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PhenoChipping of psychotic disorders: a novel approach for deconstructing and quantitating psychiatric phenotypes.

Psychiatric phenotypes as currently defined are primarily the result of clinical consensus criteria rather than empirical research. We propose, and present initial proof of principle for, a novel approach to characterizing psychiatric phenotypes. We have termed our approach PhenoChipping, by analogy with, and borrowing paradigms and tools from, gene expression microarray studies (GeneChipping). A massive parallel profiling of cognitive and affective state is done with a PhenoChip composed of a battery of existing and new quantitative psychiatric rating scales, as well as hand neuromotor measures. We present preliminary data from 104 subjects, 72 with psychotic disorders (bipolar disorder-41, schizophrenia-17, schizoaffective disorder-14), and 32 normal controls. Microarray data analysis software and visualization tools were used to investigate: 1. relationships between phenotypic items ("phenes"), including with objective motor measures, and 2. relationships between subjects. Our analyses revealed phenotypic overlap among, as well as phenotypic heterogeneity within, the three major psychotic disorders studied. This approach may be useful in helping us move beyond current diagnostic classifications, and suggests a combinatorial building-block (Lego-like) structure underlies psychiatric syndromes. The adaptation of microarray informatic tools for phenotypic analysis readily facilitates direct integration with gene expression profiling of lymphocytes in the same individuals, a strategy for molecular biomarker identification. Empirically derived clusterings of (endo)phenotypes and of patients will better serve genetic, pharmacological, and imaging research, as well as clinical practice.

Adult↗

Dominantly inherited cerebello-olivary atrophy is not due to a mutation at the spinocerebellar ataxia-I, Machado-Joseph disease, or Dentato-Rubro-Pallido-Luysian atrophy locus.

The dominantly inherited ataxias are characterized both by phenotypic variability (phenotypic heterogeneity) within the same genotype and overlapping phenotypes from different genotypes (genotypic heterogeneity). Therefore it is important to characterize specific clinical-neuropathologic phenotypes as precisely as possible at the genetic level. We describe a family with dominantly inherited ataxia of late adult onset with relatively "pure" cerebellar signs. Neuropathologic examination in two individuals from this family revealed findings consistent with cerebello-olivary atrophy, suggesting that this neuropathologic phenotype many run true within f families. Mutations at the spinocerebellar ataxia-I, Machado-Joseph disease, and dentatorubropallidoluysian atrophy loci were excluded by direct DNA analysis on the leukocytes of one living affected member. Thus we provide evidence that these mutations are not responsible for this particular phenotype of dominantly inherited ataxia.

Adult↗

Posterior hypothalamic and brainstem activation in hemicrania continua.

OBJECTIVE: To determine the brain structures involved in mediating the pain of hemicrania continua using positron emission tomography. BACKGROUND: Hemicrania continua is a strictly unilateral, continuous headache of moderate intensity, with superimposed exacerbations of severe intensity that are accompanied by trigeminal autonomic features and migrainous symptoms. The syndrome is exquisitely responsive to indomethacin. Its clinical phenotype overlaps with that of the trigeminal autonomic headaches and migraine in which the hypothalamus and the brainstem, respectively, have been postulated to play central pathophysiologic roles. We hypothesized, based on the clinical phenotype, that hemicrania continua may involve activations in the hypothalamus, or dorsal rostral pons, or both. METHODS: Seven patients with hemicrania continua were studied in two sessions each. In one session, the patients were scanned during baseline pain and when rendered completely pain free after being administered indomethacin 100 mg intramuscularly. In the other session, the patients were scanned during baseline pain and when still in pain after being administered placebo intramuscularly. Seven age- and sex-matched nonheadache subjects acted as the control group. The scan images were processed and analyzed using SPM99. RESULTS: There was a significant activation of the contralateral posterior hypothalamus and ipsilateral dorsal rostral pons in association with the headache of hemicrania continua. In addition, there was activation of the ipsilateral ventrolateral midbrain, which extended over the red nucleus and the substantia nigra, and bilateral pontomedullary junction. No intracranial vessel dilatation was obvious. CONCLUSIONS: This study demonstrated activations of various subcortical structures, in particular the posterior hypothalamus and the dorsal rostral pons. If posterior hypothalamic and brainstem activation are considered as markers of trigeminal autonomic headaches and migrainous syndromes, respectively, then the activation pattern demonstrated in hemicrania continua mirrors the clinical phenotype, with its overlap with trigeminal autonomic headaches and migraine.

