No abstract

Activation of brain melanocortin 4 receptors (MC4Rs) leads to reduced food intake, increased energy expenditure, increased insulin sensitivity, and reduced linear growth. MC4R effects on energy expenditure and glucose metabolism are primarily mediated by the G protein G(s)α in brain regions outside of the paraventricular nucleus of the hypothalamus (PVN). However, the G protein(s) that is involved in MC4R-mediated suppression of food intake and linear growth, which are believed to be regulated primarily though action in the PVN, is unknown. Here, we show that PVN-specific loss of G(q)α and G11α, which stimulate PLC, leads to severe hyperphagic obesity, increased linear growth, and inactivation of the hypothalamic-pituitary-adrenal axis, without affecting energy expenditure or glucose metabolism. Moreover, we demonstrate that the ability of an MC4R agonist delivered to PVN to inhibit food intake is lost in mice lacking G(q/11)α in the PVN but not in animals deficient for G(s)α. The blood pressure response to the same MC4R agonist was only lost in animals lacking G(s)α specifically in the PVN. Together, our results exemplify how different physiological effects of GPCRs may be mediated by different G proteins and identify a pathway for appetite regulation that could be selectively targeted by G(q/11)α-biased MC4R agonists as a potential treatment for obesity.

CRISPR (Clustered Regularly-Interspaced Short Palindromic Repeats)-Cas9 (CRISPR associated protein 9) has rapidly become the most promising genome editing tool with great potential to revolutionize medicine. Through guidance of a 20 nucleotide RNA (gRNA), CRISPR-Cas9 finds and cuts target protospacer DNA precisely 3 base pairs upstream of a PAM (Protospacer Adjacent Motif). The broken DNA ends are repaired by either NHEJ (Non-Homologous End Joining) resulting in small indels, or by HDR (Homology Directed Repair) for precise gene or nucleotide replacement. Theoretically, CRISPR-Cas9 could be used to modify any genomic sequences, thereby providing a simple, easy, and cost effective means of genome wide gene editing. However, the off-target activity of CRISPR-Cas9 that cuts DNA sites with imperfect matches with gRNA have been of significant concern because clinical applications require 100% accuracy. Additionally, CRISPR-Cas9 has unpredictable efficiency among different DNA target sites and the PAM requirements greatly restrict its genome editing frequency. A large number of efforts have been made to address these impeding issues, but much more is needed to fully realize the medical potential of CRISPR-Cas9. In this article, we summarize the existing problems and current advances of the CRISPR-Cas9 technology and provide perspectives for the ultimate perfection of Cas9-mediated genome editing.

Among Escherichia coli strains isolated from stool specimens from patients with acute diarrhea, 1.4% were found to harbor cdtB by use of enrichment cytolethal distending toxin (CDT) PCR. These isolates were identified as being enteropathogenic E. coli (EPEC). In a retrospective study using a probe hybridization assay, 6 of 138 EPEC strains were found to harbor the cdtB locus. cdtB-positive isolates mostly belong to the O86a and O127a serogroups, with the former being associated with higher expression of CDT. Pulsed-field gel electrophoresis profiles showed that the EPEC strains harboring cdtB strains are genetically diverse.Cytolethal distending toxin (CDT) is a novel class of bacterial genotoxin that induces characteristic elongation of eukaryotic cells followed by progressive cellular distention and death (12,14,23). CDT is considered to be an important factor in intestinal pathogenesis (3), as this toxin is able to induce tissue damage and fluid accumulation in the descending colon of orally infected suckling mice (21). Three genes, cdtA, cdtB, and cdtC, arranged in an apparent operon are required for the production of active CDT (25). The deduced amino acid sequences of these genes from Escherichia coli strains E6468-62 (serogroup O86) and 9142-88 (serogroup O128) are 38, 56, and 37% homologous, respectively (24, 25), and the corresponding toxins are called . The amino acid sequence of Cdt-III from strain S5 (serogroup O15) has Ͼ90% homology to Cdt-II and 55 to 69% homology to . The presence of cdt in different bacterial species (8,20,24,28) and the results of analysis of its flanking regions suggest that this gene has been acquired from heterologous species by horizontal gene transfer (7,18,22) or through a phage (13). Even though the data on the structural and functional aspects of CDT are expanding, knowledge of the epidemiological association of E. coli harboring cdt remains scanty (1,15,17,19).To investigate the incidence of cdt-harboring E. coli, a total of 284 stool specimens collected from acute-diarrhea patients of all age groups admitted to the Infectious Diseases Hospital and B. C. Roy Memorial Hospital for Children (Calcutta, India) from May to July 2002 were examined. Relevant clinical information such as presence of fever, vomiting, dehydration status, and type and duration of diarrhea was recorded for each patient. For enrichment CDT PCR, overnight stool cultures in Luria-Bertani broth (Difco, Detroit, Mich.) were directly tested for the presence of the cdtB gene in a standard PCR assay. The primer pair used in this study was based on the cdt nucleotide sequence of E. coli (25) and had the sequences 5Ј-GATTTTGCCGGGTATTTCT-3Ј and 5Ј-CCCTCAACAG AGGAAGAA-3Ј. These primers are specific for Cdt-I. After a hot start at 94°C for 5 min, the DNA was subjected to 30 cycles of denaturation at 94°C for 30 s, annealing at 55°C for 30 s, and extension at 72°C for 1 min 30 s. The expected size of the PCR amplicon was 707 bp. The sensitivity of the CDT PCR assay was 10 3 CFU. For confirmation, a PCR amplicon...