Primary mitochondrial disorders and mimics: Insights from a large French cohort

OBJECTIVE

The objective of this study was to evaluate the implementation of NGS within the French mitochondrial network, MitoDiag, from targeted gene panels to whole exome sequencing (WES) or whole genome sequencing (WGS) focusing on mitochondrial nuclear-encoded genes.

METHODS

Over 2000 patients suspected of Primary Mitochondrial Diseases (PMD) were sequenced by either targeted gene panels, WES or WGS within MitoDiag. We described the clinical, biochemical, and molecular data of 397 genetically confirmed patients, comprising 294 children and 103 adults, carrying pathogenic or likely pathogenic variants in nuclear-encoded genes.

RESULTS

The cohort exhibited a large genetic heterogeneity, with the identification of 172 distinct genes and 253 novel variants. Among children, a notable prevalence of pathogenic variants in genes associated with oxidative phosphorylation (OXPHOS) functions and mitochondrial translation was observed. In adults, pathogenic variants were primarily identified in genes linked to mtDNA maintenance. Additionally, a substantial proportion of patients (54% (42/78) and 48% (13/27) in children and adults, respectively), undergoing WES or WGS testing displayed PMD mimics, representing pathologies that clinically resemble mitochondrial diseases.

INTERPRETATION

We reported the largest French cohort of patients suspected of PMD with pathogenic variants in nuclear genes. We have emphasized the clinical complexity of PMD and the challenges associated with recognizing and distinguishing them from other pathologies, particularly neuromuscular disorders. We confirmed that WES/WGS, instead of panel approach, was more valuable to identify the genetic basis in patients with "possible" PMD and we provided a genetic testing flowchart to guide physicians in their diagnostic strategy.

What importance do donors and recipients attribute to the nuclear DNA-related genetic heritage of oocyte donation?

STUDY QUESTION

How do oocyte donors and recipients perceive the genetic link related to the transfer of nuclear DNA between donors and offspring?

SUMMARY ANSWER

Whether they are donors or recipients, individuals attach great importance to the transmission of their genetic heritage, since 94.5% would opt for the pronuclear transfer method to preserve this genetic link in the context of oocyte donation.

WHAT IS KNOWN ALREADY

Since 1983, the use of oocyte donation has increased worldwide. Performed in France since the late 1980s and initially offered to women with premature ovarian insufficiency, its indications have progressively expanded and now it is proposed in many indications to prevent the transmission of genetically inherited diseases. This has resulted in an increase in the waiting time for access to oocyte donation due to the difficulty in recruiting oocyte donors in French ART centres. Several articles have discussed how to fairly distribute donor oocytes to couples, but few have interviewed women in the general population to record their feelings about oocyte donation, as either the donor or recipient and the importance given to the genetic link between the oocyte donors and the children born. Mitochondrial replacement therapy (MRT) is a technique originally developed for women at risk of transmitting a mitochondrial DNA mutation. Recently, MRT has been considered for embryo arrest and oocyte rejuvenation as it could help females to reproduce with their own genetic material through the transfer of their oocyte nucleus into a healthy donor oocyte cytoplasm.

STUDY DESIGN, SIZE, DURATION

We conducted an opinion survey from January 2021 to December 2021, during which 1956 women completed the questionnaire. Thirteen participants were excluded from the analysis due to incomplete responses to all the questions. Consequently, 1943 women were included in the study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We specifically developed a questionnaire for this study, which was created and distributed using the Drag'n Survey® software. The questionnaire consisted of 21 items presented alongside a video created with whiteboard animation software. The aim was to analyse whether certain factors, such as age, education level, marital status, number of children, use of ART for pregnancy, video viewing, and knowledge about oocyte donation, were associated with feelings towards oocyte donation, by using a univariate conditional logistic regression model. This statistical method was also used to assess whether women would be more inclined to consider oocyte donation with the pronuclear transfer technique rather than the whole oocyte donation. All parameters found to be statistically significant in the univariate analysis were subsequently tested in a multivariate model using logistic regression.

MAIN RESULTS AND THE ROLE OF CHANCE

Most women were concerned about the biological genetic contribution of the donated oocyte (94.8%). The most common reason for a women's reluctance to donate their oocytes was their unwillingness to pass on their genetic material (33.3%). Nearly 70% of women who were initially hesitant to donate their oocytes indicated that they would reconsider their decision if the oocyte donation was conducted using donated cytoplasm and the pronuclear transfer technique. Concomitantly, >75% of the respondents mentioned that it would be easier to receive a cytoplasm donation. The largest proportion of the population surveyed (94.5%) expressed their support for its legalization.

LIMITATIONS, REASONS FOR CAUTION

In this study, a substantial portion of the responses came from individuals with medical or paramedical backgrounds, potentially introducing a recruitment bias among potential donors. The rate of missing responses to the question regarding the desire to become an oocyte donor was 13.6%, while the question about becoming an oocyte cytoplasm donor had a missing response rate of 23%. These missing responses may introduce a bias in the interpretation of the data.

WIDER IMPLICATIONS OF THE FINDINGS

This study was the first to demonstrate that, for the French population studied, the combination of oocyte cytoplasm donation with pronuclear transfer could offer a promising approach to enhance the acceptance of oocyte donation for both the donor and the recipient.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used for this study. The authors have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

PGT and deferred embryo transfer: Is blastocyst biopsy more effective than cleaved embryo biopsy?

OBJECTIVE

Blastocyst biopsy has recently been implemented in our laboratory for PGT with a "freeze all" indication. The aim of this study is to compare PGT results between embryos biopsied at the cleaved and embryos biopsied at the blastocyst stage.

STUDY DESIGN

This is a retrospective cohort study conducted from January 2017 to December 2022 in France. All couples with a "freeze all" indication the day of hCG trigerring during the study period were included in the study. Patients were retrospectively assigned in one group of two groups based on the day of embryo biopsy: the cleavage group if a blastomere biopsy was performed on day 3/4 or the blastocyst group if a trophectoderm biopsy was performed on day 5/6. We evaluated and compared the results between the two groups for biological parameters and clinical outcomes.

RESULTS

In total, 325 PGT cycles (291 patients) were included in our study. Frozen-thawed embryo transfer was performed for 285 cycles, 122 in the blastocyst group and 163 in the cleavage group. The number of biopsied embryos per cycle is significantly higher in the cleavage group with a mean of 7.2 ± 4.1 embryos biopsied per cycle vs. 2.9 ± 2.8 embryos in the blastocyst group (p < 0.001). The rate of the useful embryos was similar between the two groups with 14.6 % of frozen healthy embryos among the 1352 cleaved embryos obtained in blastocyst group, compared to 17.1 % in the cleavage group. No significant differences in clinical pregnancy rate per transfer and implantation rate were observed between the blastocyst and cleavage groups (36.4% vs. 40.4 % and 33.1% vs. 33.2 % respectively).

CONCLUSIONS

For "freeze all" PGT cycles, the day of embryo biopsy (cleaved vs blastocyst biopsy) does not impact pregnancy outcomes. Knowing how to perform embryo biopsy at different stages helps to better organize daily laboratory activity and to rescue some undiagnosed embryos after day 3 biopsy.

Lessons from two series by physicians and caregivers' self-reported data in DDX3X-related disorders

INTRODUCTION AND METHODS

We report two series of individuals with DDX3X variations, one (48 individuals) from physicians and one (44 individuals) from caregivers.

