A child with multiple congenital anomalies due to partial trisomy 7q22.1 → qter resulting from a maternally inherited balanced translocation: a case report and review of literature.

BACKGROUND: Parental balanced reciprocal translocations can result in partial aneuploidies in the offspring due to unbalanced meiotic segregation during gametogenesis. Herein, we report the phenotypic and molecular cytogenetic characterization of a 2 years and 4 months old female child with partial trisomy 7q22 → qter. This is the first such reported case resulting from a parental balanced translocation involving the long arms of chromosomes 7 and 14. The phenotype of the proband was compared with that of previously reported cases of trisomy 7q21 → qter or 7q22 → qter resulting from parental balanced translocations. CASE PRESENTATION: The proband was born pre-term to a 34-year-old mother with a history of two first trimester miscarriages and an early infant death. She was referred at the age of 8 months for genetic evaluation due to prenatal and postnatal growth retardation, developmental delay and multiple congenital anomalies. On clinical evaluation, she had craniofacial dysmorphic features such as scaphocephaly, large anterior fontanelle with open posterior fontanelle, prominent occiput, triangular face, high forehead, hypertelorism, down slanting eyes, flat nasal bridge, small nose, low set ears, micro-retrognathia, high arched palate and short neck. Cranial computerized tomography scan showed lateral ventriculomegaly with features of early cerebral atrophy. Conventional cytogenetic analysis showed the karyotype 46,XX,der(14)t(7;14)(q22;q32)mat in the proband due to an unbalanced segregation of a maternal balanced translocation t(7;14)(q22;q32). Fluorescence in-situ hybridization analysis confirmed the partial trisomy 7q22 → qter in the proband with a minimal loss of genetic material on chromosome 14. Single nucleotide polymorphism array further confirmed the duplication on chromosome 7q22.1 → qter and a small terminal deletion on chromosome 14q32.3 → qter. CONCLUSION: We report the longest-surviving child with trisomy 7q22 → qter due to a parental balanced translocation between chromosomes 7 and 14. Clinical features observed in the proband were consistent with the consensus phenotype of partial trisomy 7q22 → qter reported in the scientific literature. Early diagnosis of these patients using molecular cytogenetic techniques is important for establishing the precise diagnosis and for making decisions pertaining to the prognostication and management of affected individuals.

Bi-allelic IARS mutations in a child with intra-uterine growth retardation, neonatal cholestasis, and mild developmental delay.

Recently, bi-allelic mutations in cytosolic isoleucyl-tRNA synthetase (IARS) have been described in three individuals with growth delay, hepatic dysfunction, and neurodevelopmental disabilities. Here we report an additional subject with this condition identified by whole-exome sequencing. Our findings support the association between this disorder and neonatal cholestasis with distinct liver pathology. Furthermore, we provide functional data on two novel missense substitutions and expand the phenotype to include mild developmental delay, skin hyper-elasticity, and hypervitaminosis D.

Linkage and association analysis of ADHD endophenotypes in extended and multigenerational pedigrees from a genetic isolate.

Attention-deficit/hyperactivity disorder (ADHD) is a heritable, chronic, neurodevelopmental disorder with serious long-term repercussions. Despite being one of the most common cognitive disorders, the clinical diagnosis of ADHD is based on subjective assessments of perceived behaviors. Endophenotypes (neurobiological markers that cosegregate and are associated with an illness) are thought to provide a more powerful and objective framework for revealing the underlying neurobiology than syndromic psychiatric classification. Here, we present the results of applying genetic linkage and association analyses to neuropsychological endophenotypes using microsatellite and single nucleotide polymorphisms. We found several new genetic regions linked and/or associated with these endophenotypes, and others previously associated to ADHD, for example, loci harbored in the LPHN3, FGF1, POLR2A, CHRNA4 and ANKFY1 genes. These findings, when compared with those linked and/or associated to ADHD, suggest that these endophenotypes lie on shared pathways. The genetic information provided by this study offers a novel and complementary method of assessing the genetic causes underpinning the susceptibility to behavioral conditions and may offer new insights on the neurobiology of the disorder.

