Preimplantation genetic diagnosis for familial amyloidotic polyneuropathy (FAP)

Chinese experts' consensus guideline on preimplantation genetic testing of monogenic disorders

Recent developments in molecular biological technologies and genetic diagnostic methods, accompanying with updates of relevant terminologies, have enabled the improvements of new strategies of preimplantation genetic testing for monogenic (single gene) disorders (PGT-M) to prevent the transmission of inherited diseases. However, there has been much in the way of published consensus on PGT-M. To properly regulate the application of PGT-M, Chinese experts in reproductive medicine and genetics have jointly developed this consensus statement. The consensus includes indications for patient selection, genetic and reproductive counseling, informed consent, diagnostic strategies, report generation, interpretation of results and patient follow-ups. This consensus statement serves to assist in establishment of evidence-based clinical and laboratory practices for PGT-M.

Preimplantation genetic testing for familial amyloid polyneuropathy

Background

Embryo selection in Familial amyloid polyneuropathy eradicates the disease, but the widespread application of preimplantation genetic testing (PGT) for this monogenic disease still requires greater political and clinical commitment.

Main body

Familial amyloid polyneuropathy is a fatal, chronic, hereditary autosomal dominant neurodegenerative disorder caused by a single nucleotide mutation in the transthyretin gene. The disease courses with infertility, cachexia, blindness, renal failure, cardiovascular collapse, and premature death. Treatments include organ transplantation, transthyretin stabilizers, silencers and gene editing. Unfortunately, these treatments only improve the patient’s quality of life.

Short conclusion

The application of PGT would prevent the disease, the birth of children with this devastating disease and the enormous health costs associated. For PGT to become the first reproductive option for patients, a paradigm shift in governmental, social and medical policies is necessary.

Review: Preimplantation genetic diagnosis (PGD) as a reproductive option in patients with neurodegenerative disorders

Preimplantation genetic diagnosis (PGD) was introduced in the late 1980s and represents an option for couples at risk of transmitting an inherited, debilitating or neurological disorder to their children. From a cleavage or blastocyst stage embryo, cell(s) are collected and then genetically analyzed for disease; enabling an unaffected embryo to be transferred into the uterus cavity. Nowadays, PGD has been carried out for several hundreds of heritable conditions including myotonic dystrophy, and for susceptibility genes involved in cancers of the nervous system. Currently, advanced molecular technologies with better resolution, such as array comparative genomic hybridisation, quantitative polymerase chain reaction, and next generation sequencing, are on the verge of becoming the gold standard in embryo preimplantation screening. Given this, it may be time for neurological societies to consider the published evidence to develop new guidelines for the integration of PGD into modern preventative neurology. Therefore, the main aim of this review is to illustrate the option of PGD to enable conception of an unaffected baby, and to assist clinicians and neurologists in the counseling of the patient at risk of transmitting an inherited disease, to explore the genetic journey throughout in vitro fertilization IVF with PGD.

Societal costs and burden of hereditary transthyretin amyloidosis polyneuropathy

Background: Hereditary transthyretin amyloidosis polyneuropathy (ATTRv-PN) is a rare life-threatening disease that imposes considerable mortality and morbidity associated with increased costs, high social support and productivity losses. This study aims to estimate the societal costs and burden of ATTRv-PN.Methods: A cost-of-illness (COI) and burden of disease model were specified from a societal perspective, using a prevalence-based approach. Direct and indirect costs were included. Healthcare resource use was retrieved from public databases, previous Portuguese studies and the literature. The burden of disease was expressed in terms of disability-adjusted life years (DALYs), as defined by the World Health Organisation.Results: In 2016, the total annual COI of ATTRv-PN in Portugal was 52,502,796€ and the mean cost per patient was 28,152€ (79% direct; 21% indirect costs). Treatments accounted for 52% of total costs, while 0.18% were devoted to disease prevention. A total of 2056 DALYs were lost, 26% due to disability and 74% due to death.Conclusions: Annual costs and burden of ATTRv-PN were considerable but within the range of other rare diseases. Policies and public interventions to prevent and reduce the burden of disease should be prioritised, since patients experience excess morbidity, mortality and total costs will likely increase in the future.

