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.

Microdeletion at chromosome 4q21 defines a new emerging syndrome with marked growth restriction, mental retardation and absent or severely delayed speech.

BACKGROUND Genome-wide screening of large patient cohorts with mental retardation using microarray-based comparative genomic hybridisation (array-CGH) has recently led to identification several novel microdeletion and microduplication syndromes. METHODS Owing to the national array-CGH network funded by the French Ministry of Health, shared information about patients with rare disease helped to define critical intervals and evaluate their gene content, and finally determine the phenotypic consequences of genomic array findings. RESULTS In this study, nine unrelated patients with overlapping de novo interstitial microdeletions involving 4q21 are reported. Several major features are common to all patients, including neonatal muscular hypotonia, severe psychomotor retardation, marked progressive growth restriction, distinctive facial features and absent or severely delayed speech. The boundaries and the sizes of the nine deletions are different, but an overlapping region of 1.37 Mb is defined; this region contains five RefSeq genes: PRKG2, RASGEF1B, HNRNPD, HNRPDL and ENOPH1. DISCUSSION Adding new individuals with similar clinical features and 4q21 deletion allowed us to reduce the critical genomic region encompassing two genes, PRKG2 and RASGEF1B. PRKG2 encodes cGMP-dependent protein kinase type II, which is expressed in brain and in cartilage. Information from genetically modified animal models is pertinent to the clinical phenotype. RASGEF1B is a guanine nucleotide exchange factor for Ras family proteins, and several members have been reported as key regulators of actin and microtubule dynamics during both dendrite and spine structural plasticity. CONCLUSION Clinical and molecular delineation of 4q21 deletion supports a novel microdeletion syndrome and suggests a major contribution of PRKG2 and RASGEF1B haploinsufficiency to the core phenotype.

Genotype phenotype correlation of 30 patients with Smith-Magenis syndrome (SMS) using comparative genome hybridisation array: cleft palate in SMS is associated with larger deletions.

BACKGROUND: Smith-Magenis syndrome (SMS) is rare (prevalence 1 in 25 000) and is associated with psychomotor delay, a particular behavioural pattern and congenital anomalies. SMS is often due to a chromosomal deletion of <4 Mb at the 17p11.2 locus, leading to haploinsufficiency of numerous genes. Mutations of one of these gemes, RAI1, seems to be responsible for the main features found with heterozygous 17p11.2 deletions. METHODS: We studied DNA from 30 patients with SMS using a 300 bp amplimers comparative genome hybridisation array encompassing 75 loci from a 22 Mb section from the short arm of chromosome 17. RESULTS: Three patients had large deletions (10%). Genotype-phenotype correlation showed that two of them had cleft palate, which was not found in any of the other patients with SMS (p<0.007, Fisher's exact test). The smallest extra-deleted region associated with cleft palate in SMS is 1.4 Mb, contains <16 genes and is located at 17p11.2-17p12. Gene expression array data showed that the ubiquitin B precursor (UBB) is significantly expressed in the first branchial arch in the fourth and fifth weeks of human development. CONCLUSION: These data support UBB as a good candidate gene for isolated cleft palate.

Array-based comparative genomic hybridisation identifies high frequency of cryptic chromosomal rearrangements in patients with syndromic autism spectrum disorders.

BACKGROUND: Autism spectrum disorders (ASD) refer to a broader group of neurobiological conditions, pervasive developmental disorders. They are characterised by a symptomatic triad associated with qualitative changes in social interactions, defect in communication abilities, and repetitive and stereotyped interests and activities. ASD is prevalent in 1 to 3 per 1000 people. Despite several arguments for a strong genetic contribution, the molecular basis of a most cases remains unexplained. About 5% of patients with autism have a chromosome abnormality visible with cytogenetic methods. The most frequent are 15q11-q13 duplication, 2q37 and 22q13.3 deletions. Many other chromosomal imbalances have been described. However, most of them remain undetectable using routine karyotype analysis, thus impeding diagnosis and genetic counselling. METHODS AND RESULTS: 29 patients presenting with syndromic ASD were investigated using a DNA microarray constructed from large insert clones spaced at approximately 1 Mb intervals across the genome. Eight clinically relevant rearrangements were identified in 8 (27.5%) patients: six deletions and two duplications. Altered segments ranged in size from 1.4 to 16 Mb (2-19 clones). No recurrent abnormality was identified. CONCLUSION: These results clearly show that array comparative genomic hybridisation should be considered to be an essential aspect of the genetic analysis of patients with syndromic ASD. Moreover, besides their importance for diagnosis and genetic counselling, they may allow the delineation of new contiguous gene syndromes associated with ASD. Finally, the detailed molecular analysis of the rearranged regions may pave the way for the identification of new ASD genes.

