Variability in the heterochromatin regions of the chromosomes and chromosomal anomalies in children with autism: identification of genetic markers of autistic spectrum disorders

Quantitative FISHing: Implications for Chromosomal Analysis

Quantifying signals substantially increases the efficiency of fluorescence in situ hybridization (FISH). Quantitative FISH analysis or QFISHing may be useful for differentiation between chromosome loss and chromosomal associations, detection of amplification of chromosomal loci, and/or quantification of chromosomal heteromorphisms (chromosomal DNAs). The latter is applicable to uncovering the parental origin of chromosomes, which is an important FISH application in genome research. In summary, one may acknowledge that QFISHing has a variety of applications in cancer chromosome research. Accordingly, a protocol for this technique is certainly required. Here, QFISHing protocol is described step-by-step.

Cytogenomic epileptology

Molecular cytogenetic and cytogenomic studies have made a contribution to genetics of epilepsy. However, current genomic research of this devastative condition is generally focused on the molecular genetic aspects (i.e. gene hunting, detecting mutations in known epilepsy-associated genes, searching monogenic causes of epilepsy). Nonetheless, chromosomal abnormalities and copy number variants (CNVs) represent an important part of genetic defects causing epilepsy. Moreover, somatic chromosomal mosaicism and genome/chromosome instability seem to be a possible mechanism for a wide spectrum of epileptic conditions. This idea becomes even more attracting taking into account the potential of molecular neurocytogenetic (neurocytogenomic) studies of the epileptic brain. Unfortunately, analyses of chromosome numbers and structure in the affected brain or epileptogenic brain foci are rarely performed. Therefore, one may conclude that cytogenomic area of genomic epileptology is poorly researched. Accordingly, molecular cytogenetic and cytogenomic studies of the clinical cohorts and molecular neurocytogenetic analyses of the epileptic brain appear to be required. Here, we have performed a theoretical analysis to define the targets of the aforementioned studies and to highlight future directions for molecular cytogenetic and cytogenomic research of epileptic disorders in the widest sense. To succeed, we have formed a consortium, which is planned to perform at least a part of suggested research. Taking into account the nature of the communication, "cytogenomic epileptology" has been introduced to cover the research efforts in this field of medical genomics and epileptology. Additionally, initial results of studying cytogenomic variations in the Russian neurodevelopmental cohort are reviewed with special attention to epilepsy. In total, we have concluded that (i) epilepsy-associated cytogenomic variations require more profound research; (ii) ontological analyses of epilepsy genes affected by chromosomal rearrangements and/or CNVs with unraveling pathways implicating epilepsy-associated genes are beneficial for epileptology; (iii) molecular neurocytogenetic (neurocytogenomic) analysis of postoperative samples are warranted in patients suffering from epileptic disorders.

Klinefelter syndrome mosaicism in boys with neurodevelopmental disorders: a cohort study and an extension of the hypothesis

BACKGROUND

Klinefelter syndrome is a common chromosomal (aneuploidy) disorder associated with an extra X chromosome in males. Regardless of numerous studies dedicated to somatic gonosomal mosaicism, Klinefelter syndrome mosaicism (KSM) has not been systematically addressed in clinical cohorts. Here, we report on the evaluation of KSM in a large cohort of boys with neurodevelopmental disorders. Furthermore, these data have been used for an extension of the hypothesis, which we have recently proposed in a report on Turner's syndrome mosaicism in girls with neurodevelopmental disorders.

RESULTS

Klinefelter syndrome-associated karyotypes were revealed in 49 (1.1%) of 4535 boys. Twenty one boys (0.5%) were non-mosaic 47,XXY individuals. KSM was found in 28 cases (0.6%) and manifested as mosaic aneuploidy (50,XXXXXY; 49,XXXXY; 48,XXXY; 48,XXYY; 47,XXY; and 45,X were detected in addition to 47,XXY/46,XY) and mosaic supernumerary marker chromosomes derived from chromosome X (ring chromosomes X and rearranged chromosomes X). It is noteworthy that KSM was concomitant with Rett-syndrome-like phenotypes caused by MECP2 mutations in 5 boys (0.1%).

