Homozygous GLI3 variants observed in three unrelated patients presenting with syndromic polydactyly

Polydactyly is a hallmark of GLI3 pathogenic variants, with Greig cephalopolysyndactyly syndrome and Pallister-Hall syndrome being the two main associated clinical presentations. Homozygous GLI3 variants are rare instances in the literature, and mendelian dominance is the accepted framework for GLI3-related diseases. Herein, we report three unrelated probands, presenting with polydactyly, and homozygous variants in the GLI3 gene. First, a 10-year-old girl, whose parents were first-degree cousins, presented with bilateral postaxial polydactyly of the hands, developmental delay and multiple malformations. Second, a male newborn, whose parents were first-degree cousins, presented with isolated bilateral postaxial polysyndactyly of the hands and the feet. Third, an adult male, whose parents were first-degree cousins, had bilateral mesoaxial polydactyly of the hands, with severe intellectual disability and multiple malformations. All three probands carried homozygous GLI3 variants. Strikingly, the parents also carried the child's variant, in the heterozygous state, without any clinical sign of GLI3 disease. Given the clinical presentation of our patients, the rarity and predicted high pathogenicity of the variants observed, and the absence of other pathogenic variants, we suggest that these GLI3 homozygous variants are causal. Moreover, the parents were heterozygous for the observed variants, but were clinically unremarkable, suggesting that these variants are hypomorphic alleles.

Cost-effectiveness of five prenatal screening strategies for trisomies and other unbalanced chromosomal abnormalities: model-based analysis

OBJECTIVE

To evaluate the cost-effectiveness of five prenatal screening strategies for trisomies (13/18/21) and other unbalanced chromosomal abnormalities (UBCA), following the introduction of cell-free DNA (cfDNA) analysis.

METHODS

A model-based cost-effectiveness analysis was performed to estimate prevalence, safety, screening-program costs and healthcare costs of five different prenatal screening strategies, using a virtual cohort of 652 653 pregnant women in France. Data were derived from the French Biomedicine Agency and published articles. Uncertainty was addressed using one-way sensitivity analysis. The five strategies compared were: (i) cfDNA testing for women with a risk following first-trimester screening of ≥ 1/250; (ii) cfDNA testing for women with a risk of ≥ 1/1000 (currently recommended); (iii) cfDNA testing in the general population (regardless of risk); (iv) invasive testing for women with a risk of ≥ 1/250 (historical strategy); and (v) invasive testing for women with a risk of ≥ 1/1000.

RESULTS

In our virtual population, at similar risk thresholds, cfDNA testing compared with invasive testing was cheaper but less effective. Compared with the historical strategy, cfDNA testing at the ≥ 1/1000 risk threshold was a more expensive strategy that detected 158 additional trisomies, but also 175 fewer other UBCA. Implementation of cfDNA testing in the general population would give an incremental cost-effectiveness ratio of €9 166 689 per additional anomaly detected compared with the historical strategy.

CONCLUSION

Extending cfDNA to lower risk thresholds or even to all pregnancies would detect more trisomies, but at greater expense and with lower detection rate of other UBCA, compared with the historical strategy. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Novel de novo ZBTB20 mutations in three cases with Primrose syndrome and constant corpus callosum anomalies

Corpus callosum (CC) is the major brain commissure connecting homologous areas of cerebral hemispheres. CC anomalies (CCAs) are the most frequent brain anomalies leading to variable neurodevelopmental outcomes making genetic counseling difficult in the absence of a known etiology that might inform the prognosis. Here, we used whole exome sequencing, and a targeted capture panel of syndromic CCA known causal and candidate genes to screen a cohort of 64 fetuses with CCA observed upon autopsy, and 34 children with CCA and intellectual disability. In one fetus and two patients, we identified three novel de novo mutations in ZBTB20, which was previously shown to be causal in Primrose syndrome. In addition to CCA, all cases presented with additional features of Primrose syndrome including facial dysmorphism and macrocephaly or megalencephaly. All three variations occurred within two out of the five zinc finger domains of the transcriptional repressor ZBTB20. Through homology modeling, these variants are predicted to result in local destabilization of each zinc finger domain suggesting subsequent abnormal repression of ZBTB20 target genes. Neurohistopathological analysis of the fetal case showed abnormal regionalization of the hippocampal formation as well as a reduced density of cortical upper layers where originate most callosal projections. Here, we report novel de novo ZBTB20 mutations in three independent cases with characteristic features of Primrose syndrome including constant CCA. Neurohistopathological findings in fetal case corroborate the observed key role of ZBTB20 during hippocampal and neocortical development. Finally, this study highlights the crucial role of ZBTB20 in CC development in human.

Women's Attitudes Toward Invasive and Noninvasive Testing When Facing a High Risk of Fetal Down Syndrome

IMPORTANCE

Noninvasive prenatal testing (NIPT) using cell-free DNA in maternal blood is increasingly common compared with invasive testing (IT) in routine antenatal detection of Down syndrome (DS).

OBJECTIVE

To assess attitudes and decision making in pregnant women facing a risk of fetal DS greater than 1 in 250 as established by combined first trimester screening at 11 to 14 weeks of gestation.

DESIGN, SETTING, AND PARTICIPANTS

Survey study in which data were collected from pregnant women at high risk of fetal DS participating in a randomized clinical trial. Data were collected from April 8, 2014, to April 7, 2016, in 57 prenatal diagnosis centers in France. Data were analyzed in 2018.

INTERVENTIONS

Data on attitudes were collected prior to offering randomization between NIPT and IT, whereas data on decision making and test results were collected as part of the clinical trial.

MAIN OUTCOME AND MEASURES

The primary outcome related to attitudes. A hierarchical cluster analysis was conducted to identify clusters with contrasting attitudes. Logistic regression analyses were used to identify factors associated with attitudes.

