American Journal of Human Genetics, a group of researchers analyzed this p53 variation in Asian populations that are closely related genetically (at least compared to European vs. African populations), but nonetheless live at very different latitudes. Their results were somewhat surprising. The p53 variation does vary with latitude, but it’s not correlated with UV radiation level. Instead, it’s how cold it gets in the winter that seems to matter.Researchers analyzed rs1042522 in 4,029 people from 67 populations located throughout eastern Asia, from 11° south of the equator (Indonesia) to 65° north (northern China). They found that the C version of this SNP is more common at higher latitudes, as was expected based on the work in European and African populations.The amount of UV radiation a locale receives, however, showed no correlation with the frequency of the C version of the SNP. Instead, it was chillier winter temperatures that seemed to translate into more people in the population having the C version of rs1042522. blizzard babies” might disagree, but the authors point out that in cattle at least, cold temperatures have been shown to have an effect.Bonus:
The researchers also looked at rs2279744, a variation in the MDM2 gene that (like rs1042522 in p53) is found at different frequencies in different populations. The MDM2 variation did not vary with latitude or temperature, but did correlate with UV radiation levels. Populations with higher UV radiation exposures had higher frequencies of the G version of rs2279744.The MDM2 gene encodes a protein that reduces cellular levels of the p53 tumor suppressor protein. The G version of rs2279744 leads to higher levels of MDM2 protein, and thus lowers levels of p53. The researchers speculate that as people moved out of Africa and into Asia, the lower levels of DNA-damaging UV light meant they could afford to have less p53 in their cells. Because lower p53 levels are better for embryonic development, the scientists think nature would have favored the G version of rs2279744.Bonus Bonus:
Do p53 and MDM2 sound familiar? Last week the Spittoon covered recent reports linking rs1042522 to colorectal cancer survival in African Americans and rs2279744 in MDM2 to melanoma risk in young women.Map of rs1042522 frequencies is from the HGDP Selection Browser.
Baby, It’s Cold Outside: Researchers Tie Variation in Cancer Gene to Winter Temperatures
April 9, 2009