Analysis of the genetic ancestry of patients with oral clefts from South American admixed populations

Orofacial Cleft Frequency Differences Depending on Geographic Origin: Coast vs. Inland

Objective: Cleft lip and/or palate is the most common congenital anomaly in a human face, with a multifactorial and complex etiology. Although many studies have been developed, the role of the environment is still unclear. This study aims to test the hypothesis that differences in lifestyle and environment change the reproductive risks of orofacial clefts.

Methods: A total of 2,422 medical records of individuals born with cleft lip and/or palate in a reference center in the northeast of Brazil over a period of 30 years were analyzed. Data on the cleft type, geographic origin of the patient (coast or inland), presence of associated congenital anomalies or syndromes, maternal age, and maternal parity were recorded. Differences in frequencies between the cleft types were compared based on geographic origin, maternal age, and parity. Chi-square, Student's t, Kruskal–Wallis, and logistic regression were used to analyze the interference of covariables on the cleft type.

Results: The distribution of cleft types was significantly different between the coastal and inland areas (chi-square test, p < 0.0001). A higher frequency of cleft lip with or without palate was observed the inland area (chi-square test, p = 0.0006), while cleft palate only (chi-square test, p = 0.003) and rare facial clefts (chi-square test, p = 0.004) were more frequent in the coastal area. No difference was found in the distribution of maternal age (t-test, p > 0.05) between the two geographic areas, but parity was higher inland (t-test, p = 0.04). Logistic regression suggested that parity explained just a small portion of the differences in frequency between cleft types of the coast vs. inland.

Conclusion: Frequency of orofacial cleft types differs by geographic area in this region of the South American continent.

miRNAs as biomarkers of orofacial clefts: A systematic review

Orofacial clefts are facial malformations caused by the improper development of the lips and palate. Many genetic and epigenetic molecules have been involved in the mechanisms of orofacial clefts, one of which are miRNAs. This systematic review aimed to identify miRNAs associated to non-syndromic orofacial clefts in humans. After applying a series of criteria, four studies were selected for analysis. In total, one hundred miRNAs were observed in the literature, of which 57 were reported as upregulated and 43 as downregulated in all orofacial cleft classifications. Moreover, nine miRNAs were differentially expressed only in cleft palate patients, which might suggest distinct regulatory mechanisms for the etiology of cleft lips and palates. We suggest broader population sampling in order to include diverse ethnic groups in the future, as well as analyses toward identifying miRNA target genes and pathways. We highlight the need for experimental validation and of these results to allow further translational approaches and clinical applications.

A systematic scoping review of the genetic ancestry of the Brazilian population

The genetic background of the Brazilian population is mainly characterized by three parental populations: European, African, and Native American. The aim of this study was to overview the genetic ancestry estimates for different Brazilian geographic regions and analyze factors involved in these estimates. In this systematic scoping review were included 51 studies, comprehending 81 populations of 19 states from five regions of Brazil. To reduce the potential of bias from studies with different sampling methods, we calculated the mean genetic ancestry weighted by the number of individuals. The weighted mean proportions of European, African, and Native American ancestries were 68.1%, 19.6%, and 11.6%, respectively. At the regional level, the highest European contribution occurred in the South, while the highest African and Native American contributions occurred in the Northeastern and Northern regions, respectively. Among states in the Northeast region, Bahia and Ceará showed significant differences, suggesting distinct demographic histories. This review contributes for a broader understanding of the Brazilian ancestry and indicates that the ancestry estimates are influenced by the type of molecular marker and the sampling method.