RESULTS

All 2436 consecutive women to whom the study was proposed (mean [SD] age, 36.3 [5.0] years) answered the questionnaire: 515 (21.1%) expressed preference toward IT with complete karyotyping, whereas 1843 (75.7%) favored NIPT with almost certain but limited information. Hierarchical cluster analysis yielded 4 different clusters that mainly differed in attitudes toward risk taking and extent of information seeking. Factors likely associated with attitudes driven by risk aversion were mostly age and religious beliefs (adjusted odds ratio [aOR], 1.03; 95% CI, 1.00-1.05; P = .03 and aOR, 1.62; 95% CI, 1.29-2.04; P < .001, respectively), whereas higher nuchal translucency measurements by ultrasonography were associated with attitudes driven by ambiguity aversion (aOR, 1.67; 95% CI, 1.27-2.20; P < .001). For attitudes involving both risk and ambiguity aversion at different extents, lower education was associated with highly valuing all possibilities of getting information on pregnancy, whereas higher education was associated with highly valuing information on fetal DS as a primary concern (aOR, 0.54; 95% CI, 0.44-0.67; P < .001 and aOR, 1.44; 95% CI, 1.20-1.74; P < .001, respectively). In all, decision making was in line with attitudes.

CONCLUSIONS AND RELEVANCE

Aversion to risk of fetal loss related to IT and aversion to ambiguity generated by incomplete information from NIPT played a major role in shaping attitudes and decision making. Informed decision making should require pregnant women at high risk of DS to receive extensive information on targeted abnormalities by both tests.

Diagnostic yield of chromosomal microarray analysis in fetuses with isolated increased nuchal translucency: a French multicenter study

OBJECTIVE

To determine the frequency and nature of copy number variants (CNVs) identified by chromosomal microarray analysis (CMA) in a large cohort of fetuses with isolated increased nuchal translucency thickness (NT) ≥ 3.5 mm.

METHODS

This was a retrospective, multicenter study, including 11 French hospitals, of data from the period between April 2012 and December 2015. In total, 720 fetuses were analyzed by rapid aneuploidy test and the fetuses identified as euploid underwent CMA. CNVs detected were evaluated for clinical significance and classified into five groups: pathogenic CNVs; benign CNVs; CNVs predisposing to neurodevelopmental disorders; variants of uncertain significance (VOUS); and CNVs not related to the phenotype (i.e. incidental findings).

RESULTS

In 121 (16.8%) fetuses, an aneuploidy involving chromosome 13, 18 or 21 was detected by rapid aneuploidy test and the remaining 599 fetuses were euploid. Among these, 53 (8.8%) had a CNV detected by CMA: 16/599 (2.7%) were considered to be pathogenic, including 11/599 (1.8%) that were cryptic (not visible by karyotyping); 7/599 (1.2%) were CNVs predisposing to neurodevelopmental disorders; and 8/599 (1.3%) were VOUS. Additionally, there was one (0.2%) CNV that was unrelated to the reason for referral diagnosis (i.e. an incidental finding) and the remaining 21 were benign CNVs, without clinical consequence. Interestingly, we identified five genomic imbalances of the 1q21.1 or 15q11.2 regions known to be associated with congenital heart defects.

CONCLUSION

Our study demonstrates the benefit of CMA in the etiological diagnosis of fetuses with isolated increased NT. It is worth noting that most (69%) of the detected pathogenic CNVs were cryptic. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Corpus Callosum Abnormalities and Short Femurs in Beckwith-Wiedemann Syndrome: A Report of Two Fetal Cases

INTRODUCTION

Beckwith-Wiedemann syndrome (BWS) is the most common overgrowth syndrome. Clinical features are highly variable, including occasional posterior fossa malformations but no femoral shortening.

CASE REPORT

We report two fetuses with BWS associated with short femurs and corpus callosum hypoplasia. Case 2 was growth restricted. BWS was confirmed by molecular studies showing a loss of methylation at ICR2 at 11p15 chromosomic region in case 1 and a gain of methylation at ICR1 and a loss of methylation at ICR2 locus in case 2.

CONCLUSION

Although the phenotype and the genotype of BWS is now well-known, the presence of corpus callosum abnormalities and short femurs expand the phenotypic spectrum of the disorder.

A clinical and histopathological study of malformations observed in fetuses infected by the Zika virus

BACKGROUND

The recent outbreak of Zika virus (ZIKV) infection and the associated increased prevalence of microcephaly in Brazil underline the impact of viral infections on embryo fetal development. The aim of the present study is to provide a detailed clinical and histopathological study of the fetal disruption caused by the ZIKV, with a special focus on the associated neuropathological findings.

METHODS

A detailed feto-placental examination, as well as neuropathological and neurobiological studies were performed on three fetuses collected after pregnancy termination between 22 and 25 weeks of gestation (WG), because brain malformations associated with a maternal and fetal ZIKV infection was diagnosed.

RESULTS

In all three cases, the maternal infection occurred during the first trimester of pregnancy. A small head was observed on the ultrasound examination of the second trimester of pregnancy and led to the diagnosis of ZIKV fetopathy and pregnancy termination. The fetal histopathological examination was unremarkable on the viscera but showed on the testis an interstitial lymphocytic infiltrate. The placenta contained a Hofbauer cells hyperplasia with signs of inflammation. Neuropathological findings included a meningoencephalitis and an ex vacuo hydrocephalus. Immunohistochemical studies showed the presence of T lymphocytic and histiocytic meningitis associated with an abundant cerebral astroglial and macrophagic reaction. In situ hybridization demonstrated, abundant ZIKV particles within the cerebral parenchyma mainly in the ventricular/subventricular zone and in the cortical plate. In addition massive cells death and endoplasmic reticulum damage were present.

CONCLUSION

The present study reports on the clinical and histopathological findings observed in three fetuses infected by the ZIKV. It emphasizes the severity of brain damages and the minimal visceral and placental changes observed upon ZIKV infection. This confirms the selective neurotropism of ZIKV. Finally, it allows us to describe the cascade of multifactorial developmental defects leading to microcephaly.