Preimplantation Genetic Diagnosis of Neurodegenerative Diseases: Review of Methodologies and Report of Our Experience as a Regional Reference Laboratory

Preimplantation genetic diagnosis (PGD) has become a crucial approach in helping carriers of inherited disorders to give birth to healthy offspring. In this study, we review PGD methodologies and explore the use of amplification refractory mutation system quantitative polymerase chain reaction (ARMS-qPCR) and/or linkage analysis for PGD in neurodegenerative diseases that are clinically relevant with typical features, such as late onset, and which are severely debilitating. A total of 13 oocyte retrieval cycles were conducted in 10 cases with various neurodegenerative diseases. Among the 59 embryos analyzed, 49.2% (29/59) were unaffected and 50.8% (30/59) were affected. Of the 12 embryo transfer cycles, three resulted in pregnancy, and all pregnancies were delivered. The implantation rate and livebirth rate were 23.1% (3/13) per oocyte retrieval cycle and 25.0% (3/12) per embryo transfer cycle. Allele dropout (ADO) was noted in two embryos that were classified as unaffected by ARMS-qPCR but were evidenced as affected after prenatal diagnosis, rendering the false negative rate as 6.3% (2/32). Four among the 13 cycles underwent PGD by ARMS-qPCR coupled with linkage analysis, and all were correctly diagnosed. We conclude that PGD by ARMS-qPCR and/or linkage analysis is a feasible strategy, whereas ADO is a concern when ARMS-qPCR is used as the sole technology in PGD, especially in autosomal dominant diseases.

Life paths of patients with transthyretin-related familial amyloid polyneuropathy Val30Met: a descriptive study

Transthyretin-related familial amyloid polyneuropathy Val30Met is a fatal progressive disease. It is a rare hereditary amyloidosis, manifesting as a sensorimotor neuropathy and autonomic dysfunction. It begins during adulthood and is a disabling disease, posing a great psychological burden to patients and their families. Our aim was to describe and characterize life events related to the disease and discuss its psychosocial implications. Social and demographic data and a questionnaire on history of family and personal disease, and biographic events, were applied to 209 subjects attending an outpatient specialized clinic. Descriptive and statistical analyses were performed. They were 84 men and 127 women belonging to three groups: pre-symptomatic carriers, patients, and subjects with no established diagnosis. Most subjects were married/lived with a partner and had children (mean of 4). Most (96.3%) had contact with the disease before having a diagnosis; the affected or at-risk parent was the mother in 53.8% and the father in 43.3%; 71.8% of these had deceased. At their parent's death, many subjects were aged under 10 (9.9%), 10-14 (15.5%), or 15-24 years (31.7%). Most were under age 14 (44.9%) at their parent's disease onset; 37.2% referred this brought life changes with psychological and familial impact; most had been parent's caregivers; 7.5% had not been raised by the parents. Some (8.4%) declined to know their genetic tests results for over 1 year. Parent's disease and death are very common early in these patient's lives. During childhood or youth, many subjects became caregivers, implying changes in family roles. This disease and its life implications pose a significant psychosocial burden since childhood. TTR-FAP patients and their relatives are highly vulnerable to emotional stress and psychopathology during their lifetime. Psychological and psychiatric support, implying a multidisciplinary group, must thus be available for all of them.

Management of asymptomatic gene carriers of transthyretin familial amyloid polyneuropathy

Transthyretin familial amyloid polyneuropathy (TTR‐FAP) is a rare, severe, and irreversible, adult‐onset, hereditary disorder caused by autosomal‐dominant mutations in the TTR gene that increase the intrinsic propensity of transthyretin protein to misfold and deposit systemically as insoluble amyloid fibrils in nerve tissues, the heart, and other organs. TTR‐FAP is characterized by relentless, progressively debilitating polyneuropathy, and leads to death, on average, within 10 years of symptom onset without treatment. With increased availability of disease‐modifying treatment options for a wider spectrum of patients with TTR‐FAP, timely detection of the disease may offer substantial clinical benefits. This review discusses mutation‐specific predictive genetic testing in first‐degree relatives of index patients diagnosed with TTR‐FAP and the structured clinical follow‐up of asymptomatic gene carriers for prompt diagnosis and early therapeutic intervention before accumulation of substantial damage. Muscle Nerve54: 353–360, 2016

