Solid organ transplantation after hematopoietic stem cell transplantation in childhood: A multicentric retrospective survey.

We report data obtained from a retrospective multicenter pediatric survey on behalf of the European Society for Blood and Marrow Transplantation (EBMT). Information on solid organ transplantation (SOT) performed in pediatric recipients of either autologous or allogeneic hematopoietic stem cell transplantation (HSCT) between 1984 and 2016 was collected in 20 pediatric EBMT Centers (25.6%). Overall, we evaluated data on 44 SOTs following HSCT including 20 liver (LTx), 12 lung (LuTx), 6 heart (HTx), and 6 kidney (KTx) transplantations. The indication for SOT was organ failure related to intractable graft-vs-host disease in 16 children (36.3%), acute or chronic HSCT-related toxicity in 18 (40.9%), and organ dysfunction related to the underlying disease in 10 (22.8%). The median follow-up was 10.9 years (95% confidence interval: 1.7-29.5). The overall survival rate at 1 and 5 years after SOT was 85.7% and 80.4%, respectively: it was 74% and 63.2% after LTx, 83.2% after HTx, and 100% equally after LuTx and KTx. This multicenter survey confirms that SOT represents a promising option in children with severe organ failure occurring after HSCT. Additional studies are needed to further establish the effectiveness of SOT after HSCT and to better understand the mechanism underlying this encouraging success.

Polymorphic tandem repeats within gene promoters act as modifiers of gene expression and DNA methylation in humans.

Despite representing an important source of genetic variation, tandem repeats (TRs) remain poorly studied due to technical difficulties. We hypothesized that TRs can operate as expression (eQTLs) and methylation (mQTLs) quantitative trait loci. To test this we analyzed the effect of variation at 4849 promoter-associated TRs, genotyped in 120 individuals, on neighboring gene expression and DNA methylation. Polymorphic promoter TRs were associated with increased variance in local gene expression and DNA methylation, suggesting functional consequences related to TR variation. We identified >100 TRs associated with expression/methylation levels of adjacent genes. These potential eQTL/mQTL TRs were enriched for overlaps with transcription factor binding and DNaseI hypersensitivity sites, providing a rationale for their effects. Moreover, we showed that most TR variants are poorly tagged by nearby single nucleotide polymorphisms (SNPs) markers, indicating that many functional TR variants are not effectively assayed by SNP-based approaches. Our study assigns biological significance to TR variations in the human genome, and suggests that a significant fraction of TR variations exert functional effects via alterations of local gene expression or epigenetics. We conclude that targeted studies that focus on genotyping TR variants are required to fully ascertain functional variation in the genome.

Mirror extreme BMI phenotypes associated with gene dosage at the chromosome 16p11.2 locus.

Both obesity and being underweight have been associated with increased mortality. Underweight, defined as a body mass index (BMI) ≤ 18.5 kg per m(2) in adults and ≤ -2 standard deviations from the mean in children, is the main sign of a series of heterogeneous clinical conditions including failure to thrive, feeding and eating disorder and/or anorexia nervosa. In contrast to obesity, few genetic variants underlying these clinical conditions have been reported. We previously showed that hemizygosity of a ∼600-kilobase (kb) region on the short arm of chromosome 16 causes a highly penetrant form of obesity that is often associated with hyperphagia and intellectual disabilities. Here we show that the corresponding reciprocal duplication is associated with being underweight. We identified 138 duplication carriers (including 132 novel cases and 108 unrelated carriers) from individuals clinically referred for developmental or intellectual disabilities (DD/ID) or psychiatric disorders, or recruited from population-based cohorts. These carriers show significantly reduced postnatal weight and BMI. Half of the boys younger than five years are underweight with a probable diagnosis of failure to thrive, whereas adult duplication carriers have an 8.3-fold increased risk of being clinically underweight. We observe a trend towards increased severity in males, as well as a depletion of male carriers among non-medically ascertained cases. These features are associated with an unusually high frequency of selective and restrictive eating behaviours and a significant reduction in head circumference. Each of the observed phenotypes is the converse of one reported in carriers of deletions at this locus. The phenotypes correlate with changes in transcript levels for genes mapping within the duplication but not in flanking regions. The reciprocal impact of these 16p11.2 copy-number variants indicates that severe obesity and being underweight could have mirror aetiologies, possibly through contrasting effects on energy balance.

