Sex differences in the effects of inherited bitter thiourea sensitivity on body weight in 4-6-year-old children.

Previous studies have shown that inherited taste blindness to bitter compounds like 6-n-propylthiouracil (PROP) may be a risk factor for obesity, but this literature has been highly controversial. The objectives of this study were (i) to confirm findings that show an interaction between PROP status and sex on BMI z-score, and (ii) to determine if sex also interacts with variations in TAS2R38 (phenylthiocarbamide (PTC) genotype) to influence weight status in 4-6 year olds. Also, we tested whether nontaster children consumed more fat and total energy at laboratory-based meals. Seventy-two ethnically diverse children who ranged in weight status were classified as tasters (N = 52) or nontasters (N = 20) using a standard PROP screening solution. Anthropometric measures were taken, and at the end of each visit, children ate ad libitum from test meals intended for exploratory purposes. Genomic DNA was extracted from saliva and alleles at TAS2R38 were genotyped for A49P polymorphisms. In 75.8% of children, PTC genotype predicted PROP phenotype, whereas in 24.4%, genotype did not predict phenotype. PROP nontaster males had higher BMI z-scores than taster-males and females in both groups (P < 0.05), but due to a three-way interaction between PROP phenotype, TAS2R38 genotype, and sex, this relationship was only true for children who were homozygous for the bitter-insensitive allele (P < 0.0005). There were no differences in test-meal intake as a function of PROP phenotype or TAS2R38 genotype. These results suggest that the TAS2R38 variation, PROP phenotype, and sex interact to impact obesity risk in children. Future studies should be done to determine how this trait influences energy balance.

Changes in alternative brain-derived neurotrophic factor transcript expression in the developing human prefrontal cortex.

In this study, we determined when and through which promoter brain-derived neurotrophic factor (BDNF) transcription is regulated during the protracted period of human frontal cortex development. Using quantitative real-time polymerase chain reaction, we examined the expression of the four most abundant alternative 5' exons of the BDNF gene (exons I, II, IV, and VI) in RNA extracted from the prefrontal cortex. We found that expression of transcripts I-IX and VI-IX was highest during infancy, whereas that of transcript II-IX was lowest just after birth, slowly increasing to reach a peak in toddlers. Transcript IV-IX was significantly upregulated within the first year of life, and was maintained at this level until school age. Quantification of BDNF protein revealed that levels followed a similar developmental pattern as transcript IV-IX. In situ hybridization of mRNA in cortical sections showed the highest expression in layers V and VI for all four BDNF transcripts, whereas moderate expression was observed in layers II and III. Interestingly, although low expression of BDNF was observed in cortical layer IV, this BDNF mRNA low-zone decreased in prominence with age and showed an increase in neuronal mRNA localization. In summary, our findings show that dynamic regulation of BDNF expression occurs through differential use of alternative promoters during the development of the human prefrontal cortex, particularly in the younger age groups, when the prefrontal cortex is more plastic.

Use of RNA interference to elucidate the effect of MYCN on cell cycle in neuroblastoma.

BACKGROUND: MYCN amplification marks poor prognosis in neuroblastoma (NB) tumors. In evaluating the mechanisms by which retinoic acid (RA) or nerve growth factor (NGF) decrease cell number in MYCN amplified NB cells, we have identified a number of proteins whose expression either decreases (E2F, CDC2, CDK6, cyclin dependent kinase activity) or increases (p27) in association with a decrease in MYCN expression. However, it was still unclear which were MYCN dependent effects or not. PROCEDURE: This study aimed to determine which changes in cell cycle gene expression are modulated as a consequence of the decrease in MYCN. We silenced MYCN expression using siRNA targeted to the coding region of MYCN. Then, by using siRNA transient transfections, we analyzed the change of cell cycle related genes and cell cycle in MYCN amplified NB cell lines. RESULTS: We demonstrate that expression of MYCN can be suppressed by almost 60% in MYCN amplified NB cell using siRNAs targeted to MYCN. Functionally, the decrease in MYCN leads to a decrease in cells in the S-phase of the cell cycle. Decreases in MYCN are associated with decreases in E2F1-2 and ID2 along with increases in p27 protein levels by post-transcriptional modification. Moreover, we find that a decrease in MYCN is accompanied by a decrease in cdk6 mRNA and protein expression. CONCLUSIONS: These results show that E2F and ID2 expression is associated with MYCN regulation and that cdk6 is a possible new transcriptional target of MYCN.