Clinical and molecular characterization of 17q21.31 microdeletion syndrome in 14 French patients with mental retardation.

International audienceChromosome 17q21.31 microdeletion was one of the first genomic disorders identified by chromosome microarrays. We report here the clinical and molecular characterization of a new series of 14 French patients with this microdeletion syndrome. The most frequent clinical features were hypotonia, developmental delay and facial dysmorphism, but scaphocephaly, prenatal ischemic infarction and perception deafness were also described. Genotyping of the parents showed that the parent from which the abnormality was inherited carried the H2 inversion polymorphism, confirming that the H2 allele is necessary, but not sufficient to generate the 17q21.31 microdeletion. Previously reported molecular analyses of patients with 17q21.31 microdeletion syndrome defined a 493 kb genomic fragment that was deleted in most patients after taking into account frequent copy number variations in normal controls, but the deleted interval was significantly smaller (205 kb) in one of our patients, encompassing only the MAPT, STH and KIAA1267 genes. As this patient presents the classical phenotype of 17q21.31 syndrome, these data make it possible to define a new minimal critical region of 160.8 kb, strengthening the evidence for involvement of the MAPT gene in this syndrome

Candidate genes retrieval for developmental abnormalities by molecular characterization of chromosomal rearrangements

L'identification de gènes responsables d'anomalies du développement passe par des approches de clonage positionnel parmi lesquelles la caractérisation moléculaire d'anomalies chromosomiques. La cartographie précise de réarrangements chromosomiques permet de mieux cerner des gènes candidats impliqués dans les maladies génétiques, grâce à l'utilisation d'outils de cytogénétique et de biologie moléculaire. L'array-CGH a ainsi conduit à identifier des microremaniements chromosomiques jusqu'alors inconnus et à préciser les gènes candidats dans les affections étudiées.Nous présentons dans une première partie, les résultats de la cartographie et de la caractérisation moléculaire de deux anomalies microcytogénétiques associées à un retard mental, une délétion 20q13.33 et une délétion 21q22. Ces données ont contribué à la sélection de gènes candidats et à améliorer la prise en charge clinique et le conseil génétique.Par ailleurs, la caractérisation moléculaire d'une translocation réciproque t(3;18)(p12.3;q23) de novo associée à une dystonie précoce généralisée avec retard de développement a été réalisée. Le gène ROBO1 impliqué dans le guidage axonal s'est révélé interrompu. Des explorations complémentaires ont été conduites (array-CGH, étude de l'ARN, étude protéique, migration cellulaire et séquençage du gène ROBO1 chez d'autres patients avec une dystonie syndromique) afin de mieux cerner les conséquences de cette anomalie sur la survenue de cette dystonie syndromique. Les résultats de ces études soulignent les difficultés d'interprétation liées à la découverte de tels réarrangements et la nécessité d'apporter la preuve de leur implication dans le phénotype observé par des moyens appropriésPositional candidate gene approach and molecular characterization of chromosomal abnormalities can elucidate the genetic basis of many human developmental diseases. Mapping of such rearrangements allows the identification of disease candidate genes by using cytogenetic and molecular biology approaches. Array-CGH serves the critical need for identification of causal genes related to disease by detection of unknown chromosomal imbalances.We report here the results of mapping and molecular characterization of two unbalanced chromosomal rearrangements related to mental retardation : 20q13.33 and 21q21 deletions. This study led to candidate genes identification and contributed to improve clinical monitoring and genetic counseling.Moreover, the breakpoints characterization of a balanced de novo translocation t(3;18)(p12.3;q23) associated with an early-onset generalized dystonia and developmental delay revealed the disruption of ROBO1, a gene mediating axone guidance. Additional analysis including array-CGH, RNA and protein analysis, leukocyte chemotaxis and search for ROBO1 mutations in 20 independent patients with syndromic dystonia were performed in order to evaluate the correlation beetween ROBO1 disruption and dystonia. The results presented here underline the difficulties in elucidating the role of such rearrangements, and the need to provide further evidences in defining their involvment in the development of a genetic diseas

Hybridation génomique comparative en microréseau (évolutions techniques et place dans la stratégie diagnostique, expérience dans le cadre du retard mental)

NANCY1-SCD Pharmacie-Odontologie (543952101) / SudocNANCY1-Bib. numérique (543959902) / SudocSudocFranceF

