Exome Sequencing and High-Density Microarray Testing in Monozygotic Twin Pairs Discordant for Features of VACTERL Association.

Exome sequencing offers an efficient and affordable method to interrogate genetic factors involved in human disease. Performing exome sequencing of monozygotic twins discordant for VACTERL (Vertebral anomalies, Anal atresia, Cardiac malformations, Tracheo-Esophageal fistula, Renal anomalies, and Limb abnormalities) association-type congenital malformations was hypothesized to potentially reveal discordant variants that could demonstrate disease cause(s). After demonstrating monozygosity, we applied high-density microarrays and exome sequencing to 2 twin pairs in which 1 twin had features of VACTERL association while the other was phenotypically normal (demonstrated through comprehensive clinical and radiological evaluation). No obvious discordant genotypic results were found that would explain phenotypic discordance. We conclude that VACTERL association is a complex disease, and while performing microarray analysis and exome sequencing on phenotypically discordant monozygotic twins may hypothetically reveal genetic causes of disorders, challenges remain in applying these methods in this circumstance.

Applying Genomic Analysis to Newborn Screening.

Large-scale genomic analysis such as whole-exome and whole-genome sequencing is becoming increasingly prevalent in the research arena. Clinically, many potential uses of this technology have been proposed. One such application is the extension or augmentation of newborn screening. In order to explore this application, we examined data from 3 children with normal newborn screens who underwent whole-exome sequencing as part of research participation. We analyzed sequence information for 151 selected genes associated with conditions ascertained by newborn screening. We compared findings with publicly available databases and results from over 500 individuals who underwent whole-exome sequencing at the same facility. Novel variants were confirmed through bidirectional dideoxynucleotide sequencing. High-density microarrays (Illumina Omni1-Quad) were also performed to detect potential copy number variations affecting these genes. We detected an average of 87 genetic variants per individual. After excluding artifacts, 96% of the variants were found to be reported in public databases and have no evidence of pathogenicity. No variants were identified that would predict disease in the tested individuals, which is in accordance with their normal newborn screens. However, we identified 6 previously reported variants and 2 novel variants that, according to published literature, could result in affected offspring if the reproductive partner were also a mutation carrier; other specific molecular findings highlight additional means by which genomic testing could augment newborn screening.

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 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.