RESULTS

These two series include several symptoms in common, with fairly similar distribution, which suggests that caregivers' data are close to physicians' data. For example, both series identified early childhood symptoms that were not previously described: feeding difficulties, mean walking age, and age at first words.

DISCUSSION

Each of the two datasets provides complementary knowledge. We confirmed that symptoms are similar to those in the literature and provides more details on feeding difficulties. Caregivers considered that the symptom attention-deficit/hyperactivity disorder were most worrisome. Both series also reported sleep disturbance. Recently, anxiety has been reported in individuals with DDX3X variants. We strongly suggest that attention-deficit/hyperactivity disorder, anxiety, and sleep disorders need to be treated.

Preimplantation genetic testing for mitochondrial DNA mutation: ovarian response to stimulation, outcomes and follow-up

RESEARCH QUESTION

How do carriers of pathogenic mitochondrial DNA (mtDNA) respond to ovarian stimulation?

DESIGN

A single-centre, retrospective study conducted between January 2006 and July 2021 in France. Ovarian reserve markers and ovarian stimulation cycle outcomes were compared for couples undergoing preimplantation genetic testing (PGT) for maternally inherited mtDNA disease (n = 18) (mtDNA-PGT group) with a matched-control group of patients undergoing PGT for male indications (n = 96). The PGT outcomes for the mtDNA-PGT group and the follow-up of these patients in case of unsuccessful PGT was also reported.

RESULTS

For carriers of pathogenic mtDNA, parameters of ovarian response to FSH and ovarian stimulation cycle outcomes were not different from those of matched-control ovarian stimulation cycles. The carriers of pathogenic mtDNA needed a longer ovarian stimulation and higher dose of gonadotrophins. Three patients (16.7%) obtained a live birth after the PGT process, and eight patients (44.4%) achieved parenthood through alternative methods: oocyte donation (n = 4), natural conception with prenatal diagnosis (n = 2) and adoption (n = 2).

CONCLUSION

To the best of our knowledge, this is the first study of women carrying a mtDNA variant who have undergone a PGT for monogenic (single gene defects) procedure. It is one of the possible options to obtain a healthy baby without observing an impairment in ovarian response to stimulation.

Insights into the expanding intestinal phenotypic spectrum of SOCS1 haploinsufficiency and therapeutic options

PURPOSE

Hyper activation of the JAK-STAT signaling underlies the pathophysiology of many human immune-mediated diseases. Herein, the study of 2 adult patients with SOCS1 haploinsufficiency illustrates the severe and pleomorphic consequences of its impaired regulation in the intestinal tract.

METHODS

Two unrelated adult patients presented with gastrointestinal manifestations, one with Crohn's disease-like ileo-colic inflammation refractory to anti-TNF and the other with lymphocytic leiomyositis causing severe chronic intestinal pseudo-occlusion. Next-generation sequencing was used to identify the underlying monogenic defect. One patient received anti-IL-12/IL-23 treatment while the other received the JAK1 inhibitor, ruxolitinib. Peripheral blood, intestinal tissues, and serum samples were analyzed before-and-after JAK1 inhibitor therapy using mass cytometry, histology, transcriptomic, and Olink assay.

RESULTS

Novel germline loss-of-function variants in SOCS1 were identified in both patients. The patient with Crohn-like disease achieved clinical remission with anti-IL-12/IL-23 treatment. In the second patient with lymphocytic leiomyositis, ruxolitinib induced rapid resolution of the obstructive symptoms, significant decrease of the CD8+ T lymphocyte muscular infiltrate, and normalization of serum and intestinal cytokines. Decreased frequencies of circulating Treg cells, MAIT cells, and NK cells, with altered CD56^bright:CD16^lo:CD16^hi NK subtype ratios were not modified by ruxolitinib.

CONCLUSION

SOCS1 haploinsufficiency can result in a broad spectrum of intestinal manifestations and need to be considered as differential diagnosis in cases of severe treatment-refractory enteropathies, including the rare condition of lymphocytic leiomyositis. This provides the rationale for genetic screening and considering JAK inhibitors in such cases.

Knowledge, acceptability and personal attitude toward pre-implantation 1 genetic testing (PGT) and pre-natal diagnosis (PND) for females carrying BRCA pathogenic variant according to fertility preservation experience

PURPOSE

Preimplantation genetic testing (PGT-M) and prenatal diagnosis (PND) followed by medical termination of pregnancy when the fetus is affected are two procedures developed to avoid the transmission of a severe hereditary disease which can be proposed to females that carried BRCA pathogenic variants. These females can also be offered fertility preservation (FP) when diagnosed with cancer or even before a malignancy occurs. The aim of the study was to evaluate the acceptability and personal attitude of women carrying a BRCA mutation toward techniques that can prevent BRCA transmission to their progeny.

METHODS

Female mutated for BRCA1 or BRCA2 were invited to complete an online survey of 49 queries anonymously between June and August 2022.

RESULTS

A total of 87 participants responded to the online survey. Overall, 86.2% of women considered that PGT-M should be proposed to all BRCA mutation carriers regardless of the severity of the family history, and 47.1% considered or would consider PGT-M for themselves. For PND, these percentages were lower reaching 66.7% and 29.9%, respectively. Females with personal history of breast cancer or FP achievement were more prone to undergo PND for themselves despite the overall acceptability of this procedure. Among the subgroup who had undergone FP (n = 58), there was no significant difference in acceptance of principle and personal attitude toward PGT-M and PND compared to the group without FP.

CONCLUSION

BRCA pathogenic variants female carriers do need information about reproductive issues, even if they are not prone to undergo PGT-M nor PND for themselves.

TRIAL REGISTRATION NUMBER

N/A.

A shared pattern of altered gene expression in human embryos affected by mitochondrial diseases

STUDY QUESTION

Does mitochondrial deficiency affect human embryonic preimplantation development?

SUMMARY ANSWER

The presence of a pathogenic mitochondrial variant triggers changes in the gene expression of preimplantation human embryos, compromising their development, cell differentiation, and survival.

WHAT IS KNOWN ALREADY

Quantitative and qualitative anomalies of mitochondrial DNA (mtDNA) are reportedly associated with impaired human embryonic development, but the underlying mechanisms remain unexplained.

STUDY DESIGN, SIZE, DURATION

Taking advantage of the preimplantation genetic testing for mitochondrial disorders in at-risk couples, we have compared gene expression of 9 human embryos carrying pathogenic variants in either mtDNA genes or nuclear genes encoding mitochondrial protein to 33 age-matched control embryos.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Single-embryo transcriptomic analysis was performed on whole human blastocyst embryos donated to research.

MAIN RESULTS AND THE ROLE OF CHANCE

Specific pathogenic mitochondrial variants downregulate gene expression in preimplantation human embryos [566 genes in oxidative phosphorylation (OXPHOS)-deficient embryos], impacting transcriptional regulators, differentiation factors, and nuclear genes encoding mitochondrial proteins. These changes in gene expression primarily alter OXPHOS and cell survival pathways.

LIMITATIONS, REASONS FOR CAUTION

The number of OXPHOS-deficient embryos available for the study was limited owing to the rarity of this material. However, the molecular signature shared by all these embryos supports the relevance of the findings.