Corino de Andrade disease: mechanisms and impact on reproduction

Familial amyloid polyneuropathy was first described by Corino de Andrade in 1952 in Northern Portugal. It is a fatal autosomal dominant neurodegenerative disorder characterized by a progression of neurologic symptoms, beginning early in the reproductive life. The Transthyretin gene mutation originates a mutated protein that precipitates in the connective tissue as amyloid deposits. This disease is presently named Transthyretin-related hereditary amyloidosis. We performed an extensive review on this disease based on searches in Medical databases and in paper references. In this review, we briefly summarize the epidemiology and the mechanisms involved on amyloid deposition; we detailed how to evaluate the mechanisms implicated on the development of the major signs and symptoms associated with reproductive dysfunction; and we discuss the mechanisms involved in secondary sexual dysfunction after psychological treatments. Treatment of the disease is directed towards relieving specific symptoms in association with liver transplant, and molecular and genetic therapeutics. Although the current clinical trials indicate symptoms relief, no data on the reproductive function was reported. Thus, preimplantation genetic diagnosis is presently the only available technique that eradicates the disease as it avoids the birth of new patients.

Evolving landscape in the management of transthyretin amyloidosis

Transthyretin (TTR) amyloidosis (ATTR amyloidosis) is a multisystemic, multigenotypic disease resulting from deposition of insoluble ATTR amyloid fibrils in various organs and tissues. Although considered rare, the prevalence of this serious disease is likely underestimated because symptoms can be non-specific and diagnosis largely relies on amyloid detection in tissue biopsies. Treatment is guided by which tissues/organs are involved, although therapeutic options are limited for patients with late-stage disease. Indeed, enthusiasm for liver transplantation for familial ATTR amyloidosis with polyneuropathy was dampened by poor outcomes among patients with significant neurological deficits or cardiac involvement. Hence, there remains an unmet medical need for new therapies. The TTR stabilizers tafamidis and diflunisal slow disease progression in some patients with ATTR amyloidosis with polyneuropathy, and the postulated synergistic effect of doxycycline and tauroursodeoxycholic acid on dissolution of amyloid is under investigation. Another therapeutic approach is to reduce production of the amyloidogenic protein, TTR. Plasma TTR concentration can be significantly reduced with ISIS-TTR(Rx), an investigational antisense oligonucleotide-based drug, or with patisiran and revusiran, which are investigational RNA interference-based therapeutics that target the liver. The evolving treatment landscape for ATTR amyloidosis brings hope for further improvements in clinical outcomes for patients with this debilitating disease.

Transthyretin familial amyloid polyneuropathy

TTR FAP is characterized by phenotypic and genotypic heterogeneity. The severity of polyneuropathy along with autonomic dysfunction and heart involvement makes it a life-threatening disease. This protein is mainly produced by the liver. Molecular genetic testing is essential in the diagnostic strategy. TTR-Val30Met is the most frequent substitution, resulting in a guanine to cytosine mutation in exon 2 of the gene. It is virtually the only variant detected in Portugal, Brazil, and Sweden. By contrast, as many as 30 different TTR variants are reported in Japan and in other European countries. A less severe phenotype with late onset has been reported. Diagnosis should be performed as early as possible since upcoming pharmacological therapeutic approaches are now available, in addition to liver transplantation.

Familial amyloid polyneuropathy

Familial amyloid polyneuropathies (FAPs) are a group of life-threatening multisystem disorders transmitted as an autosomal dominant trait. Nerve lesions are induced by deposits of amyloid fibrils, most commonly due to mutated transthyretin (TTR). Less often the precursor of amyloidosis is mutant apolipoprotein A-1 or gelsolin. The first identified cause of FAP-the TTR Val30Met mutation-is still the most common of more than 100 amyloidogenic point mutations identified worldwide. The penetrance and age at onset of FAP among people carrying the same mutation vary between countries. The symptomatology and clinical course of FAP can be highly variable. TTR FAP typically causes a nerve length-dependent polyneuropathy that starts in the feet with loss of temperature and pain sensations, along with life-threatening autonomic dysfunction leading to cachexia and death within 10 years on average. TTR is synthesised mainly in the liver, and liver transplantation seems to have a favourable effect on the course of neuropathy, but not on cardiac or eye lesions. Oral administration of tafamidis meglumine, which prevents misfolding and deposition of mutated TTR, is under evaluation in patients with TTR FAP. In future, patients with FAP might benefit from gene therapy; however, genetic counselling is recommended for the prevention of all types of FAP.