Recherche de gènes candidats responsables d'anomalies du développement grâce à la caractérisation moléculaire de microremaniements chromosomiques

L'identification de gènes responsables d'anomalies du développement passe par des approches de clonage positionnel parmi lesquelles la caractérisation moléculaire d'anomalies chromosomiques. La cartographie précise de réarrangements chromosomiques permet de mieux cerner des gènes candidats impliqués dans les maladies génétiques, grâce à l'utilisation d'outils de cytogénétique et de biologie moléculaire. L'array-CGH a ainsi conduit à identifier des microremaniements chromosomiques jusqu'alors inconnus et à préciser les gènes candidats dans les affections étudiées.Nous présentons dans une première partie, les résultats de la cartographie et de la caractérisation moléculaire de deux anomalies microcytogénétiques associées à un retard mental, une délétion 20q13.33 et une délétion 21q22. Ces données ont contribué à la sélection de gènes candidats et à améliorer la prise en charge clinique et le conseil génétique.Par ailleurs, la caractérisation moléculaire d'une translocation réciproque t(3;18)(p12.3;q23) de novo associée à une dystonie précoce généralisée avec retard de développement a été réalisée. Le gène ROBO1 impliqué dans le guidage axonal s'est révélé interrompu. Des explorations complémentaires ont été conduites (array-CGH, étude de l'ARN, étude protéique, migration cellulaire et séquençage du gène ROBO1 chez d'autres patients avec une dystonie syndromique) afin de mieux cerner les conséquences de cette anomalie sur la survenue de cette dystonie syndromique. Les résultats de ces études soulignent les difficultés d'interprétation liées à la découverte de tels réarrangements et la nécessité d'apporter la preuve de leur implication dans le phénotype observé par des moyens appropriésPositional candidate gene approach and molecular characterization of chromosomal abnormalities can elucidate the genetic basis of many human developmental diseases. Mapping of such rearrangements allows the identification of disease candidate genes by using cytogenetic and molecular biology approaches. Array-CGH serves the critical need for identification of causal genes related to disease by detection of unknown chromosomal imbalances.We report here the results of mapping and molecular characterization of two unbalanced chromosomal rearrangements related to mental retardation : 20q13.33 and 21q21 deletions. This study led to candidate genes identification and contributed to improve clinical monitoring and genetic counseling.Moreover, the breakpoints characterization of a balanced de novo translocation t(3;18)(p12.3;q23) associated with an early-onset generalized dystonia and developmental delay revealed the disruption of ROBO1, a gene mediating axone guidance. Additional analysis including array-CGH, RNA and protein analysis, leukocyte chemotaxis and search for ROBO1 mutations in 20 independent patients with syndromic dystonia were performed in order to evaluate the correlation beetween ROBO1 disruption and dystonia. The results presented here underline the difficulties in elucidating the role of such rearrangements, and the need to provide further evidences in defining their involvment in the development of a genetic diseaseNANCY1-Bib. numérique (543959902) / SudocSudocFranceF

Immune constitution monitoring after PBMC transplantation in complete DiGeorge syndrome: an eight-year follow-up.

International audienceA young boy with a confirmed complete DiGeorge Syndrome (cDGS) underwent a peripheral blood mononuclear cell transplantation (PBMCT) from his HLA-identical sister at 4.5 years of age, without a conditioning regimen. Eight years later, he is healthy with good immunological functions in the presence of a stable mixed T-cell chimerism. Absence of recent thymic emigrants is confirmed. We observe an inverted CD4+/CD8+ ratio, related to the CD8 subset expansion, a skewing of the TCR repertoire, especially on the CD8+ subset and a telomere loss on the CD8+ cells compared to the donor. However, these anomalies do not seem to have an impact on functional immunity. PBMCT in cDGS using an HLA-matched sibling donor provides good long-lasting immunity and is an easy alternative to bone marrow transplantation and to thymic transplantation

Delineation of 15q13.3 microdeletions.

