New candidate loci identified by array-CGH in a cohort of 100 children presenting with syndromic obesity.

Syndromic obesity is defined by the association of obesity with one or more feature(s) including developmental delay, dysmorphic traits, and/or congenital malformations. Over 25 syndromic forms of obesity have been identified. However, most cases remain of unknown etiology. The aim of this study was to identify new candidate loci associated with syndromic obesity to find new candidate genes and to better understand molecular mechanisms involved in this pathology. We performed oligonucleotide microarray-based comparative genomic hybridization in a cohort of 100 children presenting with syndromic obesity of unknown etiology, after exhaustive clinical, biological, and molecular studies. Chromosomal copy number variations were detected in 42% of the children in our cohort, with 23% of patients with potentially pathogenic copy number variants. Our results support that chromosomal rearrangements are frequently associated with syndromic obesity with a variety of contributory genes having relevance to either obesity or developmental delay. A list of inherited or apparently de novo duplications and deletions including their enclosed genes and not previously linked to syndromic obesity was established. Proteins encoded by several of these genes are involved in lipid metabolism (ACOXL, MSMO1, MVD, and PDZK1) linked with nervous system function (BDH1 and LINGO2), neutral lipid storage (PLIN2), energy homeostasis and metabolic processes (CDH13, CNTNAP2, CPPED1, NDUFA4, PTGS2, and SOCS6).

NOTCH, a new signaling pathway implicated in holoprosencephaly.

Genetics of Holoprosencephaly (HPE), a congenital malformation of the developing human forebrain, is due to multiple genetic defects. Most genes that have been implicated in HPE belong to the sonic hedgehog signaling pathway. Here we describe a new candidate gene isolated from array comparative genomic hybridization redundant 6qter deletions, DELTA Like 1 (DLL1), which is a ligand of NOTCH. We show that DLL1 is co-expressed in the developing chick forebrain with Fgf8. By treating chick embryos with a pharmacological inhibitor, we demonstrate that DLL1 interacts with FGF signaling pathway. Moreover, a mutation analysis of DLL1 in HPE patients revealed a three-nucleotide deletion. These various findings implicate DLL1 in early patterning of the forebrain and identify NOTCH as a new signaling pathway involved in HPE.

A translocation breakpoint disrupts the ASPM gene in a patient with primary microcephaly.

Primary microcephaly (microcephalia vera) is a developmental abnormality resulting in a small brain, with mental retardation. It is usually transmitted as an autosomal recessive trait, and six loci have been reported to date. We analyzed a translocation breakpoint previously reported in a patient with apparently sporadic primary microcephaly, at 1q31, where locus MCPH5 maps. The patient was lost to follow-up, and we sampled a maternal aunt who carried the familial translocation. FISH analyses showed that the insert of BAC clone RP11-32D17 spanned the breakpoint. The breakpoint was further located within a fragment of this insert corresponding to intron 17 of the ASPM gene, resulting in a predicted transcript truncated of more than half of its coding sequence. It is very likely that the proband carried a second ASPM mutation in trans, but he was not available for sampling and hence we could not confirm this hypothesis. Our observation adds to the mutation spectrum of ASPM in primary microcephaly, and is to our knowledge the second example of a constitutional, reciprocal translocation responsible for a bona fide autosomal recessive phenotype.

An excess of chromosome 1 breakpoints in male infertility.

In a search for potential infertility loci, which might be revealed by clustering of chromosomal breakpoints, we compiled 464 infertile males with a balanced rearrangement from Mendelian Cytogenetics Network database (MCNdb) and compared their karyotypes with those of a Danish nation-wide cohort. We excluded Robertsonian translocations, rearrangements involving sex chromosomes and common variants. We identified 10 autosomal bands, five of which were on chromosome 1, with a large excess of breakpoints in the infertility group. Some of these could potentially harbour a male-specific infertility locus. However, a general excess of breakpoints almost everywhere on chromosome 1 was observed among the infertile males: 26.5 versus 14.5% in the cohort. This excess was observed both for translocation and inversion carriers, especially pericentric inversions, both for published and unpublished cases, and was significantly associated with azoospermia. The largest number of breakpoints was reported in 1q21; FISH mapping of four of these breakpoints revealed that they did not involve the same region at the molecular level. We suggest that chromosome 1 harbours a critical domain whose integrity is essential for male fertility.

Maternal serum urea resistant alkaline phosphatase in Down syndrome pregnancy.

