Studies of cytokines in nerve tissue cultures

Association between 5q23.2-located polymorphism of CTXN3 gene (Cortexin 3) and schizophrenia in European-Caucasian males; implications for the aetiology of schizophrenia

BACKGROUND

The objective of the study was to examine several polymorphisms in DISC1 and CTNX3 genes as possible risk factors in schizophrenia. DISC1 (disrupted-in-schizophrenia 1) has been studied extensively in relation to mental disease while CTXN3, has only recently emerged as a potential "candidate" gene in schizophrenia. CTXN3 resides in a genomic region (5q21-34) known to be associated with schizophrenia and encodes a protein cortexin 3 which is highly enriched in brain.

METHODS

We used ethnically homogeneous samples of 175 male patients and 184 male control subjects. All patients were interviewed by two similarly qualified psychiatrists. Controls were interviewed by one of the authors (O.S.). Genotyping was performed, following amplification by polymerase chain reaction (PCR), using fragment analysis in a standard commercial setting (Applied Biosystems, USA).

RESULTS

We have found a statistically significant association between rs6595788 polymorphism of CTXN3 gene and the risk of schizophrenia; the presence of AG genotype increased the risk 1.5-fold. Polymorphisms in DISC1 gene showed only marginally statistically significant association with schizophrenia (rs17817356) or no association whatsoever (rs821597 and rs980989) while two polymorphisms (rs9661837 and rs3737597) were found to be only slightly polymorphic in the samples.

CONCLUSION

Evidence available in the literature suggests that altered expression of cortexin 3, either alone, or in parallel with changes in DISC1, could subtly perturb GABAergic neurotransmission and/or metabolism of amyloid precursor protein (APP) in developing brain, thus potentially exposing the affected individual to an increased risk of schizophrenia later in life.

Genomic profiling reveals Pitx2 controls expression of mature extraocular muscle contraction-related genes

PURPOSE

To assess the influence of the Pitx2 transcription factor on the global gene expression profile of extraocular muscle (EOM) of mice.

METHODS

Mice with a conditional knockout of Pitx2, designated Pitx2(Δflox/Δflox) and their control littermates Pitx2(flox/flox), were used. RNA was isolated from EOM obtained at 3, 6, and 12 weeks of age and processed for microarray-based profiling. Pairwise comparisons were performed between mice of the same age and differentially expressed gene lists were generated. Select genes from the profile were validated using real-time quantitative polymerase chain reaction and protein immunoblot. Ultrastructural analysis was performed to evaluate EOM sarcomeric structure.

RESULTS

The number of differentially expressed genes was relatively small. Eleven upregulated and 23 downregulated transcripts were identified common to all three age groups in the Pitx2-deficient extraocular muscle compared with littermate controls. These fell into a range of categories including muscle-specific structural genes, transcription factors, and ion channels. The differentially expressed genes were primarily related to muscle contraction. We verified by protein and ultrastructural analysis that myomesin 2 was expressed in the Pitx2-deficient mice, and this was associated with development of M lines evident in their orbital region.

CONCLUSIONS

The global transcript expression analysis uncovered that Pitx2 primarily regulates a relatively select number of genes associated with muscle contraction. Pitx2 loss led to the development of M line structures, a feature more typical of other skeletal muscle.