Effect of Cell-Free DNA Screening vs Direct Invasive Diagnosis on Miscarriage Rates in Women With Pregnancies at High Risk of Trisomy 21: A Randomized Clinical Trial

IMPORTANCE

Cell-free DNA (cfDNA) tests are increasingly being offered to women in the first trimester of pregnancies at a high risk of trisomy 21 to decrease the number of required invasive fetal karyotyping procedures and their associated miscarriages. The effect of this strategy has not been evaluated.

OBJECTIVE

To compare the rates of miscarriage following invasive procedures only in the case of positive cfDNA test results vs immediate invasive testing procedures (amniocentesis or chorionic villus sampling) in women with pregnancies at high risk of trisomy 21 as identified by first-trimester combined screening.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial conducted from April 8, 2014, to April 7, 2016, in 57 centers in France among 2111 women with pregnancies with a risk of trisomy 21 between 1 in 5 and 1 in 250 following combined first-trimester screening.

INTERVENTIONS

Patients were randomized to receive either cfDNA testing followed by invasive testing procedures only when cfDNA tests results were positive (n = 1034) or to receive immediate invasive testing procedures (n = 1017). The cfDNA testing was performed using an in-house validated method based on next-generation sequencing.

MAIN OUTCOMES AND MEASURES

The primary outcome was number of miscarriages before 24 weeks' gestation. Secondary outcomes included cfDNA testing detection rate for trisomy 21. The primary outcome underwent 1-sided testing; secondary outcomes underwent 2-sided testing.

RESULTS

Among 2051 women who were randomized and analyzed (mean age, 36.3 [SD, 5.0] years), 1997 (97.4%) completed the trial. The miscarriage rate was not significantly different between groups at 8 (0.8%) vs 8 (0.8%), for a risk difference of -0.03% (1-sided 95% CI, -0.68% to ∞; P = .47). The cfDNA detection rate for trisomy 21 was 100% (95% CI, 87.2%-100%).

CONCLUSIONS AND RELEVANCE

Among women with pregnancies at high risk of trisomy 21, offering cfDNA screening, followed by invasive testing if cfDNA test results were positive, compared with invasive testing procedures alone, did not result in a significant reduction in miscarriage before 24 weeks. The study may have been underpowered to detect clinically important differences in miscarriage rates.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02127515.

A neuropathological study of novel RTTN gene mutations causing a familial microcephaly with simplified gyral pattern

BACKGROUND

The RTTN gene encodes Rotatin, a large centrosomal protein involved in ciliary functions. RTTN mutations have been reported in seven families and are associated with two phenotypes: polymicrogyria associated with seizures and primary microcephaly associated with primordial dwarfism.

CASE

A targeted exome sequencing of morbid genes causing cerebral malformations identified novel RTTN compound heterozygous mutations in a family where three pregnancies were terminated because a severe fetal microcephaly was diagnosed. An autopsy performed on the second sib showed moderate growth restriction and a microcephaly with simplified gyral pattern. The histopathological study discovered a malformed cortical plate.

CONCLUSIONS

The present study confirms the involvement of RTTN gene mutations in microcephaly with simplified gyral pattern and describes the observed abnormal neuropathological findings.

In utero ultrasound diagnosis of corpus callosum agenesis leading to the identification of orofaciodigital type 1 syndrome in female fetuses

BACKGROUND

OFD1 syndrome is a rare ciliopathy inherited on a dominant X-linked mode, typically lethal in males in the first or second trimester of pregnancy. It is characterized by oral cavity and digital anomalies possibly associated with cerebral and renal signs. Its prevalence is between 1/250,000 and 1/50,000 births. It is due to heterozygous mutations of OFD1 and mutations are often de novo (75%). Familial forms show highly variable phenotypic expression. OFD1 encodes a protein involved in centriole growth, distal appendix formation, and ciliogenesis.

CASES

We report the investigation of three female fetuses in which corpus callosum agenesis was detected by ultrasound during the second trimester of pregnancy. In all three fetuses, fetopathological examination allowed the diagnosis of OFD1 syndrome, which was confirmed by molecular analysis.

CONCLUSIONS

To our knowledge, these are the first case reports of antenatal diagnosis of OFD1 syndrome in the absence of familial history, revealed following detection of agenesis of the corpus callosum. They highlight the impact of fetal examination following termination of pregnancy for brain malformations. They also highlight the contribution of ciliary genes to corpus callosum development.

Large Duplications Can Be Benign Copy Number Variants: A Case of a 3.6-Mb Xq21.33 Duplication

Segmental aneusomies are usually associated with clinical consequences, but an increasing number of nonpathogenic cytogenetically visible as well as large cryptic chromosomal imbalances have been reported. Here, we report a 3.6-Mb Xq21.33 microduplication detected prenatally on a female fetus which was inherited from a phenotypically normal mother and grandfather. It is assumed that male patients harboring Xq or Xp duplication present with syndromic intellectual disability because of functional disomy of the corresponding genes. Female carriers are generally asymptomatic because of preferential inactivation of the abnormal X. In the present case, the 3.6-Mb-duplicated segment encompasses only 2 genes, DIAPH2 and RPL4A. Since the asymptomatic grandfather carries the duplication, we hypothesize that these genes are not dosage sensitive and/or involved in cognitive function. Our observation further illustrates that large copy number variants can be associated with a normal phenotype, especially where gene density is low. Reporting rare cases of large genomic imbalances without a phenotypic effect can be very helpful, especially for genetic counseling in the prenatal setting.

