Recurrent distal 7q11.23 deletion including HIP1 and YWHAG identified in patients with intellectual disabilities, epilepsy, and neurobehavioral problems.

We report 26 individuals from ten unrelated families who exhibit variable expression and/or incomplete penetrance of epilepsy, learning difficulties, intellectual disabilities, and/or neurobehavioral abnormalities as a result of a heterozygous microdeletion distally adjacent to the Williams-Beuren syndrome region on chromosome 7q11.23. In six families with a common recurrent ∼1.2 Mb deletion that includes the Huntingtin-interacting protein 1 (HIP1) and tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein gamma (YWHAG) genes and that is flanked by large complex low-copy repeats, we identified sites for nonallelic homologous recombination in two patients. There were no cases of this ∼1.2 Mb distal 7q11.23 deletion copy number variant identified in over 20,000 control samples surveyed. Three individuals with smaller, nonrecurrent deletions (∼180-500 kb) that include HIP1 but not YWHAG suggest that deletion of HIP1 is sufficient to cause neurological disease. Mice with targeted mutation in the Hip1 gene (Hip1⁻(/)⁻) develop a neurological phenotype characterized by failure to thrive, tremor, and gait ataxia. Overall, our data characterize a neurodevelopmental and epilepsy syndrome that is likely caused by recurrent and nonrecurrent deletions, including HIP1. These data do not exclude the possibility that YWHAG loss of function is also sufficient to cause neurological phenotypes. Based on the current knowledge of Hip1 protein function and its proposed role in AMPA and NMDA ionotropic glutamate receptor trafficking, we believe that HIP1 haploinsufficiency in humans will be amenable to rational drug design for improved seizure control and cognitive and behavioral function.

Clinical improvement of the aggressive neurobehavioral phenotype in a patient with a deletion of PITX3 and the absence of L-DOPA in the cerebrospinal fluid.

The development of midbrain dopamine (DA) neurons is regulated by several transcription factors, including Nurr1, Wnt1, Lmx1a/1b, En1, En2, Foxa1, Foxa2, and Pitx3. PITX3 is an upstream co-activator of the TH (tyrosine hydroxylase) promoter. Pitx3(-/-) mice have a selective loss of dopaminergic neurons in the substantia nigra and ventral tegmental area, leading to the significantly reduced DA levels in the nigrostriatal pathway and in the dorsal striatum and manifest anomalous striatum-dependent cognitive impairment and neurobehavioral activity. Treatment with L-DOPA, dopamine, or dopamine receptor agonists in these mice reversed several of their sensorimotor impairments. Heterozygous missense mutations in PITX3 have been reported in patients with autosomal dominant congenital cataract and anterior segment (ocular) mesenchymal dysgenesis (ASMD) whereas homozygous missense mutations have been found in patients with microphthalmia and neurological impairment. Using a clinical oligonucleotide array comparative genomic hybridization (aCGH), we have identified an ∼317 kb hemizygous deletion in 10q24.32, involving PITX3 in a 17-year-old male with a Smith-Magenis syndrome-like phenotype, including mild intellectual impairment, sleep disturbance, hyperactivity, and aggressive and self-destructive behavior. Interestingly, no eye anomalies were found in our patient. Analysis of neurotransmitters in his cerebrospinal fluid revealed an absence of L-DOPA and significantly decreased levels of catecholamine metabolites. Importantly, L-DOPA treatment of our patient has led to mild mitigation of his aggressive behavior and mild improvement of his attention span, extended time periods of concentration, and better sleep.

Application of array comparative genomic hybridization in 102 patients with epilepsy and additional neurodevelopmental disorders.