CONCLUSION

Our study provides data on the occurrence of KSM in neurodevelopmental disorders among males. Accordingly, it is proposed that KSM may be a possible element of pathogenic cascades in psychiatric and neurodegenerative diseases. These observations allowed us to extend the hypothesis proposed in our previous report on the contribution of somatic gonosomal mosaicism (Turner's syndrome mosaicism) to the etiology of neurodevelopmental disorders. Thus, it seems to be important to monitor KSM (a possible risk factor or a biomarker for adult-onset multifactorial brain diseases) and analysis of neuromarkers for aging in individuals with Klinefelter syndrome. Cases of two or more supernumerary chromosomes X were all associated with KSM. Finally, Rett syndrome-like phenotypes associated with KSM appear to be more common in males with neurodevelopmental disorders than previously recognized.

Turner's syndrome mosaicism in girls with neurodevelopmental disorders: a cohort study and hypothesis

BACKGROUND

Turner's syndrome is associated with either monosomy or a wide spectrum of structural rearrangements of chromosome X. Despite the interest in studying (somatic) chromosomal mosaicism, Turner's syndrome mosaicism (TSM) remains to be fully described. This is especially true for the analysis of TSM in clinical cohorts (e.g. cohorts of individuals with neurodevelopmental disorders). Here, we present the results of studying TSM in a large cohort of girls with neurodevelopmental disorders and a hypothesis highlighting the diagnostic and prognostic value.

RESULTS

Turner's syndrome-associated karyotypes were revealed in 111 (2.8%) of 4021 girls. Regular Turner's syndrome-associated karyotypes were detected in 35 girls (0.9%). TSM was uncovered in 76 girls (1.9%). TSM manifested as mosaic aneuploidy (45,X/46,XX; 45,X/47,XXX/46,XX; 45,X/47,XXX) affected 47 girls (1.2%). Supernumerary marker chromosomes derived from chromosome X have been identified in 11 girls with TSM (0.3%). Isochromosomes iX(q) was found in 12 cases (0.3%); one case was non-mosaic. TSM associated with ring chromosomes was revealed in 5 girls (0.1%).

CONCLUSION

The present cohort study provides data on the involvement of TSM in neurodevelopmental disorders among females. Thus, TSM may be an element of pathogenic cascades in brain diseases (i.e. neurodegenerative and psychiatric disorders). Our data allowed us to propose a hypothesis concerning ontogenetic variability of TSM levels. Accordingly, it appears that molecular cytogenetic monitoring of TSM, which is a likely risk factor/biomarker for adult-onset multifactorial diseases, is required.

Ontogenetic and Pathogenetic Views on Somatic Chromosomal Mosaicism

Intercellular karyotypic variability has been a focus of genetic research for more than 50 years. It has been repeatedly shown that chromosome heterogeneity manifesting as chromosomal mosaicism is associated with a variety of human diseases. Due to the ability of changing dynamically throughout the ontogeny, chromosomal mosaicism may mediate genome/chromosome instability and intercellular diversity in health and disease in a bottleneck fashion. However, the ubiquity of negligibly small populations of cells with abnormal karyotypes results in difficulties of the interpretation and detection, which may be nonetheless solved by post-genomic cytogenomic technologies. In the post-genomic era, it has become possible to uncover molecular and cellular pathways to genome/chromosome instability (chromosomal mosaicism or heterogeneity) using advanced whole-genome scanning technologies and bioinformatic tools. Furthermore, the opportunities to determine the effect of chromosomal abnormalities on the cellular phenotype seem to be useful for uncovering the intrinsic consequences of chromosomal mosaicism. Accordingly, a post-genomic review of chromosomal mosaicism in the ontogenetic and pathogenetic contexts appears to be required. Here, we review chromosomal mosaicism in its widest sense and discuss further directions of cyto(post)genomic research dedicated to chromosomal heterogeneity.

[Structural variations of the genome in autistic spectrum disorders with intellectual disability]

AIM

To analyze structural variations in the genome in children with autism and intellectual disability.

MATERIAL AND METHODS

Using high-resolution karyotyping (AffymetrixCytoScan HD Array) and original bioinformatic technology, 200 children with autism and intellectual disability were studied.