A tumor profile in Edwards syndrome (trisomy 18)

Constitutional trisomy 18 causes Edwards syndrome, which is characterized by intellectual disability and a particular set of malformations. Although this condition carries high mortality during prenatal and early postnatal life, some of the rare infants who survive the first months develop benign and malignant tumors. To determine the tumor profile associated with Edwards syndrome, we performed a systematic review of the literature. This review reveals a tumor profile differing from those of Down (trisomy 21) and Patau (trisomy 13) syndromes. The literature covers 45 malignancies: 29 were liver cancers, mainly hepatoblastomas found in Japanese females; 13 were kidney tumors, predominantly nephroblastomas; 1 was neuroblastoma; 1 was a Hodgkin disease; and 1 was acute myeloid leukemia in an infant with both trisomy 18 and type 1 neurofibromatosis. No instances of the most frequent malignancies of early life-cerebral tumors, germ cell tumors, or leukemia--are reported in children with pure trisomy 18. Tumor occurrence does not appear to correlate with body weight, tissue growth, or cancer genes mapping to chromosome 18. Importantly, the most recent clinical histories report successful treatment; this raises ethical concerns about cancer treatment in infants with Edwards syndrome. In conclusion, knowledge of the Edwards' syndrome tumor profile will enable better clinical surveillance in at-risk organs (i.e., liver, kidney). This knowledge also provides clues to understanding oncogenesis, including the probably reduced frequency of some neoplasms in infants and children with this genetic condition. © 2016 Wiley Periodicals, Inc.

Non-invasive prenatal testing for trisomy 21 based on analysis of cell-free fetal DNA circulating in the maternal plasma

OBJECTIVE

By-the-book implementation of non-invasive prenatal test and clinical validation for trisomy 21.

STUDY DESIGN

Publicly funded prospective study of 225 cases. Women at risk for trisomy 21 > 1/250 based on combined ultrasound and serum markers during first or second trimester were eligible following an informed consent. The technique was established from the available literature and performed on 10 mL of venous blood collected prior to chorionic villus sampling or amniocentesis. Investigators were blinded to the fetal karyotype. Results were expressed in Z-scores of the percentage of each chromosome.

RESULTS

Among 976 eligible cases, 225 were processed: 8 were used for pretesting phase and 23 to build a reference set. One hundred thirty six euploid cases and 47 with trisomy 21 were then run randomly. Eleven cases yielded no result (4.8%). Z-scores were above 3 (7.58+/-2.41) for chromosome 21 in all 47 trisomies and in none of the euploid cases (0.11+/-1.0). Z-scores were within normal range for the other chromosomes in both groups. Using a cut-off of 3, sensitivity and specificity were of 100% 95% CI [94.1, 100] and 100% 95% CI [98, 100], respectively.

CONCLUSION

Non-invasive prenatal test for trisomy 21 is a robust strategy that can be translated from seminal publications. Publicly funded studies should refine its indications and cost-effectiveness in prenatal screening and diagnosis. © 2015 John Wiley & Sons, Ltd.

A French Approach to Test Fetuses with Ultrasound Abnormalities Using a Customized Microarray as First-Tier Genetic Test

Cytogenetic microarray analysis is now the first-tier genetic test used in a postnatal clinical setting to explore genomic imbalances in individuals with developmental disability and/or birth defects. However, in a prenatal setting, this technique is not widely implemented, largely because the clinical impact of some copy number variants (CNVs) remains difficult to assess. This limitation is especially true in France where termination of pregnancy for medical reasons may be performed at any stage of gestation. During a period of 15 months, we investigated 382 fetuses presenting with ultrasound anomalies, using a customized microarray designed to avoid the detection of CNVs raising challenges for genetic counseling. After excluding common aneuploidies, 20/374 (5.3%) fetuses had a pathogenic CNV, among which 12/374 (3.2%) could have been detected by karyotyping, whereas 8/374 (2.1%) were cryptic. Within these 374 cases, 300 were ongoing pregnancies at the time of array comparative genomic hybridization (aCGH) testing. For these pregnancies, we detected 18/300 (6%) pathogenic CNVs, among which 6/300 (2%) were cryptic. Using this approach, only 2/300 (0.6%) of the detected CNVs raised difficulties for genetic counseling. This study confirms the added value of this strategy in a prenatal clinical setting to minimize ethical issues for genetic counseling while enhancing the detection of genomic imbalances.

Transmission of HIV Drug Resistance and the Predicted Effect on Current First-line Regimens in Europe

Transmitted human immunodeficiency virus drug resistance in Europe is stable at around 8%. The impact of baseline mutation patterns on susceptibility to antiretroviral drugs should be addressed using clinical guidelines. The impact on baseline susceptibility is largest for nonnucleoside reverse transcriptase inhibitors.

Background. Numerous studies have shown that baseline drug resistance patterns may influence the outcome of antiretroviral therapy. Therefore, guidelines recommend drug resistance testing to guide the choice of initial regimen. In addition to optimizing individual patient management, these baseline resistance data enable transmitted drug resistance (TDR) to be surveyed for public health purposes. The SPREAD program systematically collects data to gain insight into TDR occurring in Europe since 2001.

Methods. Demographic, clinical, and virological data from 4140 antiretroviral-naive human immunodeficiency virus (HIV)–infected individuals from 26 countries who were newly diagnosed between 2008 and 2010 were analyzed. Evidence of TDR was defined using the WHO list for surveillance of drug resistance mutations. Prevalence of TDR was assessed over time by comparing the results to SPREAD data from 2002 to 2007. Baseline susceptibility to antiretroviral drugs was predicted using the Stanford HIVdb program version 7.0.

Results. The overall prevalence of TDR did not change significantly over time and was 8.3% (95% confidence interval, 7.2%–9.5%) in 2008–2010. The most frequent indicators of TDR were nucleoside reverse transcriptase inhibitor (NRTI) mutations (4.5%), followed by nonnucleoside reverse transcriptase inhibitor (NNRTI) mutations (2.9%) and protease inhibitor mutations (2.0%). Baseline mutations were most predictive of reduced susceptibility to initial NNRTI-based regimens: 4.5% and 6.5% of patient isolates were predicted to have resistance to regimens containing efavirenz or rilpivirine, respectively, independent of current NRTI backbones.

Conclusions. Although TDR was highest for NRTIs, the impact of baseline drug resistance patterns on susceptibility was largest for NNRTIs. The prevalence of TDR assessed by epidemiological surveys does not clearly indicate to what degree susceptibility to different drug classes is affected.