WIDER IMPLICATIONS OF THE FINDINGS

While identification of reliable markers of normal embryonic development is urgently needed in ART, our study prompts us to consider under-expression of the targeted genes reported here, as predictive biomarkers of mitochondrial dysfunction during preimplantation development.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the 'Association Française contre les Myopathies (AFM-Téléthon)' and the 'La Fondation Maladies Rares'. No competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Tubulin mutations in human neurodevelopmental disorders

Mutations causing dysfunction of tubulins and microtubule-associated proteins, also known as tubulinopathies, are a group of recently described entities that lead to complex brain malformations. Anatomical and functional consequences of the disruption of tubulins include microcephaly, combined with abnormal corticogenesis due to impaired migration or lamination and abnormal growth cone dynamics of projecting and callosal axons. Key imaging features of tubulinopathies are characterized by three major patterns of malformations of cortical development (MCD): lissencephaly, microlissencephaly, and dysgyria. Additional distinctive MRI features include dysmorphism of the basal ganglia, midline commissural structure hypoplasia or agenesis, and cerebellar and brainstem hypoplasia. Tubulinopathies can be diagnosed as early as 21-24 gestational weeks using imaging and neuropathology, with possible extreme microlissencephaly with an extremely thin cortex, lissencephaly with either thick or thin/intermediate cortex, and dysgyria combined with cerebellar hypoplasia, pons hypoplasia and corpus callosum dysgenesis. More than 100 MCD-associated mutations have been reported in TUBA1A, TUBB2B, or TUBB3 genes, whereas fewer than ten are known in other genes such TUBB2A, TUBB or TUBG1. Although these mutations are scattered along the α- and β-tubulin sequences, recurrent mutations are consistently associated with almost identical cortical dysgenesis. Much of the evidence supports that these mutations alter the dynamic properties and functions of microtubules in several fashions. These include diminishing the abundance of functional tubulin heterodimers, altering GTP binding, altering longitudinal and lateral protofilament interactions, and impairing microtubule interactions with kinesin and/or dynein motors or with MAPs. In this review we discuss the recent advances in our understanding of the effects of mutations of tubulins and microtubule-associated proteins on human brain development and the pathogenesis of malformations of cortical development.

P-250 A shared gene expression signature in human blastocyst embryos affected by a mitochondrial disorder

Study question

Do human blastocyst embryos affected by mitochondrial disorders have gene expression disruption?

Summary answer

A global transcriptional repression was found in embryos carrying mutations in mitochondrial genes, primarily affecting oxidative phosphorylation and cell survival pathways.

What is known already

Mitochondria are thought to play a critical role for embryo development by supplying adequate energy levels. Whether a metabolic rescue through mitochondrial metabolism modifications is taking place during the blastocyst stage, remained to be elucidated. For instance, abnormally elevated mtDNA levels were detected in human blastocyst embryos carrying the m.3243&gt;G pathogenic variant, suggestive of a compensatory response, while this was not the case for embryos carrying another mtDNA mutation (m.8344A&gt;G).

Study design, size, duration

To investigate if mitochondrial mutations affect gene expression of human blastocysts, transcriptome profiling between 33 control and 9 mitochondrial embryos was performed and analyzed by RNA-Sequencing.

Participants/materials, setting, methods

In total, 42 blastocyst embryos (Day-5/6/7) from 27 unrelated couples were collected after a preimplantation genetic testing analysis, concluding in an affected status. Among them, 33 were affected by a non-metabolic, non-mitochondrial genetic disorder (control group), and 9 were affected by a mitochondrial disorder (mitochondrial group). Transcriptomic analyses were performed on whole blastocyst embryos, by RNA-Sequencing.

Main results and the role of chance

Gene expression profiling of human blastocyst embryos revealed a global transcriptional repression in mitochondrial embryos, with a total of 566 genes being down-regulated, while only 52 genes were up-regulated (p ≤ 0.05; fold-change=2). A similar pattern was observed among all mitochondrial embryos, affecting a significant proportion of differentiation factors (such as KLF4, p = 1.88x10-2; OXT2, p = 3.32x10-3 and POU5F1, p = 8.03x10-3), as well as nuclear genes encoding mitochondrial proteins (n = 59). If oxidative phosphorylation was at the top of the most significant deregulated pathways (p = 6.32x10-14), cell survival (p = 2.19x10−10) and autophagy (p = 4.56x10-9) were found to be significantly decreased in these embryos, questioning their viability.

Limitations, reasons for caution

The number of mitochondrial embryos was limited due to the rarity of the material, however similar molecular profiles were detected among them. The control group included embryos affected by genetic disorders, although the resulting potential transcriptional biases were neutralized by selecting embryos affected by various and distinct genetic disorders.

Wider implications of the findings

The differentially expressed genes identified in this study represent biomarkers predictive of mitochondrial dysfunction, which will be useful for the establishment of therapeutic or mitochondrial replacement trials. Because of the role of mitochondria, they are also interesting to test in the context of in-vitro fertilization, as biomarkers of preimplantation development.

Trial registration number

Not applicable

P-553 Response to controlled ovarian stimulation and preimplantation genetic testing for molecular disease (PGT-M) outcomes for Myotonic dystrophy type I (DM1) : A French multicentric study

Study question

Does ovarian response to controlled ovarian hyperstimulation (COH) is altered in female affected by DM1 ?

Summary answer

Ovarian response to COH is not altered in female affected by DM1 as compared to partners of affected males

What is known already

Myotonic dystrophy type 1 is the most common adult muscular dystrophy caused by a CTG trinucleotide repeat expansion which may expand across generation. As this pathology presents an autosomal dominant inheritance, PGT may be an option to achieve a pregnancy with healthy baby. There are conflicting reports about response to COH for affected female. Moreover, few data are available concerning the chance to have a healthy baby after PGT for couple with one member affected by DM1

Study design, size, duration

The present study is a retrospective observational study carried out from January 2006 through January 2020. This multicentric study was conducted in all the five centers performing PGT-M in France.

Participants/materials, setting, methods

A total of 229 couples started at least one COH cycle for the PGT procedure. The patient carrying the mutation was the female for 178 couples and the male for the 51 others. Overall, 648 COH cycles started and 560 oocytes retrieval for subsequent PGT were performed (430 for affected female and 130 for affected male). Parameters of ovarian response and PGT outcomes were compared according to the member affected by DM1.

Main results and the role of chance

Age and BMI at the first COH cycle were not significantly different between both group but female carried mutation presented lower AMH level than partner of affected male. The starting and total doses of gonadotrophin were significantly higher for mutated females. The number of retrieved and mature oocytes per cycle were not statistically different (12 [8–16] versus 11 [8–16] retrieved oocytes, p = 0.63 and 9 [6–13] versus 9 [6-13] mature oocytes, p = 0.73, respectively). In both group, more than 70% of oocyte retrieval led to embryo biopsy.

The proportion of started cycle allowing the obtention of at least one healthy embryo was significantly lower when the female was affected with DM1 (58.6% vs 70.4%, p = 0.012). In the female affected group, 49.7% of the cycles with oocytes retrieval lead to a fresh embryo transfer and a subsequent live birth rate per transfer of 21.4%. These results were not statistically different from the couple with affected male (58.5% of cycles with fresh embryo transfer (p = 0.08) and 23.6% live birth rate per transfer).

Overall, after fresh or frozen embryo transfer, 30.8% of females with DM1and 41.2% of parter of affected males had at least one live birth from PGT.

