An aetiological study of 25 mentally retarded adults with autism

A novel relationship for schizophrenia, bipolar and major depressive disorder Part 3: Evidence from chromosome 3 high density association screen

Familial clustering of schizophrenia (SCZ), bipolar disorder (BPD), and major depressive disorder (MDD) was systematically reported (Aukes et al, Genet Med 2012, 14, 338-341) and convergent evidence from genetics, symptomatology, and psychopharmacology imply that there are intrinsic connections between these three major psychiatric disorders, for example, any two or even three of these disorders could co-exist in some families. A total of 60, 838 single-nucleotide polymorphisms (SNPs) on chromosome 3 were genotyped by Affymetrix Genome-Wide Human SNP array 6.0 on 119 SCZ, 253 BPD (type-I), 177 MDD patients and 1,000 controls. The population of Shandong province was formed in 14 century and believed that it belongs to homogenous population. Associated SNPs were systematically revealed and outstanding susceptibility genes (CADPS, GRM7,KALRN, LSAMP, NLGN1, PRICKLE2, ROBO2) were identified. Unexpectedly, flanking genes for the associated SNPs distinctive for BPD and/or MDD were replicated in an enlarged cohort of 986 SCZ patients. The evidence from this chromosome 3 analysis supports the notion that both of bipolar and MDD might be subtypes of schizophrenia rather than independent disease entity. Also, a similar finding was detected on chromosome 5, 6, 7, and 8 (Chen et al. Am J Transl Res 2017;9 (5):2473-2491; Curr Mol Med 2016;16(9):840-854; Behav Brain Res 2015;293:241-251; Mol Neurobiol 2016. doi: 10.1007/s12035-016-0102-1). Furthermore, PRICKLE2 play an important role in the pathogenesis of three major psychoses in this population.

Etiological heterogeneity in autism spectrum disorders: more than 100 genetic and genomic disorders and still counting

There is increasing evidence that autism spectrum disorders (ASDs) can arise from rare highly penetrant mutations and genomic imbalances. The rare nature of these variants, and the often differing orbits of clinical and research geneticists, can make it difficult to fully appreciate the extent to which we have made progress in understanding the genetic etiology of autism. In fact, there is a persistent view in the autism research community that there are only a modest number of autism loci known. We carried out an exhaustive review of the clinical genetics and research genetics literature in an attempt to collate all genes and recurrent genomic imbalances that have been implicated in the etiology of ASD. We provide data on 103 disease genes and 44 genomic loci reported in subjects with ASD or autistic behavior. These genes and loci have all been causally implicated in intellectual disability, indicating that these two neurodevelopmental disorders share common genetic bases. A genetic overlap between ASD and epilepsy is also apparent in many cases. Taken together, these findings clearly show that autism is not a single clinical entity but a behavioral manifestation of tens or perhaps hundreds of genetic and genomic disorders. Increased recognition of the etiological heterogeneity of ASD will greatly expand the number of target genes for neurobiological investigations and thereby provide additional avenues for the development of pathway-based pharmacotherapy. Finally, the data provide strong support for high-resolution DNA microarrays as well as whole-exome and whole-genome sequencing as critical approaches for identifying the genetic causes of ASDs.

Accelerated head and body growth in infants later diagnosed with autism spectrum disorders: a comparative study of optimal outcome children

Previous research has demonstrated accelerated head and body growth during infancy in children with autism spectrum disorders. No study has yet examined head growth in children who lose their autism spectrum disorder diagnoses. Head circumference, length, and weight growth during infancy for 24 children who maintained their diagnoses were compared with 15 children who lost their diagnoses, and to 37 typically developing controls. Results showed that head circumference and weight growth were significantly greater in both autism spectrum disorder groups compared with controls, with no significant differences between autism spectrum disorder groups. However, when length and weight were controlled for, accelerated head growth remained significant in the children who lost their diagnoses. Findings suggest that children who lose their autism spectrum disorder diagnoses and children who maintain their diagnoses show similar head circumference, length, and weight growth trajectories during infancy, although subtle differences in body growth between groups may exist.