RESULTS AND CONCLUSION

Data on structural variations in the genome in children with autism and intellectual disability are provided. Causative genomic pathology (chromosome abnormalities and copy number variations - CNV) was determined in 97 cases (48.5%). Based on these

RESULTS

24 candidate genes for autism with intellectual disability were selected. In 16 cases (8%), the chromosome mosaicism manifested as aneuploidy of whole autosomes and sex chromosomes (gonosomes) was identified. In 87 children (43.5%), there were genomic variations, which are characteristic of the so-called «grey zone» of genetic pathology in mental illnesses. Bioinformatic analysis showed that these genomic variations had a pleiotropic effect on the phenotype.

Aneuploidy in stem cells

Stem cells hold enormous promise for regenerative medicine as well as for engineering of model systems to study diseases and develop new drugs. The discovery of protocols that allow for generating induced pluripotent stem cells (IPSCs) from somatic cells has brought this promise steps closer to reality. However, as somatic cells might have accumulated various chromosomal abnormalities, including aneuploidies throughout their lives, the resulting IPSCs might no longer carry the perfect blueprint for the tissue to be generated, or worse, become at risk of adopting a malignant fate. In this review, we discuss the contribution of aneuploidy to healthy tissues and how aneuploidy can lead to disease. Furthermore, we review the differences between how somatic cells and stem cells respond to aneuploidy.

Complex intrachromosomal rearrangement in 1q leading to 1q32.2 microdeletion: a potential role of SRGAP2 in the gyrification of cerebral cortex

Background

Van der Woude syndrome (MIM: 119300, VWS) is a dominantly inherited and the most common orofacial clefting syndrome; it accounts for ~2 % of all cleft lip and palate cases. Intellectual disability (ID) is characterized by significant limitations, both in intellectual functioning (cognitive deficit) and in adaptive behavior as expressed in conceptual, social and practical adaptive skills. Karyotyping has been the first standard test for the detection of genetic imbalance in patients with ID for more than 35 years. Advances in genetic diagnosis have laid chromosomal microarrays (CMA) as a new standard and first first-line test for diagnosis of patients with ID, as well as other conditions, such as autism spectrum disorders or multiple congenital anomalies.

Case Presentation

The present case was initially studied due to unexplained cognitive deficit. Physical examination at the age of 18 years revealed cleft palate, lower lip pits and hypodontia, accompanied with other dysmorphic features and absence of speech. Brain MRI uncovered significantly reduced overall volume of gray matter and cortical gyrification. Banding cytogenetics revealed an indistinct intrachromosomal rearrangement in the long arm of one chromosome 1, and subsequent microarray analyses identified a 5.56 Mb deletion in 1q32.1-1q32.3, encompassing 52 genes; included were the entire IRF6 gene (whose mutations/deletions underlay VWS) and SRGAP2, a gene with an important role in neuronal migration during development of cerebral cortex. Besides, a duplication in 3q26.32 (1.9 Mb in size) comprising TBL1XR1 gene was identified. Multicolor banding for chromosome 1 and molecular cytogenetics applying a battery of locus-specific probes covering 1q32.1 to 1q44 characterized a four breakpoint-insertional-rearrangement-event, resulting in 1q32.1-1q32.3 deletion.

Conclusions

Considering that the human-specific three-fold segmental duplication of SRGAP2 gene evolutionary corresponds to the beginning of neocortical expansion, we hypothesize that aberrations in SRGAP2 are strong candidates underlying specific brain abnormalities, namely reduced volume of grey matter and reduced gyrification.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-016-0221-4) contains supplementary material, which is available to authorized users.

3p22.1p21.31 microdeletion identifies CCK as Asperger syndrome candidate gene and shows the way for therapeutic strategies in chromosome imbalances

BACKGROUND

In contrast to other autism spectrum disorders, chromosome abnormalities are rare in Asperger syndrome (AS) or high-functioning autism. Consequently, AS was occasionally subjected to classical positional cloning. Here, we report on a case of AS associated with a deletion of the short arm of chromosome 3. Further in silico analysis has identified a candidate gene for AS and has suggested a therapeutic strategy for manifestations of the chromosome rearrangement.

