Periodic notch inhibition by lunatic fringe underlies the chick segmentation clock

The segmented aspect of the vertebrate body plan first arises through the sequential formation of somites. The periodicity of somitogenesis is thought to be regulated by a molecular oscillator, the segmentation clock, which functions in presomitic mesoderm cells. This oscillator controls the periodic expression of 'cyclic genes', which are all related to the Notch pathway. The mechanism underlying this oscillator is not understood. Here we show that the protein product of the cyclic gene lunatic fringe (Lfng), which encodes a glycosyltransferase that can modify Notch activity, oscillates in the chick presomitic mesoderm. Overexpressing Lfng in the paraxial mesoderm abolishes the expression of cyclic genes including endogenous Lfng and leads to defects in segmentation. This effect on cyclic genes phenocopies inhibition of Notch signalling in the presomitic mesoderm. We therefore propose that Lfng establishes a negative feedback loop that implements periodic inhibition of Notch, which in turn controls the rhythmic expression of cyclic genes in the chick presomitic mesoderm. This feedback loop provides a molecular basis for the oscillator underlying the avian segmentation clock.

Effect of literacy on breast-feeding outcomes

BACKGROUND

We studied the effect of functional health literacy on the initiation and continuance of breast-feeding in women at a public health clinic.

METHODS

Subjects were 61 first-time mothers aged 18 years or older who spoke English as their first language. They were divided into two groups, one who exclusively breast-fed for at least the first 2 months and one who never initiated breast-feeding or did not exclusively breast-feed for at least 2 months. The Rapid Estimate of Adult Literacy in Medicine (REALM) was administered, providing reading grade-level estimates for each subject.

RESULTS

An association between functional health literacy and breast-feeding was seen, with only 23% of the women in the lower literacy group exclusively breast-feeding during the first 2 months compared with 54% of women in the higher literacy group.

CONCLUSION

Many patients need simpler health education materials encouraging breastfeeding. These materials are needed both before and during pregnancy.

Identification of a protein-binding sequence involved in expression of an esterase gene from Streptomyces scabies

Expression of an esterase gene from Streptomyces scabies is regulated by zinc in both Streptomyces scabies and Streptomyces lividans. A specific protein-binding site was identified on an esterase promoter fragment by using an S-30 extract from S. scabies. The location of the protein-binding site was determined by gel shift assays of promoter deletion fragments and by DNase I footprinting analysis. The protein-binding site maps from nucleotides -59 to -81 relative to the start of transcription. An esterase gene construct cloned and expressed in S. lividans was used to assess the importance of the protein-binding site. Deletion of the 23-bp protein-binding site resulted in a 10-fold decrease in esterase production when cells were grown in zinc-inducing conditions. The protein-binding site may represent a region involved in positive regulation of the S. scabies esterase gene.

Heterologous expression and secretion of a Streptomyces scabies esterase in Streptomyces lividans and Escherichia coli

The esterase gene from Streptomyces scabies FL1 was cloned and expressed in Streptomyces lividans on plasmids pIJ486 and pIJ702. In S. lividans, the esterase gene was expressed during later stages of growth and was regulated by zinc, as is seen with S. scabies. The 36-kDa secreted form of the esterase was purified from S. lividans. N-terminal amino acid sequencing indicated that the processing site utilized in S. lividans for the removal of the signal sequence was the same as that recognized for processing in S. scabies. Western blots (immunoblots) revealed the presence of a 40-kDa precursor form of the esterase in cytoplasmic extracts. A 23-amino-acid deletion was introduced into the putative signal sequence for the esterase. When this deleted form of the esterase was expressed in S. lividans, a cytoplasmic 38-kDa precursor protein was produced but no secreted esterase was detected, suggesting the importance of the deleted sequence for efficient processing and secretion. The esterase gene was also cloned into the pUC119 plasmid in Escherichia coli. By using the lac promoter sequence, the esterase gene was expressed, and the majority of the esterase was localized to the periplasmic space.