First fetal case of the 8q24.3 contiguous genes syndrome

Molecular cytogenetics, particularly array-CGH, opened the way to the « genotype first approach » and for the discovery of new micro rearrangement syndromes. This was the case for the 8q24.3 microdeletion syndrome. Here, we describe the phenotype of a fetus with a 8q24.3 deletion. This rare condition has to be considered as a contiguous genes syndrome because its phenotype is generated by the SCRIB and PUF60 adjacent gene endophenotypes. The fetus presented atrioventricular septal defect and hypoplastic aortic arch, facial dysmorphism, microretrognathia, dysmorphic ears, clinodactyly of the 5th digit on both hands, mild rocker bottom feet and abnormal third sacral vertebra. This fetus is the first case where the endophenotype produced by SCRIB gene is absent. This case is compared with the previous published cases.

[HIGH INCIDENCE AND BROAD GENETIC VARIABILITY OF MECKEL-GRUBER SYNDROME IN THE ARAB POPULATION RESIDING IN NORTH-EAST ISRAEL]

BACKGROUND

Meckel-Gruber syndrome (MKS) is a lethal rare inherited autosomal recessive disease. The syndrome is characterized by multiple congenital anomalies including polycystic kidneys, occipital encephalocele and polydactyly. The presence of two out of these anomalies is sufficient for a definitive diagnosis. At least 11 genes have been reported to-date to underlie MKS.

METHODS

In the current study we have retrospectively analyzed all the families at the Ha'Emek Medical Center in which the diagnosis of MKS was determined.

RESULTS

In total, 17 affected individuals are reported, originating from 12 sibships. The diagnoses were conducted or suspected by prenatal sonography, and some of the newborns were examined. Polycystic kidneys were present in 94% of cases, occipital encephalocele in 82% and polydactyly in about half of all cases. The underlying genetic cause was identified in 11 of our families, comprising mutations in 7 different genes, revealing high genetic heterogeneity.

CONCLUSION

The identification of the genetic basis of MKS in our region allows focused and data-based genetic counseling and serves as an important tool for reproductive decisions, including the prevention of recurrence of pregnancies affected with this lethal syndrome. In the near future we plan to study the prevalence of the different MKS mutations found in each community in order to consider the expansion of national genetic screening in high risk populations.

Mutations in KIAA0586 Cause Lethal Ciliopathies Ranging from a Hydrolethalus Phenotype to Short-Rib Polydactyly Syndrome

KIAA0586, the human ortholog of chicken TALPID3, is a centrosomal protein that is essential for primary ciliogenesis. Its disruption in animal models causes defects attributed to abnormal hedgehog signaling; these defects include polydactyly and abnormal dorsoventral patterning of the neural tube. Here, we report homozygous mutations of KIAA0586 in four families affected by lethal ciliopathies ranging from a hydrolethalus phenotype to short-rib polydactyly. We show defective ciliogenesis, as well as abnormal response to SHH-signaling activation in cells derived from affected individuals, consistent with a role of KIAA0586 in primary cilia biogenesis. Whereas centriolar maturation seemed unaffected in mutant cells, we observed an abnormal extended pattern of CEP290, a centriolar satellite protein previously associated with ciliopathies. Our data show the crucial role of KIAA0586 in human primary ciliogenesis and subsequent abnormal hedgehog signaling through abnormal GLI3 processing. Our results thus establish that KIAA0586 mutations cause lethal ciliopathies.

Identification of a novel ARL13B variant in a Joubert syndrome-affected patient with retinal impairment and obesity

Joubert syndrome (JS) is a genetically heterogeneous autosomal recessive ciliopathy with 22 genes implicated to date, including a small, ciliary GTPase, ARL13B. ARL13B is required for cilia formation in vertebrates. JS patients display multiple symptoms characterized by ataxia due to the cerebellar vermis hypoplasia, and that can also include ocular abnormalities, renal cysts, liver fibrosis or polydactyly. These symptoms are shared with other ciliopathies, some of which display additional phenotypes, such as obesity. Here we identified a novel homozygous missense variant in ARL13B/JBTS8 in a JS patient who displayed retinal defects and obesity. We demonstrate the variant disrupts ARL13B function, as its expression did not rescue the mutant phenotype either in Arl13b(scorpion) zebrafish or in Arl13b(hennin) mouse embryonic fibroblasts, while the wild-type ARL13B did. Finally, we show that ARL13B is localized within the primary cilia of neonatal mouse hypothalamic neurons consistent with the known link between hypothalamic ciliary function and obesity. Thus our data identify a novel ARL13B variant that causes JS and retinopathy and suggest an extension of the phenotypic spectrum of ARL13B mutations to obesity.

Phenotype-genotype correlations in 17 new patients with an Xp11.23p11.22 microduplication and review of the literature

Array comparative genomic hybridization (array CGH) has proven its utility in uncovering cryptic rearrangements in patients with X-linked intellectual disability. In 2009, Giorda et al. identified inherited and de novo recurrent Xp11.23p11.22 microduplications in two males and six females from a wide cohort of patients presenting with syndromic intellectual disability. To date, 14 females and 5 males with an overlapping microduplication have been reported in the literature. To further characterize this emerging syndrome, we collected clinical and microarray data from 17 new patients, 10 females, and 7 males. The Xp11.23p11.2 microduplications detected by array CGH ranged in size from 331 Kb to 8.9 Mb. Five patients harbored 4.5 Mb recurrent duplications mediated by non-allelic homologous recombination between segmental duplications and 12 harbored atypical duplications. The chromosomal rearrangement occurred de novo in eight patients and was inherited in six affected males from three families. Patients shared several common major characteristics including moderate to severe intellectual disability, early onset of puberty, language impairment, and age related epileptic syndromes such as West syndrome and focal epilepsy with activation during sleep evolving in some patients to continuous spikes-and-waves during slow sleep. Atypical microduplications allowed us to identify minimal critical regions that might be responsible for specific clinical findings of the syndrome and to suggest possible candidate genes: FTSJ1 and SHROOM4 for intellectual disability along with PQBP1 and SLC35A2 for epilepsy. Xp11.23p11.22 microduplication is a recently-recognized syndrome associated with intellectual disability, epilepsy, and early onset of puberty in females. In this study, we propose several genes that could contribute to the phenotype.

