Misexpression of the Caenorhabditis elegans miRNA let-7 is sufficient to drive developmental programs.

The Caenorhabditis elegans microRNAs (miRNAs) lin-4 and let-7 promote transitions between stage-specific events in development by down-regulating the translation of their target genes. Expression of let-7 is required at the fourth larval stage for the proper transition from larval to differentiated, adult fates in the hypodermis; however, it was not known whether expression of let-7 is sufficient to specify these adult fates. To test this, we created fusion genes between lin-4 and let-7 that direct the expression of let-7 two stages early, at the L2 stage. We find that animals bearing the fusion genes show precocious adult development at the L4 stage, indicating that temporal misexpression of let-7 is sufficient to direct the larval-to-adult transition. Additionally, an RNA interference (RNAi)-based screen for enhancers of the precocious phenotype identified the period ortholog lin-42, among other genes, which are candidate modulators of the effects of let-7 expression. let-7 is conserved throughout bilaterian phylogeny, and orthologs of its targets have roles in vertebrate development, suggesting the importance of understanding how let-7 promotes terminal differentiation in C. elegans and other organisms.

Mentally abnormal homicide--a review of a special hospital male population.

The clinical, criminological and demographic characteristics of a Special Hospital population of male patients convicted of homicide are described. The results confirm much previous work on mentally abnormal homicide. Typically the patients come from a disadvantaged social background with poor employment records, a prior history of aggressive behaviour and a diagnosis of schizophrenia. Victims were usually known to the patient and often came from within his circle of family and friends. Only 25% of the patients were receiving treatment at the time of the offence. These findings are discussed in the light of the current literature.