Digital genotyping of macrosatellites and multicopy genes reveals novel biological functions associated with copy number variation of large tandem repeats.

Tandem repeats are common in eukaryotic genomes, but due to difficulties in assaying them remain poorly studied. Here, we demonstrate the utility of Nanostring technology as a targeted approach to perform accurate measurement of tandem repeats even at extremely high copy number, and apply this technology to genotype 165 HapMap samples from three different populations and five species of non-human primates. We observed extreme variability in copy number of tandemly repeated genes, with many loci showing 5-10 fold variation in copy number among humans. Many of these loci show hallmarks of genome assembly errors, and the true copy number of many large tandem repeats is significantly under-represented even in the high quality 'finished' human reference assembly. Importantly, we demonstrate that most large tandem repeat variations are not tagged by nearby SNPs, and are therefore essentially invisible to SNP-based GWAS approaches. Using association analysis we identify many cis correlations of large tandem repeat variants with nearby gene expression and DNA methylation levels, indicating that variations of tandem repeat length are associated with functional effects on the local genomic environment. This includes an example where expansion of a macrosatellite repeat is associated with increased DNA methylation and suppression of nearby gene expression, suggesting a mechanism termed "repeat induced gene silencing", which has previously been observed only in transgenic organisms. We also observed multiple signatures consistent with altered selective pressures at tandemly repeated loci, suggesting important biological functions. Our studies show that tandemly repeated loci represent a highly variable fraction of the genome that have been systematically ignored by most previous studies, copy number variation of which can exert functionally significant effects. We suggest that future studies of tandem repeat loci will lead to many novel insights into their role in modulating both genomic and phenotypic diversity.

[Suspicion of constitutional abnormality at diagnosis of childhood leukemia: Update of the leukemia committee of the French Society of Childhood Cancers]. / Suspicion d'anomalie constitutionnelle au diagnostic de leucémie chez l'enfant : mise au point du comité leucémies de la Société française des cancers de l'enfant.

The spectrum of childhood leukemia predisposition syndromes has grown significantly over last decades. These predisposition syndromes mainly involve CEBPA, ETV6, GATA2, IKZF1, PAX5, RUNX1, SAMD9/SAMD9L, TP53, RAS-MAPK pathway, DNA mismatch repair system genes, genes associated with Fanconi anemia, and trisomy 21. The clinico-biological features leading to the suspicion of a leukemia predisposition are highly heterogeneous and require varied exploration strategies. The study of the initial characteristics of childhood leukemias includes high-throughput sequencing techniques, which have increased the frequency of situations where a leukemia predisposing syndrome is suspected. Identification of a leukemia predisposition syndrome can have a major impact on the choice of chemotherapy, the indication for hematopoietic stem cell transplantation, and screening for associated malformations and pathologies. The diagnosis of a predisposition syndrome can also lead to the exploration of family members and genetic counseling. Diagnosis and management should be based on dedicated and multidisciplinary care networks.

Rapid multiplexed genotyping of simple tandem repeats using capture and high-throughput sequencing.

Although simple tandem repeats (STRs) comprise ~2% of the human genome and represent an important source of polymorphism, this class of variation remains understudied. We have developed a cost-effective strategy for performing targeted enrichment of STR regions that utilizes capture probes targeting the flanking sequences of STR loci, enabling specific capture of DNA fragments containing STRs for subsequent high-throughput sequencing. Utilizing a capture design targeting 6,243 STR loci <94 bp and multiplexing eight individuals in a single Illumina HiSeq2000 sequencing lane we were able to call genotypes in at least one individual for 67.5% of the targeted STRs. We observed a strong relationship between (G+C) content and genotyping rate. STRs with moderate (G+C) content were recovered with >90% success rate, whereas only 12% of STRs with ≥ 80% (G+C) were genotyped in our assay. Analysis of a parent-offspring trio, complete hydatidiform mole samples, repeat analyses of the same individual, and Sanger sequencing-based validation indicated genotyping error rates between 7.6% and 12.4%. The majority of such errors were a single repeat unit at mono- or dinucleotide repeats. Altogether, our STR capture assay represents a cost-effective method that enables multiplexed genotyping of thousands of STR loci suitable for large-scale population studies.

