HLA-A3-B14 and the origin of the haemochromatosis C282Y mutation: founder effects and recombination events during 12 generations in a Scandinavian family with major iron overload

Blood donor biobank as a resource in personalised biomedical genetic research

Health questionnaires and donation criteria result in accumulation of highly selected individuals in a blood donor population. To understand better the usefulness of a blood donor-based biobank in personalised disease-associated genetic studies, and for possible personalised blood donation policies, we evaluated the occurrence and distributions of common and rare disease-associated genetic variants in Finnish Blood Service Biobank. We analysed among 31,880 blood donors the occurrence and geographical distribution of (i) 53 rare Finnish-enriched disease-associated variants, (ii) mutations assumed to influence blood donation: four Bernard-Soulier syndrome and two hemochromatosis mutations, (iii) type I diabetes risk genotype HLA-DQ2/DQ8. In addition, we analysed the level of consanguinity in Blood Service Biobank. 80.3% of blood donors carried at least one (range 0-9 per donor) of the rare variants, many in homozygous form, as well. Donors carrying multiple rare variants were enriched in Eastern Finland. Haemochromatosis mutation HFE C282Y homozygosity was 43.8% higher than expected, whereas mutations leading to Bernard-Soulier thrombocytopenia were rare. The frequency of HLA-DQ2/DQ8 genotype was slightly lower than expected. First-degree consanguinity was higher in Blood Service Biobank than in the general population. We demonstrate that despite donor selection, the Blood Service Biobank is a valuable resource for personalised medical research and for genotype-selected samples from unaffected individuals. The geographical genetic substructure of Finland enables efficient recruitment of donors carrying rare variants. Furthermore, we show that blood donor biobank material can be utilised for personalised blood donation policies.

Common founder effects of hereditary hemochromatosis, Wilson´s disease, the long QT syndrome and autosomal recessive deafness caused by two novel mutations in the WHRN and TMC1 genes

Background

Genealogy and molecular genetic studies of a Swedish river valley population resulted in a large pedigree, showing that the hereditary hemochromatosis (HH) HFE/p.C282Y mutation is inherited with other recessive disorders such as Wilson´s disease (WND), a rare recessive disorder of copper overload. The population also contain individuals with the Swedish long QT syndrome (LQTS1) founder mutation (KCNQ1/p.Y111C) which in homozygotes causes the Jervell & Lange Nielsen syndrome (JLNS) and hearing loss (HL).

Aims of the study were to test whether the Swedish long QT founder mutation originated in an ancestral HFE family and if carriers had an increased risk for hemochromatosis (HH), a treatable disorder. We also aimed to identify the pathogenic mutation causing the hearing loss disorder segregating in the pedigree.

Methods

LQTS patients were asked about their ancestry and possible origin in a HH family. They were also offered a predictive testing for the HFE genotype. Church books were screened for families with hearing loss. One HH family had two members with hearing loss, who underwent molecular genetic analysis of the LQTS founder mutation, connexin 26 and thereafter exome sequencing. Another family with hearing loss in repeat generations was also analyzed for connexin 26 and underwent exome sequencing.

Results

Of nine LQTS patients studied, four carried a HFE mutation (two p.C282Y, two p.H63D), none was homozygous. Three LQTS patients confirmed origin in a female founder ( b 1694, identical to AJ b 1694, a HFE pedigree member from the Fax river. Her descent of 44 HH families, included also 29 families with hearing loss (HL) suggesting JLNS. Eleven LQTS probands confirmed origin in a second founder couple (b 1614/1605) in which the woman b 1605 was identical to a HFE pedigree member from the Fjällsjö river. In her descent there were not only 64 HH, six WND families, one JLNS, but also 48 hearing loss families. Most hearing loss was non syndromic and caused by founder effects of the late 16^th century. One was of Swedish origin carrying the WHRN, c.1977delC, (p.S660Afs*30) mutation, the other was a TMC1(NM_138691),c.1814T>C,(p.L605P) mutation, possibly of Finnish origin.

Conclusions

Deep human HFE genealogies show HFE to be associated with other genetic disorders like Wilson´s disease, LQTS, JLNS, and autosomal recessive hearing loss. Two new homozygous HL mutations in WHRN/p.S660Afs*30 and TMC1/p.L605P were identified,none of them previously reported from Scandinavia. The rarity of JLNS was possibly caused by miscarriage or intrauterine death. Most hearing loss (81.7%) was seen after 1844 when first cousin marriages were permitted. However, only 10 (10.3%) came from 1^st cousin unions and only 2 (2.0 %) was born out of wedlock.