International audienceThe increasing use of array-comparative genomic hybridization (array-CGH) to identify copy number variations (CNVs) in patients with developmental delay (DD), mental retardation and/or dysmorphic features has allowed the recent recognition of numerous genomic imbalances, including the 15q13.3 microdeletion. Patients with this microdeletion generally present with relatively consistent breakpoints at BP4 and BP5, which include the CHRNA7 gene. About 100 index cases have been reported since the first publication in 2008. This large number of patients ascertained through highly variable samples has been necessary to describe the full phenotypic spectrum of this microdeletion, ranging from mental retardation with dysmorphic features, epilepsy, neuropsychiatric disturbances with or without cognitive impairment to complete absence of anomalies. Here, we describe a collaborative study reporting a new cohort of 12 index patients and 13 relatives carrying a heterozygous BP4-BP5 microdeletion out of a series of 4625 patients screened by array-CGH for DD. We confirm the clinical expressivity of the disease as well as the incomplete penetrance in seven families. We showed through a review of the literature that males are more likely to be symptomatic. Sequence analysis of CHRNA7 yielded no data to support the unmasking of recessive variants as a cause of phenotypic variability. We also report the first patient carrying a 15q13.3 homozygous microdeletion inherited from both parents. He had severe epileptic encephalopathy with retinopathy, autistic features and choreoathetosis. Besides the classical approximately 1.5 Mb BP4-BP5 microdeletion, we also describe three index patients and two relatives with a smaller 500 kb microdeletion, including the CHRNA7 gene

The 2q37-deletion syndrome: an update of the clinical spectrum including overweight, brachydactyly and behavioural features in 14 new patients

International audienceThe 2q37 locus is one of the most commonly deleted subtelomeric regions. Such a deletion has been identified in >100 patients by telomeric fluorescence in situ hybridization (FISH) analysis and, less frequently, by array-based comparative genomic hybridization (array-CGH). A recognizable ‘2q37-deletion syndrome’ or Albright’s hereditary osteodystrophy-like syndrome has been previously described. To better map the deletion and further refine this deletional syndrome, we formed a collaboration with the Association of French Language Cytogeneticists to collect 14 new intellectually deficient patients with a distal or interstitial 2q37 deletion characterized by FISH and array-CGH. Patients exhibited facial dysmorphism (13/14) and brachydactyly (10/14), associated with behavioural problems, autism or autism spectrum disorders of varying severity and overweight or obesity. The deletions in these 14 new patients measured from 2.6 to 8.8 Mb. Although the major role of HDAC4 has been demonstrated, the phenotypic involvement of several other genes in the deleted regions is unknown. We further refined the genotype–phenotype correlation for the 2q37 deletion. To do this, we examined the smallest overlapping deleted region for candidate genes for skeletal malformations (facial dysmorphism and brachydactyly), overweight, behavioural problems and seizures, using clinical data, a review of the literature, and the Manteia database. Among the candidate genes identified, we focus on the roles of PRLH, PER2, TWIST2, CAPN10, KIF1A, FARP2, D2HGDH and PDCD1

Further delineation of the MECP2 duplication syndrome phenotype in 59 French male patients, with a particular focus on morphological and neurological features

IF 5.751International audienceThe Xq28 duplication involving the MECP2 gene (MECP2 duplication) has been mainly described in male patients with severe developmental delay (DD) associated with spasticity, stereotypic movements and recurrent infections. Nevertheless, only a few series have been published. We aimed to better describe the phenotype of this condition, with a focus on morphological and neurological features. Through a national collaborative study, we report a large French series of 59 affected males with interstitial MECP2 duplication. Most of the patients (93%) shared similar facial features, which evolved with age (midface hypoplasia, narrow and prominent nasal bridge, thick lower lip, large prominent ears), thick hair, livedo of the limbs, tapered fingers, small feet and vasomotor troubles. Early hypotonia and global DD were constant, with 21% of patients unable to walk. In patients able to stand, lower limbs weakness and spasticity led to a singular standing habitus: flexion of the knees, broad-based stance with pseudo-ataxic gait. Scoliosis was frequent (53%), such as divergent strabismus (76%) and hypermetropia (54%), stereotypic movements (89%), without obvious social withdrawal and decreased pain sensitivity (78%). Most of the patients did not develop expressive language, 35% saying few words. Epilepsy was frequent (59%), with a mean onset around 7.4 years of age, and often (62%) drug-resistant. Other medical issues were frequent: constipation (78%), and recurrent infections (89%), mainly lung. We delineate the clinical phenotype of MECP2 duplication syndrome in a large series of 59 males. Pulmonary hypertension appeared as a cause of early death in these patients, advocating its screening early in life