BACKGROUND: The normal levels of alkaline phosphatase (AP) activity in maternal serum are virtually the same as those observed in Down syndrome (DS) pregnancies at 14-20 weeks' gestation. Using urea inhibition of AP, we observed an atypical AP isoenzyme in the neutrophils of mothers with trisomy 21 fetuses. AIM: To assess the use of urea as a selective inhibitor of serum AP in order to seek a possible diagnostic difference between normal and DS pregnancies. STUDY DESIGN AND SUBJECTS: Serum AP samples from 24 DS pregnancies and 204 control cases were examined at 12-22 weeks' gestation with and without 2.5 M urea AP inhibition at 18 degrees C for 2 h. The levels of AP activity obtained without urea and the percentage urea AP inhibition were analyzed in the two groups. RESULTS: Without urea treatment, no significant difference of total alkaline phosphatase activity levels was detected between the 204 normal controls and the 24 DS samples. Using 2.5 M urea AP inhibition, after 120 min of exposure at 18 degrees C, the residual activity, as a percentage of initial values of AP, showed significantly higher resistance in the DS samples (> or = 50 IU/l of total AP activity) at 15-22 weeks' gestation. However, at 12-14 weeks (< or = 45 IU/l of total AP activity), no significant difference was found between the DS and control cases. CONCLUSION: Serum urea resistant alkaline phosphatase in DS pregnancies showed a significant difference only at 15-22 weeks' gestation, compared with normal controls.

Distal 10q monosomy: new evidence for a neurobehavioral condition?

Pure distal monosomy of the long arm of chromosome 10 is a rare cytogenetic abnormality. The location and size of the deletions described in this region are variable. Nevertheless, the patients share characteristic facial appearance, variable cognitive impairment and neurobehavioral manifestations. A Minimal Critical Region corresponding to a 600 kb Smallest Region of deletion Overlap (SRO) has been proposed. In this report, we describe four patients with a distal 10q26 deletion, who displayed attention-deficit/hyperactivity disorders (ADHD). One of them had a marked behavioral profile and relatively preserved cognitive functions. Interestingly, the SRO was not included in the deleted segment of this patient suggesting that this deletion could contain candidate genes involved in the control of neurobehavioral functions. One of these candidates was the CALY gene, known for its association with ADHD patients and whose expression level was shown to be correlated with neurobehavioral disturbances in varying animal models. This report emphasizes the importance of the behavioral problems as a cardinal feature of the 10q microdeletion syndrome. Haploinsufficiency of CALY could play a crucial role in the development of the behavioral troubles within these patients.

Polyvalvular heart disease with joint hypermobility, characteristic facies, and particular skin abnormalities: new cases of "polyvalvular heart disease syndrome" or new association?

Polyvalvular heart disease has been reported in a handful of "private" syndromes that have been recently suggested to represent a single dominantly inherited condition, the polyvalvular heart disease syndrome. We report five cases in two unrelated families (one sporadic case in the first family and three siblings and their father in the second family) with the same association of polyvalvular heart disease, distinctive facial appearance, and, except the father in family 2, major joint hypermobility. Interestingly, in three of our patients (2 siblings and the sporadic case), electron microscopy revealed characteristic ultrastructural skin abnormalities with abnormal amorphous or microfibrillar deposits under the capillary basal membrane in the papillary dermis, suggestive of a connective tissue disorder, but different from Marfan syndrome or Ehlers-Danlos syndrome. Moreover, in family 2, three others sibs died in early infancy of their heart defect. Our two families and the other published cases might illustrate intrafamilial and interfamilial variability within a single condition. However, our two families disclose major joint hypermobility, normal stature, and ultrastructural skin abnormalities that were not described in the previous reports. These discrepancies let us to consider them as affected by a distinct disorder of the connective tissue.

Subtelomeric 6p deletion: clinical, FISH, and array CGH characterization of two cases.

Thirty patients have been described with cytogenetically visible deletion of the short arm of chromosome 6. However, subtelomeric 6p deletion detected by subtelomeric specific probes has been reported only twice. We report two new patients with terminal 6p deletion detected by subtelomeric screening using fluorescence in situ hybridization (FISH). The two patients exhibited mental retardation, ocular abnormalities, hearing loss, and a characteristic facial appearance. Detailed FISH analyses with probes covering the distal 6p25 region estimated the size of the terminal deletions to approximately 5.5 Mb and approximately 4.8 Mb. Array-based comparative genomic hybridization (array CGH) was used to confirm the cryptic deletions. Most patients with subtelomeric defects lack a characteristic phenotype. However, some of the subtelomeric deletions result in a specific phenotype, which can direct the clinician towards the diagnosis. Submicroscopic 6p deletion appears to be a recognizable clinical phenotype, and this region should be thoroughly investigated with FISH probes, including at least a subtelomeric 6p probe and a probe covering FOXC1, for patients presenting with a characteristic facial appearance, ocular abnormalities, predominantly anterior-chamber eye defects, hearing loss, and mental retardation.