Molecular cytogenetic analysis of five 2q37 deletions: refining the brachydactyly candidate region.

Deletions of the 2q37 region are associated with a recognizable pattern of MCA/MR so-called the AHO-like syndrome. Brachydactyly is a variable but characteristic feature of this clinical entity. Here we report on five cases of cytogenetically visible de novo deletions of this 2q37 chromosome region. Using FISH, we characterized at the molecular level the breakpoints of these deletions using a set of 15 BACs, PACs and YACs. In four patients, terminal deletions of variable size ranged between 6.2 and 10 Mb. The fifth patient had an interstitial deletion with an AHO-like phenotype including brachydactyly. These findings when compared to previous observations allowed us to narrow down the brachydactyly critical region between BACs RP11-585E12 and RP11-351E10. It contains HDAC4 and STK25 candidate genes loci.

Characterization of a human ovarian adenocarcinoma line, IGROV1, in tissue culture and in nude mice.

A cell line, IGROV1, originating from an ovarian carcinoma of a 47-year-old woman was established in tissue culture and in nude mice. Maintained in monolayer cultures, IGROV1 cells exhibited a 20-h doubling time and highly tumorigenic properties. The s.c. injection of 2 X 10(6) cultured cells into nude mice gave rise to fast growing tumors, while the i.p. route induced a peritoneal carcinomatosis with ascites which killed the animals in 2 months. The epithelial morphology of IGROV1 cells was retained during in vitro and in vivo passages, as judged by both the light and the electron microscopes. Two cytogenetic markers characterize IGROV1 cells: a paracentric inversion of chromosome 3, and a translocation between chromosomes 2 and 5. The constitutional karyotype of the patient was normal. These characteristics make the IGROV1 cell line a suitable experimental model for the treatment of human ovarian carcinomas and for biological studies of human solid tumors.

beta(1)-adrenergic antagonists improve sleep and behavioural disturbances in a circadian disorder, Smith-Magenis syndrome.

Smith-Magenis syndrome (SMS) is a clinically recognisable contiguous gene syndrome ascribed to interstitial deletions of chromosome 17p11.2. Patients have a phase shift of their circadian rhythm of melatonin with a paradoxical diurnal secretion of the hormone. Serum melatonin levels and day-night behaviour were studied in nine SMS children (aged 4 to 17 years) given acebutolol, a selective beta(1)-adrenergic antagonist (10 mg/kg early in the morning). Cardiac examination, serum melatonin, motor activity recordings, and sleep diaries were monitored before and after drug administration. The present study shows that a single morning dose of acebutolol suppressed the inappropriate secretion of melatonin in SMS. A significant improvement of inappropriate behaviour with increased concentration, delayed sleep onset, increased hours of sleep, and delayed waking were also noted. These results suggest that beta(1)-adrenergic antagonists help to manage hyperactivity, enhance cognitive performance, and reduce sleep disorders in SMS.

Automated fluorescent genotyping detects 10% of cryptic subtelomeric rearrangements in idiopathic syndromic mental retardation.

Recent studies have shown that cryptic unbalanced subtelomeric rearrangements contribute to a significant proportion of idiopathic syndromic mental retardation cases. Using a fluorescent genotyping based strategy, we found a 10% rate of cryptic subtelomeric rearrangements in a large series of 150 probands with severe idiopathic syndromic mental retardation and normal RHG-GTG banded karyotype. Fourteen children were found to carry deletions or duplications of one or more chromosome telomeres and two children had uniparental disomy. This study clearly shows that fluorescent genotyping is a sensitive and cost effective method that not only detects cryptic subtelomeric rearrangements but also provides a unique opportunity to detect uniparental disomies. We suggest giving consideration to systematic examination of subtelomeric regions in the diagnostic work up of patients with unexplained syndromic mental retardation.

A novel automated strategy for screening cryptic telomeric rearrangements in children with idiopathic mental retardation.

Cryptic unbalanced subtelomeric rearrangements are known to cause a significant proportion of idiopathic mental retardation in childhood. Because of the limited sensitivity of routine analyses, the cytogenetic detection of such rearrangements requires molecular techniques, namely FISH and comparative genomic hybridisation (CGH). An alternative approach consists in using genetic markers to detect segmental aneusomy. Here, we describe a new strategy based upon automated fluorescent genotyping to search for non mendelian segregation of telomeric microsatellites. A total of 29 individuals belonging to 24 unrelated families were screened and three abnormal patterns of segregation were detected (two rearrangements and one parental disomy). This study gives strong support to the view that cryptic telomeric rearrangements significantly contribute to idiopathic mental retardation and demonstrates that fluorescent genotyping is a very sensitive and cost-effective method to detect deletions, duplications and uniparental disomies.

Ebstein anomaly associated with rearrangements of chromosomal region 11q.

