Moneef Shoukier

Brain-derived neurotrophic factor (BDNF) gene polymorphisms shape cortical plasticity in humans

BACKGROUND The brain-derived neurotrophic factor (BDNF) gene is involved in mechanisms of synaptic plasticity in the adult brain. It has been demonstrated that BDNF also plays a significant role in shaping externally induced human brain plasticity. Plasticity induced in the human motor cortex by intermittent theta-burst stimulation (iTBS) was impaired in individuals expressing the Val66Met polymorphism. METHODS To explore whether this polymorphism is also important for other neuroplasticity-inducing tools in humans with modes of action differing from that of iTBS, namely, transcranial direct current (tDCS) and random noise stimulation (tRNS), we retrospectively analyzed the data of 64 subjects studied in our laboratory with regard to BDNF genotype. RESULTS Fifteen subjects with the Val66Met allele, 46 subjects with the Val66Val allele, and 3 Met66Met carriers were identified. The response of the Val66Met allele carriers to stimulation differed in two protocols compared with the response of Val66Val individuals. For iTBS (15 subjects, 5 heterozygotes), plasticity could be only induced in the Val66Val allele carriers. However, for facilitatory tDCS (24 subjects, 10 heterozygotes), as well as for inhibitory tDCS, (19 subjects, 8 heterozygotes), carriers of the Val66Met allele displayed enhanced plasticity, whereas for transcranial random noise stimulation (29 subjects, 8 heterozygotes), the difference between groups was not so pronounced. CONCLUSIONS BDNF polymorphism has a definite impact on plasticity in humans, which might differ according to the mechanism of plasticity induction. This impact of BDNF on plasticity should be taken into account for future studies, as well as having wider ranging implications for the treatment of neuropsychiatric disorders with transcranial stimulation tools, as it may predetermine their efficacy for the treatment of disease and rehabilitation.

PATHWAYS OF PROLIFERATION AND ANTIAPOPTOSIS DRIVEN IN BREAST CANCER STEM CELLS BY STEM CELL PROTEIN PIWIL2

Cancer stem cell studies may improve understanding of tumor pathophysiology and identify more effective strategies for cancer treatment. In a variety of organisms, Piwil2 has been implicated in multiple roles including stem cell self-renewal, RNA silencing, and translational control. In this study, we documented specific expression of the stem cell protein Piwil2 in breast cancer with predominant expression in breast cancer stem cells. In patients who were evaluated, we determined that 90% of invasive carcinomas and 81% of carcinomas in situ exhibited highest expression of Piwil2. In breast cancer cells, Piwil2 silencing suppressed the expression of signal transducer and activator of transcription 3, a pivotal regulator of Bcl-X(L) and cyclin D1, whose downregulation paralleled a reduction in cell proliferation and survival. Our findings define Piwil2 and its effector signaling pathways as key factors in the proliferation and survival of breast cancer stem cells.

Array CGH in patients with developmental delay or intellectual disability: are there phenotypic clues to pathogenic copy number variants?

Shoukier M, Klein N, Auber B, Wickert J, Schröder J, Zoll B, Burfeind P, Bartels I, Alsat EA, Lingen M, Grzmil P, Schulze S, Keyser J, Weise D, Borchers M, Hobbiebrunken E, Röbl M, Gärtner J, Brockmann K, Zirn B. Array CGH in patients with developmental delay or intellectual disability: are there phenotypic clues to pathogenic copy number variants?

Functional evaluation of paraplegin mutations by a yeast complementation assay

An autosomal recessive form of hereditary spastic paraplegia (AR‐HSP) is primarily caused by mutations in the SPG7 gene, which codes for paraplegin, a subunit of the hetero‐oligomeric m‐AAA protease in mitochondria. In the current study, sequencing of the SPG7 gene in the genomic DNA of 25 unrelated HSP individuals/families led to the identification of two HSP patients with compound heterozygous mutations (p.G349S/p.W583C and p.A510V/p.N739KfsX741) in the coding sequence of the SPG7 gene. We used a yeast complementation assay to evaluate the functional consequence of novel SPG7 sequence variants detected in the HSP patients. We assessed the proteolytic activity of hetero‐oligomeric m‐AAA proteases composed of paraplegin variant(s) and proteolytically inactive forms of AFG3L2 (AFG3L2E575Q or AFG3L2K354A) upon expression in m‐AAA protease‐deficient yeast cells. We demonstrate that the newly identified paraplegin variants perturb the proteolytic function of hetero‐oligomeric m‐AAA protease. Moreover, commonly occurring silent polymorphisms such as p.T503A and p.R688Q could be distinguished from mutations (p.G349S, p.W583C, p.A510V, and p.N739KfsX741) in our HSP cohort. The yeast complementation assay thus can serve as a reliable system to distinguish a pathogenic mutation from a silent polymorphism for any novel SPG7 sequence variant, which will facilitate the interpretation of genetic data for SPG7. Hum Mutat 31:1–5, 2010.