High Intellectual Function in Individuals with Mutation-Positive Microform Holoprosencephaly.

Holoprosencephaly is the most common malformation of the forebrain and typically results in severe neurocognitive impairment with accompanying midline facial anomalies. Holoprosencephaly is heterogeneous and may be caused by chromosome aberrations or environmental factors, occur in the context of a syndrome or be due to heterozygous mutations in over 10 identified genes. The presence of these mutations may result in an extremely wide spectrum of severity, ranging from brain malformations incompatible with life to individuals with normal brain findings and subtle midline facial differences. Typically, clinicians regard intellectual disability as a sign that a parent or relative of a severely affected patient may be a mildly affected mutation 'carrier' with what is termed microform holoprosencephaly. Here we present 5 patients with clear phenotypic signs of microform holoprosencephaly, all of whom have evidence of above-average intellectual function. In 4 of these 5 individuals, the molecular cause of holoprosencephaly has been identified and includes mutations affecting SHH, SIX3, GLI2, and FGF8. This report expands the phenotypic spectrum of holoprosencephaly and is important in the counseling of patient and affected families.

A cooperative interaction between LPHN3 and 11q doubles the risk for ADHD.

In previous studies of a genetic isolate, we identified significant linkage of attention deficit hyperactivity disorder (ADHD) to 4q, 5q, 8q, 11q and 17p. The existence of unique large size families linked to multiple regions, and the fact that these families came from an isolated population, we hypothesized that two-locus interaction contributions to ADHD were plausible. Several analytical models converged to show significant interaction between 4q and 11q (P<1 × 10(-8)) and 11q and 17p (P<1 × 10(-6)). As we have identified that common variants of the LPHN3 gene were responsible for the 4q linkage signal, we focused on 4q-11q interaction to determine that single-nucleotide polymorphisms (SNPs) harbored in the LPHN3 gene interact with SNPs spanning the 11q region that contains DRD2 and NCAM1 genes, to double the risk of developing ADHD. This interaction not only explains genetic effects much better than taking each of these loci effects by separated but also differences in brain metabolism as depicted by proton magnetic resonance spectroscopy data and pharmacogenetic response to stimulant medication. These findings not only add information about how high order genetic interactions might be implicated in conferring susceptibility to develop ADHD but also show that future studies of the effects of genetic interactions on ADHD clinical information will help to shape predictive models of individual outcome.

Contribution of LPHN3 to the genetic susceptibility to ADHD in adulthood: a replication study.

Attention-deficit/hyperactivity disorder (ADHD) is a common and highly heritable developmental disorder characterized by a persistent impairing pattern of inattention and/or hyperactivity-impulsivity. Using families from a genetic isolate, the Paisa population from Colombia, and five independent datasets from four different populations (United States, Germany, Norway and Spain), a highly consistent association was recently reported between ADHD and the latrophilin 3 (LPHN3) gene, a brain-specific member of the LPHN subfamily of G-protein-coupled receptors that is expressed in ADHD-related regions, such as amygdala, caudate nucleus, cerebellum and cerebral cortex. To replicate the association between LPHN3 and ADHD in adults, we undertook a case-control association study in 334 adult patients with ADHD and 334 controls with 43 single nucleotide polymorphisms (SNPs) covering the LPNH3 gene. Single- and multiple-marker analyses showed additional evidence of association between LPHN3 and combined type ADHD in adulthood [P = 0.0019; df = 1; odds ratio (OR) = 1.82 (1.25-2.70) and P = 5.1e-05; df = 1; OR = 2.25 (1.52-3.34), respectively]. These results further support the LPHN3 contribution to combined type ADHD, and specifically to the persistent form of the disorder, and point at this new neuronal pathway as a common susceptibility factor for ADHD throughout the lifespan.

A two-locus genetic interaction between LPHN3 and 11q predicts ADHD severity and long-term outcome.

