Genetic diagnosis of developmental disorders in the DDD study: a scalable analysis of genome-wide research data.

Background: Human genome sequencing has transformed our understanding of genomic variation and its relevance to health and disease, and is now starting to enter clinical practice for the diagnosis of rare diseases. The question of whether and how some categories of genomic findings should be shared with individual research participants is currently a topic of international debate, and development of robust analytical workflows to identify and communicate clinically relevant variants is paramount.

Methods: The Deciphering Developmental Disorders (DDD) study has developed a UK-wide patient recruitment network involving over 180 clinicians across all 24 regional genetics services, and has performed genome-wide microarray and whole exome sequencing on children with undiagnosed developmental disorders and their parents.

UBE2QL1 is disrupted by a constitutional translocation associated with renal tumor predisposition and is a novel candidate renal tumor suppressor gene.

Investigation of rare familial forms of renal cell carcinoma (RCC) has led to the identification of genes such as VHL and MET that are also implicated in the pathogenesis of sporadic RCC. In order to identify a novel candidate renal tumor suppressor gene, we characterized the breakpoints of a constitutional balanced translocation, t(5;19)(p15.3;q12), associated with familial RCC and found that a previously uncharacterized gene UBE2QL1 was disrupted by the chromosome 5 breakpoint.

Massively parallel sequencing reveals the complex structure of an irradiated human chromosome on a mouse background in the Tc1 model of Down syndrome.

Down syndrome (DS) is caused by trisomy of chromosome 21 (Hsa21) and presents a complex phenotype that arises from abnormal dosage of genes on this chromosome. However, the individual dosage-sensitive genes underlying each phenotype remain largely unknown. To help dissect genotype--phenotype correlations in this complex syndrome, the first fully transchromosomic mouse model, the Tc1 mouse, which carries a copy of human chromosome 21 was produced in 2005.

A familial case with interstitial 2q36 deletion: variable phenotypic expression in full and mosaic state.

Submicroscopic chromosomal anomalies play an important role in the etiology of craniofacial malformations, including midline facial defects with hypertelorism (MFDH). MFDH is a common feature combination in several conditions, of which Frontonasal Dysplasia is the most frequently encountered manifestation; in most cases the etiology remains unknown. We identified a parent to child transmission of a 6.

Auditory function in the Tc1 mouse model of down syndrome suggests a limited region of human chromosome 21 involved in otitis media.

Down syndrome is one of the most common congenital disorders leading to a wide range of health problems in humans, including frequent otitis media. The Tc1 mouse carries a significant part of human chromosome 21 (Hsa21) in addition to the full set of mouse chromosomes and shares many phenotypes observed in humans affected by Down syndrome with trisomy of chromosome 21. However, it is unknown whether Tc1 mice exhibit a hearing phenotype and might thus represent a good model for understanding the hearing loss that is common in Down syndrome.

Maternally inherited partial monosomy 9p (pter → p24.1) and partial trisomy 20p (pter → p12.1) characterized by microarray comparative genomic hybridization.

We report on a 17-year-old patient with midline defects, ocular hypertelorism, neuropsychomotor development delay, neonatal macrosomy, and dental anomalies. DNA copy number investigations using a Whole Genome TilePath array consisting, of 30K BAC/PAC clones showed a 6.36 Mb deletion in the 9p24.

Comprehensive assessment of array-based platforms and calling algorithms for detection of copy number variants.

We have systematically compared copy number variant (CNV) detection on eleven microarrays to evaluate data quality and CNV calling, reproducibility, concordance across array platforms and laboratory sites, breakpoint accuracy and analysis tool variability. Different analytic tools applied to the same raw data typically yield CNV calls with <50% concordance. Moreover, reproducibility in replicate experiments is <70% for most platforms.

Array painting: a protocol for the rapid analysis of aberrant chromosomes using DNA microarrays.

Array painting is a technique that uses microarray technology to rapidly map chromosome translocation breakpoints. Previous methods to map translocation breakpoints have used fluorescence in situ hybridization (FISH) and have consequently been labor-intensive, time-consuming and restricted to the low breakpoint resolution imposed by the use of metaphase chromosomes. Array painting combines the isolation of derivative chromosomes (chromosomes with translocations) and high-resolution microarray analysis to refine the genomic location of translocation breakpoints in a single experiment.

Reduced TFAP2A function causes variable optic fissure closure and retinal defects and sensitizes eye development to mutations in other morphogenetic regulators.

Mutations in the transcription factor encoding TFAP2A gene underlie branchio-oculo-facial syndrome (BOFS), a rare dominant disorder characterized by distinctive craniofacial, ocular, ectodermal and renal anomalies. To elucidate the range of ocular phenotypes caused by mutations in TFAP2A, we took three approaches. First, we screened a cohort of 37 highly selected individuals with severe ocular anomalies plus variable defects associated with BOFS for mutations or deletions in TFAP2A.

Genomic and genic deletions of the FOX gene cluster on 16q24.1 and inactivating mutations of FOXF1 cause alveolar capillary dysplasia and other malformations.

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare, neonatally lethal developmental disorder of the lung with defining histologic abnormalities typically associated with multiple congenital anomalies (MCA). Using array CGH analysis, we have identified six overlapping microdeletions encompassing the FOX transcription factor gene cluster in chromosome 16q24.1q24.

