relative risk ‫؍‬ 3.6; 95% confidence interval [95% CI] ‫؍‬ 1.5 to 11.13). Pretreatment of KK saliva with antibody to LTF reduced S. mutans killing in a dose-dependent manner (P ‫؍‬ 0.02). KK subjects were less likely to have caries (P ‫؍‬ 0.02). A synthetic 11-mer LTF/K peptide killed S. mutans and other caries-related bacteria, while the LTF/R peptide had no effect (P ‫؍‬ 0.01). Our results provide functional evidence that the LTF/K variant results in both anti-S. mutans activity and reduced decay. We suggest that the LTF/K variant can influence oral microbial ecology in general and caries-provoking microbes specifically.

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Aggregatibacter actinomycetemcomitans leukotoxin (LtxA) is a major virulence factor that kills leukocytes permitting it’s escape from host immune surveillance. A. actinomycetemcomitans strains can produce high or low levels of toxin. Genetic differences reside in the “so called JP2” ltxA promoter region. These hyper-leukotoxin producing strains with the 530 bp deletion have been studied in detail. However, regions contained within the 530 bp deletion that could be responsible for modulation of leukotoxin production have not been defined. Here, we report, for the first time, on regions within the 530 bp that are responsible for high-levels of ltxA expression. We constructed a deletion of 530 bps in a primate isolate of A. actinomycetemcomitans, which produced leukotoxin equivalent to the JP2 strain. We then constructed sequential deletions in regions that span the 530 bps. Results indicated that expression of the ltxA transcript was reduced by a potential transcriptional terminator in promoter region 298 to 397 with a ΔG = −7.9 kcal/mol. We also confirmed previous findings that transcriptional fusion between the orfX region and ltxC increased ltxA expression. In conclusion, we constructed a hyper-leukotoxin producing A. actinomycetemcomitans strain and identified a terminator located in the promoter region extending from 298–397 that alters ltxA expression.