RESULTS

Using array comparative genomic hybridization, an interstitial deletion of 3p22.1p21.31 (~2.5 Mb in size) in a child with Asperger's syndrome, seborrheic dermatitis and chronic pancreatitis was detected. Original bioinformatic approach to the prioritization of candidate genes/processes identified CCK (cholecystokinin) as a candidate gene for AS. In addition to processes associated with deleted genes, bioinformatic analysis of CCK gene interactome indicated that zinc deficiency might be a pathogenic mechanism in this case. This suggestion was supported by plasma zinc concentration measurements. The increase of zinc intake produced a rise in zinc plasma concentration and the improvement in the patient's condition.

CONCLUSIONS

Our study supported previous linkage findings and had suggested a new candidate gene in AS. Moreover, bioinformatic analysis identified the pathogenic mechanism, which was used to propose a therapeutic strategy for manifestations of the deletion. The relative success of this strategy allows speculating that therapeutic or dietary normalization of metabolic processes altered by a chromosome imbalance or genomic copy number variations may be a way for treating at least a small proportion of cases of these presumably incurable genetic conditions.

Long contiguous stretches of homozygosity spanning shortly the imprinted loci are associated with intellectual disability, autism and/or epilepsy

BACKGROUND

Long contiguous stretches of homozygosity (LCSH) (regions/runs of homozygosity) are repeatedly detected by single-nucleotide polymorphism (SNP) chromosomal microarrays. Providing important clues regarding parental relatedness (consanguinity), uniparental disomy, chromosomal recombination or rearrangements, LCSH are rarely considered as a possible epigenetic cause of neurodevelopmental disorders. Additionally, despite being relevant to imprinting, LCSH at imprinted loci have not been truly addressed in terms of pathogenicity. In this study, we examined LCSH in children with unexplained intellectual disability, autism, congenital malformations and/or epilepsy focusing on chromosomal regions which harbor imprinted disease genes.

RESULTS

Out of 267 cases, 14 (5.2 %) were found to have LCSH at imprinted loci associated with a clinical outcome. There were 5 cases of LCSH at 15p11.2, 4 cases of LCSH at 7q31.2, 3 cases of LCSH at 11p15.5, and 2 cases of LCSH at 7q21.3. Apart from a case of LCSH at 7q31.33q32.3 (~4 Mb in size), all causative LCSH were 1-1.5 Mb in size. Clinically, these cases were characterized by a weak resemblance to corresponding imprinting diseases (i.e., Silver-Russell, Beckwith-Wiedemann, and Prader-Willi/Angelman syndromes), exhibiting distinctive intellectual disability, autistic behavior, developmental delay, seizures and/or facial dysmorphisms. Parental consanguinity was detected in 8 cases (3 %), and these cases did not exhibit LCSH at imprinted loci.

CONCLUSIONS

This study demonstrates that shorter LCSH at chromosomes 7q21.3, 7q31.2, 11p15.5, and 15p11.2 occur with a frequency of about 5 % in the children with intellectual disability, autism, congenital malformations and/or epilepsy. Consequently, this type of epigenetic mutations appears to be the most common one among children with neurodevelopmental diseases. Finally, since LCSH less than 2.5-10 Mb in size are generally ignored in diagnostic SNP microarray studies, one can conclude that an important epigenetic cause of intellectual disability, autism or epilepsy is actually overlooked.

Genetic testing in children with autism spectrum disorders

OBJECTIVE

The aim of this study was to investigate karyotype abnormalities, MECP2 mutations, and Fragile X in a clinical population of children with Autism Spectrum Disorders (ASD) using The Clinical Report published by the American Academy of Pediatrics.

METHODS

Ninety-six children with ASD were evaluated for genetic testing and factors associated with this testing.

RESULTS

Abnormalities were found on karyotype in 9.7% and in DNA for fragile X in 1.4%. Karyotype abnormalities include inv(9)(p12q13); inv(9)(p11q13); inv(Y)(p11q11); Robertsonian translocation (13;14)(8q10q10) and (13,14)(q10q10); 9qh+; Yqh+; 15ps+; deletion 13(p11.2).

