LGI1 microdeletions are not a frequent cause of partial epilepsy with auditory features (PEAF).

Heterozygous mutations of the leucine-rich, glioma-inactivated 1 gene (LGI1) are the major known cause of partial epilepsy with auditory features (PEAF), accounting for roughly 50% of families. Recently, a partial gene microdeletion has been reported in a single family. To assess the contribution of LGI1 microrearrangements to the pathogenesis of PEAF, we screened 50 patients negative for point mutations through multiplex ligation-dependent probe amplification (MLPA) analysis. No cryptic imbalances were found in LGI1, suggesting that LGI1 microdeletions are not a frequent cause of PEAF. Despite the small number of examined patients and the need for replication studies, these findings support the hypothesis that diagnostic screening for LGI1 microrearrangements lacks clinical utility, especially for sporadic cases, and further highlight genetic heterogeneity of familial and sporadic PEAF.

9q31.1q31.3 deletion in two patients with similar clinical features: a newly recognized microdeletion syndrome?

Interstitial deletions of the long arm of chromosome 9 are rare and most patients have been detected by conventional cytogenetic techniques. Disparities in size and localization are large and no consistent region of overlap has been delineated. We report two similar de novo deletions of 6.3 Mb involving the 9q31.1q31.3 region, identified in two monozygotic twins and one unrelated patient through array-CGH analysis. By cloning the deletion breakpoints, we could show that these deletions are not mediated by segmental duplications. The patients displayed a distinct clinical phenotype characterized by mild intellectual disability, short stature with high body mass index, thick hair, arched eyebrows, flat profile with broad chin and mild prognathism, broad, and slightly overhanging tip of the nose, short neck with cervical gibbus. The twin patients developed a metabolic syndrome (type 2 diabetes, hypercholesterolemia, vascular hypertension) during the third decade of life. Although long-term follow-up and collection of additional patients will be needed to obtain a better definition of the phenotype, our findings characterize a previously undescribed syndromic disorder associated with haploinsufficiency of the chromosome 9q31.1q31.3 region.

[Clinical and genetic analysis of idiopathic intellectual disability based on array comparative genomic hybridization].

In this study authors searched for chromosomal aberrations in 71 children with developmental delay or idiopathic mental retardation using Human Genome CGH Microarray Kits 4×44K and 8×60K (Agilent Technologies, USA). Microdeletions and microduplications, as well as CNV, which may be related to intellectual disability and associated with regions of known hereditary diseases or chromosomal syndromes were identified in 14 (20%) children (these patients are described in this article). During the analysis, candidate genes localized within the regions of aberrations and associated with development and functioning of nervous system were denoted.

Olfactory Receptor-Related Duplicons Mediate a Microdeletion at 11q13.2q13.4 Associated with a Syndromic Phenotype.

By array-CGH, we identified a cryptic deletion of about 3.4 Mb involving the chromosomal region 11q13.2q13.4 in a child with speech and developmental delay. Highly homologous segmental duplications related to the well-known olfactory receptor (OR)-containing clusters at 8p and 4p are located at the breakpoints of the imbalance and may be involved in its occurrence. Although these structural features are known to promote recurrent chromosomal rearrangements and previous studies had included the 11q13.2q13.4 deletion region among those considered potentially more unstable, neither deletions nor duplications of this region had been reported until now. Among the deleted genes, SHANK2 might play a role in the phenotype of the patient since it encodes a postsynaptic scaffolding protein similar to SHANK3, whose haploinsufficiency is a well-known cause of severe speech delay and autistic-like behavior, and recently deletions and mutations of SHANK2 have been described in patients with an autistic spectrum disorder or mental retardation.

Cryptic deletions are a common finding in "balanced" reciprocal and complex chromosome rearrangements: a study of 59 patients.

Using array comparative genome hybridisation (CGH) 41 de novo reciprocal translocations and 18 de novo complex chromosome rearrangements (CCRs) were screened. All cases had been interpreted as "balanced" by conventional cytogenetics. In all, 27 cases of reciprocal translocations were detected in patients with an abnormal phenotype, and after array CGH analysis, 11 were found to be unbalanced. Thus 40% (11 of 27) of patients with a "chromosomal phenotype" and an apparently balanced translocation were in fact unbalanced, and 18% (5 of 27) of the reciprocal translocations were instead complex rearrangements with >3 breakpoints. Fourteen fetuses with de novo, apparently balanced translocations, all but two with normal ultrasound findings, were also analysed and all were found to be normal using array CGH. Thirteen CCRs were detected in patients with abnormal phenotypes, two in women who had experienced repeated spontaneous abortions and three in fetuses. Sixteen patients were found to have unbalanced mutations, with up to 4 deletions. These results suggest that genome-wide array CGH may be advisable in all carriers of "balanced" CCRs. The parental origin of the deletions was investigated in 5 reciprocal translocations and 11 CCRs; all were found to be paternal. Using customized platforms in seven cases of CCRs, the deletion breakpoints were narrowed down to regions of a few hundred base pairs in length. No susceptibility motifs were associated with the imbalances. These results show that the phenotypic abnormalities of apparently balanced de novo CCRs are mainly due to cryptic deletions and that spermatogenesis is more prone to generate multiple chaotic chromosome imbalances and reciprocal translocations than oogenesis.