Copy-number variants (CNVs) collectively represent an important cause of neurodevelopmental disorders such as developmental delay (DD)/intellectual disability (ID), autism, and epilepsy. In contrast to DD/ID, for which the application of microarray techniques enables detection of pathogenic CNVs in -10-20% of patients, there are only few studies of the role of CNVs in epilepsy and genetic etiology in the vast majority of cases remains unknown. We have applied whole-genome exon-targeted oligonucleotide array comparative genomic hybridization (array CGH) to a cohort of 102 patients with various types of epilepsy with or without additional neurodevelopmental abnormalities. Chromosomal microarray analysis revealed 24 non-polymorphic CNVs in 23 patients, among which 10 CNVs are known to be clinically relevant. Two rare deletions in 2q24.1q24.3, including KCNJ3 and 9q21.13 are novel pathogenic genetic loci and 12 CNVs are of unknown clinical significance. Our results further support the notion that rare CNVs can cause different types of epilepsy, emphasize the efficiency of detecting novel candidate genes by whole-genome array CGH, and suggest that the clinical application of array CGH should be extended to patients with unexplained epilepsies.

Early-onset seizures due to mosaic exonic deletions of CDKL5 in a male and two females.

PURPOSE: Mutations in the CDKL5 gene have been associated with an X-linked dominant early infantile epileptic encephalopathy-2. The clinical presentation is usually of severe encephalopathy with refractory seizures and Rett syndrome (RTT)-like phenotype. We attempted to assess the role of mosaic intragenic copy number variation in CDKL5. METHODS: We have used comparative genomic hybridization with a custom-designed clinical oligonucleotide array targeting exons of selected disease and candidate genes, including CDKL5. RESULTS: We have identified mosaic exonic deletions of CDKL5 in one male and two females with developmental delay and medically intractable seizures. These three mosaic changes represent 60% of all deletions detected in 12,000 patients analyzed by array comparative genomic hybridization and involving the exonic portion of CDKL5. CONCLUSION: We report the first case of an exonic deletion of CDKL5 in a male and emphasize the importance of underappreciated mosaic exonic copy number variation in patients with early-onset seizures and RTT-like features of both genders.

Novel mutation of IL1RAPL1 gene in a nonspecific X-linked mental retardation (MRX) family.

Mental retardation (MR) affects approximately 2% of the population. About 10% of all MR cases result from defects of X-linked genes. Mutations in most of more than 20 known genes causing nonspecific form of X-linked MR (MRX) are very rare and may account for less than 0.5-1% of MR. Linkage studies in extended pedigrees followed by mutational analysis of known MRX genes in the linked interval are often the only way to identify a genetic cause of the disorder. We performed linkage analysis in several MRX families, and in one family with four males with MR we mapped the disease to an interval encompassing Xp21.2-22.11 (with a maximum LOD score of 2.71). Subsequent mutation analysis of genes located in this interval allowed us to identify a partial deletion of the IL1RAPL1 gene. Different nonoverlapping deletions involving IL1RAPL1 have been reported previously, suggesting that this region could be deletion-prone. In this report, we present the results of the molecular analyses and clinical examinations of four affected family members with the deletion in IL1RAPL1. Our data further confirm the importance and usefulness of linkage studies for gene mapping in MRX families and demonstrate that IL1RAPL1 plays an important role in the etiology of MRX. With the development of new methods (aCGH, MLPA), further rearrangements in this gene (including deletions and duplications) might be discovered in the nearest future.

[Variability in clinical expression of Noonan syndrome--the report of two familial cases]. / Zmiennosc ekspresji klinicznej zespolu Noonan--analiza dwóch przypadków rodzinnych.

Noonan syndrome (NS) belongs to one of the most frequent genetic disorders with autosomal dominant pattern of inheritance. The main symptoms of NS are short stature, congenital heart defects, thorax deformities and specific dysmorphic features: hypertelorism, low set ears. short and wide neck, wide spaced nipples. The clinical picture ofNS changes with the age, which impedes the proper diagnosis in adults. We present two familial cases of Noonan syndrome with mutated PTPN11 gene in probands and one of their parents and siblings. We analyzed clinical features with regards to NS diagnostic criteria.

Molecular cytogenetic characterization of eight small supernumerary marker chromosomes originating from chromosomes 2, 4, 8, 18, and 21 in three patients.