Finishing the finished human chromosome 22 sequence.

Background: Although the human genome sequence was declared complete in 2004, the sequence was interrupted by 341 gaps of which 308 lay in an estimated approximately 28 Mb of euchromatin. While these gaps constitute only approximately 1% of the sequence, knowledge of the full complement of human genes and regulatory elements is incomplete without their sequences.

Results: We have used a combination of conventional chromosome walking (aided by the availability of end sequences) in fosmid and bacterial artificial chromosome (BAC) libraries, whole chromosome shotgun sequencing, comparative genome analysis and long PCR to finish 8 of the 11 gaps in the initial chromosome 22 sequence.

Breakpoint mapping and array CGH in translocations: comparison of a phenotypically normal and an abnormal cohort.

We report the analyses of breakpoints in 31 phenotypically normal and 14 abnormal carriers of balanced translocations. Our study assesses the differences between balanced translocations in normal carriers and those in abnormal carriers, focusing on the presence of genomic imbalances at the breakpoints or elsewhere in the genome, presence of cryptic chromosome rearrangements, and gene disruption. Our hypothesis is that all four features will be associated with phenotypic abnormalities and absent or much less frequent in a normal population.

Characterization of a 3;6 translocation associated with renal cell carcinoma.

The most frequent cause of familial clear cell renal cell carcinoma (RCC) is von Hippel-Lindau disease and the VHL tumor suppressor gene (TSG) is inactivated in most sporadic clear cell RCC. Although there is relatively little information on the mechanisms of tumorigenesis of clear cell RCC without VHL inactivation, a subset of familial cases harbors a balanced constitutional chromosome 3 translocation. To date nine different chromosome 3 translocations have been associated with familial or multicentric clear cell RCC; and in three cases chromosome 6 was also involved.

Microdeletion encompassing MAPT at chromosome 17q21.3 is associated with developmental delay and learning disability.

Recently, the application of array-based comparative genomic hybridization (array CGH) has improved rates of detection of chromosomal imbalances in individuals with mental retardation and dysmorphic features. Here, we describe three individuals with learning disability and a heterozygous deletion at chromosome 17q21.3, detected in each case by array CGH.

Micro-array analyses decipher exceptional complex familial chromosomal rearrangement.

Recently there has been an increased interest in large-scale genomic variation and clinically in the consequences of haploinsufficiency of genomic segments or disruption of normal gene function by chromosome rearrangements. Here, we present an extraordinary case in which both mother and daughter presented with unexpected chromosomal rearrangement complexity, which we characterized with array-CGH, array painting and multicolor large insert clone hybridizations. We found the same 12 breakpoints involving four chromosomes in both mother and daughter.

Heterogeneous duplications in patients with Pelizaeus-Merzbacher disease suggest a mechanism of coupled homologous and nonhomologous recombination.

We describe genomic structures of 59 X-chromosome segmental duplications that include the proteolipid protein 1 gene (PLP1) in patients with Pelizaeus-Merzbacher disease. We provide the first report of 13 junction sequences, which gives insight into underlying mechanisms. Although proximal breakpoints were highly variable, distal breakpoints tended to cluster around low-copy repeats (LCRs) (50% of distal breakpoints), and each duplication event appeared to be unique (100 kb to 4.

Molecular cytogenetic analyses of breakpoints in apparently balanced reciprocal translocations carried by phenotypically normal individuals.

To test the hypothesis that translocation breakpoints in normal individuals are simple and do not disrupt genes, we characterised the breakpoints in 13 phenotypically normal individuals incidentally ascertained with an apparently balanced reciprocal translocation. Cases were karyotyped, and the breakpoints were refined by fluorescence in situ hybridisation until breakpoint-spanning clones were identified. 1 Mb array-CGH was performed as a whole genome analysis tool to detect any imbalances in chromatin not directly involved in the breakpoints.

The DNA sequence of the human X chromosome.

The human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. We have determined 99.3% of the euchromatic sequence of the X chromosome.

Chromosome paints from single copies of chromosomes.

We have used OmniPlex library technology to construct chromosome painting probes from single copies of flow sorted chromosomes. We show that this whole genome amplification technology is particularly efficient at amplifying single copies of chromosomes for the production of paints and that single aberrant chromosomes can be analysed in this way using reverse chromosome painting. The efficient generation of painting probes from single copies of sorted chromosomes has the advantage that the probe must be specific for the chromosome sorted and will not suffer from contamination from other chromosomes particularly in situations where flow karyotype peaks are poorly resolved.

Cloning of a new familial t(3;8) translocation associated with conventional renal cell carcinoma reveals a 5 kb microdeletion and no gene involved in the rearrangement.

This study describes the molecular cloning of a familial translocation, t(3;8)(p14.2;q24.2), that segregates with the conventional renal cell carcinoma (conventional RCC).

Genomic imbalances in CML blast crisis: 8q24.12-q24.13 segment identified as a common region of over-representation.

The acute phase of chronic myeloid leukemia (CML) is accompanied by secondary chromosomal changes. The additional changes have a non-random pattern; however, highly abnormal (marker) chromosomes are reported in some 20% of abnormal karyotypes. These marker chromosomes have proved to be beyond the resolution of conventional G-banding analysis.