MECP2 coding sequence and 3'UTR variation in 172 unrelated autistic patients

Mutations in the coding sequence of the methyl-CpG-binding protein 2 gene (MECP2), which cause Rett syndrome (RTT), have been found in male and female autistic subjects without, however, a causal relation having unequivocally been established. In this study, the MECP2 gene was scanned in a Portuguese autistic population, hypothesizing that the phenotypic spectrum of mutations extends beyond the traditional diagnosis of RTT and X-linked mental retardation, leading to a non-lethal phenotype in male autistic patients. The coding region, exon-intron boundaries, and the whole 3'UTR were scanned in 172 patients and 143 controls, by Detection of Virtually All Mutations-SSCP (DOVAM-S). Exon 1 was sequenced in 103 patients. We report 15 novel variants, not found in controls: one missense, two intronic, and 12 in the 3'UTR (seven in conserved nucleotides). The novel missense change, c.617G > C (p.G206A), was present in one autistic male with severe mental retardation and absence of language, and segregates in his maternal family. This change is located in a highly conserved residue within a region involved in an alternative transcriptional repression pathway, and likely alters the secondary structure of the MeCP2 protein. It is therefore plausible that it leads to a functional modification of MeCP2. MECP2 mRNA levels measured in four patients with 3'UTR conserved changes were below the control range, suggesting an alteration in the stability of the transcripts. Our results suggest that MECP2 can play a role in autism etiology, although very rarely, supporting the notion that MECP2 mutations underlie several neurodevelopmental disorders.

Correlates of head circumference growth in infants later diagnosed with autism spectrum disorders

Previous research has demonstrated that children diagnosed with autism spectrum disorder show an abnormal acceleration of head growth during the first year of life. This study attempts to replicate these findings and to determine whether overgrowth is associated with clinical outcome. Measurements of head circumference, body length, and body weight taken during the first 2 years of life were obtained from a sample of 35 children diagnosed with autism spectrum disorder and compared to both national normative data (Centers for Disease Control and Prevention) and a control group of 37 healthy infants. Results demonstrated that compared to national averages, infants who were later diagnosed with autism spectrum disorder had a significantly smaller head circumference at birth to 2 weeks and a significantly larger head circumference by 10 to 14 months. Children with autism spectrum disorder were also significantly longer and heavier beginning at 1 to 2 months. However, when overall length and weight were controlled, head circumference was not bigger in the autistic spectrum disorder group compared to local controls. Correlations between head circumference and clinical outcome were significant for 5 of the 30 clinical variables that were run, suggesting that there appears to be no simple or straightforward relationship between head circumference and clinical outcome. Smaller head circumference at birth to 2 weeks was associated with a greater number of symptoms related to social impairment and a greater total number of autism spectrum disorder symptoms based on the Diagnostic and Statistical Manual of Mental Disorders , Fourth Edition criteria. Larger head circumference at 15 to 25 months was also associated with a greater number of symptoms of social impairment. In addition, greater head circumference change during the first 2 years was associated with poorer performance on the visual reception subtest of the Mullen Scales of Early Learning and a smaller number of stereotyped and repetitive behaviors and interests based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria. These findings support previous findings of accelerated brain growth during the first year of life in autism spectrum disorder and question whether growth factors might contribute to both accelerated brain growth and overall body growth.

The genetics of autistic disorders and its clinical relevance: a review of the literature

Twin and family studies in autistic disorders (AD) have elucidated a high heritability of the narrow and broad phenotype of AD. In this review on the genetics of AD, we will initially delineate the phenotype of AD and discuss aspects of differential diagnosis, which are particularly relevant with regard to the genetics of autism. Cytogenetic and molecular genetic studies will be presented in detail, and the possibly involved aetiopathological pathways will be described. Implications of the different genetic findings for genetic counselling will be mentioned.

Autism spectrum disorders – Exogenous protein insult

The immune-response perspective described herein is intended to explore how certain environmental proteins may affect neuro-cognitive development in children. Specifically, proteins inherent in natural rubber latex are known to cause severe and pervasive immune responses. More specifically, the Hevea Brasiliensis proteins in natural rubber latex may trigger immunoglobulin-E mediated reaction antibodies and influence cross-react immune responses to other exogenous/endogenous proteins. In adults, repeated exposure to the Hevea Brasiliensis proteins has been shown to cause an increased incidence of sensitization, adverse allergic reactions, and even death through anaphylactic shock. Natural rubber latex has seen a dramatic increase in usage over the last 30-years (e.g., health care industry, consumer products). The timing, frequency, intensity, and type of exposure to such proteins may influence the incidence, degree of atypicality, and prevalence of autism spectrum disorders. Therefore, research efforts should be directed at exploring how immune responses to such proteins affect lymphocyte sensitivity, enzyme regulation, and neural formation during prenatal/neonatal development.