Electronic supplementary material

The online version of this article (10.1186/s41065-017-0052-2) contains supplementary material, which is available to authorized users.

Autoimmune Conditions in 235 Hemochromatosis Probands with HFE C282Y Homozygosity and Their First-Degree Relatives

We performed a retrospective study of autoimmune conditions (ACs) in 235 hemochromatosis probands at diagnosis by analyzing age, sex, ACs, history of first-degree family members with ACs (FH), diabetes, heavy ethanol consumption, elevated serum ALT/AST, nonalcoholic fatty liver disease, viral hepatitis, cirrhosis, iron removed to achieve iron depletion (QFe), and positivity for human leukocyte antigen (HLA) haplotypes A^∗01, B^∗08; A^∗02, B^∗44; A^∗03, B^∗07; A^∗03, B^∗14; and A^∗29, B^∗44. There were 138 men (58.7%). Median followup was 19.6 y. One or more of 19 ACs were diagnosed in each of 35 probands (14.9%). Prevalences of Hashimoto's thyroiditis, rheumatoid arthritis, and ankylosing spondylitis were 8.1% (95% CI: [5.1, 12.5]), 1.7% [0.6, 4.6], and 0.0085 [0.0015, 0.0337], respectively. Eighteen probands (7.7%) had a FH. Eight probands with ACs had 9 family members with ACs. In a logistic regression, ACs were less likely in men (odds ratio (OR) 0.3 [0.1, 0.6]) and more likely in probands with a FH (OR 4.1 [1.4, 11.8]). Overall ACs risk was not significantly associated with QFe or HLA haplotypes. Estimated survival of probands with and without ACs did not differ significantly. We conclude that ACs are common in hemochromatosis probands, especially women and probands with a FH.

Ancestral association between HLA and HFE H63D and C282Y gene mutations from northwest Colombia

A significant association between HFE gene mutations and the HLA-A*03-B*07 and HLA-A*29-B*44 haplotypes has been reported in the Spanish population. It has been proposed that these mutations are probably connected with Celtic and North African ancestry, respectively. We aimed to find the possible ancestral association between HLA alleles and haplotypes associated with the HFE gene (C282Y and H63D) mutations in 214 subjects from Antioquia, Colombia. These were 18 individuals with presumed hereditary hemochromatosis (“HH”) and 196 controls. The HLA-B*07 allele was in linkage disequilibrium (LD) with C282Y, while HLA-A*23, A*29, HLA-B*44, and B*49 were in LD with H63D. Altogether, our results show that, although the H63D mutation is more common in the Antioquia population, it is not associated with any particular HLA haplotype, whereas the C282Y mutation is associated with HLA-A*03-B*07, this supporting a northern Spaniard ancestry.

Mismatch repair genes founder mutations and cancer susceptibility in Lynch syndrome

Founder mutations in specific populations are common in several Mendelian disorders. They are shared by apparently unrelated families that inherited them from a common ancestor that existed hundreds to thousands of years ago. They have been proven to impact in molecular diagnostics strategies in specific populations, where they can be assessed as the first screening step and, if positive, avoid further expensive gene scanning. In Lynch syndrome (LS), a dominantly inherited colorectal cancer disease, more than 50 founder pathogenic mutations have been described so far in the mismatch repair (MMR) genes (MLH1, MSH2, MSH6 and PMS2). We here provide a comprehensive summary of the founder mutations found in the MMR genes and an overview of their main characteristics. At a time when high-throughput strategies are being introduced in the molecular diagnostics of cancer, genetic testing for founder mutations can complement next generation sequencing (NGS) technologies to most efficiently identify MMR gene mutations in any given population. Additionally, special attention is paid to MMR founder mutations with interesting anthropological significance.