A rapid and sensitive prenatal diagnosis of familial amyloidotic polyneuropathy ATTR Val30Met by mass spectrometry

OBJECTIVE

To make a prenatal diagnosis of familial amyloidotic polyneuropathy (FAP) by mass spectrometry with the amniotic fluid.

METHODS

Amniotic-fluid samples of three non-FAP pregnant women and six amniotic-fluid samples of fetal mice whose mother was a heterozygotic FAP amyloidgenic transthyretin (ATTR) Val30Met gene carrier were collected. Electro spray ionization mass spectrometry (ESI-MS) was employed to identify and quantitatively measure the molecular weight of the human transthyretin (TTR) in the amniotic fluid.

RESULTS

TTR was detected in the amniotic fluid of all the human samples. In four of the six fetuses of the transgenic mice, human TTR Val30Met was detected. The other two samples showed only mouse TTR without human TTR Val30Met. DNA analysis revealed that the four fetuses were TTR Val30Met positive, but two were negative. The data from the DNA analysis and ESI-MS showed a 100% concordance.

CONCLUSION

Mass spectrometry analysis of the amniotic fluid might be a useful tool to make a prenatal diagnosis of FAP ATTR Val30Met.

Well-devised quantification analysis for duplication mutation of Duchenne muscular dystrophy aimed at preimplantation genetic diagnosis

PURPOSE

Preimplantation genetic diagnosis (PGD) has been performed for deletion and point mutation type of Duchenne muscular dystrophy (DMD). Our aim was to develop a PGD technique, not yet established, to directly detect duplication mutation instead of substitute diagnosis similar to gender determination.

METHODS

Our method is based on comparative quantification using conventional duplex PCR, real-time PCR and gender determination. We evaluated this method in single lymphocytes from a duplication type of DMD patient and a normal male.

RESULTS

There was a significant difference in the mean values of the ratios (the mutation locus/a normal reference): mean value +/- SE was 1.84 +/- 0.15 in the duplication patient, and 1.00 +/- 0.09 in the normal male (p < 0.001).

CONCLUSION

It is suggested that our comparative quantification method could be a new option in PGD for carriers with duplication mutation who wish to have an unaffected son.

[The diagnosis and management of familial amyloid polyneuropathy]

INTRODUCTION

Familial amyloid polyneuropathy designates a group of dominantly inherited neuropathies, with extracellular deposition of amyloid substance in various tissues.

BACKGROUND

The 3 main precursor proteins encountered in these disorders are transthyretin, apolipoprotein A1 or gelsolin. Among them, transthyretin neuropathies are by far the most frequent type with a severe sensori-motor and autonomic neuropathy as the hallmark of the disease, most often associated with cardiac manifestations. First described in Portugal, the affection was subsequently reported across the world, although Portugal, Japan and Sweden are the 3 main areas of prevalence. In the past years, an increasing number of mutations have been identified in the TTR gene, along with a larger clinical spectrum than initially thought. Variable age of onset and penetrance are also largely reported with unclear phenotypic-genotypic correlations. Indeed, the contribution of the molecular genetics is important to ensure the diagnosis at an early stage, but also for predictive diagnosis, in the setting of genetic counselling.

PERSPECTIVES

Over the last 15 years, liver transplantation (LT) has enabled improved prognosis of this devastating condition.

FUTURE PROSPECTS

at present, such procedure should be performed in Val30Met patients, as early as possible in the course of the disease. Experience with such procedure in patients with other TTR variants remains scarce. Other therapeutic strategies are awaited.

CONCLUSION

This review summarizes the recent data on the diagnosis and management of patients and families affected with TTR amyloid neuropathy.