A homozygous PDE6D mutation in Joubert syndrome impairs targeting of farnesylated INPP5E protein to the primary cilium

Joubert syndrome (JS) is characterized by a distinctive cerebellar structural defect, namely the << molar tooth sign >>. JS is genetically heterogeneous, involving 20 genes identified to date, which are all required for cilia biogenesis and/or function. In a consanguineous family with JS associated with optic nerve coloboma, kidney hypoplasia, and polydactyly, combined exome sequencing and mapping identified a homozygous splice-site mutation in PDE6D, encoding a prenyl-binding protein. We found that pde6d depletion in zebrafish leads to renal and retinal developmental anomalies and wild-type but not mutant PDE6D is able to rescue this phenotype. Proteomic analysis identified INPP5E, whose mutations also lead to JS or mental retardation, obesity, congenital retinal dystrophy, and micropenis syndromes, as novel prenyl-dependent cargo of PDE6D. Mutant PDE6D shows reduced binding to INPP5E, which fails to localize to primary cilia in patient fibroblasts and tissues. Furthermore, mutant PDE6D is unable to bind to GTP-bound ARL3, which acts as a cargo-release factor for PDE6D-bound INPP5E. Altogether, these results indicate that PDE6D is required for INPP5E ciliary targeting and suggest a broader role for PDE6D in targeting other prenylated proteins to the cilia. This study identifies PDE6D as a novel JS disease gene and provides the first evidence of prenyl-binding-dependent trafficking in ciliopathies.

New insights into genotype-phenotype correlation for GLI3 mutations

The phenotypic spectrum of GLI3 mutations includes autosomal dominant Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS). PHS was first described as a lethal condition associating hypothalamic hamartoma, postaxial or central polydactyly, anal atresia and bifid epiglottis. Typical GCPS combines polysyndactyly of hands and feet and craniofacial features. Genotype-phenotype correlations have been found both for the location and the nature of GLI3 mutations, highlighting the bifunctional nature of GLI3 during development. Here we report on the molecular and clinical study of 76 cases from 55 families with either a GLI3 mutation (49 GCPS and 21 PHS), or a large deletion encompassing the GLI3 gene (6 GCPS cases). Most of mutations are novel and consistent with the previously reported genotype-phenotype correlation. Our results also show a correlation between the location of the mutation and abnormal corpus callosum observed in some patients with GCPS. Fetal PHS observations emphasize on the possible lethality of GLI3 mutations and extend the phenotypic spectrum of malformations such as agnathia and reductional limbs defects. GLI3 expression studied by in situ hybridization during human development confirms its early expression in target tissues.

Delineation of EFTUD2 haploinsufficiency-related phenotypes through a series of 36 patients

Mandibulofacial dysostosis, Guion-Almeida type (MFDGA) is a recently delineated multiple congenital anomalies/mental retardation syndrome characterized by the association of mandibulofacial dysostosis (MFD) with external ear malformations, hearing loss, cleft palate, choanal atresia, microcephaly, intellectual disability, oesophageal atresia (OA), congenital heart defects (CHDs), and radial ray defects. MFDGA emerges as a clinically recognizable entity, long underdiagnosed due to highly variable presentations. The main differential diagnoses are CHARGE and Feingold syndromes, oculoauriculovertebral spectrum, and other MFDs. EFTUD2, located on 17q21.31, encodes a component of the major spliceosome and is disease causing in MFDGA, due to heterozygous loss-of-function (LoF) mutations. Here, we describe a series of 36 cases of MFDGA, including 24 previously unreported cases, and we review the literature in order to delineate the clinical spectrum ascribed to EFTUD2 LoF. MFD, external ear anomalies, and intellectual deficiency occur at a higher frequency than microcephaly. We characterize the evolution of the facial gestalt at different ages and describe novel renal and cerebral malformations. The most frequent extracranial malformation in this series is OA, followed by CHDs and skeletal abnormalities. MFDGA is probably more frequent than other syndromic MFDs such as Nager or Miller syndromes. Although the wide spectrum of malformations complicates diagnosis, characteristic facial features provide a useful handle.

Novel KIF7 mutations extend the phenotypic spectrum of acrocallosal syndrome

BACKGROUND

Acrocallosal syndrome (ACLS) is a rare recessive disorder characterised by corpus callosum agenesis or hypoplasia, craniofacial dysmorphism, duplication of the hallux, postaxial polydactyly, and severe mental retardation. Recently, we identified mutations in KIF7, a key component of the Sonic hedgehog pathway, as being responsible for this syndrome.

METHODS

We sequenced KIF7 in five suspected ACLS cases, one fetus and four patients, based on facial dysmorphism and brain anomalies.

RESULTS

Seven mutations were identified at the KIF7 locus in these five cases, six of which are novel. We describe the first four compound heterozygous cases. In all patients, the diagnosis was suspected based on the craniofacial features, despite the absence of corpus callosum anomaly in one and of polydactyly in another. Hallux duplication was absent in 4/5 cases.

CONCLUSIONS

These results show that ACLS has a variable expressivity and can be diagnosed even in the absence of the two major features, namely polydactyly or agenesis or hypoplasia of the corpus callosum. Facial dysmorphism with hypertelorism and prominent forehead in all the cases, as well as vermis dysgenesis with brainstem anomalies (molar tooth sign), strongly indicated the diagnosis. KIF7 should be tested in less typical patients in whom craniofacial features are suggestive of ACLS.

