In situ hybridization analysis of the expression of futsch, tau, and MESK2 homologues in the brain of the European honeybee (Apis mellifera L.).

BACKGROUND: The importance of visual sense in Hymenopteran social behavior is suggested by the existence of a Hymenopteran insect-specific neural circuit related to visual processing and the fact that worker honeybee brain changes morphologically according to its foraging experience. To analyze molecular and neural bases that underlie the visual abilities of the honeybees, we used a cDNA microarray to search for gene(s) expressed in a neural cell-type preferential manner in a visual center of the honeybee brain, the optic lobes (OLs). METHODOLOGY/PRINCIPAL FINDINGS: Expression analysis of candidate genes using in situ hybridization revealed two genes expressed in a neural cell-type preferential manner in the OLs. One is a homologue of Drosophila futsch, which encodes a microtubule-associated protein and is preferentially expressed in the monopolar cells in the lamina of the OLs. The gene for another microtubule-associated protein, tau, which functionally overlaps with futsch, was also preferentially expressed in the monopolar cells, strongly suggesting the functional importance of these two microtubule-associated proteins in monopolar cells. The other gene encoded a homologue of Misexpression Suppressor of Dominant-negative Kinase Suppressor of Ras 2 (MESK2), which might activate Ras/MAPK-signaling in Drosophila. MESK2 was expressed preferentially in a subclass of neurons located in the ventral region between the lamina and medulla neuropil in the OLs, suggesting that this subclass is a novel OL neuron type characterized by MESK2-expression. These three genes exhibited similar expression patterns in the worker, drone, and queen brains, suggesting that they function similarly irrespective of the honeybee sex or caste. CONCLUSIONS: Here we identified genes that are expressed in a monopolar cell (Amfutsch and Amtau) or ventral medulla-preferential manner (AmMESK2) in insect OLs. These genes may aid in visualizing neurites of monopolar cells and ventral medulla cells, as well as in analyzing the function of these neurons.

Distribution of Kakugo virus and its effects on the gene expression profile in the brain of the worker honeybee Apis mellifera L.

We previously identified a novel insect picorna-like virus, termed Kakugo virus (KV), obtained from the brains of aggressive honeybee worker bees that had counterattacked giant hornets. Here we examined the tissue distribution of KV and alterations of gene expression profiles in the brains of KV-infected worker bees to analyze possible effects of KV infection on honeybee neural and physiological states. By use of in situ hybridization, KV was broadly detected in the brains of the naturally KV-infected worker bees. When inoculated experimentally into bees, KV was detected in restricted parts of the brain at the early infectious stage and was later detected in various brain regions, including the mushroom bodies, optic lobes, and ocellar nerve. KV was detected not only in the brain but also in the hypopharyngeal glands and fat bodies, indicating systemic KV infection. Next, we compared the gene expression profiles in the brains of KV-inoculated and noninoculated bees. The expression of 11 genes examined was not significantly affected in KV-infected worker bees. cDNA microarray analysis, however, identified a novel gene whose expression was induced in the periphery of the brains of KV-infected bees, which was commonly observed in naturally infected and experimentally inoculated bees. The gene encoded a novel hypothetical protein with a leucine zipper motif. A gene encoding a similar protein was found in the parasitic wasp Nasonia genome but not in other insect genomes. These findings suggest that KV infection may affect brain functions and/or physiological states in honeybees.

Differential expression of HR38 in the mushroom bodies of the honeybee brain depends on the caste and division of labor.

We used a cDNA microarray to identify genes expressed in a caste (worker)- and division of labor (nurse bees or foragers)-dependent manner in the honeybee brain. Among the identified genes, one encoded a putative orphan receptor (HR38) homologue that mediates ecdysteroid-signaling. Real-time reverse transcription-polymerase chain reaction indicated that expression of this gene is higher in forager brains, as compared to nurse bees and queens. In the forager brain, expression was concentrated in a subset of the mushroom body neurons, suggesting that ecdysteroid-signaling in the mushroom bodies might be involved in the division of labor of the workers.

EICO (Expression-based Imprint Candidate Organizer): finding disease-related imprinted genes.

We have developed an integrated database that is specialized for the study of imprinted disease genes. The database contains novel candidate imprinted genes identified by the RIKEN full-length mouse cDNA microarray study, information on validated single nucleotide polymorphisms (SNPs) to confirm imprinting using reciprocal mouse crosses and the predicted physical position of imprinting-related disease loci in the mouse and human genomes. It has two user-friendly search interfaces: the SNP-central view (MuSCAT: MoUse SNP CATalog) and the candidate gene-central view (CITE: Candidate Imprinted Transcripts by Expression). The database, EICO (Expression-based Imprint Candidate Organizer), can be accessed via the World Wide Web (http://fantom2.gsc.riken.jp/EICODB/) and the DAS client software. These data and interfaces facilitate understanding of the mechanism of imprinting in mammalian inherited traits.