Psychological aspects of pre-symptomatic testing for Machado-Joseph disease and familial amyloid polyneuropathy type I

Machado-Joseph disease [MJD, also spinocerebellar ataxia type 3 (SCA3)] and familial amyloid polyneuropathy type I (FAP-I or ATTR V30M) are neurodegenerative disorders, inherited in an autosomal dominant fashion, which have a high prevalence in Portugal, probably due to a founder effect. MJD and FAP-I are late-onset diseases, with symptoms emerging usually during adulthood. CGPP, which is the national reference centre for these disorders, has a genetic lab that offers diagnostic, pre-symptomatic and prenatal testing and an outpatient clinic to counsel and follow relatives at risk for hereditary ataxias, FAP-I and Huntington disease (HD). The present work is a review of our 10-year experience with psychological counselling of individuals at risk for MJD and FAP-I. Persons at risk for FAP-I may show a better response to pre-symptomatic testing than those who are at risk for MJD and HD because of the availability of liver transplantation, which may improve their health and life expectancy. Psychological well-being and specific distress of MJD and FAP-I test applicants, before undergoing genetic testing (baseline level) and 3 to 6 months after disclosure of test results, have shown a low level of change, both in identified carriers and non-carriers. A major goal of psychological characterization of at-risk individuals for MJD and FAP-I is to determine the factors that influence the uptake of genetic testing.

Current status of preimplantation diagnosis for single gene disorders

Preimplantation genetic diagnosis (PGD) has become an established procedure for avoiding the birth of affected children with single gene disorders. PGD is performed through polar body or blastomere biopsy, which has no deleterious effect on pre- and post-implantation development. This review describes the most recent developments and current changes in the spectrum of conditions for which PGD has been applied. The most recent applications of PGD include congenital malformations, blood group incompatibility and an increasing number of late onset disorders with genetic predisposition, all of which have not previously been diagnosed using PGD. Despite ethical concerns, PGD has also been used for preselection of unaffected and HLA matched embryos, and recently for preimplantation HLA matching without testing for the causative gene. This extends the practical value of PGD, with its utility being no longer limited to prevention of single gene disorders, by expanding it to treatment of siblings requiring stem cell transplantation.

Preimplantation genetic diagnosis using FISH for carriers of Robertsonian translocations: the Portuguese experience

Preimplantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis for couples at risk of transmitting genetic disorders to their offspring. We present a fluorescence in situ hybridization (FISH) analysis of embryos obtained after seven PGD cycles in six couples with Robertsonian translocations and male factor infertility: 4 der(13;14), 1 der(14;21) and 1 der(15;21). Of 74 metaphase II (MII) injected oocytes, 61 (82.4%) fertilized normally and cleaved. Of these, 37/61 (60.7%) embryos were of high morphological quality with >or=6 blastomeres. After biopsy of 44 embryos at day 3 of development, seven degenerated, seven arrested in development and 30/44 (68.2%) evolved, of which 25/30 (83.3%) reached the morula/blastocyst stage. Analysis of biopsied blastomeres showed 23/44 (52.3%) of normal/balanced embryos, of which 15 (11 at the morula/blastocyst stage) were transferred in six cycles. One term pregnancy was achieved, which ended by cesarean section at 37 weeks of gestation, giving birth to two healthy newborn. Analysis of 49 embryos (excluding 12 inconclusive cases) showed a predominance of alternate segregation (38/49, 77.6%) over adjacent segregation (7/49, 14.3%), with one (2%) being a polyploid mosaic and three (6.1%) chaotic.

Preimplantation genetic diagnosis

Preimplantation genetic diagnosis is essentially an alternative to prenatal diagnosis, in which genetic testing is performed on embryos before a clinical pregnancy is established. Preimplantation genetic diagnosis has been applied to patients carrying chromosomal rearrangements, such as translocations, in which it has been proven to decrease the number of spontaneous abortions and prevent the birth of children affected with chromosome imbalance. Preimplantation genetic diagnosis techniques have also been applied to increase implantation rates, reduce the incidence of spontaneous abortion and prevent trisomic offspring in women of advanced maternal age undergoing fertility treatment. A third group of patients receiving preimplantation genetic diagnosis are those at risk of transmitting a single gene disorder to their children. The number of monogenic disorders that have been diagnosed in preimplantation embryos has increased each year. Recent protocols have tended to be more complex and more reliable than previous methods, making greater use of multiplex polymerase chain reaction. As well as an expansion in the variety of disorders for which preimplantation genetic diagnosis is offered, new indications have been reported including the use of human leukocyte antigen histocompatibility typing and the application of preimplantation genetic diagnosis to late onset diseases.