Temperature-dependent growth rates and gene expression patterns of various medaka Oryzias latipes cell lines derived from different populations

Medaka Oryzias latipes has several geographically and genetically distinct populations. We examined temperature acclimation response in various medaka cell lines derived from different populations. Measurement of cell growth at various temperatures suggested that 15°C was the permissive growth temperature in all cell lines from the Northern Japanese and East Korean populations, but not in those from the Southern Japanese population and medaka-related species Oryzias celebensis, which inhabits a tropical zone. RT-PCR for 102 temperature-responsive genes, previously reported in other species, revealed that the accumulated mRNA level of a gene encoding HSP47 was lower at 25°C than at 33°C, and vice versa for 12 genes including IκBα and Rab-1c, in OLHNI-1 cell line from the Northern Japanese population. Further analysis by real-time PCR demonstrated that the accumulated mRNA levels of IκBα and Rab-1c in OLHNI-1 and OLSOK-e7 cell lines from the East Korean population were increased when the culture temperature was shifted from 33 to 15°C, but not in OLHdrR-e3 cell line from the Southern Japanese population. Since IκBα and Rab-1c are related to the NFκB cascade and endoplasmic reticulum-to-Golgi transport, respectively, it is inferred that immune responses and intracellular transport are possibly critical to temperature adaptation for medaka.