Microduplication of 3p26.3 in Nonsyndromic Intellectual Disability Indicates an Important Role of CHL1 for Normal Cognitive Function

Terminal deletions of chromosome 3p26.3 confined to the CHL1 gene have previously been described in children with intellectual disability and epilepsy. Here, we report for the first time, a 3p26.3 duplication including only the CHL1 gene in an intellectually disabled girl with epilepsy. The penetrance of both deletions and duplications in 3p26.3 is reduced because all chromosomal imbalances were inherited from healthy parents. Further studies are needed to specify the pathogenic mechanism of 3p26.3 imbalances and to estimate recurrence risks in genetic counseling. However, the description of both deletions and duplications of chromosome 3p26.3 in nonsyndromic intellectual disability suggests that CHL1 is a dosage-sensitive gene with an important role for normal cognitive development.

Familial intellectual disability and autistic behavior caused by a small FMR2 gene deletion.

Alterations of the Fragile Mental Retardation 2 gene (FMR2, synonym AFF2) can result in non‐specific, mild to borderline X‐linked intellectual disability (XLID), and behavioral problems. The well‐known molecular pathomechanism of this condition, also referred to as FRAXE, is a (CCG)n trinucleotide repeat expansion which leads to silencing of the FMR2 gene. However, deletions within the FMR2 gene may also be causative of the disorder. Here, we report on two brothers diagnosed with FRAXE in whom a small deletion in the FMR2 gene was detected by whole genome array comparative genomic hybridization (CGH). The deletion was also present in their clinically healthy mother and maternal uncle who was similarly affected, but not in a healthy older brother of the two patients. Our observation demonstrates that FMR2 gene deletions may contribute to the FRAXE phenotype. Therefore, we suggest that screening for FMR2 gene deletions using array CGH should be considered in patients with non‐specific XLID and absent trinucleotide expansion.

Characterization of five novel large deletions causing hereditary haemorrhagic telangiectasia

Using quantitative real‐time polymerase chain reaction (QRT‐PCR), molecular genetic analysis was carried out for endoglin (ENG) and activin A receptor type II‐like kinase 1 (ACVRL1/ALK1) gene rearrangements in a group of 45 clinically confirmed hereditary haemorrhagic telangiectasia (HHT) families with negative direct sequencing results. We detected five large novel deletions, four in the ALK1 gene and one in the ENG gene. In two families, the whole ALK1 gene was deleted. One of these two deletions spanned at least 216 kb and included five neighbouring genes (LOC728503, ANKRD33, ACVR1B, GRASP, and NR4A1). The lack of additional symptoms in the patient carrying this large deletion indicates that heterozygous loss of these five genes has no obvious phenotypical effect. To our knowledge, this is the first report on whole ALK1 gene deletions in HHT patients. We rescreened our 45 families for large rearrangements using the multiplex ligation‐dependent probe amplification (MLPA) method. No discrepancies between the results of QRT‐PCR and MLPA were found. Our present work proves QRT‐PCR as a reliable and sensitive method. Thus, our study supports that screening for large rearrangements should be considered to improve the genetic analysis in HHT patients with no apparent mutations in ALK1 and ENG using direct sequencing.

Discordant phenotype in monozygotic twins with mosaic trisomy 12p in lymphocytes.

We report on monochorionic diamniotic male twins discordant for the trisomy 12p syndrome. Trisomy 12p mosaicism with a supernumerary der(12)(pter > q12) was detected in approximately 50% of lymphocytes in both children. Fluorescence in situ hybridisation (FISH) revealed a high grade mosaicism of approximately 77% trisomy 12p cells in buccal smear and 85% in hair follicles in the affected twin, while in the normal developing brother an additional 12p chromosome fragment could not be detected in those tissues. Instead, in 3% of buccal smear and hair follicle cells a minute supernumerary marker chromosome comprising central portions of chromosome 12 was observed. Trisomy 12p mosaicism, confined to the lymphocytes of the unaffected twin, may be due to prenatal twin-to-twin transfusion, explaining the conspicuously discordant clinical phenotype. We discuss the possible sequence of events leading to the cytogenetic findings and compare the clinical phenotype presented in the affected twin with other cases of trisomy 12p and tetrasomy 12p (Pallister-Killian syndrome).

Ring chromosome 22 and neurofibromatosis type II: proof of two-hit model for the loss of the NF2 gene in the development of meningioma

Zirn B, Arning L, Bartels I, Shoukier M, Hoffjan S, Neubauer B, Hahn A. Ring chromosome 22 and neurofibromatosis type II: proof of two‐hit model for the loss of the NF2 gene in the development of meningioma.

A de novo interstitial deletion of 2p23.3–24.3 in a boy presenting with intellectual disability, overgrowth, dysmorphic features, skeletal myopathy, dilated cardiomyopathy†

Interstitial deletions of the distal part of chromosome 2p are rare, with only six reported cases involving regions from 2p23 to 2pter. Most of these were cytogenetic investigations. We describe a 14‐year‐old boy with an 8.97 Mb deletion of 2p23.3–24.3 detected by array comparative genomic hybridization (array CGH) who had intellectual disability (ID), unusual facial features, cryptorchidism, skeletal myopathy, dilated cardiomyopathy (DCM), and postnatal overgrowth (macrocephaly and tall stature). We compared the clinical features of the present case to previously described patients with an interstitial deletion within this chromosomal region and conclude that our patient exhibits a markedly different phenotype. Additional patients are needed to further delineate phenotype–genotype correlations