The severity of attention-deficit/hyperactivity disorder (ADHD) symptoms is a major predictor of long-term ADHD outcome. To investigate if two-locus interactions might predict ADHD severity, we studied a sample of 1341 individuals from families clustering ADHD, using the Vanderbilt Assessment Scale for Parents. Latent class cluster analysis was used to construct symptom profiles and classify ADHD severity. Single nucleotide polymorphisms (SNPs) spanning ADHD-linked chromosomal regions on chromosomes 4, 5, 10, 11, 12 and 17 were genotyped. SNPs associated with ADHD severity were identified and potential two-locus genetic interactions were tested. We found that SNPs within the LPHN3 gene interact with SNPs spanning the 11q region that contains DRD2 and NCAM1 not only to increase the risk of developing ADHD but also to increase ADHD severity. All these genes are identified to have a major role in shaping both brain development and function. These findings demonstrate that genetic interactions may predict the severity of ADHD, which in turn may predict long-term ADHD outcome.

A Hypomorphic Allele in the FGF8 Gene Contributes to Holoprosencephaly and Is Allelic to Gonadotropin-Releasing Hormone Deficiency in Humans.

Holoprosencephaly (HPE), the most common malformation of the human forebrain, may arise due to interacting genetic and environmental factors. To date, at least 12 contributory genes have been identified. Fibroblast growth factor 8 (Fgf8) belongs to the FGF family of genes expressed in several developmental signaling centers, including the anterior neural ridge, which is implicated in midline anomalies in mice. In humans, FGF8 mutations have been previously reported in facial clefting and in hypogonadotropic hypogonadism, but have not been reported in patients with HPE. We screened 360 probands with HPE for sequence variations in FGF8 using High Resolution DNA Melting (HRM) and sequenced all identified variations. Here we describe a total of 8 sequence variations in HPE patients, including a putative loss-of-function mutation in 3 members of a family with variable forms of classic HPE, and relate these findings to the phenotypes seen in other conditions.

TGIF Mutations in Human Holoprosencephaly: Correlation between Genotype and Phenotype.

Holoprosencephaly (HPE), which results from failed or incomplete midline forebrain division early in gestation, is the most common forebrain malformation. The etiology of HPE is complex and multifactorial. To date, at least 12 HPE-associated genes have been identified, including TGIF (transforming growth factor beta-induced factor), located on chromosome 18p11.3. TGIF encodes a transcriptional repressor of retinoid responses involved in TGF-ß signaling regulation, including Nodal signaling. TGIF mutations are reported in approximately 1-2% of patients with non-syndromic, non-chromosomal HPE. We combined data from our comprehensive studies of HPE with a literature search for all individuals with HPE and evidence of mutations affecting TGIF in order to establish the genotypic and phenotypic range. We describe 2 groups of patients: 34 with intragenic mutations and 21 with deletions of TGIF. These individuals, which were ascertained from our research group, in collaboration with other centers, and through a literature search, include 38 probands and 17 mutation-positive relatives. The majority of intragenic mutations occur in the TGIF homeodomain. Patients with mutations affecting TGIFrecapitulate the entire phenotypic spectrum observed in non-chromosomal, non-syndromic HPE. We identified a statistically significant difference between the 2 groups with respect to inheritance, as TGIF deletions were more likely to be de novo in comparison to TGIF mutations (χ(2) ((2)) = 6.97, p(permutated) = 0.0356). In addition, patients with TGIF deletions were also found to more commonly present with manifestations beyond the craniofacial and neuroanatomical features associated with HPE (p = 0.0030). These findings highlight differences in patients with intragenic mutations versus deletions affecting TGIF, and draw attention to the homeodomain region, which appears to be particularly relevant to HPE. These results may be useful for genetic counseling of affected patients.

[Attention deficit hyperactivity behavioral phenotype dimensions of adults from Antioquian families using the Wender-Utah Scale -Spanish version]. / Dimensiones del fenotipo conductual del trastorno por déficit de atención/hiperactividad en adultos de familias antioqueñas utilizando la escala Wender-Utah en Español.