Limitations, reasons for caution

This a retrospective study included patients who were selected ovarian reserve parameters before PGT process. Moreover, the large time of inclusion may influence our conclusion.

Wider implications of the findings

Information provided herein extends knowledge about the current state of COH for DM1 affected female. Moreover, PGT results presented here allow to provide patients with proposer counseling before starting PGT process.

Trial registration number

CEROG-2020-GYN-0603

Broadening the phenotypic spectrum of TUBA1A tubulinopathy to syndromic arthrogryposis multiplex congenita

The recent finding that some patients with fetal akinesia deformation sequence (FADS) carry variants in the TUBB2B gene has prompted us to add to the existing literature a first description of two fetal FADS cases carrying TUBA1A variants. Hitherto, only isolated cortical malformations have been described with TUBA1A mutation, including microlissencephaly, lissencephaly, central pachygyria and polymicrogyria-like cortical dysplasia, generalized polymicrogyria cortical dysplasia, and/or the "simplified" gyral pattern. The neuropathology of our fetal cases shows several common features of tubulinopathies, in particular, the dysmorphism of the basal ganglia, as the most pathognomonic sign. The cortical ribbon anomalies were extremely severe and concordant with the complex cortical malformation. In conclusion, we broaden the phenotypic spectrum of TUBA1A variants, to include FADS.

Cyclic fertilin-derived peptide stimulates in vitro human embryo development

OBJECTIVE

To study the cyclic fertilin peptide effects on preimplantation human embryogenesis. Cyclic fertilin peptide reproduces the structure of the binding site of the sperm Fertilin β (also named A Disintegrin and Metalloprotease 2: ADAM2) disintegrin domain. It binds to the oocyte membrane and increases sperm-oocyte fusion index in human and fertilization rate in mouse, providing healthy pups. It also improves human oocyte maturation and chromosome segregation in meiosis I and binds to human embryo blastomeres, suggesting that it has a membrane receptor.

DESIGN

Thawed human embryos at the 3 to 4 cells stage were randomly included in a dose-response study with cyclic fertilin peptide. Inner cell mass (ICM), trophectoderm (TE), and total cell numbers were evaluated in top- and good-quality blastocysts.

SETTING

The study was performed in an academic hospital and research laboratory.

PATIENT(S)

Human embryos donated for research. This project was approved by the French "Agence de la Biomédecine."

INTERVENTION(S)

Immunofluorescence and tissue-specific gene expression analysis, using Clariom D microarrays, were performed to study its mechanism of action.

MAIN OUTCOME MEASURE(S)

Cyclic fertilin peptide improves blastocyst formation by almost 20%, the concentration of 1 μM being the lowest most efficient concentration. It significantly increases twice the TE cell number, without modifying the ICM. It increases the in vitro hatching rate from 14% to 45%.

RESULT(S)

Cyclic fertilin peptide stimulates TE growth. In the ICM, it induces transcriptional activation of intracellular protein and vesicle-mediated transport.

CONCLUSION(S)

Cyclic fertilin peptide dramatically improves human embryo development potential. It could be used to supplement culture medium and improve the in vitro human embryo development. Starting supplementation immediately after fertilization, instead of day 2, could significantly upgrade assisted reproductive technology outcome.

A fertilin-derived peptide improves in vitro maturation and ploidy of human oocytes

OBJECTIVE

To analyze the effect of a cyclic fertilin-derived peptide (cFEE) on in vitro maturation of human oocytes.

DESIGN

Randomized study.

SETTING

Fertility center in an academic hospital.

PATIENT(S)

Not applicable.

INTERVENTION(S)

Human immature germinal vesicle-stage oocytes (n = 1,629) donated for research according to French bioethics laws were randomly allocated to groups treated with 1 or 100 μM of cFEE or to a control group. They were incubated at 37 °C in 6% CO₂ and 5% O₂, and their maturation was assessed using time-lapse microscopy over 24 hours. In vitro maturated metaphase II oocytes were analyzed for chromosomal content using microarray comparative genomic hybridization, and their transcriptomes were analyzed using Affymetrix Clariom D microarrays.

MAIN OUTCOME MEASURE(S)

The percentage of oocytes undergoing maturation in vitro was observed. Aneuploidy and euploidy were assessed for all chromosomes, and differential gene expression was analyzed in oocytes treated with cFEE compared with the control to obtain insights into its mechanism of action.

RESULT(S)

cFEE significantly increased the percentage of oocytes that matured in vitro and improved euploidy in meiosis II oocytes by the up-regulation of FMN1 and FLNA genes, both of which encode proteins involved in spindle structure.

CONCLUSION(S)

cFEE improves human oocyte maturation in vitro and reduces aneuploidy. It may prove useful for treating oocytes before fertilization in assisted reproductive technology and for in vitro maturation in fertility preservation programs to improve oocyte quality and the chances for infertile couples to conceive.

What is the threshold of mature oocytes to obtain at least one healthy transferable cleavage-stage embryo after preimplantation genetic testing for fragile X syndrome?

STUDY QUESTION

What are the chances of obtaining a healthy transferable cleavage-stage embryo according to the number of mature oocytes in fragile X mental retardation 1 (FMR1)-mutated or premutated females undergoing preimplantation genetic testing (PGT)?

SUMMARY ANSWER

In our population, a cycle with seven or more mature oocytes has an 83% chance of obtaining one or more healthy embryos.

WHAT IS KNOWN ALREADY

PGT may be an option to achieve a pregnancy with a healthy baby for FMR1 mutation carriers. In addition, FMR1 premutation is associated with a higher risk of diminished ovarian reserve and premature ovarian failure. The number of metaphase II (MII) oocytes needed to allow the transfer of a healthy embryo following PGT has never been investigated.

STUDY DESIGN, SIZE, DURATION

The study is a monocentric retrospective observational study carried out from January 2006 to January 2020 that is associated with a case-control study and that analyzes 38 FMR1 mutation female carriers who are candidates for PGT; 16 carried the FMR1 premutation and 22 had the full FMR1 mutation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 95 controlled ovarian stimulation (COS) cycles for PGT for fragile X syndrome were analyzed, 49 in premutated patients and 46 in fully mutated women. Only patients aged ≤38 years with anti-Müllerian hormone (AMH) >1 ng/ml and antral follicle count (AFC) >10 follicles were eligible for the PGT procedure. Each COS cycle of the FMR1-PGT group was matched with the COS cycles of partners of males carrying any type of translocation (ratio 1:3). Conditional logistic regression was performed to compare the COS outcomes. We then estimated the number of mature oocytes needed to obtain at least one healthy embryo after PGT using receiver operating characteristic curve analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, in the FMR1-PGT group, the median number of retrieved and mature oocytes per cycle was 11 (interquartile range 7-15) and 9 (6-12), respectively. The COS outcomes of FMR1 premutation or full mutation female carriers were not altered compared with the matched COS cycles in partners of males carrying a balanced translocation in their karyotype. Among the 6 (4-10) Day 3 embryos obtained in the FMR1-PGT group, a median number of 3 (1-6) embryos were morphologically eligible for biopsy, leading to 1 (1-3) healthy embryo. A cutoff value of seven MII oocytes yielded a sensitivity of 82% and a specificity of 61% of having at least one healthy embryo, whereas a cutoff value of 10 MII oocytes led to a specificity of 85% and improved positive predictive value.

