In violation of the 'one gene, one polypeptide' rule, alternative splicing allows individual genes to produce multiple protein isoforms - thereby playing a central part in generating complex proteomes. Alternative splicing also has a largely hidden function in quantitative gene control, by targeting RNAs for nonsense-mediated decay. Traditional gene-by-gene investigations of alternative splicing mechanisms are now being complemented by global approaches. These promise to reveal details of the nature and operation of cellular codes that are constituted by combinations of regulatory elements in pre-mRNA substrates and by cellular complements of splicing regulators, which together determine regulated splicing pathways.

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Using 2 new global measures, social functioning was found to be a stable trait, unchanged by treatment, with considerable potential to be a marker of schizophrenia. Role functioning, by contrast, may be a more direct barometer of clinical change and may be responsive to treatment and environmental change.

Polypyrimdine tract binding protein (PTB) is a regulator of alternative splicing, mRNA 3' end formation, mRNA stability and localization, and IRES-mediated translation. Transient overexpression of PTB can influence alternative splicing, sometimes resulting in nonphysiological splicing patterns. Here, we show that alternative skipping of PTB exon 11 leads to an mRNA that is removed by NMD and that this pathway consumes at least 20% of the PTB mRNA in HeLa cells. We also show that exon 11 skipping is itself promoted by PTB in a negative feedback loop. This autoregulation may serve both to prevent disruptively high levels of PTB expression and to restore nuclear levels when PTB is mobilized to the cytoplasm. Our findings suggest that alternative splicing can act not only to generate protein isoform diversity but also to quantitatively control gene expression and complement recent bioinformatic analyses, indicating a high prevalence of human alternative splicing leading to NMD.

To gain global insights into the role of the well-known repressive splicing regulator PTB we analyzed the consequences of PTB knockdown in HeLa cells using high-density oligonucleotide splice-sensitive microarrays. The major class of identified PTB-regulated splicing event was PTB-repressed cassette exons, but there was also a substantial number of PTB-activated splicing events. PTB repressed and activated exons showed a distinct arrangement of motifs with pyrimidine-rich motif enrichment within and upstream of repressed exons, but downstream of activated exons. The N-terminal half of PTB was sufficient to activate splicing when recruited downstream of a PTB-activated exon. Moreover, insertion of an upstream pyrimidine tract was sufficient to convert a PTB-activated to a PTB-repressed exon. Our results demonstrate that PTB, an archetypal splicing repressor, has variable splicing activity that predictably depends upon its binding location with respect to target exons.

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Despite the widespread acceptance of the neurodevelopmental model of schizophrenia, its application to research concerned with the prodromal phase of illness is limited. Little recognition has been given to the concept of an enduring biological vulnerability to illness that may be responsive to early intervention. Rather, the focus of most prodromal studies is on emerging positive symptoms. The Recognition and Prevention (RAP) program follows the strategy of being equally concerned with the nonspecific symptoms reflecting the core of schizophrenia and those directly related to psychosis. Data were collected from 62 adolescents (mean age = 16.4 years) during the initial 3-year pilot phase of the RAP program (1998-2001). Subjects were divided into three clinical high-risk groups, characterized by (1) negative and nonspecific symptoms (e.g., social isolation, school failures), the earliest prodrome stage; (2) emerging attenuated positive symptoms of moderate intensity; and (3) severe attenuated (but subpsychotic) positive symptoms, considered most proximal to psychosis. Four risk factors, derived from the neurodevelopmental literature, were selected to reflect the vulnerability core: cognitive deficits, affective disturbances, social isolation, and school failure. All four domains were equally impaired across the three risk groups, supporting the presence of the underlying vulnerability core regardless of the magnitude of emerging positive symptoms. An observational pilot study was also conducted to identify the medications typically used to treat emerging positive symptoms. Antidepressants were used as frequently as antipsychotics to treat adolescents presenting with moderate attenuated positive symptoms. Regardless of type of medication, moderately symptomatic youngsters did quite well over the approximately 1-year followup period. By contrast, adolescents presenting with more severe (but nonpsychotic) attenuated symptoms were treated with antipsychotics, often in combination with other agents. Outcome for the more symptomatic youngsters was, however, more guarded, with nearly half (i.e., 47%) of the group converting to a schizophrenia spectrum psychotic disorder. Nonadherence to medication appeared to be a major risk factor in this group. We conclude that a neurodevelopmental model of schizophrenia is supported by our data and that a range of novel treatment strategies may be neuroprotective by directly affecting the disorder's vulnerability core.

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