Adult↗

Nosologic groups. An overview.

A general analysis is made of the concept of nosologic groups. It is concluded that, even when 'artificial',they may prove to be useful research, didactic and differential diagnosis purposes. Nosologic groupings must, however, progress toward the finding of 'phenotypic communities' whose component syndromes share multiple foci of dysmorphogenetically intimate phenotypic overlap. The concepts of syndrome, anomalad, association, combination, dysplasia, phenotypic community and family of diseases are briefly analysed.

Abnormalities, Multiple↗

Genetic analysis of the S-mephenytoin polymorphism in a Chinese population.

The 4'-hydroxylation of S-mephenytoin exhibits a polymorphism in humans, with the poor metabolizer phenotype exhibiting a lower frequency in white (3% to 5%) than in Oriental populations (13% to 23%). Two mutations in CYP2C19 (CYP2C19m1 and CYP2C19m2) have recently been described that account for approximately 85% of white and 100% of Japanese poor metabolizers. This study examines whether these mutations account for the poor metabolizer phenotype in the Chinese population. The metabolism of S-mephenytoin exhibited a bimodal distribution in 244 unrelated Chinese subjects, although the distribution of the two phenotypes overlapped. In 75 selected Chinese subjects, CYP2C19 genotype analysis predicted the phenotype with 100% accuracy. The frequency of the poor metabolizer phenotype was approximately 11% (95% confidence interval 7% to 15%). The frequency of the CYP2C19m1 allele was 0.289, whereas that of CYP2C19m2 was 0.044. Homozygous extensive metabolizers had slightly lower ratios of S/R-mephenytoin compared with heterozygous extensive metabolizers, showing a gene-dosage effect. These data show the advantages of genotype analysis in investigations of the mephenytoin phenotype in Oriental subjects.

Adolescent↗

Mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5/STK9) gene are associated with severe neurodevelopmental retardation.

Recently, we showed that truncation of the X-linked cyclin-dependent kinase-like 5 (CDKL5/STK9) gene caused mental retardation and severe neurological symptoms in two female patients. Here, we report that de novo missense mutations in CDKL5 are associated with a severe phenotype of early-onset infantile spasms and clinical features that overlap those of other neurodevelopmental disorders, such as Rett syndrome and Angelman syndrome. The mutations are located within the protein kinase domain and affect highly conserved amino acids; this strongly suggests that impaired CDKL5 catalytic activity plays an important role in the pathogenesis of this neurodevelopmental disorder. In view of the overlapping phenotypic spectrum of CDKL5 and MECP2 mutations, it is tempting to speculate that these two genes play a role in a common pathogenic process.

Amino Acid Sequence↗

Autosomal dominant "Opitz" GBBB syndrome due to a 22q11.2 deletion.

We report on a family with autosomal dominant paternally inherited "Opitz" GBBB syndrome and an additional case with findings which have been reported in that syndrome. In each case the propositus presented with a vascular ring. Since a vascular ring may be a sign of a 22q11.2 deletion [Zacki et al., 1995], FISH (fluorescence in situ hybridization) studies were performed. These studies demonstrated a 22q11.2 deletion in the 3 affected individuals. Review of Opitz GBBB syndrome and the 22q11.2 microdeletion syndrome demonstrates significant overlap of manifestations including both facial characteristics and structural anomalies. Based on the phenotypic overlap and the presence of a 22q11.2 deletion in our patients with Opitz GBBB syndrome and the presence of a deletion in a patient with lung hypoplasia, absent pulmonary artery, and long segment tracheomalacia, we propose that, in some cases, the Opitz GBBB syndrome may be due to a 22q11.2 deletion. This enlarges the list of "syndromes" associated with the 22q11.2 deletion, which presently includes most patients with DiGeorge, velocardiofacial, and conotruncal anomaly face syndrome.