CONCLUSION

Genetic testing should be offered to all families of a child with an ASD, even not all of them would follow this recommendation. Although karyotype and FRAXA assessment will yield almost 10% positive results, a detailed history and physical examination are still the most important aspect of the etiological evaluation for children with ASD. Also, it is important to have geneticists to help in interpreting the information obtained from genetic testing.

Effect of chromosomal polymorphisms of different genders on fertilization rate of fresh IVF-ICSI embryo transfer cycles

To explore whether chromosomal polymorphisms of different genders affect outcomes of fresh IVF and intracytoplasmic sperm injection (ICSI) embryo transfer cycles differently, 37 couples with chromosomal polymorphisms were identified out of 614 infertile couples undergoing IVF-ICSI treatments. Group 1 included 20 couples in which only the male carried chromosomal polymorphisms; group 2 included 17 couples with female carriers only; group 3 included 19 infertile couples with normal karyotypes randomly selected as controls. A significantly lower fertilization rate was found in group 1 compared with groups 2 and 3 (56.68% in Group 1, 78.02% in group 2 and 71.74% in group 3; group 1 versus group 2, P < 0.001; group 1 versus group 3, P = 0.001; respectively). When stratified according to fertilization method, the fertilization rate in IVF cycles of group 1 was significantly lower than group 3 (50.00% in Group 1, 73.89% in Group 3, P < 0.001). Fertilization rates in ICSI cycles between groups 1 and 3 were not significantly different. This study suggests that male chromosomal polymorphisms adversely influence fertilization rates of IVF cycles. The use of ICSI may improve the success of infertility treatment by increasing the fertilization rate for men with chromosomal polymorphisms.

Xq28 (MECP2) microdeletions are common in mutation-negative females with Rett syndrome and cause mild subtypes of the disease

BACKGROUND

Rett syndrome (RTT) is an X-linked neurodevelopmental disease affecting predominantly females caused by MECP2 mutations. Although RTT is classically considered a monogenic disease, a stable proportion of patients, who do not exhibit MECP2 sequence variations, does exist. Here, we have attempted at uncovering genetic causes underlying the disorder in mutation-negative cases by whole genome analysis using array comparative genomic hybridization (CGH) and a bioinformatic approach.

RESULTS

Using BAC and oligonucleotide array CGH, 39 patients from RTT Russian cohort (in total, 354 RTT patients), who did not bear intragenic MECP2 mutations, were studied. Among the individuals studied, 12 patients were those with classic RTT and 27 were those with atypical RTT. We have detected five 99.4 kb deletions in chromosome Xq28 affecting MECP2 associated with mild manifestations of classic RTT and five deletions encompassing MECP2 spanning 502.428 kb (three cases), 539.545 kb (one case) and 877.444 kb (one case) associated with mild atypical RTT. A case has demonstrated somatic mosaicism. Regardless of RTT type and deletion size, all the cases exhibited mild phenotypes.

CONCLUSIONS

Our data indicate for the first time that no fewer than 25% of RTT cases without detectable MECP2 mutations are caused by Xq28 microdeletions. Furthermore, Xq28 (MECP2) deletions are likely to cause mild subtypes of the disease, which can manifest as both classical and atypical RTT.

Molecular karyotyping by array CGH in a Russian cohort of children with intellectual disability, autism, epilepsy and congenital anomalies

BACKGROUND

Array comparative genomic hybridization (CGH) has been repeatedly shown to be a successful tool for the identification of genomic variations in a clinical population. During the last decade, the implementation of array CGH has resulted in the identification of new causative submicroscopic chromosome imbalances and copy number variations (CNVs) in neuropsychiatric (neurobehavioral) diseases. Currently, array-CGH-based technologies have become an integral part of molecular diagnosis and research in individuals with neuropsychiatric disorders and children with intellectual disability (mental retardation) and congenital anomalies. Here, we introduce the Russian cohort of children with intellectual disability, autism, epilepsy and congenital anomalies analyzed by BAC array CGH and a novel bioinformatic strategy.