Small supernumerary marker chromosomes (sSMCs) are a morphologically heterogeneous group of additional structurally abnormal chromosomes that cannot be identified unambiguously by conventional banding techniques alone. Molecular cytogenetic methods enable detailed characterization of sSMCs; however, in many cases interpretation of their clinical significance is problematic. The aim of our study was to characterize precisely sSMCs identified in three patients with dysmorphic features, psychomotor retardation and multiple congenital anomalies. We also attempted to correlate the patients' genotypes with phenotypes by inclusion of data from the literature. The sSMCs were initially detected by G-banding analysis in peripheral blood lymphocytes in these patients and were subsequently characterized using multicolor fluorescence in situ hybridization (M-FISH), (sub)centromere-specific multicolor FISH (cenM-FISH, subcenM-FISH), and multicolor banding (MCB) techniques. Additionally, the sSMCs in two patients were also studied by hybridization to whole-genome bacterial artificial chromosome (BAC) arrays (array-CGH) to map the breakpoints on a single BAC clone level. In all three patients, the chromosome origin, structure, and euchromatin content of the sSMCs were determined. In patient RS, only a neocentric r(2)(q35q36) was identified. It is a second neocentric sSMC(2) in the literature and the first marker chromosome derived from the terminal part of 2q. In the other two patients, two sSMCs were found, as M-FISH detected additional sSMCs that could not be characterized in G-banding analysis. In patient MK, each of four cell lines contained der(4)(:p11.1-->q12:) accompanied by a sSMC(18): r(18)(:p11.2-->q11.1::p11.2-->q11.1:), inv dup(18)(:p11.1-->q11.1::q11.1-->p11.1:), or der(18) (:p11.2-->q11.1::q11.1-->p11.1:). In patient NP, with clinical features of trisomy 8p, three sSMCs were characterized: r(8)(:p12-->q11.1::q11.1-->p21:) der(8) (:p11.22-->q11.1::q11.1-->p21::p21-->p11.22:) and der(21)(:p11.1-->q21.3:). The BAC array results confirmed the molecular cytogenetic results and refined the breakpoints to the single BAC clone resolution. However, the complex mosaic structure of the marker chromosomes derived from chromosomes 8 and 18 could only be identified by molecular cytogenetic methods. This study confirms the usefulness of multicolor FISH combined with whole-genome arrays for comprehensive analyses of marker chromosomes.

Analysis of CFTR, SPINK1, PRSS1 and AAT mutations in children with acute or chronic pancreatitis.

OBJECTIVES: Defects of PRSS1, SPINK1, CFTR and AAT are considered causative or predisposing to pancreatitis. The aim of this study was to evaluate the impact of these defects into molecular pathology of chronic pancreatitis (CP) and acute recurrent pancreatitis (ARP). METHODS: Ninety-two children with CP or ARP, 55 family members and 50 controls were investigated. The subjects were screened for PRSS1 mutations: R122H, R122C, A16V, N29I; SPINK1 N34S variant; panel of 14 CFTR defects: INNOLiPA CFTR12, CFTRdele2,3 and IVS8-T variant or panel of 3 CFTR defects-F508del, CFTRdele2,3 and IVS8-T; AAT mutations: E264V, E342K. RESULTS: We identified 1 mutated allele in at least 1 of 4 genes in 31 of 92 patients and 12 of 50 controls (P = 0.157). Mutations in SPINK1 and PRSS1 were most frequent. PRSS1 mutations were identified mainly in CP patients (9.6% of CP vs 2.5% of ARP alleles, P = 0.094), whereas N34S SPINK1 mutation was present with comparable frequency in CP and ARP patients (7.7% vs 10.0%, P = 0.768). The frequency of mutations in CFTR alleles was similar to controls (4.9% vs 5%, P = 0.587). Overall frequency of AAT mutations was lower than in the controls. Family studies showed that defects in the examined genes did not always segregate with disease. CONCLUSIONS: PRSS1 defects seem to be causative for pancreatitis, whereas defects in SPINK1 are suggested to be associated with the disease. No association between CFTR mutations and pancreatitis was observed. The importance of AAT variants remains speculative.