INTRODUCTION: The Wender-Utah Rating Scale (WURS) has been used for retrospective screening of attention deficit hyperactivity disorders (ADHD) symptoms and its comorbidities. AIM: To establish the ADHD behavioral phenotype dimensions of adults from 140 Antioquian families with genetic segregation for ADHD diagnosis, using the WURS -Spanish version. SUBJECTS AND METHODS: 392 adults from both genders, belonging to nuclear and multigenerational families with one or more ADHD affected members were selected. The Composite International Diagnostic Interview (CIDI) for mental disorder was administered to establish the gold standard diagnosis of ADHD through the long life. All participants fulfill the WURS. Exploratory and confirmatory factor analyses were done to determine the behavioral dimensions of the ADHD phenotype. RESULTS: A factor structure of four dimensions was derived, measuring behavioral decontrol, hyperactivity, inattention and anxiety, and which explained the 60% of the total variance. CONCLUSIONS: The behavioral adult ADHD phenotype in the Antioquian families was conformed by four dimensions, which could be used in heritability and linkage future studies.

Clinical spectrum of SIX3-associated mutations in holoprosencephaly: correlation between genotype, phenotype and function.

BACKGROUND: Holoprosencephaly (HPE) is the most common structural malformation of the human forebrain. There are several important HPE mutational target genes, including the transcription factor SIX3, which encodes an early regulator of Shh, Wnt, Bmp and Nodal signalling expressed in the developing forebrain and eyes of all vertebrates. OBJECTIVE: To characterise genetic and clinical findings in patients with SIX3 mutations. METHODS: Patients with HPE and their family members were tested for mutations in HPE-associated genes and the genetic and clinical findings, including those for additional cases found in the literature, were analysed. The results were correlated with a mutation-specific functional assay in zebrafish. RESULTS: In a cohort of patients (n = 800) with HPE, SIX3 mutations were found in 4.7% of probands and additional cases were found through testing of relatives. In total, 138 cases of HPE were identified, 59 of whom had not previously been clinically presented. Mutations in SIX3 result in more severe HPE than in other cases of non-chromosomal, non-syndromic HPE. An over-representation of severe HPE was found in patients whose mutations confer greater loss of function, as measured by the functional zebrafish assay. The gender ratio in this combined set of patients was 1.5:1 (F:M) and maternal inheritance was almost twice as common as paternal. About 14% of SIX3 mutations in probands occur de novo. There is a wide intrafamilial clinical range of features and classical penetrance is estimated to be at least 62%. CONCLUSIONS: Our data suggest that SIX3 mutations result in relatively severe HPE and that there is a genotype-phenotype correlation, as shown by functional studies using animal models.

Loss-of-function mutations in growth differentiation factor-1 (GDF1) are associated with congenital heart defects in humans.

Congenital heart defects (CHDs) are among the most common birth defects in humans (incidence 8-10 per 1,000 live births). Although their etiology is often poorly understood, most are considered to arise from multifactorial influences, including environmental and genetic components, as well as from less common syndromic forms. We hypothesized that disturbances in left-right patterning could contribute to the pathogenesis of selected cardiac defects by interfering with the extrinsic cues leading to the proper looping and vessel remodeling of the normally asymmetrically developed heart and vessels. Here, we show that heterozygous loss-of-function mutations in the human GDF1 gene contribute to cardiac defects ranging from tetralogy of Fallot to transposition of the great arteries and that decreased TGF- beta signaling provides a framework for understanding their pathogenesis. These findings implicate perturbations of the TGF- beta signaling pathway in the causation of a major subclass of human CHDs.

Abnormal sterol metabolism in holoprosencephaly: studies in cultured lymphoblasts.