RESULTS

Among 54 individuals highly selected according to clinical criteria and molecular and cytogenetic data (from 2426 patients evaluated cytogenetically and molecularly between November 2007 and May 2012), chromosomal imbalances were detected in 26 individuals (48%). In two patients (4%), a previously undescribed condition was observed. The latter has been designated as meiotic (constitutional) genomic instability resulted in multiple submicroscopic rearrangements (including CNVs). Using bioinformatic strategy, we were able to identify clinically relevant CNVs in 15 individuals (28%). Selected cases were confirmed by molecular cytogenetic and molecular genetic methods. Eight out of 26 chromosomal imbalances (31%) have not been previously reported. Among them, three cases were co-occurrence of subtle chromosome 9 and 21 deletions.

CONCLUSIONS

We conducted an array CGH study of Russian patients suffering from intellectual disability, autism, epilepsy and congenital anomalies. In total, phenotypic manifestations of clinically relevant genomic variations were found to result from genomic rearrangements affecting 1247 disease-causing and pathway-involved genes. Obviously, a significantly lesser part of them are true candidates for intellectual disability, autism or epilepsy. The success of our preliminary array CGH and bioinformatic study allows us to expand the cohort. According to the available literature, this is the first comprehensive array CGH evaluation of a Russian cohort of children with neuropsychiatric disorders and congenital anomalies.

Somatic genome variations in health and disease

It is hard to imagine that all the cells of the human organism (about 10(14)) share identical genome. Moreover, the number of mitoses (about 10(16)) required for the organism's development and maturation during ontogeny suggests that at least a proportion of them could be abnormal leading, thereby, to large-scale genomic alterations in somatic cells. Experimental data do demonstrate such genomic variations to exist and to be involved in human development and interindividual genetic variability in health and disease. However, since current genomic technologies are mainly based on methods, which analyze genomes from a large pool of cells, intercellular or somatic genome variations are significantly less appreciated in modern bioscience. Here, a review of somatic genome variations occurring at all levels of genome organization (i.e. DNA sequence, subchromosomal and chromosomal) in health and disease is presented. Looking through the available literature, it was possible to show that the somatic cell genome is extremely variable. Additionally, being mainly associated with chromosome or genome instability (most commonly manifesting as aneuploidy), somatic genome variations are involved in pathogenesis of numerous human diseases. The latter mainly concerns diseases of the brain (i.e. autism, schizophrenia, Alzheimer's disease) and immune system (autoimmune diseases), chromosomal and some monogenic syndromes, cancers, infertility and prenatal mortality. Taking into account data on somatic genome variations and chromosome instability, it becomes possible to show that related processes can underlie non-malignant pathology such as (neuro)degeneration or other local tissue dysfunctions. Together, we suggest that detection and characterization of somatic genome behavior and variations can provide new opportunities for human genome research and genetics.

Molecular cytogenetic diagnosis and somatic genome variations

Human molecular cytogenetics integrates the knowledge on chromosome and genome organization at the molecular and cellular levels in health and disease. Molecular cytogenetic diagnosis is an integral part of current genomic medicine and is the standard of care in medical genetics and cytogenetics, reproductive medicine, pediatrics, neuropsychiatry and oncology. Regardless numerous advances in this field made throughout the last two decades, researchers and practitioners who apply molecular cytogenetic techniques may encounter several problems that are extremely difficult to solve. One of them is undoubtedly the occurrence of somatic genome and chromosome variations, leading to genomic and chromosomal mosaicism, which are related but not limited to technological and evaluative limitations as well as multiplicity of interpretations. More dramatically, current biomedical literature almost lacks descriptions, guidelines or solutions of these problems. The present article overviews all these problems and gathers those exclusive data acquired from studies of genome and chromosome instability that is relevant to identification and interpretations of this fairly common cause of somatic genomic variations and chromosomal mosaicism. Although the way to define pathogenic value of all the intercellular variations of the human genome is far from being completely understood, it is possible to propose recommendations on molecular cytogenetic diagnosis and management of somatic genome variations in clinical population.