Molecular analysis of defects in the CFTR gene and AZF locus of the Y chromosome in male infertility.

OBJECTIVE: To investigate the frequency and potential impact of mutations and polymorphisms in the CFTR gene and deletions in AZF locus of the Y chromosome in patients with azoospermia (AZOO), cryptozoospermia (CRYPTO) or oligoasthenoteratozoospermia (OAT) who were to be included in an assisted reproductive technologies (ART) program. STUDY DESIGN: A total of 188 infertile men were enrolled in the study: 100 patients with AZOO, 38 with CRYPTO and 50 with OAT. RESULTS: The CFTR gene mutations or IVS8-5T variant in at least 1 allele was identified with similar frequencies among the AZOO (33%) and CRYPTO (21%) patients; 55% of the AZOO patients with normal spermatogenesis (NS) had mutations in 1 or 2 alleles. The novel R810G mutation in exon 13 was identified in 1 NS patient. The OAT or AZOO patients with Sertoli cell only syndrome (SCO) had mutations in the CFTR gene with similar frequencies to that in the general Polish population. The deletions in the AZF locus were detected in 20% of SCO patients, 11.5% of AZOO patients with maturation arrest and in 5% of CRYPTO patients. The other groups (NS, OAT) did not carry deletions in the region studied. CONCLUSION: Molecular diagnosis of the CFTR gene, Y chromosome deletion analysis and genetic counseling are necessary diagnostic elements for patients with male infertility, especially if the are included in an ART program.

Towards a Better Molecular Diagnosis of FMR1-Related Disorders-A Multiyear Experience from a Reference Lab.

The article summarizes over 20 years of experience of a reference lab in fragile X mental retardation 1 gene (FMR1) molecular analysis in the molecular diagnosis of fragile X spectrum disorders. This includes fragile X syndrome (FXS), fragile X-associated primary ovarian insufficiency (FXPOI) and fragile X-associated tremor/ataxia syndrome (FXTAS), which are three different clinical conditions with the same molecular background. They are all associated with an expansion of CGG repeats in the 5'UTR of FMR1 gene. Until 2016, the FMR1 gene was tested in 9185 individuals with the pre-screening PCR, supplemented with Southern blot analysis and/or Triplet Repeat Primed PCR based method. This approach allowed us to confirm the diagnosis of FXS, FXPOI FXTAS in 636/9131 (6.96%), 4/43 (9.3%) and 3/11 (27.3%) of the studied cases, respectively. Moreover, the FXS carrier status was established in 389 individuals. The technical aspect of the molecular analysis is very important in diagnosis of FXS-related disorders. The new methods were subsequently implemented in our laboratory. This allowed the significance of the Southern blot technique to be decreased until its complete withdrawal. Our experience points out the necessity of implementation of the GeneScan based methods to simplify the testing procedure as well as to obtain more information for the patient, especially if TP-PCR based methods are used.

Recombination aneusomy of subtelomeric regions of chromosome 5, resulting from a large familial pericentric inversion inv(5)(p15.33q35.3).

We present a family with three cases of recombination aneusomy rec(5)dup(5q) originating from a large parental pericentric inversion of chromosome 5. The proband--a 6-year-old girl with mental retardation, speech delay, microcephaly, and slight facial dysmorphism--was referred for subtelomere testing. FISH with a Multiprobe Chromoprobe T System (CytoCell) and with several BAC clones mapping to both subtelomere regions of chromosome 5, revealed a recombinant chromosome rec(5)dup(5q) originating from a paternal pericentric inversion inv(5)(p15.33q35.3). The same inversion was present in the proband's father's twin-brother and rec(5)dup(5q) was also identified in his two mentally retarded daughters. The distance of breakpoints from the telomere was: 0.234-1.4 Mb for 5p and 4.1-4.8 Mb for 5q. HR-CGH analysis confirmed the duplication of the 5q subtelomeric region but did not identify any concomitant deletion in the 5p subtelomere. Precise mapping of the aneusomic regions in the proband enabled mapping the cat cry and speech delay to 5p15.33, making the earlier localizations of these features more precise. Our family shows that the large pericentric inversion with both breakpoints at subtelomeric regions of chromosome 5 is associated with a high risk of rec(5)dup(5q) in the progeny.

