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Two independent studies, one of them using a computational approach, identified CHRONO, a gene shown to modulate the activity of circadian transcription factors and alter circadian behavior in mice.

Fish egg yolk is largely derived from vitellogenins, which are synthesized in the liver, taken up from the maternal circulation by growing oocytes via receptor-mediated endocytosis and enzymatically processed into yolk proteins that are stored in the ooplasm. Lipid droplets are another major component of fish egg yolk, and these are mainly composed of neutral lipids that may originate from maternal plasma lipoproteins. This review aims to briefly summarize our current understanding of the molecular mechanisms underlying yolk formation in fishes. A hypothetical model of oocyte growth is proposed based on recent advances in our knowledge of fish yolk formation.

There has been general acceptance that only one type of androgen receptor (AR) exists in an individual. This contrasts with other members of the nuclear receptor superfamily where multiple forms have been reported (e.g. estrogen receptor ␣/␤, thyroid hormone receptor ␣/␤, etc.). We have previously identified 11-ketotestosterone (a potent androgen in teleosts) as the spermatogenesis-inducing hormone of the Japanese eel and have cloned its receptor (eAR1) cDNA from eel testis. Here we report on the cloning of a cDNA encoding a second type of AR (eAR2) from the eel testis and the functional characterization of the encoded protein. This cDNA contains a complete open reading frame encoding 797 amino acid residues. The amino acid sequence of eAR2 shows high homology with other ARs, including eAR1, in the DNAbinding (98 -88%) and ligand-binding (59 -85%) domains, whereas the other domains show low homology (<35%). In transient transfection assays of mammalian cells, the eAR2 protein displayed androgen-dependent activation of transcription from the androgen-responsive murine mammary tumor virus promoter. Tissue distribution of its mRNA was different from that of eAR1. We conclude that eAR2 is a novel AR in the eel, which we suggest should be named eel AR␤ to distinguish it from eAR1 (eAR␣).

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