Monozygotic twins discordant for submicroscopic chromosomal anomalies in 2p25.3 region detected by array CGH

Although discordant phenotypes in monozygotic twins with developmental disorder are not an exception, underlying genetic discordance is rarely reported. Here, we report on the clinical and cytogenetic details of 4-year-old female monozygotic twins with discordant phenotypes. Twin 1 exhibited global developmental delay, overweight and hyperactivity. Twin 2 had an autistic spectrum disorder. Molecular karyotyping in twin 1 identified a 2p25.3 deletion, further confirmed by Fluorescence in situ hybridization (FISH) analysis on leukocytes. Interestingly, array comparative genomic hybridization was normal in twin 2 but FISH analysis using the same probe as twin 1 showed mosaicism with one-third of cells with a 2p25.3 deletion, one-third of cells with a 2p25.3 duplication, and one-third of normal cells. Genotyping with microsatellite markers confirmed the monozygosity of the twins. We propose that the chromosome imbalance may be due to a mitotic non-allelic recombination occurring during blastomeric divisions of a normal zygote. Such event will result in three distinct cell populations, whose proportion in each embryo formed after separation from the zygote may differ, leading to discordant chromosomal anomalies between twins. We also discuss that the MYTL1L and the SNTG2 genes within the reported region could probably relate to the phenotypic discordance of the monozygotic twins.

Antenatal spectrum of CHARGE syndrome in 40 fetuses with CHD7 mutations

BACKGROUND

CHARGE syndrome is a rare, usually sporadic disorder of multiple congenital anomalies ascribed to a CHD7 gene mutation in 60% of cases. Although the syndrome is well characterised in children, only one series of 10 fetuses with CHARGE syndrome has been reported to date. Therefore, we performed a detailed clinicopathological survey in our series of fetuses with CHD7 mutations, now extended to 40 cases. CHARGE syndrome is increasingly diagnosed antenatally, but remains challenging in many instances.

METHOD

Here we report a retrospective study of 40 cases of CHARGE syndrome with a CHD7 mutation, including 10 previously reported fetuses, in which fetal or neonatal clinical, radiological and histopathological examinations were performed.

RESULTS

Conversely to postnatal studies, the proportion of males is high in our series (male to female ratio 2.6:1) suggesting a greater severity in males. Features almost constant in fetuses were external ear anomalies, arhinencephaly and semicircular canal agenesis, while intrauterine growth retardation was never observed. Finally, except for one, all other mutations identified in our antenatal series were truncating, suggesting a possible phenotype-genotype correlation.

CONCLUSIONS

Clinical analysis allowed us to refine the clinical description of CHARGE syndrome in fetuses, describe some novel features and set up diagnostic criteria in order to help the diagnosis of CHARGE syndrome after termination of pregnancies following the detection of severe malformations.

Transcriptome profiling of genes involved in neural tube closure during human embryonic development using long serial analysis of gene expression (long-SAGE)

BACKGROUND

Neural tube defects (NTDs) are common human birth defects with a complex etiology. To develop a comprehensive knowledge of the genes expressed during normal neurulation, we established transcriptomes from human neural tube fragments during and after neurulation using long Serial Analysis of Gene Expression (long-SAGE).

METHODS

Rostral and caudal neural tubes were dissected from normal human embryos aged between 26 and 32 days of gestation. Tissues from the same region and Carnegie stage were pooled (n ≥ 4) and total RNA extracted to construct four long-SAGE libraries. Tags were mapped using the UniGene Homo sapiens 17 bp tag-to-gene best mapping set. Differentially expressed genes were identified by chi-square or Fisher's exact test, and validation was performed for a subset of those transcripts using in situ hybridization. In silico analyses were performed with BinGO and EXPANDER.

RESULTS

We observed most genes to be similarly regulated in rostral and caudal regions, but expression profiles differed during and after closure. In silico analysis found similar enrichments in both regions for biologic process terms, transcription factor binding and miRNA target motifs. Twelve genes potentially expressing alternate isoforms by region or developmental stage, and the microRNAs miR-339-5p, miR-141/200a, miR-23ab, and miR-129/129-5p are among several potential candidates identified here for future research.

CONCLUSIONS

Time appears to influence gene expression in the developing central nervous system more than location. These data provide a novel complement to traditional strategies of identifying genes associated with human NTDs and offer unique insight into the genes associated with normal human neurulation.

Germline gain-of-function mutations of ALK disrupt central nervous system development

Neuroblastoma (NB) is a frequent embryonal tumor of sympathetic ganglia and adrenals with extremely variable outcome. Recently, somatic amplification and gain-of-function mutations of the anaplastic lymphoma receptor tyrosine kinase (ALK) gene, either somatic or germline, were identified in a significant proportion of NB cases. Here we report a novel syndromic presentation associating congenital NB with severe encephalopathy and abnormal shape of the brainstem on brain MRI in two unrelated sporadic cases harboring de novo, germline, heterozygous ALK gene mutations. Both mutations are gain-of-function mutations that have been reported in NB and NB cell lines. These observations further illustrate the role of oncogenes in both tumour predisposition and normal development, and shed light on the pleiotropic and activity-dependent role of ALK in humans. More generally, missing germline mutations relative to the spectrum of somatic mutations reported for a given oncogene may be a reflection of severe effects during embryonic development, and may prompt mutation screening in patients with extreme phenotypes.

CLMP is required for intestinal development, and loss-of-function mutations cause congenital short-bowel syndrome

BACKGROUND & AIMS

Short-bowel syndrome usually results from surgical resection of the small intestine for diseases such as intestinal atresias, volvulus, and necrotizing enterocolitis. Patients with congenital short-bowel syndrome (CSBS) are born with a substantial shortening of the small intestine, to a mean length of 50 cm, compared with a normal length at birth of 190-280 cm. They also are born with intestinal malrotation. Because CSBS occurs in many consanguineous families, it is considered to be an autosomal-recessive disorder. We aimed to identify and characterize the genetic factor causing CSBS.

METHODS

We performed homozygosity mapping using 610,000 K single-nucleotide polymorphism arrays to analyze the genomes of 5 patients with CSBS. After identifying a gene causing the disease, we determined its expression pattern in human embryos. We also overexpressed forms of the gene product that were and were not associated with CSBS in Chinese Hamster Ovary and T84 cells and generated a zebrafish model of the disease.

