Apolipoprotein B genetic variability in Brazilian Indians

Area of Science:

• Genetics
• Population Genetics
• Molecular Anthropology

Background:

• Apolipoprotein B (ApoB) plays a crucial role in lipid metabolism.
• Genetic variations in ApoB, such as restriction fragment length polymorphisms (RFLPs), can influence lipid levels and disease susceptibility.
• Understanding the distribution of these genetic markers in diverse populations like Brazilian Indians is important for anthropological and clinical genetics.

Purpose of the Study:

• To investigate the genetic diversity of four apolipoprotein B polymorphisms (XbaI, MspI, EcoRI RFLPs, and signal peptide insertion-deletion) in five Brazilian Indian tribes.
• To determine the frequency and distribution of these genetic markers and their haplotypes within this specific ethnic group.
• To explore the Amerindian origin of a specific signal peptide allele and examine linkage disequilibrium patterns.

Main Methods:

• Polymerase chain reaction (PCR) was employed to analyze DNA from 140 individuals across five Brazilian Indian tribes.
• Genotyping was performed for three apolipoprotein B restriction fragment length polymorphisms (XbaI, MspI, and EcoRI).
• The signal peptide insertion-deletion polymorphism was also analyzed, and linkage disequilibrium was assessed between markers.

Main Results:

• All four studied apolipoprotein B polymorphisms were found to be polymorphic in the Brazilian Indian populations.
• The 5' beta SP*29 insertion allele at the signal peptide, previously identified in Mexican Americans, was detected in approximately 8% of chromosomes in the Gavião and Zoró tribes, supporting its Amerindian origin.
• Negative linkage disequilibrium was observed between the signal peptide and EcoRI polymorphisms in all tribes, and between the signal peptide and XbaI polymorphisms in three tribes.
• Out of 24 possible 4-marker extended haplotypes, 14 were identified, with two specific haplotypes (haplotype 2 and haplotype 5) being common to all studied tribes.
• No significant associations were found between these polymorphisms and plasma lipid levels or body mass index in the studied sample.

Conclusions:

• The genetic markers for apolipoprotein B, including the signal peptide insertion-deletion polymorphism, exhibit diversity within Brazilian Indian populations.
• The presence of the 5' beta SP*29 allele confirms its Amerindian origin and provides insights into ancestral population movements.
• Specific haplotype patterns and linkage disequilibrium suggest genetic structuring and potential evolutionary relationships within and between these tribes.
• The lack of association with lipid levels or BMI in this sample indicates that other genetic or environmental factors may be more influential in this population.