The genetics of menarche, the onset of puberty in females, was illuminated in a genome-wide study that found 106 genetic loci that were associated with the age of menarche. The study also showed that genomic imprinting; that is, whether a key genetic factor came from the mother or father, was shown to be important in setting the age of menarche.
Genomic imprinting is a relatively new area of exploration in genetics and is being shown to have relevance in a number of aspects of health. At fertilization, the father’s genome is contributed to the offspring by the sperm cell, and the mother’s genome is contributed to the offspring by the egg cell. The embryo therefore receives a copy of each gene from the father and also from the mother, which means the embryo inherits two copies of each gene. Due to genomic imprinting, however, both copies of a gene may not be equally expressed in the offspring. Either the gene from the father or the mother could be imprinted and result in less gene expression. The mechanism of genomic imprinting is an epigenetic phenomenon and it involves methylation of the promoter region of a gene.
Different phenotypes will result if the gene that was imprinted came from the mother or if it came from the father. In this recent study on the genetics of menarche, three genetic loci showed a parent-of-origin-specific association that was concordant with known patterns of expression in parents. Genes for nuclear hormone receptors were found to be novel mechanisms that regulate the timing of the onset of puberty in humans.
The study was carried out at various universities in the United Kingdom and it was published in the journal Nature. The researchers carried out a genome-wide and custom genotyping study that involved 182,416 women of European ancestry. A total of 106 genomic loci were shown to be related to the age of onset of menarche and many of these genetic loci were also associated with other traits related to puberty in both sexes. This onset of puberty must involve many pathways and genes and what this study offered was some insight into the complexity of the physiology of puberty onset.
Showing that genomic imprinting was involved in the genetics of menarche means that they demonstrated that, in a given family, the gene from one parent may be more important in determining the age of onset of menarche in daughters compared to the gene from the other parent. Imprinting has previously been shown to affect development in an embryonic stage, however, this study was the first to show imprinted genes may affect development at a much later stage.
The age of menarche has previously been shown to be related to future risk for breast cancer, diabetes, osteoporosis and heart disease. Elucidating the genetics of menarche can lay the basis for a better understanding of how the age of menarche relates to the risks for developing these major diseases. Showing that genomic imprinting play a role in the genetics of menarche will undoubtedly be an important factor in studying how the age of menarche relates to later stage disease risk. While studying the genetics of menarche, showing how the contribution of genes from the father versus the mother; that is, genomic imprinting, affects the age of onset of menarche will certainly be an interesting research concern in the future.
By Margaret Lutze