Application of a rapid non-invasive technique in the molecular diagnosis of spinal muscular atrophy (SMA).

BACKGROUND AND PURPOSE: Proximal spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by mutations of the SMN1 gene. The most frequent mutation is biallelic deletion of exon 7 of the SMN1 gene. A small percentage of SMA patients present compound heterozygosity with a point mutation on one allele and deletion on the other. In the remaining cases the disease is unlikely to be related to SMN1 defects. The aim of our study was to estimate the frequency of the common biallelic exon 7 SMN1 deletion in our Polish SMA cohort and implement a test for assessing a molecular defect at the SMN1 locus versus defects in the other genes. MATERIAL AND METHODS: The molecular analysis was performed in a group of 269 patients fulfilling diagnostic criteria of the International SMA Consortium. The common SMN1 exon 7 deletion was tested by a standard PCR analysis. Patients lacking the common mutation were subsequently analyzed for a number of SMN1 alleles with a quantitative test based on real-time PCR. RESULTS: The frequency of homozygous loss of exon 7 in the SMN1 gene was 96.6% (260/269) in our Polish SMA cohort. In 5 of 9 non-deleted patients the real-time PCR analysis showed a decreased number of SMN1 copies. We anticipate that the non-deleted allele carries a second mutation in SMN1 which may contribute to the pathogenesis of SMA. We have also identified 4 patients (1.5%) with SMA carrying two SMN1 alleles without the exon 7 deletion. CONCLUSIONS: The molecular analysis of the biallelic exon 7 of the SMN1 deletion is a standard and reliable test in cases of SMA. Introduction of a quantitative test based on "real-time PCR" further enhances the diagnostic potential by increasing the detection rate of cases likely to be caused by point mutation of the SMN1 gene.

Application of array comparative genomic hybridization in 256 patients with developmental delay or intellectual disability.

We used whole-genome exon-targeted oligonucleotide array comparative genomic hybridization (array CGH) in a cohort of 256 patients with developmental delay (DD)/intellectual disability (ID) with or without dysmorphic features, additional neurodevelopmental abnormalities, and/or congenital malformations. In 69 patients, we identified 84 non-polymorphic copy-number variants, among which 41 are known to be clinically relevant, including two recently described deletions, 4q21.21q21.22 and 17q24.2. Chromosomal microarray analysis revealed also 15 potentially pathogenic changes, including three rare deletions, 5q35.3, 10q21.3, and 13q12.11. Additionally, we found 28 copy-number variants of unknown clinical significance. Our results further support the notion that copy-number variants significantly contribute to the genetic etiology of DD/ID and emphasize the efficacy of the detection of novel candidate genes for neurodevelopmental disorders by whole-genome array CGH.

Newborn screening for cystic fibrosis: Polish 4 years' experience with CFTR sequencing strategy.

Newborn screening for cystic fibrosis (NBS CF) in Poland was started in September 2006. Summary from 4 years' experience is presented in this study. The immunoreactive trypsin/DNA sequencing strategy was implemented. The group of 1,212,487 newborns were screened for cystic fibrosis during the programme. We identified a total of 221 CF cases during this period, including, 4 CF cases were reported to be omitted by NBS CF. Disease incidence in Poland based on the programme results was estimated as 1/4394 and carrier frequency as 1/33. The frequency of the F508del was similar (62%) to population data previously reported. This strategy allowed us to identify 29 affected infants with rare genotypes. The frequency of some mutations (eg, 2184insA, K710X) was assessed in Poland for the first time. Thus, sequencing assay seems to be accurate method for screening programme using blood spots in the Polish population.

