Kinesin superfamily protein member 4 (KIF4) is localized to midzone and midbody in dividing cells

In association with microtubules, a variety of kinesins play important roles in cellular functions such as intracellular transport of organelles or vesicles, signal transduction, and cell division. In a previous study we revealed that human kinesin superfamily protein member 4 (KIF4) is a chromokinesin that binds to chromosomes. Since localization of several kinds of kinesin at midzone called central spindle, or midbody that connects two daughter cells, or both, suggests their implication in cell division, we investigated KIF4 localization of during mitosis and cytokinesis in Hela cells. In addition to association with segregating chromosomes through entire mitosis, it also localized to the midzone and to midbody at ana/telophase through cytokinesis. Especially in cells at cytokinesis, KIF4 appeared as a doublet facing each other at the apical ends of two daughter cells. Three- dimensional analysis of architectural relationship between microtubule bundles and KIF4 indicated that KIF4 forms a ring structure wrapping around the microtubule bundles. These results suggest that KIF4 is involved in cytokinesis, although direct evidence was not provided in this study.

Donor Specific Response of Estrogen and Progesterone on Cultured Human Melanocytes

The mechanisms of estrogen and progesterone in human cutaneous pigmentation are largely unknown. The molecular identification of estrogen receptor (ER) and progesterone receptor (PR) in the human melanocytes is of great importance to understand the mechanisms. We performed immunocytochemistry analysis and demonstrated that ER and PR were expressed in the cytoplasms and nuclei of human melanocytes. Reverse transcriptase-polymerase chain reaction (RT-PCR) and sequence analysis confirmed the expression of ER and PR at the transcriptional level. Despite of the presence of ER and PR, the physiological and pregnant levels of estrogen and progesterone showed inconsistent effects on the proliferation and tyrosinase activity of cultured human melanocytes. These results suggest that human melanocytes express ER and PR, which have a donor-specific action in human pigmentation. Further studies are needed to elucidate the induction mechanism and functions of these receptors, and the role of estrogen and progesterone in melanocytes.

Assignments of the tyrosinase related protein-1 and -2 genes to human chromosome bands 9p23 and 13q32.1 by in situ hybridization

To determine the precise chromosomal localization of tyrosine related protein-1 and -2 (TRP-1 and TRP-2) genes by fluorescence in situ hybridization, we used DNAs isolated from human bacterial artificial chromosome clones. They contain genomic sequences with approximately 120 kb inserts for TRP-1 and TRP-2. The TRP-1 and TRP-2 genes were assigned to human chromosome bands 9p23 and 13q32.1, respectively. These results confirmed the previously mapped location for the TRP-1 gene and more precisely located the TRP-2 gene, which had previously been mapped to chromosome 13q31-q32.

Expression of progesterone receptor in human keratinocytes

Despite the various responses of human skin to female sex hormones, cellular and subcellular targets and the mechanisms of action of estrogen and progesterone in human skin are not well understood. The detection of estrogen receptor (ER) and progesterone receptor (PR) in the skin is of great importance to understand the effect of estrogen and progesterone. In primary cultures of human keratinocytes, expression of ER and PR was monitored by immunocytochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). Paraffin embedded skin tissues were stained with monoclonal antibodies to human ER and PR by immunohistochemistry. Cultured human keratinocytes expressed cytoplasmic PR protein and PR mRNA transcripts. By contrast, ER was detected only at the mRNA level. Suprabasal keratinocytes from samples of pruritic urticarial papules, plaques of pregnancy (PUPPP) and psoriasis were stained positively only for PR, while those from samples of erythema nodosum were negative for both ER and PR. Lesional epidermis of PUPPP showed positive PR immunoreactivity, while nonlesional epidermis did not. No other cells in the normal human skin were stained with ER and PR. The present study suggests that by expressing PR human keratinocytes act as targets for progesterone action.