Abnormalities, Multiple↗

DNA sequence analysis of the transposon Tn3: three genes and three sites involved in transposition of Tn3.

The complete nucleotide sequence of the transposon Tn3 and of 20 mutations which affect its transposition are reported. The mutations, generated in vitro by random insertion of synthetic restriction sites, proved to contain small duplications or deletions immediately adjacent to the new restriction site. By determining the phenotype and DNA sequence of these mutations we were able to generate an overlapping phenotypic and nucleotide map. This 4957 bp transposon encodes three polypeptides which account for all but 350 bp of its total coding capacity. These proteins are the transposase, a high molecular weight polypeptide (1015 amino acids) encoded by the tnpA gene; the Tn3-specific repressor, a low molecular weight polypeptide (185 amino acids) encoded by the tnpR gene; and the 286 amino acid beta-lactamase. The 38 bp inverted repeats flanking Tn3 appear to be absolutely required in cis for Tn3 to transpose. Genetic data suggest that Tn3 contains a third site (Gill et al., 1978), designated IRS (internal resolution site), whose absence results in the insertion of two complete copies of Tn3 as direct repeats into the recipient DNA. We suggest that these direct repeats of complete copies of Tn3 are intermediates in transposition, and that the IRS site is required for recombination and subsequent segregation of the direct repeats to leave a single copy of Tn3 (Gill et al., 1978). A 23 nucleotide sequence within the amino terminus of the transposase which shares strong sequence homology with the inverted repeat may be the internal resolution site.

Base Sequence↗

Analysis of 14q12 microdeletions reveals novel regulatory loci for the neurodevelopmental disorder-related gene FOXG1.

Up to 17% of neurodevelopmental disorders (NDDs) can be explained by pathogenic structural variants (SVs) that disrupt coding regions and elicit gene dosage defects. However, noncoding SVs which can perturb cis-regulatory elements (CREs) and downstream gene expression are understudied. In this study, we describe multiple 14q12 deletions downstream of NDD-related gene FOXG1 in individuals with overlapping phenotypes of FOXG1 haploinsufficiency. We show that deletion of a minimum region of overlap (MRO) reduced FOXG1 expression, disrupted CREs and altered FOXG1's native genomic interactions. Deleting the MRO did not fully eliminate FOXG1 expression, indicating that multiple CREs likely cooperate to regulate FOXG1 and would need to be deleted to completely prevent expression. The transcriptomic profiles of MRO loss overlap in part with FOXG1 loss, including direct FOXG1 targets, indicating converging molecular pathways. These findings expand the scope of FOXG1's complex regulatory region, and more broadly, of regulatory SVs in NDD susceptibility.

Forkhead Transcription Factors↗

Mutation of the type X collagen gene (COL10A1) causes spondylometaphyseal dysplasia.

Spondylometaphyseal dysplasia (SMD) comprises a heterogeneous group of heritable skeletal dysplasias characterized by modifications of the vertebral bodies of the spine and metaphyses of the tubular bones. The genetic etiology of SMD is currently unknown; however, the type X collagen gene (COL10A1) is considered an excellent candidate, for two reasons: first, Schmid metaphyseal chondrodysplasia, a condition known to result from COL10A1 mutations, shows a significant phenotypic overlap with SMD; and, second, transgenic mice carrying deletions in type X collagen show SMD phenotypes. Hence, we examined the entire coding region of COL10A1 by direct sequencing of DNA from five unrelated patients with SMD and found a heterozygous missense mutation (Gly595Glu) cosegregating with the disease phenotype in one SMD family. This initial documented identification of a mutation in SMD expands our knowledge concerning the range of the pathological phenotypes that can be produced by aberrations of type X collagen (type X collagenopathy).