LIMITATIONS, REASONS FOR CAUTION

This study is retrospective, analyzing a limited number of cycles. Moreover, the patients who were included in a fresh PGT cycle were selected on ovarian reserve parameters and show high values in ovarian reserve tests. This information could influence our conclusion.

WIDER IMPLICATIONS OF THE FINDINGS

The results relate only to the target population of this study, with a correct ovarian reserve of AMH >1 and AFC >10. However, the information provided herein extends knowledge about the current state of COS for FMR1 mutation carriers in order to provide patients with proper counseling regarding the optimal number of oocytes needed to have a chance of transferring an unaffected embryo following PGT.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

N/A.

OTC deficiency in females: Phenotype-genotype correlation based on a 130-family cohort

OTC deficiency, an inherited urea cycle disorder, is caused by mutations in the X-linked OTC gene. Phenotype-genotype correlations are well understood in males but still poorly known in females. Taking advantage of a cohort of 130 families (289 females), we assessed the relative contribution of OTC enzyme activity, X chromosome inactivation, and OTC gene sequencing to genetic counseling in heterozygous females. Twenty two percent of the heterozygous females were clinically affected, with episodic (11%), chronic (7.5%), or neonatal forms of the disease (3.5%). Overall mortality rate was 4%. OTC activity, ranging from 0% to 60%, did not correlate with phenotype at the individual level. Analysis of multiple samples from 4 mutant livers showed intra-hepatic variability of OTC activity and X inactivation profile (range of variability: 30% and 20%, respectively) without correlation between both parameters for 3 of the 4 livers. Ninety disease-causing variants were found, 27 of which were novel. Mutations were classified as "mild" or "severe," based on male phenotypes and/or in silico prediction. In our cohort, a serious disease occurred in 32% of females with a severe mutation, compared to 4% in females with a mild mutation (odds ratio = 1.365; P = 1.6e-06). These data should help prenatal diagnosis for heterozygous females and genetic counseling after fortuitous findings of OTC variants in pangenomic sequencing.

ISSCR Guidelines for Stem Cell Research and Clinical Translation: The 2021 update

The International Society for Stem Cell Research has updated its Guidelines for Stem Cell Research and Clinical Translation in order to address advances in stem cell science and other relevant fields, together with the associated ethical, social, and policy issues that have arisen since the last update in 2016. While growing to encompass the evolving science, clinical applications of stem cells, and the increasingly complex implications of stem cell research for society, the basic principles underlying the Guidelines remain unchanged, and they will continue to serve as the standard for the field and as a resource for scientists, regulators, funders, physicians, and members of the public, including patients. A summary of the key updates and issues is presented here.

Multidisciplinary consensus recommendations from a European network for the diagnosis and practical management of patients with incontinentia pigmenti

BACKGROUND

Incontinentia pigmenti (IP) is a rare multisystemic X-linked dominant genetic disorder characterized by highly diagnostic skin lesions. The disease can be misdiagnosed in infants, and complications affecting the eyes and/or the brain can be severe. Our objective was to highlight the urgency of an appropriate diagnosis and management strategy, as soon as the first symptoms appear, and the need for a well-codified monitoring strategy for each child.

METHODS

An in-depth literature review using a large number of databases was conducted. The selection criteria for articles were literature review articles on the disease, case series and retrospective studies based on the disease, clinical studies (randomized or not) on treatment, articles discussing patient care and management (treatment, diagnosis, care pathways), and recommendations. The research period was from 2000 until 2018. A group of multidisciplinary experts in IP management was involved, issued from different healthcare providers of the European Network for Rare Skin Diseases (ERN-Skin). The final recommendations have been submitted to two patient representative associations and to a general practitioner and a neonatal specialist prior to their finalization.

RESULTS AND CONCLUSION

The diagnosis of IP must be promptly performed to detect potential extracutaneous manifestations, thus allowing the timely implementation of specific therapeutic and monitoring strategies. Eye involvement can be a therapeutic urgency, and central nervous system (CNS) involvement requires a very rigorous long-term follow-up. Assessments and patient support should take into account the possible co-occurrence of various symptoms (including motor, visual and cognitive symptoms).

Biallelic <i>IARS2</i> mutations presenting as sideroblastic anemia

Not available.

A retrospective study on the efficacy of prenatal diagnosis for pregnancies at risk of mitochondrial DNA disorders

PURPOSE

Prenatal diagnosis of mitochondrial DNA (mtDNA) disorders is challenging due to potential instability of fetal mutant loads and paucity of data connecting prenatal mutant loads to postnatal observations. Retrospective study of our prenatal cohort aims to examine the efficacy of prenatal diagnosis to improve counseling and reproductive options for those with pregnancies at risk of mtDNA disorders.

METHODS

We report on a retrospective review of 20 years of prenatal diagnosis of pathogenic mtDNA variants in 80 pregnant women and 120 fetuses.

RESULTS

Patients with undetectable pathogenic variants (n = 29) consistently had fetuses free of variants, while heteroplasmic women (n = 51) were very likely to transmit their variant (57/78 fetuses, 73%). In the latter case, 26 pregnancies were terminated because fetal mutant loads were >40%. Of the 84 children born, 27 were heteroplasmic (mutant load <65%). To date, no medical problems related to mitochondrial dysfunction have been reported.

CONCLUSION

Placental heterogeneity of mutant loads questioned the reliability of chorionic villous testing. Fetal mutant load stability, however, suggests the reliability of a single analysis of amniotic fluid at any stage of pregnancy for prenatal diagnosis of mtDNA disorders. Mutant loads under 40% reliably predict lack of symptoms in the progeny of heteroplasmic women.

Hydrothorax in fetal cases of Opitz G/BBB diagnosis: Extending the phenotype?

We report two fetal cases carrying a de novo MID1 mutation and presenting with severe hydrothorax, suggesting the expansion of the phenotype of Opitz GBBB syndrome.

The challenging management of a series of 43 infants with Netherton syndrome: unexpected complications and novel mutations

BACKGROUND

Netherton syndrome (NS) is a rare disease caused by SPINK5 mutations, featuring variable skin and hair involvement and, in many cases, allergic manifestations with a risk of lethality, particularly in infants. The clinical management of NS is challenging.

OBJECTIVES

To analyse the clinical manifestations of a cohort of infants with NS managed in a reference centre and to draw up recommendations for management.

METHODS

We conducted a monocentric analysis of patients with NS. The inclusion criteria were management in our reference centre, a histologically or molecularly confirmed diagnosis of NS and available epidemiological, clinical and laboratory data.

RESULTS

A total of 43 patients with NS were included. Hypernatraemia was reported in 23 cases (54%) and associated with a greater likelihood of enteral and/or parenteral nutritional support (P < 0.001). Moreover, hypernatraemia was more frequent in patients with skin manifestations at birth (P = 0.026) and in patients bearing the c.153delT mutation in SPINK5 exon 3 (P = 0.014). The need for enteral and/or parenteral nutritional support was associated with a history of hypernatraemic dehydration (P < 0.001). Several unexpected extracutaneous complications were recorded, and new mutations were reported. The death rate (9% overall) was higher among the subset of patients bearing the c.153delT deletion.