Associations of HLA-A, HLA-B and HLA-C alleles frequency with prevalence of herpes simplex virus infections and diseases across global populations: implication for the development of an universal CD8+ T-cell epitope-based vaccine

A significant portion of the world's population is infected with herpes simplex virus type 1 and/or type 2 (HSV-1 and/or HSV-2), that cause a wide range of diseases including genital herpes, oro-facial herpes, and the potentially blinding ocular herpes. While the global prevalence and distribution of HSV-1 and HSV-2 infections cannot be exactly established, the general trends indicate that: (i) HSV-1 infections are much more prevalent globally than HSV-2; (ii) over a half billion people worldwide are infected with HSV-2; (iii) the sub-Saharan African populations account for a disproportionate burden of genital herpes infections and diseases; (iv) the dramatic differences in the prevalence of herpes infections between regions of the world appear to be associated with differences in the frequencies of human leukocyte antigen (HLA) alleles. The present report: (i) analyzes the prevalence of HSV-1 and HSV-2 infections across various regions of the world; (ii) analyzes potential associations of common HLA-A, HLA-B and HLA-C alleles with the prevalence of HSV-1 and HSV-2 infections in the Caucasoid, Oriental, Hispanic and Black major populations; and (iii) discusses how our recently developed HLA-A, HLA-B, and HLA-C transgenic/H-2 class I null mice will help validate HLA/herpes prevalence associations. Overall, high prevalence of herpes infection and disease appears to be associated with high frequency of HLA-A(∗)24, HLA-B(∗)27, HLA-B(∗)53 and HLA-B(∗)58 alleles. In contrast, low prevalence of herpes infection and disease appears to be associated with high frequency of HLA-B(∗)44 allele. The finding will aid in developing a T-cell epitope-based universal herpes vaccine and immunotherapy.

Diabetes in first-degree family members: a predictor of type 2 diabetes in 159 nonscreening Alabama hemochromatosis probands with HFE C282Y homozygosity

OBJECTIVE We sought to identify predictors of diabetes diagnosed before hemochromatosis. RESEARCH DESIGN AND METHODS We studied these 16 variables in 159 nonscreening hemochromatosis probands with HFE C282Y homozygosity: age; sex; BMI; diabetes reports in first-degree family members (dichotomous); heavy ethanol consumption; cigarette smoking; elevated serum alanine aminotransferase/aspartate aminotransferase levels; nonalcoholic fatty liver; chronic viral hepatitis; cirrhosis; hand arthropathy; iron removed by phlebotomy; and positivity for HLA-A*01, B*08; A*03, B*07; and A*03, B*14 haplotypes. We performed univariable and multivariable analyses. RESULTS Twenty-three probands (14.5%) had diabetes; 19 were men. Each of the 23 probands had type 2 diabetes. Mean BMI was greater in probands with diabetes (31.7 ± 8.5 [SD] kg/m(2) vs. 27.6 ± 5.1 kg/m(2); P = 0.032). Reports of any first-degree family member with diabetes were more prevalent in probands with than in probands without diabetes (69.6 vs. 17.6%; P < 0.0001). In probands with diabetes, the odds ratio (OR) of maternal diabetes was 6.7 (95% CI 2.3-19.7; P = 0.0005) and of sibling diabetes was 11.7 (3.0-45.5; P = 0.0004). In a logistic regression model, predictors of diabetes at hemochromatosis diagnosis in 159 probands were diabetes reports in family members (OR 8.5 [95% CI 2.9-24.8]; P < 0.0001) and BMI (1.1 [1.0-1.2]; P = 0.049). This model explained 26.0% of total deviance contributing to diabetes. CONCLUSIONS In nonscreening hemochromatosis probands with HFE C282Y homozygosity, a heritable factor(s) increases the risk of diabetes diagnosed before hemochromatosis.

Effects of highly conserved major histocompatibility complex (MHC) extended haplotypes on iron and low CD8+ T lymphocyte phenotypes in HFE C282Y homozygous hemochromatosis patients from three geographically distant areas

Hereditary Hemochromatosis (HH) is a recessively inherited disorder of iron overload occurring commonly in subjects homozygous for the C282Y mutation in HFE gene localized on chromosome 6p21.3 in linkage disequilibrium with the human leukocyte antigen (HLA)-A locus. Although its genetic homogeneity, the phenotypic expression is variable suggesting the presence of modifying factors. One such genetic factor, a SNP microhaplotype named A-A-T, was recently found to be associated with a more severe phenotype and also with low CD8⁺T-lymphocyte numbers. The present study aimed to test whether the predictive value of the A-A-T microhaplotype remained in other population settings. In this study of 304 HH patients from 3 geographically distant populations (Porto, Portugal 65; Alabama, USA 57; Nord-Trøndelag, Norway 182), the extended haplotypes involving A-A-T were studied in 608 chromosomes and the CD8⁺ T-lymphocyte numbers were determined in all subjects. Patients from Porto had a more severe phenotype than those from other settings. Patients with A-A-T seemed on average to have greater iron stores (p = 0.021), but significant differences were not confirmed in the 3 separate populations. Low CD8⁺ T-lymphocytes were associated with HLA-A*03-A-A-T in Porto and Alabama patients but not in the greater series from Nord-Trøndelag. Although A-A-T may signal a more severe iron phenotype, this study was unable to prove such an association in all population settings, precluding its use as a universal predictive marker of iron overload in HH. Interestingly, the association between A-A-T and CD8⁺ T-lymphocytes, which was confirmed in Porto and Alabama patients, was not observed in Nord-Trøndelag patients, showing that common HLA haplotypes like A*01–B*08 or A*03–B*07 segregating with HFE/C282Y in the three populations may carry different messages. These findings further strengthen the relevance of HH as a good disease model to search for novel candidate loci associated with the genetic transmission of CD8⁺ T-lymphocyte numbers.