BACKGROUND: Holoprosencephaly (HPE) is the most common structural malformation of the developing forebrain in humans. The aetiology is heterogeneous and remains unexplained in approximately 75% of patients. OBJECTIVE: To examine cholesterol biosynthesis in lymphoblastoid cell lines of 228 patients with HPE, since perturbations of cholesterol homeostasis are an important model system to study HPE pathogenesis in animals. METHODS: An in vitro loading test that clearly identifies abnormal increase of C27 sterols in lymphoblast-derived cells was developed using [2-(14)C] acetate as substrate. RESULTS: 22 (9.6%) HPE cell lines had abnormal sterol pattern in the in vitro loading test. In one previously reported patient, Smith-Lemli-Opitz syndrome was diagnosed, whereas others also had clearly reduced cholesterol biosynthesis of uncertain cause. The mean (SD) cholesterol levels were 57% (15.3%) and 82% (4.7%) of total sterols in these cell lines and controls, respectively. The pattern of accumulating sterols was different from known defects of cholesterol biosynthesis. In six patients with abnormal lymphoblast cholesterol metabolism, additional mutations in genes known to be associated with HPE or chromosomal abnormalities were observed. CONCLUSIONS: Impaired cholesterol biosynthesis may be a contributing factor in the cause of HPE and should be considered in the evaluation of causes of HPE, even if mutations in HPE-associated genes have already been found.

Revisiting the craniosynostosis-radial ray hypoplasia association: Baller-Gerold syndrome caused by mutations in the RECQL4 gene.

Baller-Gerold syndrome (BGS) is a rare autosomal recessive condition with radial aplasia/hypoplasia and craniosynostosis (OMIM 218600). Of >20 cases reported so far, a few appear atypical and have been reassigned to other nosologic entities, including Fanconi anaemia, Roberts SC phocomelia, and Pfeiffer syndromes after demonstration of corresponding cytogenetic or molecular abnormalities. Clinical overlap between BGS, Rothmund-Thomson syndrome (RTS), and RAPADILINO syndrome is noticeable. Because patients with RAPADILINO syndrome and a subset of patients with RTS have RECQL4 mutations, we reassessed two previously reported BGS families and found causal mutations in RECQL4 in both. In the first family, four affected offspring had craniosynostosis and radial defect and one of them developed poikiloderma. In this family, compound heterozygosity for a R1021W missense mutation and a g.2886delT frameshift mutation of exon 9 was found. In the second family, the affected male had craniosynostosis, radial ray defect, poikiloderma, and short stature. He had a homozygous splice site mutation (IVS17-2A>C). In both families, the affected offspring had craniosynostosis, radial defects, and growth retardation, and two developed poikiloderma. Our results confirm that BGS in a subgroup of patients is due to RECQL4 mutations and could be integrated into a clinical spectrum that encompasses RTS and RAPADILINO syndrome.

Multicolour FISH and quantitative PCR can detect submicroscopic deletions in holoprosencephaly patients with a normal karyotype.

Holoprosencephaly (HPE) is the most common structural malformation of the developing forebrain. At birth, nearly 50% of children with HPE have cytogenetic anomalies. Approximately 20% of infants with normal chromosomes have sequence mutations in one of the four main HPE genes (SHH, ZIC2, SIX3, and TGIF). The other non-syndromic forms of HPE may be due to environmental factors or mutations in other genes, or potentially due to submicroscopic deletions of HPE genes. We used two complementary assays to test for HPE associated submicroscopic deletions. Firstly, we developed a multicolour fluorescent in situ hybridisation (FISH) assay using probes for the four major HPE genes and for two candidate genes (DISP1 and FOXA2). We analysed lymphoblastoid cell lines (LCL) from 103 patients who had CNS findings of HPE, normal karyotypes, and no point mutations, and found seven microdeletions. We subsequently applied quantitative PCR to 424 HPE DNA samples, including the 103 samples studied by FISH: 339 with CNS findings of HPE, and 85 with normal CNS and characteristic HPE facial findings. Microdeletions for either SHH, ZIC2, SIX3, or TGIF were found in 16 of the 339 severe HPE cases (that is, with CNS findings; 4.7%). In contrast, no microdeletion was found in the 85 patients at the mildest end of the HPE spectrum. Based on our data, microdeletion testing should be considered as part of an evaluation of holoprosencephaly, especially in severe HPE cases.

Pedigree disequilibrium test (PDT) replicates association and linkage between DRD4 and ADHD in multigenerational and extended pedigrees from a genetic isolate.