Molecular cytogenetics and cytogenomics of brain diseases

Molecular cytogenetics is a promising field of biomedical research that has recently revolutionized our thinking on genome structure and behavior. This is in part due to discoveries of human genomic variations and their contribution to biodiversity and disease. Since these studies were primarily targeted at variation of the genome structure, it appears apposite to cover them by molecular cytogenomics. Human brain diseases, which encompass pathogenic conditions from severe neurodegenerative diseases and major psychiatric disorders to brain tumors, are a heavy burden for the patients and their relatives. It has been suggested that most of them, if not all, are of genetic nature and several recent studies have supported the hypothesis assuming them to be associated with genomic instabilities (i.e. single-gene mutations, gross and subtle chromosome imbalances, aneuploidy). The present review is focused on the intriguing relationship between genomic instability and human brain diseases. Looking through the data, we were able to conclude that both interindividual and intercellular genomic variations could be pathogenic representing, therefore, a possible mechanism for human brain malfunctioning. Nevertheless, there are still numerous gaps in our knowledge concerning the link between genomic variations and brain diseases, which, hopefully, will be filled by forthcoming studies. In this light, the present review considers perspectives of this dynamically developing field of neurogenetics and genomics.

Ontogenetic variation of the human genome

The human genome demonstrates variable levels of instability during ontogeny. Achieving the highest rate during early prenatal development, it decreases significantly throughout following ontogenetic stages. A failure to decrease or a spontaneous increase of genomic instability can promote infertility, pregnancy losses, chromosomal and genomic diseases, cancer, immunodeficiency, or brain diseases depending on developmental stage at which it occurs. Paradoxically, late ontogeny is associated with increase of genomic instability that is considered a probable mechanism for human aging. The latter is even more appreciable in human diseases associated with pathological or accelerated aging (i.e. Alzheimer's disease and ataxia-telangiectasia). These observations resulted in a hypothesis suggesting that somatic genomic variations throughout ontogeny are determinants of cellular vitality in health and disease including intrauterine development, postnatal life and aging. The most devastative effect of somatic genome variations is observed when it manifests as chromosome instability or aneuploidy, which has been repeatedly noted to produce pathologic conditions and to mediate developmental regulatory and aging processes. However, no commonly accepted concepts on the role of chromosome/genome instability in determination of human health span and life span are available. Here, a review of these ontogenetic variations is given to propose a new "dynamic genome" model for pathological and natural genomic changes throughout life that mimic those of phylogenetic diversity.

A review of recent reports on autism: 1000 studies published in 2007

From 1000 studies published in 2007 on all aspects of autism, those that reached clear conclusions or included quantitative data were selected for this review. Possible etiologies include elemental metals, especially the inconsistent evidence regarding mercury from the vaccine preservative thimerosal, not used after 2001, and chromosomes and genes with the conclusion that autism has a complex genetic architecture. Also, various parental conditions are considered, as are many different abnormalities in the central nervous system, especially underconnectivity within the cortex. Furthermore, deficiencies in mirror neurons have been proposed, leading to the "theory of mind" explanation that autistic children tend to disregard others. In addition, various global deficiencies, like an increase in inhibitory synaptic transmission, are proposed. Characteristics of these children include selective (inward) attention; underresponsiveness; stereotyped repetitive motor behavior; increased head size, weight, and height; various cognitive and communicative disorders; and also epilepsy. Therapy has emphasized risperidone, but some atypical antipsychotic medications have been helpful, as have robotic aids, massage, hyperbaric oxygen, and music. Nearly every conceivable problem that a child could have can be observed in these unfortunate children.

De novo balanced translocation t (7;16) (p22.1; p11.2) associated with autistic disorder

The high incidence of de novo chromosomal aberrations in a population of persons with autism suggests a causal relationship between certain chromosomal aberrations and the occurrence of isolated idiopathic autism. We report on the clinical and cytogenetic findings in a male patient with autism, no physical abnormalities and a de novo balanced (7;16)(p22.1;p16.2) translocation. G-banded chromosomes and fluorescent in situ hybridization (FISH) were used to examine the patient's karyotype as well as his parents'. FISH with specific RP11-BAC clones mapping near 7p22.1 and 16p11.2 was used to refine the location of the breakpoints. This is, in the best of our knowledge, the first report of an individual with autism and this specific chromosomal aberration.