Our objectives were to determine whether clinic-pathological markers and immune-related gene signatures in breast cancer exhibit any change upon brain metastasis and whether previously reported genes significantly associated with brain metastases and the epithelial-mesenchymal transition (EMT) were reproducible and consistent in our dataset. Sixteen pair-matched samples from primary breast cancers and brain metastases diagnosed were collected from the Japan Clinical Oncology Group Breast Cancer Study Group. Gene expression profiles for immune-, brain metastases-, and EMT-related genes were compared between primary breast cancers and brain metastases. Potential therapeutic target genes of 41 FDA-approved or under-investigation agents for brain metastases were explored. Immune-related signatures exhibited significantly lower gene expression in brain metastases than in primary breast cancers. No significant differences were detected for the majority of genes associated with brain metastases and EMT in the two groups. Among 41 therapeutic target candidates, VEGFA and DNMT3A demonstrated significantly higher gene expression in brain metastases. We found that distinct patterns of gene expression exist between primary breast cancers and brain metastases. Further studies are needed to explore whether these distinct expression profiles derive from or underlie disease status and compare these features between metastases to the brain and other sites.

Microphthalmia-associated transcription factor (Mitf) plays a critical role in the development of neural crest-derived melanocytes. Here, we show that exogenously added Wnt-3a protein, an intercellular signaling molecule, up-regulates the expression of endogenous melanocyte-specific Mitf (Mitf-M) mRNA in cultured melanocytes. The melanocyte-specific promoter of the human MITF gene (MITF-M promoter) contains a functional LEF-1-binding site, which is bound in vitro by LEF-1 and confers the preferential expression on a reporter gene in melanocytes and melanoma cells, as judged by the transient transfection assays. Moreover, the LEF-1-binding site is required for the transactivation of a reporter gene by LEF-1, beta-catenin, or their combination. Exogenously added Wnt-3a protein also transactivates the MITF-M promoter via the LEF-1-binding site; this activation was abolished when a dominant-negative form of LEF-1 was coexpressed. These results suggest that Wnt-3a signaling recruits beta-catenin and LEF-1 to the LEF-1-binding site of the MITF-M promoter. Therefore, the present study identifies Mitf-M/MITF-M as a direct target of Wnt signaling.

Mutations in the connexin 26 gene (GJB2), which encodes a gap-junction protein and is expressed in the inner ear, have been shown to be responsible for a major part of nonsyndromic hereditary prelingual (early-childhood) deafness in Caucasians. We have sequenced the GJB2 gene in 39 Japanese patients with prelingual deafness (group 1), 39 Japanese patients with postlingual progressive sensorineural hearing loss (group 2), and 63 Japanese individuals with normal hearing (group 3). Three novel mutations were identified in group 1: a single nucleotide deletion (235delC), a 16-bp deletion (176-191 del (16)), and a nonsense mutation (Y136X) in five unrelated patients. The 235delC mutation was most frequently observed, accounting for seven alleles in 10 mutant alleles. Screening of 203 unrelated normal individuals for the three mutations indicated that the carrier frequency of the 235delC mutation was 2/203 in the Japanese population. No mutation was found in group-2 patients. We also identified two novel polymorphisms (E114G and I203T) as well as two previously reported polymorphisms (V27I andV37I). Genotyping with these four polymorphisms allowed normal Japanese alleles to be classified into seven haplotypes. All 235delC mutant alleles identified in four patients resided only on haplotype type 1. These findings indicate that GJB2 mutations are also responsible for prelingual deafness in Japan.

DFN3, an X chromosome-linked nonsyndromic mixed deafness, is caused by mutations in the BRN-4 gene, which encodes a POU transcription factor. Brn-4-deficient mice were created and found to exhibit profound deafness. No gross morphological changes were observed in the conductive ossicles or cochlea, although there was a dramatic reduction in endocochlear potential. Electron microscopy revealed severe ultrastructural alterations in cochlear spiral ligament fibrocytes. The findings suggest that these fibrocytes, which are mesenchymal in origin and for which a role in potassium ion homeostasis has been postulated, may play a critical role in auditory function.

Neutrophils are highly motile leukocytes, and they play important roles in the innate immune response to invading pathogens. Neutrophil chemotaxis requires Rac activation, yet the Rac activators functioning downstream of chemoattractant receptors remain to be determined. We show that DOCK2, which is a mammalian homologue of Caenorhabditis elegans CED-5 and Drosophila melanogaster Myoblast City, regulates motility and polarity during neutrophil chemotaxis. Although DOCK2-deficient neutrophils moved toward the chemoattractant source, they exhibited abnormal migratory behavior with a marked reduction in translocation speed. In DOCK2-deficient neutrophils, chemoattractant-induced activation of both Rac1 and Rac2 were severely impaired, resulting in the loss of polarized accumulation of F-actin and phosphatidylinositol 3,4,5-triphosphate (PIP3) at the leading edge. On the other hand, we found that DOCK2 associates with PIP3 and translocates to the leading edge of chemotaxing neutrophils in a phosphatidylinositol 3-kinase (PI3K)–dependent manner. These results indicate that during neutrophil chemotaxis DOCK2 regulates leading edge formation through PIP3-dependent membrane translocation and Rac activation.