Risk of cancer by transferrin saturation levels and haemochromatosis genotype: population-based study and meta-analysis

OBJECTIVE

Increased iron overload, whether or not owing to the presence of the haemochromatosis genotype C282Y/C282Y, may be associated with an increased risk of cancer. The aim of this study was to test the hypothesis that elevated transferrin saturation levels (as a proxy for iron overload) and haemochromatosis genotype C282Y/C282Y are associated with an increased risk of cancer.

METHODS

We conducted a population-based study of 8763 individuals, of whom 1417 developed a first cancer during 15years of follow-up, and a meta-analysis. We stratified absolute 10-year risk of cancer by smoking status, an important risk factor.

RESULTS

In women, transferrin saturation above 60% versus below 50% was associated with a hazard ratio of 3.6 (95% confidence interval (CI): 2.0-6.5; P<0.001) for any cancer; risk of liver cancer was increased in both women and men. In women, the corresponding absolute 10-year risk of any cancer was 34% and 30% in smokers and nonsmokers, respectively. In men, haemochromatosis genotype C282Y/C282Y versus wild type/wild type was associated with a hazard ratio of 3.7 (95% CI: 1.2-12; P=0.01) for any cancer, with a similar trend in women. In men, the corresponding absolute 10-year risk of cancer was 39% and 27% in smokers and nonsmokers, respectively. Other haemochromatosis genotypes were not associated with increased risk of cancer in women or men. From the meta-analysis, the odds ratio of any cancer for transferrin saturation ≥60% versus a reference group was 1.5 (95% CI: 1.2-1.8) for women and men combined.

CONCLUSIONS

We have demonstrated that elevated transferrin saturation levels in women and haemochromatosis genotype C282Y/C282Y in men are associated with increased risk of cancer. Thus, our results support the implementation of cancer screening programmes in patients with iron overload or with C282Y/C282Y.

Was the C282Y mutation an Irish Gaelic mutation that the Vikings helped disseminate? HLA haplotype observations of hemochromatosis from the west coast of Sweden

The HLA-related hemochromatosis mutation C282Y is thought to have originated in Ireland in a person with HLA-A3-B14 and was spread by Vikings. Irish people with two HLA-A3 alleles had a high risk of hemochromatosis. In this study, from west Sweden, we wanted to test these hypotheses.

METHODS

HFE mutations in controls, bone marrow donors with HLA-A3/A3 and patients with hemochromatosis. HLA haplotypes, extended haplotype analysis and pedigree studies.

RESULTS

The allelic C282Y frequency 0.04, (CI 0.01-0.07) was lower (P < 0.001) in Sweden than in Ireland 0.10 (CI 0.08-0.11), and Swedish bone marrow donors with HLA-A3/A3 (n = 77) had a low risk of hemochromatosis. HLA haplotypes available from 239/262 (91.5%) proband patients homozygous for C282Y showed a dominance of A3-B7 and A3-B14 both in linkage disequilibrium with controls (P < 0.001). Pedigree studies extended into the 17th century supported a local founder effect of A3-B14 in the county of Bohuslän. The A3-B14 haplotype may well be the original and A3-B7 the result of centromeric recombinations. The haplotype diversity and recombination events were not different from a Celtic series. These findings do not support the hypothesis of the C282Y mutation being of an Irish Celtic origin.

CONCLUSIONS

The C282Y frequency shows a west to east decline from Ireland through the north of Europe. Vikings may have been involved in the spread of C282Y, but the mutation is probably older and may have been spread in Europe by earlier seafarers.