Yasuo Kitagawa

The expression of genes encoding visual components is regulated by a circadian clock, light environment and age in the honeybee (Apis mellifera).

The honeybee, Apis mellifera, has been used as a model to study the development of the visual system and adult bee behaviour. However, the regulation of the levels of visual component genes has never been addressed in this organism. We isolated honeybee cDNAs encoding green‐sensitive opsin and visual arrestin and then measured their mRNA levels in honeybee workers. Both mRNAs fluctuate on a daily cycle that depends on a pacemaker that functions separately from the pacemaker which controls rhythmic locomotor activity. The cycling‐patterns of opsin and arrestin mRNAs are different from each other and are modified by light. Furthermore, light exposure can increase the absolute levels of both mRNAs and the arrestin mRNA level is also dependent on age. Consistent with these results, both mRNA levels are higher in foragers than in in‐hive bees under natural conditions. This study thus shows that the expression of genes encoding visual components is regulated by multiple factors and is adjusted to the honeybees need for vision during the day, and throughout their lives. Comparison of data obtained with honeybees and other organisms indicates that there is a link between the regulation of phototransduction components and vision‐related animal behaviour.

Characterization of the two distinct subtypes of metabotropic glutamate receptors from honeybee, Apis mellifera.

L-Glutamate is a major neurotransmitter at the excitatory synapses in the vertebrate brain. It is also the excitatory neurotransmitter at neuromuscular junctions in insects, however its functions in their brains remain to be established. We identified and characterized two different subtypes (AmGluRA and AmGluRB) of metabotropic glutamate receptors (mGluRs) from an eusocial insect, honeybee. Both AmGluRA and AmGluRB form homodimers independently on disulfide bonds, and bind [3H]glutamate with K(D) values of 156.7 and 80.7 nM, respectively. AmGluRB is specifically expressed in the brain, while AmGluRA is expressed in the brain and other body parts, suggesting that AmGluRA is also present at the neuromuscular junctions. Both mGluRs are expressed in the mushroom bodies and the brain regions of honeybees, where motor neurons are clustered. Their expression in the brain apparently overlaps, suggesting that they may interact with each other to modulate the glutamatergic neurotransmission.

The Changes of Gene Expression in Honeybee (Apis mellifera) Brains Associated with Ages

Abstract Honeybee (Apis mellifera) worker bees (workers) are known to perform wide variety of tasks depending on their ages. The workers brains also show the activity and behavior-dependent chemical and structural plasticity. To test if there are any changes of gene expression associated with different ages in the worker brains, we compared the gene expression patterns between the brains of newly emerged bees and old foraging workers (foragers) by macroarray analysis. The expression of genes encoding signal transduction pathway components, ion channels, and neurotransmitter transporters is elevated in the old forager brains, suggesting that the neuronal activities would be enhanced. The mRNA levels of cell adhesion protein, transcription related factors, and plasma membrane associated proteins are also increased in the old forager brains. Meanwhile, the mRNA level of one putative cell adhesion protein is decreased in the old forager brains. These results thus suggest that the dramatic changes of gene expression occur in honeybee brains associated with ages.

Misexpression of mouse porcupine isoforms modulates the differentiation of P19 embryonic carcinoma cells

Drosophila porcupine (porc) encodes an ER membrane protein that is required for the processing of the Drosophila Wnt family. Homologs of porc have been identified in various multicellular organisms and have been implicated in the biosynthesis of Wnt proteins. In contrast to Drosophila, vertebrates generate four different porc mRNAs (A—D) by alternative splicing. Murine porcD (MporcD) mRNA levels transiently increase during the neuroectodermal differentiation of P19 cells, but diminish during mesodermal differentiation. P19 cells constitutively expressing mouse porcA (MporcA), but not MporcD, undergo apoptosis by the induction of neuroectodermal differentiation. Meanwhile, P19 cells constitutively expressing MporcD, but not MporcA, do not adopt mesodermal cell morphology and fail to express myf‐5 when induced to mesodermal differentiation. These results therefore demonstrate that the alternative splicing of Mporc is regulated in a cell‐type specific manner, and the resulting Mporc isoforms have different functions in the neuroectodermal and mesodermal differentiation of P19 cells.

Differential effect of green tea catechins on three endothelial cell clones isolated from rat adipose tissue and on human umbilical vein endothelial cells

By single colony isolation from the cells in stromal vascular fraction (SVF) dispersed from rat adipose tissues, we isolated three independent clones with different proliferation potential. All clones showed cobblestone-like morphology at the confluence and incorporated fluorescent Dil acetylated low density lipoprotein. When plated on Matrigel, they formed a capillary network-like structure. These rat adipose tissue endothelial cell (RATEC) clones showed higher expression of wnt2, wnt4, wnt5a, wnt5b, fzd1 and fzd5 whereas lower expression of cell cycle controlling genes such as CIP1, KIP1, KIP2, CDKN2A, CDKN2B, CDKN2C and CDKN2D compared to human umbilical vein endothelial cell (HUVEC). As reported for HUVEC, the growth of RATEC was inhibited by green tea catechins such as epigallocatechin, epicatechin gallate, epicatechin and epigallocatechin gallate but with higher sensitivity than HUVEC. The sensitivity of RATEC to catechins was higher for the cultures with low plating density and for the clone with higher proliferation potential.