Screening of subtelomeric rearrangements in autistic disorder: identification of a partial trisomy of 13q34 in a patient bearing a 13q;21p translocation

Within the framework of a FISH screening protocol to detect cryptic subtelomeric rearrangements in autistic disorder (AD), a patient bearing three copies of the subtelomeric portion of the q arm of chromosome 13 has been identified. Beside AD, the patient also has severe mental retardation and displays several dysmorphic features. Further FISH analyses revealed that the trisomy was caused by the translocation of a 13q subtelomeric fragment to the acrocentric tip of one chromosome 21 [46,XY.ish der(21) t(13;21) (q34;p13)(D13S1825+)]. Gene dosage experiments carried out with three multiallelic polymorphisms of the subtelomeric region of chromosome 13q showed that the putative length of the triplicate region does not exceed 300 kb about, that is, the distance from telomere to the first normally inherited marker. In addition, gene dosage analysis performed on the derivative chromosome 21, did not reveal loss of the most telomeric protein-encoding genes on 21p. The potential relationship between a postulated increased expression of genes on 13q34 and the complex phenotype in this trisomic patient is discussed.

Normal values for morphological abnormalities in school children

Clinical morphology has proven to be a strong tool in the delineation of many syndromes and a helpful instrument in molecular studies. Numerous studies have been performed investigating the prevalence of minor anomalies in various disorders; all concluding that minor anomalies can well be utilized as indicators of altered embryonic differentiation. However, for adequate evaluation, normal values for phenotypic abnormalities are essential. So far, only few studies on the frequency of phenotypic abnormalities in the normal population have been done having one thing in common: all were performed in newborn infants. We studied morphological characteristics in a group of 1,007 school children, representative for the Dutch population, through a body surface examination using detailed definitions for all morphological findings. The region of study and distribution of children over various school types was chosen in such a way that it represented the general Dutch population. The median age of the studied children was 11 years (range 8-14 years), sex ratio (M:F) was 0.93. Nine hundred twenty-three children were of Caucasian descent, 84 others of mixed ethnic backgrounds. The reliability of the examinations was tested by independent scoring of 111 children by two observers, showing a kappa score of 0.85. Normal values for the morphological findings are presented together with their age-adjusted classification. These normal values provide a valuable source for validation of classifications of phenotypic abnormalities, especially those that are depending on frequency, that is, minor anomalies and common variants. Furthermore, they will allow a proper evaluation of patterns of phenotypic abnormalities found in patient groups with specific disorders.

Does genotype predict phenotype in Rett syndrome?

Mutations in the X-linked gene encoding the methyl-CpG binding protein MeCP2 are the primary cause of classic and atypical Rett syndrome and have recently been shown to contribute to other neurodevelopmental disorders of varying severity. To determine whether there are molecular correlates to the phenotypic heterogeneity, numerous groups have performed genotype-phenotype correlation studies. These studies have yielded conflicting results, in part because they used different criteria for determining severity and classifying mutations. Evolution of the phenotype with age and variable expressivity arising from individual variability in X-chromosome inactivation patterns are among other reasons the findings varied. Nonetheless, evidence of differences in the phenotypic consequences of specific types of mutations is emerging. This review analyzes the available literature and makes recommendations for future studies.

Genetic counseling for familial conditions during pregnancy: an analysis of patient characteristics

Reproductive genetic counseling for a familial genetic risk factor preferably takes place before conception. However, of the women with a family history of genetic conditions who attend our department of clinical genetics, about 10-20% attend for the first time during a pregnancy. The current study aims to explore patient-related factors that may affect this late timing of reproductive genetic counseling. Consecutive pregnant (n = 100) and non-pregnant (n = 84) women visiting the department of clinical genetics for a genetic risk factor which was not age related completed a questionnaire immediately prior to the consultation. The questionnaire asked for (a) background characteristics, i.e. socio-demographic, obstetric, and disease characteristics (b) cognitive factors, i.e. initiative of referral, knowledge of the risk factor involved, risk perception, worry, child wish, attitudes toward abortion, and preferred participation in decision making, and (c) reasons for the timing of the consultation and for seeking genetic counseling. Pregnant women appeared to be higher educated, considered their children more often as healthy and were less often affected themselves, as compared to non-pregnant women. They also estimated their chance of having an affected child as lower, and they worried less. Furthermore, the initiative for referral was taken less often by the pregnant woman herself and more often by a medical worker. There were no major differences between the two study groups in knowledge, perceived severity of the risk factor, child wish, attitudes toward abortion, desired participation in decision making, and reasons to seek genetic counseling. Women indicated no specific reasons for their timing of referral for reproductive genetic counseling, e.g. during vs before pregnancy. Our data suggest that this timing of referral is not influenced predominantly by the women's level of knowledge. Rather, women's estimation of genetic risks and their degree of worry, which may be in accordance with the actual risk figures, seem to play a role in seeking genetic counseling. Although further studies are required, a more active role of health care providers seems warranted if we want to prevent genetic counseling for familial genetic conditions during pregnancy as much as possible.

