Hajime Tei

In 2016, a research team that included Tei discovered that clock genes, most specifically Bmal1 and Per1, are rhythmically expressed in osteoblasts to modulate the osteoblast-dependent regulation of osteoclastogenesis by regulating 1,25(OH)2D3-induced Rankl expression in osteoblasts. Specifically for Bmal1, they found that Bmal1-deficient osteoblasts promote osteoclastogenesis. These findings could lead to future studies of RAR patterns and bone turnover markers.

In 2005, Tei, G. Lundkvist, Y. Kwak, E. Davis, and G. Block proposed that the molecular clock was linked to neurons' membrane potential via voltage-dependent regulation of Ca influx, as well as secondary action of intracellular Ca on gene transcription. Additionally, the same study found that removal of Ca from the medium, as well as blocking the Ca channels, stopped the SCN's circadian clock, while hyperpolarization of a K medium led to altered rhythms in the SCN.

Tei and Shin Yamazaki developed the first rodent model that was used to monitor circadian gene expression rhythms. This was done using a luciferase reporter gene expressed under the Per1. In 2000, using their rodent model, they discovered the existence of circadian clocks in peripheral organs of mammals. This discovery led to the current understanding of mammalian circadian control as a multi-oscillatory system. He was also part of a team that discovered feeding cycles can entrain liver independently of the suprachiasmatic nucleus (SCN) and the light cycle.

In 1998, Hajime Tei, in collaboration with other researchers, identified a mammalian homolog of the Drosophila timeless gene. During this research project, timeless was analyzed in the adult mouse SCN, but only weak oscillations were observed.

In 1997, Hajime Tei, Yoshiyuki Sakaki, and Hitoshi Okamura identified the human and mouse Per homologues of the Drosophila Per gene. They discovered that hPer (the human homolog of dPer) and mPer (the mouse homolog of dPer) encoded PAS-domain-containing polypeptides that are highly homologous to dPer. They also found that mPer showed autonomous circadian oscillation in its expression in the suprachiasmatic nucleus (SCN) which acts as the primary circadian pacemaker in the mammalian brain. They were able to discover this by using a method called intra-module scanning-polymerase chain reaction (IMS-PCR), which allowed them to screen out short stretches of DNA sequences and isolate mammalian homologs of the Drosophila Per gene.

Between 1991 and 1992, Tei was a fellow for the Fellowships of the Japan Society for Japanese Junior Scientists at the University of Tokyo’s Institute of Medical Science. He later held the position of assistant professor (1992-2001) and associate professor (2001-2004). During his time as an assistant professor, Tei worked alongside Yoshiyuki Sakaki and Hitoshi Okamura to discover the mammalian period genes Per1, Per2, and Per3. They also discovered the mammalian homolog of the Drosophila gene Timeless. In 2004, Tei became the principal investigator of the Laboratory of Chronogenomics at Mitsubishi Kagaku Institute of Life Sciences. In 2009, he became a full professor at the Kanazawa University Graduate School of Natural Science & Technology, a position he currently serves to-date.