First insights into the genetics of 21-hydroxylase deficiency in the Roma population

Catalogue of inherited autosomal recessive disorders found amongst the Roma population of Europe

BACKGROUND

The Roma population are an endogamous, genetically isolated, minority population who migrated from North-Western India to Europe from the 10th Century throughout the Byzantine period and continues to the present day. Approximately 10-12 million Romani people reside in segregated settlements in Europe, and smaller populations live in North America and China. In addition to the endogamy, they also practice consanguinity. This has resulted in a higher frequency of rare autosomal recessive disorders some of which are unique to the Roma population. Some disorders result from founder variants whilst others are private variants, occurring within one nuclear family. Most are found as homozygous variants but compound heterozygosity is seen in a number of conditions.

OBJECTIVE

Clinicians and scientists with experience in managing and diagnosing rare diseases in this population in Ireland, Romania and Greece have developed a comprehensive catalogue of autosomal recessive inherited disorders found in the Roma population. Our aim is that this catalogue will aid rapid diagnosis and highlight the differential diagnoses to consider in challenging cases.

METHODS

We performed a detailed literature search to identify relevant publications and disease variants described in patients whose ethnicity was described as Roma. In addition, we interrogated data from local clinicians and colleagues in Ireland and Romania to collect additional unpublished variants which have yet to be reported in the medical literature. Where possible, we have mapped these disorders back to their European country of origin. Furthermore, we searched the variants allele frequencies on ClinVar. We analysed exome data from New Delhi, India to trace any of these founder variants back their origins.

RESULTS

We identified 90 distinct autosomal recessive disorders, manifesting as 91 distinct phenotypes and 111 pathogenic disease variants. These include both published (n = 91) and unpublished (n = 20) findings identified in the Roma population in Europe. The Indian exome data revealed that only 12/111 variants were identified.

CONCLUSION

We have assembled a catalogue of inherited autosomal recessive disorders and 111 pathogenic variants found in the Roma population. We hope that this will assist the medical and scientific community to make prompt diagnoses and consider adaptation of a targeted genetic approach to facilitate timely and cost-effective diagnoses in this population.

The prevalence and genotype of 21-hydroxylase deficiency in the Croatian Romani population

Objective

Congenital adrenal hyperplasia (CAH) owing to 21-hydroxylase deficiency (21-OHD) is a rare autosomal recessive disorder caused by pathological variants in the CYP21A2 gene. After a high prevalence of classic 21-OHD CAH in the Romani population was reported in the Republic of North Macedonia, we decided to estimate the prevalence of 21-OHD in Croatia and, if high, assess the possible causes and estimate the frequency of particular CYP21A2 variants.

Design

Cross-sectional study.

Methods

Data from a Croatian 21-OHD genetic database was reviewed, and only Romani patients were included in the study. CYP21A2 genotyping was performed using allele-specific PCR, MLPA, and Sanger sequencing.

Results

According to a survey conducted in 2017, Croatia had 22,500 Romani people and six of them had a salt-wasting (SW) form of 21-OHD. All were homozygous for the c.IVS2-13A/C-G pathological variant in intron 2 and descended from consanguineous families belonging to different Romani tribes. The calculated prevalence of 21-OHD in Croatian Romani is 1:3,750, while in the Croatian general population, it is 1:18,000. Three of the six Romani patients originated from two neighboring villages in North-western Croatia (Slavonia County), as well as the seventh patient who is of mixed Romani/Croatian descent and heterozygous for the c.IVS2-13A/C-G pathological variant (not included in the prevalence calculation).

Conclusion

A high prevalence of SW 21-OHD in the Croatian Romani population caused by the homozygous cIVS2-13A/C-G pathological variant was found. In addition to isolation and consanguinity, other possible reasons could be the heterozygous advantage of the CYP21A2 gene pathological variant and the bottleneck effect as a result of the Romani Holocaust in World War II.

Genotype-phenotype association in congenital adrenal hyperplasia due to 21-hydroxylase deficiency in children

OBJECTIVE

The purpose of this study was to investigate the clinical manifestation of various forms of congenital adrenal hyperplasia (CAH) in children of the Republic of Kazakhstan, depending on their genotype.