[What are the genetic practices of SFCE oncopediatricians? A study of the CONECT-AML ethical group]. / Quelles sont les pratiques en génétique des pédiatres onco-hématologues de la SFCE ? Une enquête du groupe socle éthique CONECT-AML.

INTRODUCTION: Somatic genetic tests carried out by new high-throughput sequencing techniques (NGS) are now integrated into the care of children with cancer and leukemia. They can reveal constitutional abnormalities. We questioned the practices of pediatricians in carrying out genetic tests. METHODS: Survey was carried out among pediatric onco-hematologists and residents who have completed a pediatric hematology-oncology internship. RESULTS: Pediatricians mainly prescribe somatic genetic analyses. They are aware that they can reveal constitutional anomalies and inform the parents. Practices in terms of consent to genetics are heterogeneous. The regulatory aspects are poorly known. The child is still little considered in decisions, including when he reaches majority. Parents are informed of the existence of genetic information consultations mainly in the event of suspicion of a constitutional anomaly. Pediatricians, like residents, consider their knowledge of genetics insufficient. Despite this, they feel more comfortable communicating with families while residents say they are uncomfortable conducting a genetic interview. CONCLUSION: Extensive use of NGS for diagnosis confronts pediatricians with ethical questions about information, consent and the return of results. The support of the child must be taken more into account. Ways are mentioned for a better appropriation of the difficulties, while respecting the regulatory framework. The place of the pediatrician and that of the geneticist would aim to be clarified. Specific training, from the internship, would improve support for families and patients.

Type I hyperprolinemia: genotype/phenotype correlations.

Type I hyperprolinemia (HPI) is an autosomal recessive disorder associated with cognitive and psychiatric troubles, caused by alterations of the Proline Dehydrogenase gene (PRODH) at 22q11. HPI results from PRODH deletion and/or missense mutations reducing proline oxidase (POX) activity. The goals of this study were first to measure in controls the frequency of PRODH variations described in HPI patients, second to assess the functional effect of PRODH mutations on POX activity, and finally to establish genotype/enzymatic activity correlations in a new series of HPI patients. Eight of 14 variants occurred at polymorphic frequency in 114 controls. POX activity was determined for six novel mutations and two haplotypes. The c.1331G>A, p.G444D allele has a drastic effect, whereas the c.23C>T, p.P8L allele and the c.[56C>A; 172G>A], p.[Q19P; A58T] haplotype result in a moderate decrease in activity. Among the 19 HPI patients, 10 had a predicted residual activity <50%. Eight out of nine subjects with a predicted residual activity > or = 50% bore at least one c.824C>A, p.T275N allele, which has no detrimental effect on activity but whose frequency in controls is only 3%. Our results suggest that PRODH mutations lead to a decreased POX activity or affect other biological parameters causing hyperprolinemia.

Mutation Screening of Candidate Genes in Patients with Nonsyndromic Sagittal Craniosynostosis.

BACKGROUND: Craniosynostosis is a condition that includes the premature fusion of one or multiple cranial sutures. Among various craniosynostosis forms, sagittal nonsyndromic craniosynostosis is the most prevalent. Although different gene mutations have been identified in some craniosynostosis syndromes, the cause of sagittal nonsyndromic craniosynostosis remains largely unknown. METHODS: To screen for candidate genes for sagittal nonsyndromic craniosynostosis, the authors sequenced DNA of 93 sagittal nonsyndromic craniosynostosis patients from a population-based study conducted in Iowa and New York states. FGFR1-3 mutational hotspots and the entire TWIST1, RAB23, and BMP2 coding regions were screened because of their known roles in human nonsyndromic or syndromic sagittal craniosynostosis, expression patterns, and/or animal model studies. RESULTS: The authors identified two rare variants in their cohort. A FGFR1 insertion c.730_731insG, which led to a premature stop codon, was predicted to abolish the entire immunoglobulin-like III domain, including the ligand-binding region. A c.439C>G variant was observed in TWIST1 at its highly conserved loop domain in another patient. The patient's mother harbored the same variant and was reported with jaw abnormalities. These two variants were not detected in 116 alleles from unaffected controls or seen in the several databases; however, TWIST1 variant was found in a low frequency of 0.000831 percent in Exome Aggregation Consortium database. CONCLUSIONS: The low mutation detection rate indicates that these genes account for only a small proportion of sagittal nonsyndromic craniosynostosis patients. The authors' results add to the perception that sagittal nonsyndromic craniosynostosis is a complex developmental defect with considerable genetic heterogeneity. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.