Association/linkage between dopamine D4 receptor (DRD4) polymorphisms and attention-deficit/hyperactivity disorder (ADHD) has been suggested by case-control- and nuclear-family-based studies. Here, we present a candidate gene analysis for DRD4 using 14 extended and multigenerational families segregating ADHD derived from the 'Paisa' community of Antioquia, Colombia, a genetic isolate. Two DRD4 polymorphisms (a 120 bp tandem duplication at the promoter and a 48 bp-VNTR at exon 3), reported associated to ADHD, were genotyped. Parametric and non-parametric linkage analyses, and a family-based association test (FBAT), the pedigree disequilibrium test (PDT), were applied to search for evidence of association/linkage. Two-point LOD scores were significantly negative, with values ranging from -3.21 (P=0.011158) to -7.66 (P=0.000091 at theta=0). Non-parametrical analysis resulted in nonsignificant evidence for linkage. The PDT showed a moderate trend toward significance of association/linkage between the 7-repeat (7R) allele at the 48 bp VNTR and ADHD (P=0.0578). Furthermore, the haplotype analysis shows a significant association/linkage of the 7R-240 bp haplotype (P=0.0467) with ADHD. Results suggest that either a moderate DRD4 genetic effect, or linkage disequilibrium of DRD4 with an ADHD disease locus in the vicinity or the linkage to a phenotypic component of the ADHD spectrum could be underlying this association/linkage. These results provide further evidence for the association of ADHD to genetic variation in or near to DRD4 and replicate the previously reported association between ADHD and the 7R allele.

The genomic structure, chromosomal localization, and analysis of SIL as a candidate gene for holoprosencephaly.

Holoprosencephaly (HPE) is the most common congenital malformation of the brain and face in humans. In this study we report the analysis of SIL (Sumacr;CL iumacr;nterrupting lumacr;ocus) as a candidate gene for HPE. Fluorescent in situ hybridization (FISH) analysis using a BAC 246e16 confirmed the assignment of SIL to 1p32. Computational analysis of SIL at the protein level revealed a 73% overall identity between the human and murine proteins. Denaturing high performance liquid chromatography (dHPLC) techniques were used to screen for mutations and these studies identified several common polymorphisms but no disease-associated mutations, suggesting that SIL is not a common factor in HPE pathogenesis in humans.

Attention-deficit/hyperactivity disorder (ADHD): feasibility of linkage analysis in a genetic isolate using extended and multigenerational pedigrees.

Segregation analyses converge in explaining the predisposition to attention-deficit/hyperactivity disorder (ADHD) as the consequence of a major gene and exclude purely environmental or cultural transmission. As a result of the ADHD phenotype restrictions, collection of extended families or design of linkage studies using families has been extremely difficult and thus currently linkage studies have been performed using only concordant or discordant sib-pairs rather than large families. On the other hand, intergenerational studies are represented by the transmission disequilibrium test (TDT) using trios. We collected pedigree data on ADHD from the Paisa community from Antioquia, Colombia, a genetic isolate. The goal of this study was to genetically map a putative gene predisposing to ADHD in a set of 27 multigenerational Paisa families. Here we present the results of a power simulation using SIMLINK to detect linkage of ADHD. ADHD was assumed to be a dichotomous trait with incomplete penetrance and a phenocopy rate of 3% in males and 0.2% in females. We simulated cosegregation of the trait and a marker locus in our pedigrees. We assumed Hardy-Weinberg and linkage equilibrium, equally frequent marker alleles and evaluated power at several recombination fractions between the trait and marker loci. Also, the ADHD trait was assumed to be genetically heterogeneous and different functions of age-dependent penetrance were simulated. We found exceptionally good power to detect linkage (expected LOD > 14 if theta is 0.1 or less), and that the presence of heterogeneity up to 50% does not affect substantially the projected LOD scores even for a theta recombination value of 0.05 (eLOD > 5.87). Having now obtained blood samples and confirmatory interviews in five families (representing 20% of the projected number of families), we performed a new analysis. The expected mean LOD in these five families reached values close to 10 and remained invariant when heterogeneity and different penetrance models were considered. We discuss the relative benefits of using extended and multigenerational families for genetic mapping studies as opposed to using nuclear families, affected sib pairs or sporadic cases which require the collection of over 1000 analytical units to get the same power exhibited by the small number of pedigrees described here.