Mylène Beri

Delineation of 15q13.3 microdeletions

Masurel‐Paulet A, Andrieux J, Callier P, Cuisset JM, Le Caignec C, Holder M, Thauvin‐Robinet C, Doray B, Flori E, Alex‐Cordier MP, Beri M, Boute O, Delobel B, Dieux A, Vallee L, Jaillard S, Odent S, Isidor B, Beneteau C, Vigneron J, Bilan F, Gilbert‐Dussardier B, Dubourg C, Labalme A, Gautier A, Pernes P, Bidon C, Pinoit JM, Huet F, Mugneret F, Aral B, Jonveaux P, Sanlaville D, Faivre L. Delineation of 15q13.3 microdeletions.

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

The 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.

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

Chromosome 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.

Aberrant GRIA3 transcripts with multi-exon duplications in a family with X-linked mental retardation.

Investigation of chromosomal rearrangements in patients with mental retardation (MR) is particularly informative in the search for novel genes involved in MR. We report on a family with a genomic duplication at Xq25 identified by oligo array‐CGH. Further characterization showed a partial tandem duplication of GRIA3 extending from exon 1 to exon 12. This duplication is present in two brothers with MR and on one allele in their sister with normal phenotype and completely skewed X‐chromosome inactivation. The duplication is inherited from the mother, whose cognitive level is low and X‐chromosome inactivation is random. This is the second family with partial duplication of GRIA3 associated with MR. GRIA3 expression studies in our case demonstrated a new mechanism for GRIA3 dysfunction with the presence of aberrant GRIA3 transcripts carrying multi‐exon duplications leading to a frameshift. Our study gives additional support to the implication of GRIA3 in X‐linked MR.

Clinical and molecular characterization of a large family with an interstitial 15q11q13 duplication

The clinical significance of an interstitial duplication of chromosome 15q11q13 is still not well documented. This abnormality has been associated with autistic spectrum disorders (ASD) and varying degrees of mental retardation. The clinical variability appears to be influenced by the parental origin of the duplication. We present here the clinical evaluation and psychological assessment of the largest reported family with 12 carriers on three generations. Patients exhibit mental retardation, motor and visuo‐motor skills impairments and adaptive functioning deficit without formal diagnosis of autism. There appeared to be evidence in the family of reduced penetrance in duplication of paternal origin. This familial 15q11q13 duplication was precisely investigated by cytogenetic and molecular techniques including fluorescence in situ hybridization (FISH), PCR analysis of microsatellite markers, array‐comparative genomic hybridization analysis (Array‐CGH) and semi‐quantitative methylation‐sensitive PCR. Results showed an inherited 15q11q13 duplication of maternal origin in 10 patients and of paternal origin in the remaining two. The size of the duplicated area was around 6 Mb with breakpoints in accordance with those previously reported. This report extends the clinical spectrum of the 15q11q13 duplication, and we recommend the investigation of 15q11q13 duplication not only in subjects with autistic spectrum disorder but also in patients with low normal intelligence and dyspraxia.

Extended spectrum of MBD5 mutations in neurodevelopmental disorders

Intellectual disability (ID) is a clinical sign reflecting diverse neurodevelopmental disorders that are genetically and phenotypically heterogeneous. Just recently, partial or complete deletion of methyl-CpG-binding domain 5 (MBD5) gene has been implicated as causative in the phenotype associated with 2q23.1 microdeletion syndrome. In the course of systematic whole-genome screening of individuals with unexplained ID by array-based comparative genomic hybridization, we identified de novo intragenic deletions of MBD5 in three patients leading, as previously documented, to haploinsufficiency of MBD5. In addition, we described a patient with an unreported de novo MBD5 intragenic duplication. Reverse transcriptase-PCR and sequencing analyses showed the presence of numerous aberrant transcripts leading to premature termination codon. To further elucidate the involvement of MBD5 in ID, we sequenced ten coding, five non-coding exons and an evolutionary conserved region in intron 2, in a selected cohort of 78 subjects with a phenotype reminiscent of 2q23.1 microdeletion syndrome. Besides variants most often inherited from an healthy parent, we identified for the first time a de novo nonsense mutation associated with a much more damaging phenotype. Taken together, these results extend the mutation spectrum in MBD5 gene and contribute to refine the associated phenotype of neurodevelopmental disorder.

Chromosomally integrated HHV-6: slow decrease of HHV-6 viral load after hematopoietic stem-cell transplantation.

