Bioethical issues of preventing hereditary diseases with late onset in the Sakha Republic (Yakutia)

PGT-M for spinocerebellar ataxia type 1: development of a STR panel and a report of two clinical cases

PURPOSE

To present the developed preimplantation genetic testing (PGT) for spinocerebellar ataxia type 1 (SCA1) and the outcomes of IVF with PGT.

METHODS

PGT was performed for two unrelated couples from the Republic of Sakha (Yakutia) with the risk of SCA1 in one spouse. We have developed a system for PGT of a monogenic disease (PGT-M) for SCA1, which includes the analysis of a panel of 11 polymorphic STR markers linked to the ATXN1 gene and a pathogenic variant of the ATXN1 gene using nested PCR and fragment analysis. IVF/ICSI programs were performed according to standard protocols. Multiple displacement amplification (MDA) was used for whole genome amplification (WGA) and array comparative genomic hybridization (aCGH) for aneuploidy testing (PGT-A).

RESULTS

Eight STRs were informative for the first couple and ten for the second. Similarity of the haplotypes carrying pathogenic variants of the ATXN1 gene was noted. In the first case, during IVF/ICSI-PGT, three embryos reached the blastocyst stage and were biopsied. One embryo was diagnosed as normal by maternal STR haplotype and the ATXN1 allele. PGT-A revealed euploidy. The embryo transfer resulted in a singleton pregnancy, and a healthy boy was born. Postnatal diagnosis confirmed normal ATXN1. In the second case, two blastocysts were biopsied. Both were diagnosed as normal by PGT-M, but PGT-A revealed aneuploidy.

CONCLUSION

Birth of a healthy child after PGT for SCA1 was the first case of successful preimplantation prevention of SCA1 for the Yakut couple and the first case of successful PGT for SCA1 in Russia.

Oocyte Donation: Three Perspectives

Background: A number of important problems remain unresolved in the field of assisted reproductive technologies (ART) using germ cells from a single donor. This study aimed to assess attitudes about the use of sex gamete donation in ART in different social groups including medical workers, oocyte recipients, and oocyte donors. Methods: To achieve this goal, we surveyed 286 participants from seven countries. Of them, 190 were medical workers from ART clinics (respondents from seven countries), 45 were oocyte recipients (Kazakhstan), and 51 were oocyte donors (Kazakhstan). Results: A survey of the three groups showed that issues related to donor health were most common in the donor selection process based on patient and doctor distrust of the health care system. The main motive for oocyte donation was financial compensation, which draws attention to the social disadvantage of the donor population. Medical workers with more than 5 years of work experience (79.7%) supported the use of programs tracking donor sex gametes and limiting the use of oocyte donors. Conclusions: The willingness and consent of the surveyed medical workers and oocyte recipients to use the donor material and create a unified registry of donor sex gametes demonstrates the importance of this issue.

The attitude of young people in the city of Yakutsk to DNA-testing

This pilot research was one of the first sociological studies with general questions on genetic testing with 300 participants, 75% of which were representatives of one people - the Sakha. A quantitative method was used: a sociological survey with quota sampling (Δ ± 5%), held in February - March 2018 in the City of Yakutsk (n = 350).Analysis of the survey results have shown that the respondents have low levels of awareness about the DNA-testing method: 72.3% "do not know about the method". Only 18.7% of respondents knew that since 2000 the Medical-Genetic Centre of the Sakha Republic (Yakutia) conducts DNA diagnostics for hereditary diseases, with 81.0% replying that they didn't know that. The questionnaire has shown that 90.3% of participants would like to undergo DNA-testing to identify their susceptibility to genetic diseases. Our questionnaire has shown high levels of self-identity among the young Sakha and their desire to learn about their belonging to a specific ethnicity (49.3%) with the assistance of DNA-testing. Furthermore, based on the answers relating to motivations for undergoing DNA-testing, we can say that the respondents have confirmed the peculiarities of their national mindset, specifically, high value of children for a family: "concern for the health of my future children" was a great motivator for taking the test (50.3%).

A case-note review of continued pregnancies found to be at a high risk of Huntington's disease: considerations for clinical practice

Huntington's disease (HD) is a severe neurodegenerative condition that impacts the whole family. Prenatal diagnosis by direct or exclusion testing is available for couples at risk of transmitting HD to their children. An ethical problem can arise after prenatal diagnosis for HD if a known 'high risk' pregnancy is continued to term: international guidelines emphasise that this situation should be avoided where possible, as it removes the resulting child's future right to make an informed, autonomous decision about predictive testing. The UK Huntington's Disease Predictive Testing Consortium recorded 21 pregnancies that were tested, identified as high-risk and then continued. In this qualitative study, health professionals reviewed the case notes of 15 of these pregnancies. This analysis generated guidelines for clinical practice. It is recommended that practitioners: (i) remind couples of the long-term consequences of continuing a high risk pregnancy, (ii) ensure couples understand the information provided, (iii) collaborate closely with other professionals involved in the couple's prenatal care, (iv) prepare couples for the procedural aspects of prenatal diagnosis and a possible termination of pregnancy, (v) allow time for in-depth pre-test counselling, (vi) explain the rationale for only making prenatal diagnosis available subject to conditions, whilst allowing for human ambivalence and acknowledging that these 'conditions' cannot be enforced, (vii) monitor the whole clinical process to ensure that it works 'smoothly', (viii) recommend couples do not disclose the result of the prenatal test to protect the confidentiality and autonomy of the future 'high-risk' child, and (ix) offer on-going contact and support.

Genetic fitness and selection intensity in a population affected with high-incidence spinocerebellar ataxia type 1

Spinocerebellar ataxia type 1 (SCA1) is the major and likely the only type of autosomal dominant cerebellar ataxia in the Sakha (Yakut) people of Eastern Siberia. The prevalence rate of SCA1 has doubled over the past 21 years peaking at 46 cases per 100,000 rural population. The age at death correlates closely with the number of CAG triplet repeats in the mutant ATXN1 gene (r = -0.81); most patients with low-medium (39-55) repeat numbers survived until the end of reproductive age. The number of CAG repeats expands in meiosis, particularly in paternal transmissions; the average total increase in intergenerational transmissions in our cohort was estimated at 1.6 CAG repeats. The fertility rates of heterozygous carriers of 39-55 CAG repeats in women were no different from those of the general Sakha population. Overall, the survival of mutation carriers through reproductive age, unaltered fertility rates, low childhood mortality in SCA1-affected families, and intergenerational transmission of increasing numbers of CAG repeats in the ATXN1 gene indicate that SCA1 in the Sakha population will be maintained at high prevalence levels. The low (0.19) Crow's index of total selection intensity in our SCA1 cohort implies that this mutation is unlikely to be eliminated through natural selection alone.