Abundant contribution of short tandem repeats to gene expression variation in humans.

The contribution of repetitive elements to quantitative human traits is largely unknown. Here we report a genome-wide survey of the contribution of short tandem repeats (STRs), which constitute one of the most polymorphic and abundant repeat classes, to gene expression in humans. Our survey identified 2,060 significant expression STRs (eSTRs). These eSTRs were replicable in orthogonal populations and expression assays. We used variance partitioning to disentangle the contribution of eSTRs from that of linked SNPs and indels and found that eSTRs contribute 10-15% of the cis heritability mediated by all common variants. Further functional genomic analyses showed that eSTRs are enriched in conserved regions, colocalize with regulatory elements and may modulate certain histone modifications. By analyzing known genome-wide association study (GWAS) signals and searching for new associations in 1,685 whole genomes from deeply phenotyped individuals, we found that eSTRs are enriched in various clinically relevant conditions. These results highlight the contribution of STRs to the genetic architecture of quantitative human traits.

The emerging role of SHANK genes in neuropsychiatric disorders.

The genetic heterogeneity of neuropsychiatric disorders is high, but some pathways emerged, notably synaptic functioning. A large number of mutations have been described in genes such as neuroligins, neurexins, and SHANK that play a role in the formation and the maintenance of synapses. This review focuses on the disorders associated with mutations in SHANK3 and the other members of its family, SHANK1 and SHANK2. SHANKs are scaffolding proteins of the postsynaptic density of glutamatergic synapses. SHANK3 has been described in the Phelan-McDermid syndrome (PMS), but also in autism spectrum disorders (ASD) and schizophrenia associated to moderate to severe intellectual disability (ID) and poor language. The evolution of patients with PMS includes symptoms of bipolar disorder and regression. SHANK2 has been identified in patients with ASD with mild to severe ID. SHANK1 has been associated with high-functioning autism in male patients, while carrier females only display anxiety and shyness. Finally, based on neuropathological findings in animal models and patients, a possible role of SHANK in Alzheimer's disease is discussed. Altogether, this review describes the clinical trajectories associated with different mutations of the SHANK genes and provides information to further investigate the role of the SHANK genes in neuropsychiatric disorders.

Recurrent rearrangements in synaptic and neurodevelopmental genes and shared biologic pathways in schizophrenia, autism, and mental retardation.

CONTEXT: Results of comparative genomic hybridization studies have suggested that rare copy number variations (CNVs) at numerous loci are involved in the cause of mental retardation, autism spectrum disorders, and schizophrenia. OBJECTIVES: To provide an estimate of the collective frequency of a set of recurrent or overlapping CNVs in 3 different groups of cases compared with healthy control subjects and to assess whether each CNV is present in more than 1 clinical category. DESIGN: Case-control study. SETTING: Academic research. PARTICIPANTS: We investigated 28 candidate loci previously identified by comparative genomic hybridization studies for gene dosage alteration in 247 cases with mental retardation, in 260 cases with autism spectrum disorders, in 236 cases with schizophrenia or schizoaffective disorder, and in 236 controls. MAIN OUTCOME MEASURES: Collective and individual frequencies of the analyzed CNVs in cases compared with controls. RESULTS: Recurrent or overlapping CNVs were found in cases at 39.3% of the selected loci. The collective frequency of CNVs at these loci is significantly increased in cases with autism, in cases with schizophrenia, and in cases with mental retardation compared with controls (P < .001, P = .01, and P = .001, respectively, Fisher exact test). Individual significance (P = .02 without correction for multiple testing) was reached for the association between autism and a 350-kilobase deletion located at 22q11 and spanning the PRODH and DGCR6 genes. CONCLUSIONS: Weakly to moderately recurrent CNVs (transmitted or occurring de novo) seem to be causative or contributory factors for these diseases. Most of these CNVs (which contain genes involved in neurotransmission or in synapse formation and maintenance) are present in the 3 pathologic conditions (schizophrenia, autism, and mental retardation), supporting the existence of shared biologic pathways in these neurodevelopmental disorders.