Human herpesvirus (HHV)-6 belongs to the Betaherpesvirinae subfamily. Similar to other herpesviruses, HHV-6 has a latent stage (1) with problematic reactivation in immunocompromised subjects, leading to fatal infections including meningoencephalitis (2, 3). A less-frequent HHV-6 persistence form consists in integration in host chromosomes (4). The prevalence of HHV-6 integration, characterized by high viral load in healthy individuals, has been estimated at approximately 0.2% to 2% in the whole population (5–7) and can thus concern up to 2% of hemotopoieticstem-cell transplantation (HSCT) donors or recipients (8). Some previous publications have described cases of integrated HHV-6 transmission through HSCT (9 –11). In those cases, the recipient has undetectable HHV-6 viral load before the transplantation and becomes positive to high values ( 10 genomic equivalent copies [gec]/10cells) for HHV-6 DNA early after transplantation ( 10 days) (9, 12). The presence of high HHV-6 viral load in an HSCT recipient could also be misinterpreted as HHV-6 reactivation and lead to unnecessary treatment with antiviral compounds, such as ganciclovir, which have drawbacks (13). Here, we describe another type of case in which high HHV-6 viral load is also caused by integrated HHV-6 and could be misinterpreted as an active infection leading to unnecessary treatment. The patient is a 25-year-old woman diagnosed with Hodgkin’s lymphoma having experienced failure after a prior autologous transplant. The disease before transplantation was chemosensitive and in good partial remission. She was given an allogeneic HSCT mobilized from peripheral blood on July 11, 2008, from a 38-year-old unrelated matched (10 of 10 loci) female donor. The reduced-intensity conditioning regimen included Fludarabine (25 mg/m/ day) on days 7 to 3, Melphalan (140 mg/m) on day 2, and ATG Fresenius (13 mg/kg/day) on days 5, 3, and 1. The prophylaxis of graft-versushost disease included cyclosporin and mycophenolate mofetil. The recipient’s whole blood (WB) samples were tested weekly for adenovirus (14), Epstein-Barr virus, cytomegalovirus (CMV), and HHV-6 (EBV R-geneTM and CMV HHV6,7,8 R-geneTM; Argène, Varilhes, France) by quantitative polymerase chain reaction (qPCR) after DNA isolation (Magna Pure LC system®, Roche, Meylan, France); the results were expressed as genomic equivalent copies per milliliter of WB. Moreover, albumin gene DNA was retrospectively amplified according to Laurendeau et al. (15) to quantify HHV-6 gec/10 cells, considering that each cell contains two copies of albumin genome (16). Retrospectively, HHV-6 DNA was tested in the donor’s peripheral blood mononuclear cells. Before the graft, a high HHV-6 viral load (1.30 10 gec/10 cells) led to treatment with intravenous foscarnet (180 mg/kg/day) from day 7 pretransplant to day 14 posttransplant, without decrease in the viral load. Other infectious events included fever of undocumented origin on day 1 and CMV infection on day 45, successfully treated with valganciclovir. The high HHV-6 viral load before transplantation was in favor of integrated HHV-6 and should have prevented patient treatment. Retrospectively, HHV-6 integration in the recipient was confirmed by HHV-6 DNA isolation in hair follicles (17) and mouth swab specimens. The recipient’s parents could not be tested for integrated HHV-6 (6). Besides, HHV-6 DNA was undetectable in donor peripheral blood mononuclear cells. Unexpectedly, 37 days after the transplantation, the HHV-6 viral load in WB remained up to 8.45 10 gec/10 cells. Quantitative analysis of hematopoietic chimerism was performed by real-time qPCR using TaqMan technology

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

A 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.

Array-CGH Analysis Suggests Genetic Heterogeneity in Rhombencephalosynapsis

Rhombencephalosynapsis is an uncommon, but increasingly recognized, cerebellar malformation defined as vermian agenesis with fusion of the hemispheres. The embryologic and genetic mechanisms involved are still unknown, and to date, no animal models are available. In the present study, we used Agilent oligonucleotide arrays in a large series of 57 affected patients to detect candidate genes. Four different unbalanced rearrangements were detected: a 16p11.2 deletion, a 14q12q21.2 deletion, an unbalanced translocation t(2p;10q), and a 16p13.11 microdeletion containing 2 candidate genes. These genes were further investigated by sequencing and in situ hybridization. This first microarray screening of a rhombencephalosynapsis series suggests that there may be heterogeneous genetic causes.

A pure familial 6q15q21 split duplication associated with obesity and transmitted with partial reduction

Familial transmission of chromosome 6 duplications is rare. We report on the first observation of a maternally‐inherited pure segmental 6q duplication split into two segments, 6q15q16.3 and 6q16.3q21, and associated with obesity. Obesity has previously been correlated to chromosome 6 q‐arm deletion but has not yet been assessed in duplications. The aim of this study was to characterize the structure of these intrachromosomal insertional translocations by classic cytogenetic banding, array‐CGH, FISH, M‐banding and genotyping using microsatellites and SNP array analysis, in a mother and four offspring. The duplicated 6q segments, 9.75 Mb (dup 1) and 7.05 Mb (dup 2) in size in the mother, were inserted distally into two distinct chromosome 6q regions. They were transmitted to four offspring. A son and a daughter inherited the two unbalanced insertions and displayed, like the mother, an abnormal phenotype with facial dysmorphism, intellectual disability, and morbid obesity. Curiously, two daughters with a normal phenotype inherited only the smaller segment, 6q16.3q21. The abnormal phenotype was associated with the larger proximal 6q15q16.3 duplication. We hypothesize a mechanism for this exceptional phenomenon of recurrent reduction and transmission of the duplication during meiosis in a family. We expect the interpretation of our findings to be useful for genetic counseling and for understanding the mechanisms underlying these large segmental 6q duplications and their evolution.