Child↗

Juvenile myoclonic epilepsy and idiopathic photosensitive occipital lobe epilepsy: is there overlap?

Although epileptic photosensitivity is well known, its genetics and syndromic associations are incompletely understood. Seizures triggered by photic stimulation are usually a manifestation of the idiopathic generalized epilepsies, especially juvenile myoclonic epilepsy (JME), or of the occipital epilepsies. Idiopathic photosensitive occipital epilepsy (IPOE) is a focal epilepsy with colourful elementary visual auras, often with conscious tonic head and eye version; myoclonus is not a feature. All seizures are induced by photic stimuli. We describe four families with phenotypic overlap between JME and IPOE. Families were identified if two or more affected individuals had visual auras and electro-clinical features of an idiopathic epilepsy. Family members underwent detailed electro-clinical assessment. In addition, 40 unrelated JME probands were investigated systematically for unrecognized features of IPOE (visual aura and conscious head version). There were 12 affected individuals in four families; 11 were female. Clinical onset was at 8-21 years of age. Of 10 patients with visual auras, six had conscious head version and five also experienced myoclonic jerks; eight had non-photic induced tonic-clonic seizures (TCS). Of the remaining individuals, one had myoclonic jerks and occipital spikes; the other had TCS without visual aura or myoclonic jerks. Of 10 patients with EEG studies, eight had generalized spike and wave (GSW) and six had occipital spikes. All had photosensitivity with GSW and four had additional occipital spikes. Of the 40 JME probands, six had visual aura and/or conscious head version; five of these were photosensitive. There is overlap between the clusters of clinical features used to diagnose IPOE and JME. Half of the affected individuals in our families with visual aura had myoclonic jerks; the former is characteristic of IPOE and the latter of JME. Importantly, visual aura is not regarded as part of JME, nor myoclonus part of IPOE, but our data emphasize that these symptoms may occur in both disorders. Moreover, two-thirds of individuals with visual aura had spontaneous TCS; the latter feature is not described in IPOE. Additionally, we demonstrate that visual aura and conscious head version are under-recognized features of JME, particularly among photosensitive patients. These findings could be explained by shared genetic determinants underlying IPOE and JME. Understanding the genetic basis of these disorders must account for the striking female predominance, the variable phenotypes associated with photosensitivity and the overlap of clinical features classically regarded as distinguishing focal and generalized syndromes.

Adolescent↗

A Second Report of a Missense Variant in AMMECR1 Causing Midface Hypoplasia, Hearing Impairment, Elliptocytosis, and Nephrocalcinosis: Case Report and Literature Review.

Pathogenic variants in AMMECR1 have been associated with a rare multisystem disorder characterized by midface hypoplasia, hearing impairment, elliptocytosis, and nephrocalcinosis (MFHIEN). To date, most reported cases involve copy number variants or presumed loss-of-function alterations, with only a single prior report describing a missense variant supported by functional studies. Here, we report a patient with a heterozygous de novo AMMECR1 missense variant, NM_015365.3:c.649G>A p.(Val217Met) presenting with clinical features consistent with MFHIEN, including midface hypoplasia, partial hearing impairment, nephrocalcinosis, and elliptocytosis identified on peripheral blood smear. Comparative review of the literature highlights that while previously reported missense variants in AMMECR1 demonstrated altered intranuclear protein distribution and reduced expression in functional assays, clinical evidence supporting pathogenicity of non-truncating variants remains limited. The phenotypic overlap between our patient and prior report strengthens the association between missense variations and the MFHIEN phenotype. Our findings support the pathogenic relevance of missense variation in AMMECR1 and emphasize the importance of integrating detailed phenotyping, including hematologic evaluation, with genomic data in the diagnosis of rare multisystem disorders. Additional cases and functional studies are needed to clarify genotype-phenotype correlations and underlying disease mechanisms.