Application of custom-designed oligonucleotide array CGH in 145 patients with autistic spectrum disorders.

Autism spectrum disorders (ASDs) are a heterogeneous group of neurodevelopmental disorders, including childhood autism, atypical autism, and Asperger syndrome, with an estimated prevalence of 1.0-2.5% in the general population. ASDs have a complex multifactorial etiology, with genetic causes being recognized in only 10-20% of cases. Recently, copy-number variants (CNVs) have been shown to contribute to over 10% of ASD cases. We have applied a custom-designed oligonucleotide array comparative genomic hybridization with an exonic coverage of over 1700 genes, including 221 genes known to cause autism and autism candidate genes, in a cohort of 145 patients with ASDs. The patients were classified according to ICD-10 standards and the Childhood Autism Rating Scale protocol into three groups consisting of 45 individuals with and 69 individuals without developmental delay/intellectual disability (DD/ID), and 31 patients, in whom DD/ID could not be excluded. In 12 patients, we have identified 16 copy-number changes, eight (5.5%) of which likely contribute to ASDs. In addition to known recurrent CNVs such as deletions 15q11.2 (BP1-BP2) and 3q13.31 (including DRD3 and ZBTB20), and duplications 15q13.3 and 16p13.11, our analysis revealed two novel genes clinically relevant for ASDs: ARHGAP24 (4q21.23q21.3) and SLC16A7 (12q14.1). Our results further confirm the diagnostic importance of array CGH in detection of CNVs in patients with ASDs and demonstrate that CNVs are an important cause of ASDs as a heterogeneous condition with a variety of contributory genes.

Assessment of the role of copy-number variants in 150 patients with congenital heart defects.

BACKGROUND: Congenital heart defects are the most common group of major birth anomalies and one of the leading causes of infant deaths. Mendelian and chromosomal syndromes account for about 20% of congenital heart defects and in some cases are associated with other malformations, intellectual disability, and/or dysmorphic features. The remarkable conservation of genetic pathways regulating heart development in animals suggests that genetic factors can be responsible for a significantly higher percentage of cases. THE AIM: Assessment of the role of CNVs in the etiology of congenital heart defects using microarray studies. MATERIAL AND METHODS: Genome-wide array comparative genomic hybridization, targeting genes known to play an important role in heart development or responsible for abnormal cardiac phenotype was used in the study on 150 patients. In addition, we have used multiplex ligation-dependent probe amplification specific for chromosome 22q11.2 region. RESULTS: We have identified 21 copy-number variants, including 13 known causative recurrent rearrangements (12 deletions 22q11.2 and one deletion 7q11.23), three potentially pathogenic duplications (5q14.2, 15q13.3, and 22q11.2), and five variants likely benign for cardiac anomalies. We suggest that abnormal copy-number of the ARRDC3 and KLF13 genes can be responsible for heart defects. CONCLUSIONS: Our study demonstrates that array comparative genomic hybridization enables detection of clinically significant chromosomal imbalances in patients with congenital heart defects.

[Alpha-thalassemia/mental retardation syndrome (ATR-X) in two brothers - clinical characteristics, diagnostics and genetic counselling issues]. / Zespol talasemi α Z niepelnosprawnoscia intelektualna (ATR-X) u dwoch braci - charakterystyka kliniczna, zasady diagnostyki i poradnictwa genetycznego.

Alpha-thalassemia/mental retardation syndrome (ATR-X) is a neurodevelopmental disorder with characteristic clinical picture as well as presence of pathognomonic haemoglobin H inclusions (HbH) on peripheral blood examination. Typical features of this condition are: severe intellectual impairment, muscular hypotonia, delay of growth, genitourinary/skeletal abnormalities and characteristic facial dysmorphism. Molecular basis of the syndrome constitute mutations in ATR-X gene located on the long arm of X chromosome (Xq13). In this work, clinical characteristics of the molecularly confirmed case of ATR-X syndrome in two brothers are presented. The mother of both affected boys is an asymptomatic mutation carrier. In one of the brothers additional studies revealed the presence of de novo 1q21.1 microdeletion. ATR-X syndrome symptomatology, differential diagnostics issues as well as the aims of genetic counselling are described.