DESIGN

The study analysed 50 patients diagnosed with CAH from 7 regions of Kazakhstan with different ethnic origins: 35 Kazakhs (70.0%), 8 Russians (16.0%), 2 Turks (4.0%), 2 Ukrainians (4.0%), 2 Uzbeks (4%), 1 Uighur (2%). All the children studied were from 0 to 18 years old, and their average age was 5.7 years ±3.9. In addition, all children were divided into groups depending on the form of the disease according to the phenotypic manifestation of the disease: salt-wasting (SW) and simple virile (SV) forms. Most of the patients suffered from SW - 32 (64.0%), and a smaller group had SV - 18 (36.0%), also one boy with SW was diagnosed with TART syndrome.

MEASUREMENTS

50 Kazakh children with the classical form of CAH were analysed. Depending on the severity of the mutations, patients were divided into 4 groups: zero groups (the most severe mutations), A, B, and C.

RESULTS

According to the results of the study, the salt-wasting form of CAH turned out to be more common than the simple virile form. A high correlation was observed in groups with mutations of high and moderate severity - 0 and A, while group C showed a strong variability of the phenotype. Thus, the correspondence between genotype and phenotype decreased along with the decrease in the severity of the disease.

CONCLUSIONS

The relationship between the genotype and the phenotype of both forms of CAH exists indirectly, through the activity of the 21-hydroxylase enzyme. Mutations in the CYP21A2 gene affect the level of the synthesized enzyme, which, in turn, determines the degree of hormone production in the blood.

Genetic Determinants of Leisure-Time Physical Activity in the Hungarian General and Roma Populations

Leisure-time physical activity (LTPA) is one of the modifiable lifestyle factors that play an important role in the prevention of non-communicable (especially cardiovascular) diseases. Certain genetic factors predisposing to LTPA have been previously described, but their effects and applicability on different ethnicities are unknown. Our present study aims to investigate the genetic background of LTPA using seven single nucleotide polymorphisms (SNPs) in a sample of 330 individuals from the Hungarian general (HG) and 314 from the Roma population. The LTPA in general and three intensity categories of it (vigorous, moderate, and walking) were examined as binary outcome variables. Allele frequencies were determined, individual correlations of SNPs to LTPA, in general, were determined, and an optimized polygenetic score (oPGS) was created. Our results showed that the allele frequencies of four SNPs differed significantly between the two study groups. The C allele of rs10887741 showed a significant positive correlation with LTPA in general (OR = 1.48, 95% CI: 1.12-1.97; p = 0.006). Three SNPs (rs10887741, rs6022999, and rs7023003) were identified by the process of PGS optimization, whose cumulative effect shows a strong significant positive association with LTPA in general (OR = 1.40, 95% CI: 1.16-1.70; p < 0.001). The oPGS showed a significantly lower value in the Roma population compared with the HG population (oPGS_Roma: 2.19 ± SD: 0.99 vs. oPGS_HG: 2.70 ± SD: 1.06; p < 0.001). In conclusion, the coexistence of genetic factors that encourage leisure-time physical activity shows a more unfavorable picture among Roma, which may indirectly contribute to their poor health status.

Characteristics of In2G Variant in Congenital Adrenal Hyperplasia Due to 21-Hydroxylase Deficiency

Substantial research has been performed during the last decades on the clinical and genetic variability of congenital adrenal hyperplasia (CAH) and its most common form, 21-hydroxylase deficiency (21OHD). CAH is one of the most prevalent autosomal recessive diseases in humans, and it can be divided into classic-further subdivided into salt wasting (SW) and simple virilizing (SV)-and non-classic (NC) forms. Pathogenic variants of CYP21A2 gene, encoding the 21-hydroxylase enzyme, have been reported with variable prevalence in different populations. NM_000500.9:c.293-13C/A>G (In2G) variant represents the most common CYP21A2 gene changes related to the classic 21OHD form. However, the phenotype of In2G carriers is variable depending on the variant homozygous/heterozygous status and combination with other CYP21A2 pathogenic variants. In addition, identical genotypes, harboring the homozygous In2G variant, can present with variable phenotypes including the SW and SV or rarely NC form of the disease. Here, we analyze and present the clinical aspects, genotype/phenotype correlations, and other characteristics related to the CYP21A2 In2G variant.