Cosmetic Innovation

Carolina Lavini Ramos

Pesquisador

The set of information responsible for the definition of skin pigmentation is written in the genes present within our cells.

Colors beyond the skin

The set of information responsible for the definition of skin pigmentation is written in the genes present within our cells. So far, nothing new, right?

Several studies have shown that genes responsible for the pigmentation phenotypes are related with transcription factors, the melanogenesis process, with transportation of enzymes during the synthesis of melanin, with structural proteins and membrane expression of the different precursors of melanin and various receptors and their ligands on membranes.

Furthermore, this genetic information is available in literature databases along with the entire human genome for researchers to use in their molecular studies. With the latest technology, some studies have used small molecular markers known as SNPs (single nucleotide polymorphisms, where the change of a single nitrogen base is capable of causing changes in the transcription of proteins) to estimate the characteristics that are found in various human phenotypes.

All this molecular information available has been used to reconstruct the evolutionary history of standards related to skin pigmentation hominid. Therefore, these genes have also been used in the fields of forensic science that attempts to reconstruct the phenotype from DNA samples.

Based on this knowledge, Cerqueira and researchers from Federal University of Rio Grande do Sul, did a study aiming to verify the reliability of the prediction of the different phenotypes of pigmentation of hair, skin and eyes using databases and genetic markers. Were selected from the literature 124 SNPs associated with pigmentation. The genotype of 11 individuals that had its genome completely sequenced, and photos were selected from two databases, called PSU USCS USCS. Besides these genotypes, 19 others, whose phenotypic information were not available, were selected for the test, including 5 of extinct hominids and 14 anonymous individuals but belonging to different ethnicities.

The authors consider the additive effect of alleles homozygous for predicting the characteristics related to multifactorial inheritance in selected genotypes. And to test the efficiency of the chosen methodology researchers checked the consistency of information comparing the predicted phenotypes the actual phenotypes from those 11 individuals who had known their phenotype.

Subsequently they tried to predict the characteristics of five other Homo species who have had their genome into a database, and 14 DNA samples from other human beings anonymous. The phenotypes of these were assigned considering the average phenotype of the population to which they belonged, and comparing them to the phenotype predicted by molecular markers.

Were chosen for the study 18 phenotypes whose genetic inheritance was associated with homozygous genes. Among them were genes related to variations in skin color, presence of freckles, eye color and hair. The results showed a 60% average agreement between the predicted and observed.

The percentage of agreement between the predicted and observed (known samples) and between predicted and probable (anonymous samples) of each of the observed characteristics varied slightly. But on average, the results showed reasonable predictive value of 60%.

Since this was a pioneering study, these results were encouraging because they suggest that genetic markers can be used to predict the human phenotype, based on genes related to the coloration of the skin, eyes and hair. Of course other studies need to be performed once the role of certain genes in pigmentation need to be further elucidated.

Certainly some moms awaiting anxiously the arrival of their baby should already be thinking at this point: why not make a prediction if my puppy is redhead with freckles and green eyes or blonde with green eyes? Maybe it will be possible in a not too distant future ...

Summarizing, are we close to get from a small DNA sample definitions of shapes and colors that are responsible for the different phenotypes? Does biology is close to reconstruct the phenotype of our ancestors in a matter of few nitrogenous bases? And the forensic medicine is close to having a "sketch" that does not depend questions or memory failure?

 

Reference:

CAIO C. S. CERQUEIRA, VANESSA R. PAIXÃO-CÔRTES, FRANCIS M. B. ZAMBRA, FRANCISCO M. SALZANO,TÁBITA HUNEMEIER, AND MARIA-CÁTIRA BORTOLINI. Predicting Homo Pigmentation Phenotype Through Genomic Data: From Neanderthal to James Watson. AMERICAN JOURNAL OF HUMAN BIOLOGY 24:705–709 (2012).