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Laboratório de Pesquisas Forenses e Genômica Universidade de São Paulo Departamento de Química - FFCLRP

Research Areas

HLA Genes and its receptors: genetic diversity and gene expression in normal conditions and in autoimmune, tumorous, and infectious diseases and transplants

The HLA genes (Human Leukocyte Antigen) compose an extensive genic complex in humans, playing a significant role in immunity. While HLA types A, B, and C are responsible for recognizing and activating the adaptive immune response, HLA-E, HLA-F, and HLA-G genes are related to immune response regulation. Genetic variations in the HLA sequence may alter protein expression levels and interfere with their receptors interactions, influencing an individual’s susceptibility to developing a specific disease. Population studies of HLA genes can help the understanding of the occurrence of some diseases, being able to contribute to the further development of early diagnosis/treatment, assisting the precision medicine field.


Genetic diversity of coding and regulatory regions of genes involved in melanin synthesis: functional and forensic implications

The presence of melanin in the epidermis, hair, and iris primarily defines human pigmentation. This pigment consists of a protein derived from tyrosine, and its synthesis occurs through a process called melanogenesis. More than 100 genes are involved in this bioprocess, including ASIP, MC1R, MITF, TYR, TYRP1, DCT, OCA2, HERC2, SLC24A5 e SLC45A2. Two different types of melanin can exist: eumelanin, responsible for dark phenotypes (brown/black pigment), and pheomelanin, responsible for light phenotypes (yellow/red pigment). Genetic variations in genes involved in melanin biosynthesis can influence the proportions of eumelanin/pheomelanin produced, influencing the resulting phenotype. In addition, some mutations can deregulate melanin production, leading to pigmentation diseases like vitiligo.
Thus, the characterization and analysis of coding and regulatory regions (promoter and 3’UTR) of genes involved in melanogenesis, as well as association analysis between polymorphisms (SNPs and InDels) and pigmentation/disease phenotypes, can help to understand the regulation of melanin biosynthesis, along with phenotype emergence.


Forensic applicability of genetic polymorphisms associated with morphologic phenotypes in Brazil

Forensic DNA Phenotyping is an area of study that aims the prediction of externally visible characteristics of an individual (e.g. skin color, hair shape, freckles presence) by the analysis of its genetic polymorphisms only. This technique intends to help police investigations on crime-solving, mass disasters, or missing person cases, by providing additional clues about the probable appearance of an individual. It would be suitable for cases where the standard DNA analysis conducted in forensic genetics laboratories fails.
In literature, many genotype-phenotype association studies describe lots of polymorphic sites related to appearance traits. Predictive tools for eye, hair, and skin color have already been proposed. Since the Brazilian population is highly admixed, it presents a unique genetic background, in which different genic interactions can occur. Thus, it is mandatory the validation of the existing tools, as well as association sites described in the literature, to ensure the development of predictive tools suitable for use in the Brazilian population. In addition, studies aiming to identify new polymorphisms related to appearance traits must be conducted, contributing to Forensic DNA Phenotyping in Brazil and worldwide.


Individual and populational genomic ancestry

The Brazilian population presents contributions of three main ethnic groups in its ancestry: Europeans, Africans, and Native-Americans. However, this contribution is not homogenous throughout the country: overall, its geographic regions present different admixture patterns. Thereby, Brazil’s population is highly admixed, being one of the most heterogeneous populations in the world. This makes it ideal for ancestry studies, at both individual and population levels.
When conducting genetic studies in admixed populations, it is imperative to estimate how much different population groups contribute to the ancestry of this population. This allows us to characterize the population, providing a better understanding of its patterns of genetic variation. Furthermore, when performing case-control association analysis, it must be controlled by individual ancestry, avoiding the identification of spurious associations.
The possibility of estimating the ancestry of an unknown sample can also play a valuable role in the forensic area, assisting the police in solving crimes in which additional clues are lacking.
Many sets of ancestry informative markers (AIMs) have already been proposed in the literature. Our lab aims to explore the effectiveness of such sets in a population sample from Brazil’s Southeast, at individual and population levels. We also intend to develop new AIMs sets suitable for the Brazilian population.