MECP2 structural and 3'-UTR variants in schizophrenia, autism and other psychiatric diseases: a possible association with autism

Mutations in the gene coding for methyl-CpG-binding protein 2 (MECP2) cause Rett syndrome (RTT) and have also been reported in a number of X-linked mental retardation syndromes. Furthermore, putative mutations recently have been described in a few autistic patients and a boy with language disorder and schizophrenia. In this study, DNA samples from individuals with schizophrenia and other psychiatric diseases were scanned in order to explore whether the phenotypic spectrum of mutations in the MECP2 gene can extend beyond the traditional diagnoses of RTT in females and severe neonatal encephalopathy in males. The coding regions, adjacent splicing junctions, and highly conserved segments of the 3'-untranslated region (3'-UTR) were examined in 214 patients, including 106 with schizophrenia, 24 with autism, and 84 patients with other psychiatric diseases by detection of virtually all mutations-single strand conformation polymorphism (SSCP) (DOVAM-S). To our knowledge, this is the first analysis of variants in conserved regions of the 3'-UTR of this gene. A total of 5.2 kb per haploid gene was analyzed (1.5 Mb for 214 patients). A higher frequency of missense and 3'-UTR variants was found in autism. One missense and two 3'-UTR variants were found in 24 patients with autism versus one patient with a missense change in 144 ethnically similar individuals without autism (P = 0.009). These mutations suggest that a possible association between MECP2 mutations and autism may warrant further study.

Phenotypic abnormalities: Terminology and classification

Clinical morphology has proved essential for the successful delineation of hundreds of syndromes and as a powerful instrument for detecting (candidate) genes (Gorlin et al. [2001]; Syndromes of the Head and Neck; Oxford: Oxford University Press. 1 p]. The major approach to reach this has been careful clinical evaluations of patients, focused on congenital anomalies. A similar careful physical examination performed in patients, who have been treated for childhood cancer, may allow detection of concurrent patterns of anomalies and provide clues for causative genes. In the past, several studies were performed describing the prevalence of anomalies in patients with cancer. However, in most studies, it was not possible to indicate the biologic relevance of the recorded anomalies, or to judge their relative importance. Are the detected anomalies common variants, and should they thus be regarded as normal, or are they minor anomalies or true abnormalities, indicating a possible developmental cause? Classification of items in the categories of common variants (disturbances of phenogenesis with a prevalence >4%), minor anomalies (disturbances of phenogenesis with a prevalence </=4%), and malformations (disturbances of embryogenesis) should allow weighing the importance of the scored items in the population under study, and should facilitate assessment of developmental disturbances (if any) in a study group. The lack of published consensus in the literature led us to produce a classification list with a twofold goal. First, we wanted to enhance uniformity in the scoring and classification of apparently abnormal physical findings by a nomenclature for errors of morphogenesis detectable on surface examination, and secondly a uniform classification system. This should allow investigators to evaluate systematically the presence of patterns in phenotypic anomalies, in the general population, and in patients with various disorders, suspected to be a developmental anomaly. Also, normal values may be obtained this way. Second, the list will allow a determination of the importance of the collected symptoms in a study population. We tested the feasibility of the application of the classification list in a study population: the list was piloted in a group of patients who have had cancer as a child, to detect patterns of anomalies related to specific types of tumors.

Absence of MeCP2 mutations in patients from the South Carolina autism project

The methyl-CpG binding protein 2 (MeCP2) gene has recently been identified as the gene responsible for Rett syndrome (RS), a pervasive developmental disorder considered by many to be one of the autism spectrum disorders. Most female patients with MeCP2 mutations exhibit the classic features of RS, including autistic behaviors. Most male patients with MeCP2 mutations exhibit moderate to severe developmental delay/mental retardation. Ninety nine patients from the South Carolina autism project (SCAP) were screened for MeCP2 mutations, including all 41 female patients from whom DNA samples were available plus the 58 male patients with the lowest scores on standard IQ tests and/or the Vineland Adaptive Behavior Scale. No pathogenic mutations were observed in these patients. One patient had the C582T variant, previously reported in the unaffected father of an RS patient. Two other patients had single nucleotide polymorphisms in the 3' UTR of the gene, G1470A and C1516G. These variants were seen in 12/82 and 1/178 phenotypically normal male controls, respectively. The findings from this and other studies suggest that mutations in the coding sequence of the MeCP2 gene are not a significant etiological factor in autism.