[Gene mapping in 14 families with X-linked nonspecific mental retardation]. / Mapowanie genów w 14 rodzinach z niespecyficzna niepelnosprawoscia intelektualna sprzezona z chromosomem X.

UNLABELLED: Mental retardation affects 2-3% of the population. The identification of nonspecific X-linked mental retardation genes represents a challenge of considerable medical and scientific importance. AIM: An attempt to identify new genes and mutations in known genes in 14 families with nonspecific X-linked mental retardation. MATERIAL AND METHODS: Linkage analysis with microsatellite markers was performed in 14 families with mental retardation segregating as an X-linked feature. Significant lod score (> 2) was obtained only for 2 families, due to insufficient number of analyzed families' members. Known MRX genes located in the linkage intervals were analysed. RESULTS: Analysis of selected known MRX genes enabled identification of pathogenic mutations in 3 out of 14 families. Sequencing of further candidate genes is in progress. In all families the critical region and the number of genes to analyze was significantly narrowed. CONCLUSIONS: Linkage analysis in families with mental retardation segregating as an X-linked feature is still a considerable approach leading to identification of new genes, and mutations in known genes. It is a first step of identification of disease background, even in small families with lod score < 2.

A family with paroxysmal nonkinesigenic dyskinesia: genetic and treatment issues.

Paroxysmal nonkinesigenic dyskinesia is a condition characterized by attacks of sudden involuntary movements triggered by caffeine or alcohol intake, stress, or fatigue. The paroxysms are usually of the generalized type and may last up to an hour. Described here is a Polish family with this disorder seen in two children and their father. Variable expressivity as well as reduced penetrance of the causative mutation were noteworthy in this kindred. Treatment options included abortive diazepam and prophylactic levetiracetam, with the latter having a more pronounced effect in this family. Favorable response to levetiracetam is probably linked to action of the drug on calcium channels in neurons, muscle cells, or both.

[Balanced chromosomal rearrangements resulting in intellectual disability. An analysis of 22 cases with application of CGH and FISH methods]. / Zrównowazone rearanzacje chromosomowe jako przyczyna niepelnosprawnosci intelektualnej. Analiza 22 przypadków z wykorzystaniem technik CGH oraz FISH.

INTRODUCTION: In approximately 6% of balanced chromosomal rearrangements carriers, intellectual disability, dysmorphic features and congenital anomalies can be found. The abnormal phenotype might be the result of genomic imbalance or aberrant expression caused by direct breakage of a dosage sensitive gene. THE AIM OF THIS STUDY: To estimate the frequency and implication of the submicroscopic chromosomal aberrations on the abnormal phenotypes present in patients with balanced chromosomal rearrangements. Also an attempt was made to define the type of genetic defect and gene identification responsible for the intellectual disability and additional clinical features. MATERIAL AND METHODS: 22 patients with intellectual disability, congenital anomalies and dysmorphic features were analysed. Molecular karyotyping was performed in all patients using FISH with region-specific BAC clones, high resolution comparative genomic hybridization (HR-CGH) or array CGH (aCGH). A targeted or whole genome microarrays were applied. RESULTS: In 5 of 22 carriers 6 microdeletions and one duplication were found (7/22, 31.8%). Only two microdeletions were mapped at the chromosomal breakpoints. Three rearrangements had more complex structure than conventional methods demonstrated. In the chromosomal breakpoints of 21 patients the 24 genes, which functions suggest the relationship between abnormal gene expression and patients' intellectual disability, were mapped. CONCLUSIONS: We showed that in a considerable group of patients with balanced chromosomal rearrangements and abnormal phenotype the cryptic aberrations, unidentified by conventional methods, are present. These results confirmed the legitimacy of detailed analysis of the chromosomal breakpoints as well as the whole genome screening with the use of new cytogenetic methods.