CONCLUSIONS

Our data emphasize that neonatal NS is a severe and sometimes lethal multisystem disorder. Patients have a high risk of variable metabolic anomalies (i.e. lethal hypernatraemia) and therefore have major nutritional needs. Cases of NS associated with c.153delT are particularly severe. Unexpected clinical manifestations broadened the phenotypic spectrum of NS. We provide recommendations on the management of the life-threatening manifestations of NS in neonates based on our multidisciplinary experience.

Improving post-natal detection of mitochondrial DNA mutations

INTRODUCTION

Currently, genetic testing of mitochondrial DNA mutations includes screening for single-nucleotide variants, several base pair insertions or deletions, large-scale deletions, or relative depletion of total mitochondrial DNA content. Within the last decade, next-generation sequencing (NGS) has resulted in remarkable advances in the field of mitochondrial diseases (MD) and has become a routine step of the diagnostic workup.

AREAS COVERED

We aimed to present an overview of current technologies employed in molecular diagnosis of mitochondrial DNA diseases. We report on the recent contributions of NGS testing to the diagnosis and understanding of MD.

EXPERT OPINION

The progress of NGS technologies allows the simultaneous detection of mutations and quantification of the heteroplasmy level, ensuring sensitivity and specificity requested for the detection of mitochondrial DNA point mutations. NGS protocols enabling the simultaneous analysis of mitochondrial and nuclear DNA are now efficient and cost-saving approaches, and have become the gold-standard technique in diagnostic laboratories.

CTG Expansion in the DMPK Gene: Semen Quality Assessment and Outcome of Preimplantation Genetic Diagnosis

CONTEXT

Myotonic dystrophy (DM) is an autosomal dominant disorder characterized mainly by myotonia but also by primary hypogonadism. No study has reported on fertility management of patients affected by DM type 1 (DM1).

OBJECTIVE

This study investigates the impact of CTG repeats in the DMPK gene on semen quality and preimplantation genetic diagnosis (PGD) outcome.

DESIGN

This is a monocentric retrospective observational study conducted from January 2003 to January 2019.

SETTING

Antoine Béclère University Hospital, Clamart, France.

PATIENTS

Three groups were compared in this study: male DM1 patients (Group A, n = 18), unaffected partners of DM1 female patients (Group B, n = 30), and proven fertile men (Group C, n = 33). Reproductive outcomes after PGD were compared between groups A and B.

RESULTS

Sperm volume was reduced in group A (2.0 mL) when compared with groups B (3.0 mL; P < 0.01) and C (3.5 mL; P < 0.01). Progressive motility in raw sperm was also decreased in group A (30%) as compared to group C (40%; P < 0.01). The median number of progressive spermatozoa retrieved after sperm preparation was 2.7 million (M) in group A, which was significantly less than those of groups B (10.0 M; P < 0.01) and C (62.2 M; P < 0.01). Sperm motility was inversely correlated to the number of CTG repeats (Spearman r2 = 0.48, Pearson r2 = 0.35). Cumulative live birth rate per transfer was similar between groups, with 32.2% in group A versus 26.8% in group B.

CONCLUSIONS

As a precautionary measure, we advise physicians to perform regular monitoring of semen quality in affected males, which would allow sperm cryopreservation should semen parameters fall. PGD allows good reproductive outcomes without disease transmission.

Xq28 copy number gain causing moyamoya disease and a novel moyamoya syndrome

BACKGROUND

The molecular anomalies causing moyamoya disease (MMD) and moyamoya syndromes (MMS) are unknown in most patients.

OBJECTIVE

This study aimed to identify de novo candidate copy number variants (CNVs) in patients with moyamoya.

METHODS

Rare de novo CNVs screening was performed in 13 moyamoya angiopathy trios using whole exome sequencing (WES) reads depth data and whole genome high density SNP array data. WES and SNP array data from an additional cohort of 115 unrelated moyamoya probands were used to search for recurrence of these rare de novo CNVs.

RESULTS

Two de novo CNVs were identified in two unrelated probands by both methods and confirmed by qPCR. One of these CNVs, located on Xq28, was detected in two additional families. This interstitial Xq28 CNV gain is absent from curated gold standard database of control genomic variants and gnomAD databases. The critical region contains five genes, including MAMLD1, a major NOTCH coactivator. Typical MMD was observed in the two families with a duplication, whereas in the triplicated patients of the third family, a novel MMS associating moyamoya and various systemic venous anomalies was evidenced.

CONCLUSION

The recurrence of this novel Xq28 CNV, its de novo occurrence in one patient and its familial segregation with the affected phenotype in two additional families strongly suggest that it is pathogenic. In addition to genetic counselling application, its association with pulmonary hypertension is of major importance for clinical care. These data also provide new insights into the genomic architecture of this emblematic, non-atherosclerotic, large vessel disease.

Clinical, neuroimaging and biochemical findings in patients and patient fibroblasts expressing ten novel GFM1 mutations

Pathogenic GFM1 variants have been linked to neurological phenotypes with or without liver involvement, but only a few cases have been reported in the literature. Here, we report clinical, biochemical, and neuroimaging findings from nine unrelated children carrying GFM1 variants, 10 of which were not previously reported. All patients presented with neurological involvement-mainly axial hypotonia and dystonia during the neonatal period-with five diagnosed with West syndrome; two children had liver involvement with cytolysis episodes or hepatic failure. While two patients died in infancy, six exhibited a stable clinical course. Brain magnetic resonance imaging showed the involvement of basal ganglia, brainstem, and periventricular white matter. Mutant EFG1 and OXPHOS proteins were decreased in patient's fibroblasts consistent with impaired mitochondrial translation. Thus, we expand the genetic spectrum of GFM1-linked disease and provide detailed clinical profiles of the patients that will improve the diagnostic success for other patients carrying GFM1 mutations.

Expanding the clinical spectrum of MTTF mutations

We report on a de novo m.586G > A MTTF mutation in a 14 yrs old boy with non-progressive muscle weakness, myalgia, normal brain MRI, normal schooling and absent central nervous system involvement. The same m.586G > A MTTF mutation has been previously reported in a 57 yrs-old woman with a progressive neurodegenerative disorder, akinesia-rigidity, abnormal movements, dementia, and psychiatric disorder. Those two strikingly different clinical presentations emphasize the impact of either mitochondrial factors (heteroplasmy, mitotic segregation) or hitherto unknown nuclear factors on the clinical expression of genetically homogeneous mtDNA mutations.

The clinical utility of PGD with HLA matching: a collaborative multi-centre ESHRE study

STUDY QUESTION

Has PGD-HLA been successful relative to diagnostic and clinical efficacy?

SUMMARY ANSWER

The diagnostic efficacy of PGD-HLA protocols was found lower in this study in comparison to published PGD-HLA protocols and to that reported for general PGD by ESHRE (78.5 vs 94.1% and vs 92.6%, respectively), while the clinical efficacy has proven very difficult to assess due to inadequate follow-up of both the ART/PGD and HSCT procedure outcomes.

WHAT IS KNOWN ALREADY

The first clinical cases for PGD-HLA were reported in 2001. It is now a well-established procedure, with an increasing number of cycles performed every year. However, PGD-HLA is still offered by relatively few PGD centres, the currently available data is fragmented and most reports on PGD-HLA applications are limited in number and scope. Published systematic details on methodology, diagnostic results, overall ART success and haematopoietic stem cell transplantation (HSCT) outcomes are limited, precluding an evaluation of the true clinical utility of PGD-HLA cycles.