RESULTS

We identified loss-of-function mutations in Coxsackie- and adenovirus receptor-like membrane protein (CLMP) in CSBS patients. CLMP is a tight-junction-associated protein that is expressed in the intestine of human embryos throughout development. Mutations in CLMP prevented its normal localization to the cell membrane. Knock-down experiments in zebrafish resulted in general developmental defects, including shortening of the intestine and the absence of goblet cells. Because goblet cells are characteristic for the midintestine in zebrafish, which resembles the small intestine in human beings, the zebrafish model mimics CSBS.

CONCLUSIONS

Loss-of-function mutations in CLMP cause CSBS in human beings, likely by interfering with tight-junction formation, which disrupts intestinal development. Furthermore, we developed a zebrafish model of CSBS.

ISL1 directly regulates FGF10 transcription during human cardiac outflow formation

The LIM homeodomain gene Islet-1 (ISL1) encodes a transcription factor that has been associated with the multipotency of human cardiac progenitors, and in mice enables the correct deployment of second heart field (SHF) cells to become the myocardium of atria, right ventricle and outflow tract. Other markers have been identified that characterize subdomains of the SHF, such as the fibroblast growth factor Fgf10 in its anterior region. While functional evidence of its essential contribution has been demonstrated in many vertebrate species, SHF expression of Isl1 has been shown in only some models. We examined the relationship between human ISL1 and FGF10 within the embryonic time window during which the linear heart tube remodels into four chambers. ISL1 transcription demarcated an anatomical region supporting the conserved existence of a SHF in humans, and transcription factors of the GATA family were co-expressed therein. In conjunction, we identified a novel enhancer containing a highly conserved ISL1 consensus binding site within the FGF10 first intron. ChIP and EMSA demonstrated its direct occupation by ISL1. Transcription mediated by ISL1 from this FGF10 intronic element was enhanced by the presence of GATA4 and TBX20 cardiac transcription factors. Finally, transgenic mice confirmed that endogenous factors bound the human FGF10 intronic enhancer to drive reporter expression in the developing cardiac outflow tract. These findings highlight the interest of examining developmental regulatory networks directly in human tissues, when possible, to assess candidate non-coding regions that may be responsible for congenital malformations.

Mutations in the planar cell polarity genes CELSR1 and SCRIB are associated with the severe neural tube defect craniorachischisis

Craniorachischisis (CRN) is a severe neural tube defect (NTD) resulting from failure to initiate closure, leaving the hindbrain and spinal neural tube entirely open. Clues to the genetic basis of this condition come from several mouse models, which harbor mutations in core members of the planar cell polarity (PCP) signaling pathway. Previous studies of humans with CRN failed to identify mutations in the core PCP genes, VANGL1 and VANGL2. Here, we analyzed other key PCP genes: CELSR1, PRICKLE1, PTK7, and SCRIB, with the finding of eight potentially causative mutations in both CELSR1 and SCRIB. Functional effects of these unique or rare human variants were evaluated using known protein-protein interactions as well as subcellular protein localization. While protein interactions were not affected, variants from five of the 36 patients exhibited a profound alteration in subcellular protein localization, with diminution or abolition of trafficking to the plasma membrane. Comparable effects were seen in the crash and spin cycle mouse Celsr1 mutants, and the line-90 mouse Scrib mutant. We conclude that missense variants in CELSR1 and SCRIB may represent a cause of CRN in humans, as in mice, with defective PCP protein trafficking to the plasma membrane a likely pathogenic mechanism.

[Preimplantation diagnosis with HLA typing: birth of the first double hope child in France]

Preimplantation genetic diagnosis (PGD) is authorized in France since 1999. After 10 years, technical results are encouraging. With the development of new technologies, our team is able to diagnosis the large majority of chromosome translocations and 75 monogenic diseases. However, PGD remains limited because of the growing augmentation of demands causing an increasing delay for the first procedure of more than 18 months. Since 2006, 19 couples asked for a PGD with HLA typing. In January 2011, 11 couples have already been included in our PGD program. The birth of the first child after PGD with HLA typing offers new perspectives of treatment for these couples.

Germline deletion of the miR-17∼92 cluster causes skeletal and growth defects in humans

MicroRNAs (miRNAs) are key regulators of gene expression in animals and plants. Studies in a variety of model organisms show that miRNAs modulate developmental processes. To our knowledge, the only hereditary condition known to be caused by a miRNA is a form of adult-onset non-syndromic deafness, and no miRNA mutation has yet been found to be responsible for any developmental defect in humans. Here we report the identification of germline hemizygous deletions of MIR17HG, encoding the miR-17∼92 polycistronic miRNA cluster, in individuals with microcephaly, short stature and digital abnormalities. We demonstrate that haploinsufficiency of miR-17∼92 is responsible for these developmental abnormalities by showing that mice harboring targeted deletion of the miR-17∼92 cluster phenocopy several key features of the affected humans. These findings identify a regulatory function for miR-17∼92 in growth and skeletal development and represent the first example of an miRNA gene responsible for a syndromic developmental defect in humans.

[Ten years' experience of preimplantation genetic diagnosis in Paris: remaining obstacles and potential solutions]

Preimplantation genetic diagnosis (PGD) has been authorized in France since 1999. Encouraging results have been obtained during the past 10 years in our Paris center, where 832 patients have undergone 1056 IVF-PGD procedures. With the advent of new techniques for the identification of genetic disease markers, our center can now offer PGD procedures for aneuploidy and 75 single-gene diseases. New indications for PGD have also been developed, such as mitochondrial DNA diseases, amyloid neuropathy, pulmonary arterial hypertension, and HLA typing The implantation rate is currently 29,6% and, by 31 December 2009, 151 healthy babies had been born. Unfortunately, demand for PGD procedures far outstrips available technical capacity, and the waiting period is longer than 18 months. Increased funding is urgently needed