Humans↗

Chromosomal fragility may be indicative of altered higher-order DNA organization as the underlying genetic diathesis in complex neurobehavioral disorders.

Preliminary observations concerning increased chromosomal fragility in association with behavioural disorders in humans allow an opportunity to suggest a cohesive theory regarding the possible importance of higher-order DNA modifications in the coordination of gene function in brain evolution and during development. Visible or submicroscopic acentric chromosomal fragments are formed as an accompaniment to chromosomal breakage and are associated with sequence amplification. During genomic reintegration of extrachromosomally amplified repeat sequence elements, functional consequences could include unequal crossing over with gain-of-function, and/or deletion with loss-of-function. This process could result in regulatory changes in gene function in association with normal coding regions, since fragile sites appear to be located at or near upstream DNaseI-hypersensitive areas. Earlier research on chromosomal breakage in relation to transposon behaviour in maize has set a precedent by which many elements in a network could be coordinately controlled, a principle which may allow transcriptional control over multiple areas in the genome simultaneously. The hypothesis proposed in this paper implies that a small number of fundamental higher-order changes may be responsible for influencing a wide range of genetic alterations leading to complex phenotypes, sometimes segregating as distinct entities within pedigrees, or alternatively, and perhaps more commonly, presenting with several overlapping phenotypes in some other families. Studying only pure multiplex families in psychiatric genetics may not be sufficient for an understanding of the underlying genetic diathesis in this group of disorders. Validation of the fragile site hypothesis for complex neurobehavioural disorders may offer additional avenues for gene therapy based either on preferential integration of exogenous DNA at fragile sites, or utilizing the acentric fragments to modify sequence amplification extrachromosomally.

Chromosome Breakage↗

Chromosomal fragility may be indicative of altered higher-order DNA organization as the underlying genetic diathesis in complex neurobehavioural disorders.

Preliminary observations concerning increased chromosomal fragility in association with certain behavioural disorders in humans allow an opportunity to suggest a cohesive theory regarding the possible importance of higher-order DNA modification in the coordination of gene function in brain evolution and during development. Visible or submicroscopic acentric chromosomal fragments are formed as an accompaniment to chromosomal breakage and are associated with sequence amplification. During genomic reintegration of such extra chromosomally amplified repeat sequence elements, functional consequences could include unequal crossing over with gain-of-function, and/or deletion with loss-of-function. This process could result in regulatory changes in gene function in association with normal coding regions, since fragile sites appear to be located at or near upstream DNase-I hypersensitive areas. Earlier research on chromosomal breakage in relation to transposon behaviour in maize has set a precedent by which many elements in a network could be coordinately controlled, a principle which may allow transcriptional control over multiple areas in the genome simultaneously. The hypothesis proposed in this paper implies that a small number of fundamental higher order changes may be responsible for influencing a wide range of genetic alterations leading to complex phenotypes, sometimes segregating as distinct entities within pedigrees, or alternatively, and perhaps more commonly, presenting with several overlapping phenotypes in some other families. Current emphasis on the investigation of only pure multiplex families in psychiatric genetics may assist with identification of a number of discrete behaviour-modifying genes, but may not be sufficient for an understanding of the broad underlying genetic diathesis in these, and perhaps other 'multifactorial type' disorders. Validation of a role for altered fragile site expression and the molecular consequences thereof as proposed in this paper may offer additional avenues for gene therapy based either on preferential integration of exogenous DNA at fragile sites, or utilizing the acentric fragments formed during chromosome breakage to modify sequence amplification extrachromosomally.

Animals↗

Molecular differential pathology of renal cell tumours.