Ebstein anomaly (EA) is a relatively uncommon congenital heart defect and it is very rarely associated with a chromosomal anomaly. We report two distinct rearrangements of the chromosomal region 11q arm in two unrelated patients with Ebstein anomaly, renal malformation, minor anomalies, and the Pierre Robin sequence. The first patient had an interstitial deletion of chromosome 11 [46,XY,del(11)(11q21q23), and the other had a tertiary trisomy of chromosome 11qter (47,XX,+der(22)t(11;22)(q23;q11.2) Its association with either a chromosome 11q deletion or a duplication in some individuals suggests that a rearrangement of the 11q region is likely to cause a shift of the individuals' underlying liability to develop EA above a certain threshold.

Absent lacrimal ducts, distichiasis, dysmorphic features, and brachydactyly: a case report.

We report a male patient presenting with the association of absent lacrimal ducts, distichiasis, dysmorphic facial features and limb abnormalities. Extensive chromosomal studies showed normal chromosomes. We discuss differential diagnoses such as Setleis, Char and Lacrimo-Auriculo-Dento-Digital (LADD) syndromes. This may represent a novel entity for which parental consanguinity would support an autosomal recessive mode of inheritance.

[Inversion of the circadian melatonin rhythm in Smith-Magenis syndrome]. / Inversion du rythme circadien de la mélatonine dans le syndrome de Smith-Magenis.

Smith-Magenis syndrome (SMS) is a genetic disease ascribed to an interstitial deletion on chromosome 17 (del 17p11); the prevalence is 1/25,000 births. The diagnosis is made on high-resolution karyotype confirmed by FISH. Clinical features include mild dysmorphism, short stature, other malformations (heart, renal, neurologic diseases). Mental retardation is constant; there are major behavioral disturbances and severe sleep disorders. We studied sleep disorders and melatonin secretion in SMS children and we have shown inversion of the circadian rhythm of melatonin, abnormally secreted during the day. This is the first biological model of behavioral and sleep disorder in a genetic disease. Therapeutic approach using beta-blockers in the morning and melatonin in the evening, reset circadian rhythm of melatonin, improve behavior and restore sleep.

[Infantile psychosis, pseudo-Alzheimer syndrome, and trisomy 21. A trial of treatment with folinic acid: preliminary report]. / Psychose infantile, syndrome pseudo-Alzheimer, et trisomie 21. Essai de médication par l'acide folinique: rapport préliminaire.

Trisomy 21 produces excess sensibility to methotrexate (dihydrofolate reductase inhibitor). A trial of medication with folinic acid (5-formyl-tetrahydrofolate) was realized on 39 trisomic 21 patients. 30 of them were affected by severe infantile psychosis and the other 9 were affected by a severe Alzheimer-like regression. On 69 assays, 37 were favorable and 32 were null. A dose/effect correlation was highly significant. It is proposed that a systematic investigation of the effects of folinic acid (associated or not with monocarbon precursors) be studied in cases of trisomy 21 complicated by precocious psychosis or severe secondary regression.

Monozygotic twins discordant for 18q21.2qter deletion detected by array CGH in amniotic fluid.

Discordant chromosomal anomalies in monozygotic twins may be caused by various timing issues of erroneous mitosis and twinning events. Here, we report a prenatal diagnosis of heterokaryotypic monozygotic twins discordant for phenotype. In a 28-year-old woman, ultrasound examination performed at 26 weeks of gestation, detected intrauterine growth restriction and unilateral cleft lip and palate in twin B, whereas twin A had normal fluid, growth and anatomy. Molecular karyotyping in twin B identified a 18q21.2qter deletion, further confirmed by FISH analysis on amniocytes. Interestingly, in twin A, cytogenetic studies (FISH analysis and karyotype) on amniocytes were normal. Genotyping with microsatellite markers confirmed the monozygosity of the twins. At 32 weeks of gestation, selective termination of twin B was performed by umbilical cord coagulation and fetal blood samples were taken from the umbilical cord in both twins. FISH analyses detected mosaicism in both twins with 75% of cells being normal and 25% harboring the 18qter deletion. After genetic counseling, the parents elected to terminate the second twin at 36 weeks of gestation. In postmortem studies, FISH analyses revealed mosaicism on several tissues in both twins. Taking into account this observation, we discuss the difficulties of genetic counseling and management concerning heterokaryotypic monozygotic twins.

[Nucleolus organizer region--centromere translocation]. / Translocation NOR--centromère.

A karyotype 45,XX,-13,-15,+psudic (13;15)(p12.9;11.200) was observed in a young woman after two spontaneous miscarriages. After R-, C-, and NOR - banding - the rearranged element was shown to include: the long arm, the active centromere, and the NOR of chromosome 13, followed by the inactivated centromere, and the long arm of chromosome 15.