Exome sequencing for bipolar disorder points to roles of de novo loss-of-function and protein-altering mutations

Although numerous genetic studies have been conducted for bipolar disorder (BD), its genetic architecture remains elusive. Here we perform, to the best of our knowledge, the first trio-based exome sequencing study for BD to investigate potential roles of de novo mutations in the disease etiology. We identified 71 de novo point mutations and one de novo copy-number mutation in 79 BD probands. Among the genes hit by de novo loss-of-function (LOF; nonsense, splice site or frameshift) or protein-altering (LOF, missense and inframe indel) mutations, we found significant enrichment of genes highly intolerant (first percentile of intolerant genes assessed by Residual Variation Intolerance Score) to protein-altering variants in general population, an observation that is also reported in autism and schizophrenia. When we performed a joint analysis using the data of schizoaffective disorder in published studies, we found global enrichment of de novo LOF and protein-altering mutations in the combined group of bipolar I and schizoaffective disorders. Considering relationship between de novo mutations and clinical phenotypes, we observed significantly earlier disease onset among the BD probands with de novo protein-altering mutations when compared with non-carriers. Gene ontology enrichment analysis of genes hit by de novo protein-altering mutations in bipolar I and schizoaffective disorders did not identify any significant enrichment. These results of exploratory analyses collectively point to the roles of de novo LOF and protein-altering mutations in the etiology of bipolar disorder and warrant further large-scale studies.

Differential expression of the immediate-early 2 and 3 proteins in developing mouse brains infected with murine cytomegalovirus

Murine cytomegalovirus (MCMV) immediate-early (IE) 2 protein has been reported to be dispensable for growth and latency in mice. Therefore, its role in viral pathogenesis and tissue tropism is not known. Here we prepared specific antibodies to the IE2 and IE3 proteins by using fusion proteins expressed in Escherichia coli as antigens. Immunostaining of MCMV-infected cultured fibroblasts revealed IE2 protein to be expressed diffusely in the nucleoplasm similar to the IE1 protein. In contrast, expression of the IE3 protein, 88 kDa, exhibited a punctate pattern in the nucleus in the early phase of infection then diminished. In the brain of neonatal mice infected with MCMV, both IE2 and IE3 proteins were detected immunohistochemically in the cells of the ventricular walls early in infection. When the infection was prolonged, the IE2 protein was expressed in neurons of the cortex and hippocampus, while the IE3 protein was preferentially expressed in glial cells in the early phase of infection, and its levels declined during the infection. These results suggest that the IE2 protein may play a role in persistent infection in neurons, whereas the IE3 protein, expressed preferentially in glial cells, may play the main role in acute infection.

DNA synthesis of cultured mesothelial cells in a high permeable state

To understand the mechanism of regeneration of the mesothelial cell in a high permeable state, in vitro experiments with cultured mesothelial cells were carried out using a type I collagen-coated multititer plate. Prior to cell seeding, each plate was filled with 100 microL of glucose solution at concentrations of 30 mmol/L, 90 mmol/L, and 150 mmol/L, and minimum essential medium (MEM), respectively. After immersion for one to five weeks at 37 degrees C, mesothelial cells were seeded at a density of 3 x 10(4)/cm2, then glucose was added at varying final concentrations between 0 and 150 mmol/L and/or albumin was added at a final concentration of 2 g/dL. After days 2 and 4, DNA synthesis was measured by incorporation of 5-bromo-2'-deoxy-uridine (BrdU). There was no significant difference of DNA synthesis between groups with and without one-week glucose immersion when mesothelial cells were cultured with only 10% FCS/MEM. However, suppression of DNA synthesis at 2 g/dL of albumin was seen no matter what concentration of glucose supplement was used. Without a high concentration of albumin, DNA synthesis was dose-dependent on glucose. The longer the immersion period, the lesser the suppression. It is speculated that process of glycation with collagen may relate to growth of mesothelial cells.