Recent application of molecular cytogenetic techniques to the evaluation of renal cell tumours revealed four subtypes, each with a characteristic combination of genetic alterations within the chromosomal and mitochondrial DNA. The most common, nonpapillary renal cell carcinomas are characterized by the loss of chromosome 3p sequences, rearrangement of the chromosome 5q region and loss of the chromosome 14q sequences. Papillary renal cell tumours can be divided into two groups. Tumours with a combined trisomy of chromosomes 7 and 17 as well as loss of the Y chromosome are papillary renal cell adenomas. Tumours with additional trisomies such as trisomy 16, 20 or 12 are papillary renal cell carcinomas. Chromophobe renal cell carcinomas show a combination of allelic losses, which do not occur in other types of renal tumours. In addition, they have a rearrangement in the mitochondrial DNA. Renal oncocytomas are benign tumours marked by normal or abnormal karyotypes with balanced or unbalanced translocations and an altered restriction pattern of the mitochondrial DNA. Although the major cytological characteristics of renal cell tumours, such as clear, granular, chromophobe and oncocytic cell phenotypes correspond to nonpapillary, papillary and chromophobe renal cell carcinomas and renal oncocytomas, there are many cases with overlapping phenotype. Therefore, a classification of renal cell tumours based on specific genetic alterations is proposed.

Adenoma↗

Twin fetuses with abnormalities that overlap with three midline malformation complexes.

Twin fetuses aborted at an estimated gestational age of 145 days were concordant for oral, facial, skeletal, and central nervous system malformations. The twins were discordant for other anomalies including cardiac defects, polydactyly, and malrotated short bowel. The combination of malformations observed overlaps with that of the oral-facial-digital syndrome, hydrolethalus syndrome, and Pallister-Hall syndrome. The problem of phenotypic overlap between these syndromes is discussed.

Abnormalities, Multiple↗

Linkage mapping and phenotypic analysis of autosomal dominant Pallister-Hall syndrome.

Pallister-Hall syndrome is a human developmental disorder that is inherited in an autosomal dominant pattern. The phenotypic features of the syndrome include hypothalamic hamartoma, polydactyly, imperforate anus, laryngeal clefting, and other anomalies. Here we describe the clinical characterisation of a family with 22 affected members and the genetic mapping of the corresponding locus. Clinical, radiographic, and endoscopic evaluations showed that this disorder is a fully penetrant trait with variable expressivity and low morbidity. By analysing 60 subjects in two families using anonymous STRP markers, we have established linkage to 7p13 by two point analysis with D7S691 resulting in a lod score of 7.0 at theta = 0, near the GLI3 locus. Deletions and translocations in GLI3 are associated with the Greig cephalopolysyndactyly syndrome. Although Greig cephalopolysyndactyly syndrome has some phenotypic overlap with Pallister-Hall syndrome, these two disorders are clinically distinct. The colocalisation of loci for these distinct phenotypes led us to analyse GLI3 for mutations in patients with Pallister-Hall syndrome. We have previously shown GLI3 mutations in two other small, moderately affected families with Pallister-Hall syndrome. The linkage data reported here suggest that these larger, mildly affected families may also have mutations in GLI3.

Abnormalities, Multiple↗

The distorted shell method for clustering for syndrome classification.

Syndrome classification may be described as the arrangement of individuals into groups on the basis of their phenotypic resemblance. This paper describes how phenotypic resemblance may be quantified and demonstrates a numerical method called distorted shell clustering, which isolates groups of phenotypically similar individuals representing syndromes. This new method takes into consideration apparent biological properties of syndromes. It allows for overlapping phenotypes between syndromes, and differing character association and variability within syndromes. This method is compared to four other clustering methods by using suspects for a syndrome of known etiology (Down syndrome). The numerical results based on the phenotype then can be compared with the actual diagnosis. Only the distorted shell method classifies patients, without error, into two major clusters: the Down and the non-Down, while maintaining a high level of efficiency.

Disease↗