Genomic continuity of Argentinean Mennonites

Clinical characteristics of headaches in an urban Mennonite group in South Brazil

BACKGROUND

Genetic variants play a pathophysiological role in headaches, especially in migraine. The Mennonite group (MG) has been geographically and genetically isolated throughout its history, harboring a distinctive distribution of diseases.

OBJECTIVE

To determine the characteristics of headaches in a group with direct Mennonite ancestry contrasting with other urban community members (control group [CG]).

METHODS

Subjects with headaches were asked to complete a questionnaire covering: the type of headache, presence of aura, frequency and duration of attacks, pain location and severity, analgesic consumption, premonitory and postdromic manifestations, Depressive Thoughts Scale, Epworth Sleepiness Scale (ESS), General Anxiety Disorder-7, Patient Health Questionnaire-9 (PHQ-9), Migraine Disability Assessment, and Composite Autonomic System Score.

RESULTS

We included 103 participants (CG: 45, Mennonite group [MG]: 58). Migraine was the most common headache (CG: 91.1%; MG: 81.0%; p = 0.172), followed by tension-type headache (CG: 8.9%; MG: 15.5%; p = 0.381). Aura was identified by 44.4% and 39.7% in the CG and MG, respectively (p = 0.689). The groups differed only concerning the frequency of retro-orbital pain (CG: 55.6%; MG: 32.8%; p = 0.027), PHQ-9 (CG: median 7, range 0 to 22; MG: median 5, range 0 to 19; p = 0.031) and ESS (CG: median 0, range 0 to 270; MG: median 0, range 0 to 108; p = 0.048) scores.

CONCLUSION

There were no major differences in the prevalence and clinical characterization of headaches between the MG and the CG. However, the latter showed more diffuse pain, sleepiness, and depressive symptoms. Specific genetic or epigenetic variants in Mennonite descendants might account for these differences.

The Second Highest Prevalence of Celiac Disease Worldwide: Genetic and Metabolic Insights in Southern Brazilian Mennonites

Celiac disease (CD), despite its high morbidity, is an often-underdiagnosed autoimmune enteropathy. Using a modified version of the Brazilian questionnaire of the 2013 National Health Survey, we interviewed 604 Mennonites of Frisian/Flemish origin that have been isolated for 25 generations. A subgroup of 576 participants were screened for IgA autoantibodies in serum, and 391 participants were screened for HLA-DQ2.5/DQ8 subtypes. CD seroprevalence was 1:29 (3.48%, 95% CI = 2.16-5.27%) and biopsy-confirmed CD was 1:75 (1.32%, 95% CI = 0.57-2.59%), which is superior to the highest reported global prevalence (1:100). Half (10/21) of the patients did not suspect the disease. HLA-DQ2.5/DQ8 increased CD susceptibility (OR = 12.13 [95% CI = 1.56-94.20], p = 0.003). The HLA-DQ2.5 carrier frequency was higher in Mennonites than in Brazilians (p = 7 × 10^-6). HLA-DQ8 but not HLA-DQ2.5 carrier frequency differed among settlements (p = 0.007) and was higher than in Belgians, a Mennonite ancestral population (p = 1.8 × 10^-6), and higher than in Euro-Brazilians (p = 6.5 × 10^-6). The glutathione pathway, which prevents reactive oxygen species-causing bowel damage, was altered within the metabolic profiles of untreated CD patients. Those with lower serological positivity clustered with controls presenting close relatives with CD or rheumatoid arthritis. In conclusion, Mennonites have a high CD prevalence with a strong genetic component and altered glutathione metabolism that calls for urgent action to alleviate the burden of comorbidities due to late diagnosis.

Ancestry patterns inferred from massive RNA-seq data

There is a growing body of evidence suggesting that patterns of gene expression vary within and between human populations. However, the impact of this variation in human diseases has been poorly explored, in part owing to the lack of a standardized protocol to estimate biogeographical ancestry from gene expression studies. Here we examine several studies that provide new solid evidence indicating that the ancestral background of individuals impacts gene expression patterns. Next, we test a procedure to infer genetic ancestry from RNA-seq data in 25 data sets where information on ethnicity was reported. Genome data of reference continental populations retrieved from The 1000 Genomes Project were used for comparisons. Remarkably, only eight out of 25 data sets passed FastQC default filters. We demonstrate that, for these eight population sets, the ancestral background of donors could be inferred very efficiently, even in data sets including samples with complex patterns of admixture (e.g., American-admixed populations). For most of the gene expression data sets of suboptimal quality, ancestral inference yielded odd patterns. The present study thus brings a cautionary note for gene expression studies highlighting the importance to control for the potential confounding effect of ancestral genetic background.

Whole Exome Sequencing reveals new candidate genes in host genomic susceptibility to Respiratory Syncytial Virus Disease

Respiratory syncytial virus (RSV) is an important cause of serious lower respiratory tract disease in infants. Several studies have shown evidence pointing to the genome of the host as an important factor determining susceptibility to respiratory disease caused by RSV. We sequenced the complete exomes of 54 patients infected by RSV that needed hospitalization due to development of severe bronchiolitis. The Iberian sample (IBS) from The 1000 Genomes Project (1000G) was used as control group; all the association results were pseudo-replicated using other 1000G-European controls and Spanish controls. The study points to SNP rs199665292 in the olfactory receptor (OR) gene OR13C5 as the best candidate variant (P-value = 1.16 × 10-12; OR = 5.56). Genetic variants at HLA genes (HLA-DQA1, HLA-DPB1), and in the mucin 4 gene (MUC4) also emerge as susceptibility candidates. By collapsing rare variants in genes and weighing by pathogenicity, we obtained confirmatory signals of association in the OR gene OR8U1/OR8U8, the taste receptor TAS2R19, and another mucin gene (MUC6). Overall, we identified new predisposition variants and genes related to RSV infection. Of special interest is the association of RSV to olfactory and taste receptors; this finding is in line with recent evidence pointing to their role in viral infectious diseases.