STUDY DESIGN, SIZE, DURATION

This retrospective multi-centre cohort study aimed to investigate the diagnostic and clinical efficacy of the PGD-HLA procedure and the aspects of PGD-HLA cycles influencing positive outcomes: birth of genetically suitable donor-baby (or babies) and HSCT. In April 2014, 32 PGD centres (Consortium members and non-members) with published/known PGD-HLA activity were invited to participate. Between February and September 2015, 14 centres submitted their data, through a custom-designed secure database, with unique login access for each centre. Data parameters covered all aspects of PGD-HLA cycles (ART, embryology and genetic diagnosis), donor-babies born and HSCT.

PARTICIPANTS/MATERIALS, SETTING, METHODS

From 716 cycles submitted by 14 centres (performed between August 2001 and September 2015), the quality evaluation excluded 12 cycles, leaving 704, from 364 couples. The online database, based on REDCap, a free, secure, web-based data-capture application, was customized by Centre for Clinical Epidemiology and Outcomes Research (CLEO), Athens. Continuous variables are presented using mean, standard deviation, median and interquartile range, and categorical variables are presented as absolute and relative frequencies.

MAIN RESULTS AND THE ROLE OF CHANCE

The data included 704 HLA-PGD cycles. Mean maternal age was 33.5 years. Most couples (81.3%) requested HLA-typing with concurrent exclusion of a single monogenic disease (58.6% for beta-thalassaemia). In 92.5% couples, both partners were fertile, with an average 1.93 HLA-PGD cycles/couple. Overall, 9751 oocytes were retrieved (13.9/cycle) and 5532 embryos were analysed (7.9/cycle). Most cycles involved fresh oocytes (94.9%) and Day 3 embryo biopsy (85.3%). In 97.5% of cycles, the genotyping method involved PCR only. Of 4343 embryos diagnosed (78.5% of analysed embryos), 677 were genetically suitable (15.4% of those analysed for HLA alone, 11.6% of those analysed for HLA with exclusion of monogenic disease). Of the 364 couples, 56.6% achieved an embryo transfer (ET) and 598 embryos were transferred in 382 cycles, leading to 164 HCG-positive pregnancies (pregnancy rate/ET 41.3%, pregnancy rate/initiated cycle 23.3%) and 136 babies born (live birth rate/ET 34.3%, live birth rate/initiated cycle 19.3%) to 113 couples. Data analysis identified the following limitations to the overall success of the HLA-PGD procedure: the age of the mother undergoing the treatment cycle, the number of oocytes collected per cycle and genetic chance. HSCT was reported for 57 cases, of which 64.9% involved combined umbilical cord-blood and bone marrow transplantation from the HLA-identical sibling donor; 77.3% of transplants reported no complications.

LIMITATIONS REASONS FOR CAUTION

The findings of the study may be limited as not all PGD centres with PGD-HLA experience participated. Reporting bias on completion of the online database may be another potential limitation. Furthermore, the study is based on retrospective data collection from centres with variable practices and strategies for ART, embryology and genetic diagnosis.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first multi-centre study evaluating the clinical utility of PGD-HLA, indicating variations in practice and outcomes throughout 15 years and between centres. The study highlights parameters important for positive outcomes and provides important information for both scientists and couples interested in initiating a cycle. Above all, the study underlines the need for better collaboration between all specialists involved in the ART-PGD/HLA procedure, as well as the need for comprehensive and prospective long-term data collection, and encourages all specialists to aim to properly evaluate and follow-up all procedures, with the ultimate aim to promote best practice and encourage patient informed decision making.

STUDY FUNDING/COMPETING INTEREST(S)

The study wishes to acknowledge ESHRE for funding the customization of the REDCap database. There are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Increased incidence of obstetric complications in women carrying mitochondrial DNA mutations: a retrospective cohort study in a single tertiary centre

OBJECTIVE

To investigate the obstetric outcome of women carriers of the oxidative phosphorylation (OXPHOS) disorder mutation.

DESIGN

A retrospective cohort study in a single tertiary centre.

SETTING

A review of the obstetric history of women referred for prenatal screening of a mitochondrial disorder was performed.

POPULATION

Women were divided into three groups: (1) women carrying mitochondrial DNA (mtDNA) mutations; (2) healthy women with a family history of mtDNA-related OXPHOS disorder; and (3) healthy women carrying heterozygote nuclear DNA mutations.

METHODS

Obstetric history and pregnancy complications were evaluated separately in the three groups and compared with the control group. MAIN OUTCOME MEASURES PREGNANCY COMPLICATIONS.

RESULTS

Seventy-five women were included with 287 cumulative pregnancies. Groups 1 and 3 had a significantly greater proportion of terminations of pregnancy (20 and 13% versus 0.8%, P < 0.001), and a lower percentage of live births (52 and 72% versus 87%, P = 0.001), compared with controls. Apart from this, the rate of obstetric complications in group 3 did not differ from the controls. The obstetric history of women in group 1 was marked by higher rates of early miscarriages (26 versus 11%, P = 0.004), gestational diabetes (14 versus 3%, P = 0.02), intrauterine growth restriction (IUGR, 10 versus 1%, P = 0.008), and postpartum haemorrhage than were reported for controls (12 versus 2%, P = 0.01).

CONCLUSION

Women who are heteroplasmic for OXPHOS mutations have a higher incidence of pregnancy losses, gestational diabetes, IUGR, and post postpartum haemorrhage.

TWEETABLE ABSTRACT

Women heteroplasmic for mitochondrial DNA mutations have a higher incidence of obstetric complications, compared with the control group.

Increased incidence of obstetric complications in women carrying mitochondrial DNA mutations: a retrospective cohort study in a single tertiary centre

OBJECTIVE

To investigate the obstetric outcome of women carriers of the oxidative phosphorylation (OXPHOS) disorder mutation.

DESIGN

A retrospective cohort study in a single tertiary centre.

SETTING

A review of the obstetric history of women referred for prenatal screening of a mitochondrial disorder was performed.

POPULATION

Women were divided into three groups: (1) women carrying mitochondrial DNA (mtDNA) mutations; (2) healthy women with a family history of mtDNA-related OXPHOS disorder; and (3) healthy women carrying heterozygote nuclear DNA mutations.

METHODS

Obstetric history and pregnancy complications were evaluated separately in the three groups and compared with the control group. MAIN OUTCOME MEASURES PREGNANCY COMPLICATIONS.

RESULTS

Seventy-five women were included with 287 cumulative pregnancies. Groups 1 and 3 had a significantly greater proportion of terminations of pregnancy (20 and 13% versus 0.8%, P < 0.001), and a lower percentage of live births (52 and 72% versus 87%, P = 0.001), compared with controls. Apart from this, the rate of obstetric complications in group 3 did not differ from the controls. The obstetric history of women in group 1 was marked by higher rates of early miscarriages (26 versus 11%, P = 0.004), gestational diabetes (14 versus 3%, P = 0.02), intrauterine growth restriction (IUGR, 10 versus 1%, P = 0.008), and postpartum haemorrhage than were reported for controls (12 versus 2%, P = 0.01).

CONCLUSION

Women who are heteroplasmic for OXPHOS mutations have a higher incidence of pregnancy losses, gestational diabetes, IUGR, and post postpartum haemorrhage.

TWEETABLE ABSTRACT

Women heteroplasmic for mitochondrial DNA mutations have a higher incidence of obstetric complications, compared with the control group.

