If your parents are big-headed (literally), so are you. This week, we’re not going to explore arrogance, but the physical size of your head and how this relates to your genes.
You might be thinking, “Who cares if my head is small or big?” Well, head size is actually a good marker for early childhood development. After all, the size of your skull determines the upper limit of your brain size and influences its shape. In the first two years of life, head size is highly correlated with body size and nutritional status, which can give a sense of how healthy the baby is. In recent news, we have seen how babies experience reduced head size and neurodevelopmental issues if their mothers were infected with Zika while they were in the womb.
Although we see how head size is heavily influenced by environmental conditions and exposures, the high degree of heritability of this trait suggests the importance of genetic factors as well. In a genome-wide association study of over 45,000 children and adults of European decent, Haworth and colleagues found nine gene loci associated with head size that were shared between the two age groups. Among these, rare mutations within the TP53 gene have been associated with 0.5-centimeter larger heads in mid-childhood compared to those who did not carry the mutated copies of this gene. The TP53 gene codes for the important protein p53, dubbed the ‘guardian of the genome.’ p53 is a tumor suppressor, which means it functions to prevent uncontrolled growth of cells (here’s one scary fact to show how important it really is: it has been observed that 30% of tumor samples had some form of mutation of the TP53 gene).
The study’s finding that the TP53 gene was most strongly associated with head size and human cranial development is novel and may have been surprising, but it turns out that experimental mice embryos whose copies of TP53 gene were removed altogether from their DNA had defects that affected skeletal, neural, and muscle tissues of the head. So the findings in humans aren’t so out-there after all. Want to know more? Check out the article here: https://www.ncbi.nlm.nih.gov/pubmed/30664637
A final thing to note is that the study’s large sample size was sufficient for detecting certain genetic factors, but the investigators admit that an even larger sample is necessary to detect infrequent variants that could be associated with head size. Scaling up this research would help validate the findings of this study.
Ready to know how you stack up? Find out on Genomelink what your DNA says about your head size!