Pitfalls in molecular diagnosis of Friedreich ataxia

Freidreich ataxia (FRDA) is the most common hereditary ataxia, nearly 98% of patients harbouring homozygous GAA expansions in intron 1 of the FXN gene (NM_000144.4). The remaining patients are compound heterozygous for an expansion and a point mutation or an exonic deletion. Molecular screening for FXN expansion is therefore focused on (GAA)n expansion analysis, commonly performed by triplet repeat primed PCR (PT-PCR). We report on an initial pitfall in the molecular characterization of a 15 year-old girl with Freidreich ataxia (FRDA) who carried a rare deletion in intron 1 of the FXN gene. Due to this deletion TP-PCR failed to amplify the GAA expansion. This exceptional configuration induced misinterpretation of the molecular defect in this patient, who was first reported as having no FXN expansion. NGS analysis of a panel of 212 genes involved in nuclear mitochondrial disorders further revealed an intragenic deletion encompassing exons 4-5 of the FXN gene. Modified TP-PCR analysis confirmed the presence of a classical (GAA)n expansion located in trans. This case points out the possible pitfalls in molecular diagnosis of FRDA in affected patients and their relatives: detection of the FXN expansion may be impaired by several non-pathological or pathological variants around the FXN (GAA)n repeat. We propose a new molecular strategy to accurately detect expansion by TP-PCR in FRDA patients.

Severe neuroimaging anomalies are usually associated with random X inactivation in leucocytes circulating DNA in X-linked dominant Incontinentia Pigmenti

Incontinentia Pigmenti (IP) is a skin disorder with neurological impairment in 30% of cases. The most common disease causing mutation is a deletion of exons 4-10 of the IKBKG gene, located on chromosome Xq28, with skewed X-chromosome inactivation in females, but few cases of random X-inactivation have been reported. We have correlated brain anomalies with X-chromosome inactivation status determined on leucocytes circulating DNA. We reviewed MRI of 18 girls with genetically proven IP. We found three patterns of MRI, normal MRI (n=5), mild white matter abnormalities with cortical and corpus callosum atrophy (n=6), and severe cortical abnormalities suggesting a vascular disease (n=7). Most patients with severe abnormalities had random X-inactivation (6/7,86%), while 80% (4/5) of patients with normal MRI and 100% (6/6) of patients with mild white matter abnormalities had skewed inactivation. These results suggest that skewed chromosome X-inactivation may protect brain from damage, while in case of random inactivation, expression of the mutated IKBKG gene may lead to severe brain lesions.

[Nuclear transfer to prevent transmission of mtDNA disorders: where are we?]

The recent birth from a mitochondrial DNA mutation carrier of a child, conceived after transfer in a donor oocyte of the meiotic spindle, taken from the maternal oocyte, revived the debate on the safety of these procedures. The doubts concern mainly the possibility of genetic reversion, the uncertainties about potential disturbances of the dialogue between nuclear and mitochondrial genomes and the side effects of a heteroplasmic state induced by these techniques. The possibility to expand nuclear transfer applications to patients experiencing in vitro fertilization failure, urges us to answer these questions rapidly.

Segregation of mitochondrial DNA mutations in the human placenta: implication for prenatal diagnosis of mtDNA disorders

Background

Mitochondrial DNA (mtDNA) disorders have a high clinical variability, mainly explained by variation of the mutant load across tissues. The high recurrence risk of these serious diseases commonly results in requests from at-risk couples for prenatal diagnosis (PND), based on determination of the mutant load on a chorionic villous sample (CVS). Such procedures are hampered by the lack of data regarding mtDNA segregation in the placenta.

The objectives of this report were to determine whether mutant loads (1) are homogeneously distributed across the whole placentas, (2) correlate with those in amniocytes and cord blood cells and (3) correlate with the mtDNA copy number.

Methods

We collected 11 whole placentas carrying various mtDNA mutations (m.3243A>G, m.8344A>G, m.8993T>G, m.9185T>C and m.10197G>A) and, when possible, corresponding amniotic fluid samples (AFSs) and cord blood samples. We measured mutant loads in multiple samples from each placenta (n= 6–37), amniocytes and cord blood cells, as well as total mtDNA content in placenta samples.

Results

Load distribution was homogeneous at the sample level when average mutant load was low (<20%) or high (>80%) at the whole placenta level. By contrast, a marked heterogeneity was observed (up to 43%) in the intermediate range (20%–80%), the closer it was to 40%–50% the mutant load, the wider the distribution. Mutant loads were found to be similar in amniocytes and cord blood cells, at variance with placenta samples. mtDNA content correlated to mutant load in m.3243A>G placentas only.

Conclusion

These data indicate that (1) mutant load determined from CVS has to be interpreted with caution for PND of some mtDNA disorders and should be associated with/substituted by a mutant load measurement on amniocytes; (2) the m.3243A>G mutation behaves differently from other mtDNA mutations with respect to the impact on mtDNA copy number, as previously shown in human preimplantation embryogenesis.

Lack of interaction between NEMO and SHARPIN impairs linear ubiquitination and NF-κB activation and leads to incontinentia pigmenti

BACKGROUND

Incontinentia pigmenti (IP; MIM308300) is a severe, male-lethal, X-linked, dominant genodermatosis resulting from loss-of-function mutations in the IKBKG gene encoding nuclear factor κB (NF-κB) essential modulator (NEMO; the regulatory subunit of the IκB kinase [IKK] complex). In 80% of cases of IP, the deletion of exons 4 to 10 leads to the absence of NEMO and total inhibition of NF-κB signaling. Here we describe a new IKBKG mutation responsible for IP resulting in an inactive truncated form of NEMO.

OBJECTIVES

We sought to identify the mechanism or mechanisms by which the truncated NEMO protein inhibits the NF-κB signaling pathway.

METHODS

We sequenced the IKBKG gene in patients with IP and performed complementation and transactivation assays in NEMO-deficient cells. We also used immunoprecipitation assays, immunoblotting, and an in situ proximity ligation assay to characterize the truncated NEMO protein interactions with IKK-α, IKK-β, TNF receptor-associated factor 6, TNF receptor-associated factor 2, receptor-interacting protein 1, Hemo-oxidized iron regulatory protein 2 ligase 1 (HOIL-1), HOIL-1-interacting protein, and SHANK-associated RH domain-interacting protein. Lastly, we assessed NEMO linear ubiquitination using immunoblotting and investigated the formation of NEMO-containing structures (using immunostaining and confocal microscopy) after cell stimulation with IL-1β.

RESULTS

We identified a novel splice mutation in IKBKG (c.518+2T>G, resulting in an in-frame deletion: p.DelQ134_R256). The mutant NEMO lacked part of the CC1 coiled-coil and HLX2 helical domain. The p.DelQ134_R256 mutation caused inhibition of NF-κB signaling, although the truncated NEMO protein interacted with proteins involved in activation of NF-κB signaling. The IL-1β-induced formation of NEMO-containing structures was impaired in fibroblasts from patients with IP carrying the truncated NEMO form (as also observed in HOIL-1^-/- cells). The truncated NEMO interaction with SHANK-associated RH domain-interacting protein was impaired in a male fetus with IP, leading to defective linear ubiquitination.

CONCLUSION

We identified a hitherto unreported disease mechanism (defective linear ubiquitination) in patients with IP.