Duplication Of Chromosomal Segments Research Articles

Genomics insights into flowering and floral pattern formation: regional duplication and seasonal pattern of gene expression in Camellia

BackgroundThe formation and domestication of ornamental traits are influenced by various aspects, such as the recognition of esthetic values and cultural traditions. Camellia japonica is widely appreciated and domesticated around the world mainly due to its rich variations in ornamental traits. Ornamental camellias have a diverse range of resources, including different bud variations from Camellia spp. as well as inter- and intra- specific hybridization. Despite research on the formation of ornamental traits, a basic understanding of their genetics and genomics is still lacking.ResultsHere, we report the chromosomal-level reference genome of C. japonica through combining multiple DNA-sequencing technologies and obtain a high-density genetic linkage map of 4255 markers by sequencing 98 interspecific F1 hybrids between C. japonica and C. chekiangoleosa. We identify two whole-genome duplication events in C. japonica: one is a shared ancient γ event, and the other is revealed to be specific to genus Camellia. Based on the micro-collinearity analysis, we find large-scale segmental duplication of chromosome 8, resulting to two copies of the AGAMOUS loci, which may play a key role in the domestication of floral shapes. To explore the regulatory mechanisms of seasonal flowering, we have analyzed year-round gene expression patterns of C. japonica and C. azalea—a sister plant of continuous flowering that has been widely used for cross breeding. Through comparative analyses of gene co-expression networks and annual gene expression patterns, we show that annual expression rhythms of some important regulators of seasonal growth and development, including GIGANTEA and CONSTANS of the photoperiod pathway, have been disrupted in C. azalea. Furthermore, we reveal that the distinctive expression patterns of FLOWERING LOCUS T can be correlated with the seasonal activities of flowering and flushing. We demonstrate that the regulatory module involved in GIGANTEA, CONSTANS, and FLOWERING LOCUS T is central to achieve seasonality.ConclusionsThrough the genomic and comparative genomics characterizations of ornamental Camellia spp., we propose that duplication of chromosomal segments as well as the establishment of gene expression patterns has played a key role in the formation of ornamental traits (e.g., flower shape, flowering time). This work provides a valuable genomic platform for understanding the molecular basis of ornamental traits.

OTSUCNV: an adaptive segmentation and OTSU-based anomaly classification method for CNV detection using NGS data

Copy-number variations (CNVs), which refer to deletions and duplications of chromosomal segments, represent a significant source of variation among individuals, contributing to human evolution and being implicated in various diseases ranging from mental illness and developmental disorders to cancer. Despite the development of several methods for detecting copy number variations based on next-generation sequencing (NGS) data, achieving robust detection performance for CNVs with arbitrary coverage and amplitude remains challenging due to the inherent complexity of sequencing samples. In this paper, we propose an alternative method called OTSUCNV for CNV detection on whole genome sequencing (WGS) data. This method utilizes a newly designed adaptive sequence segmentation algorithm and an OTSU-based CNV prediction algorithm, which does not rely on any distribution assumptions or involve complex outlier factor calculations. As a result, the effective detection of CNVs is achieved with lower computational complexity. The experimental results indicate that the proposed method demonstrates outstanding performance, and hence it may be used as an effective tool for CNV detection.

Neo-Darwinian Principles Exemplified in Cancer Genomics.

Within the last two decades, the advent of next-generation sequencing accompanied by single-cell technologies has enabled cancer researchers to study in detail mutations and other genetic aberrations that transpire during transformation of cells to a neoplastic state. This article covers the insights gained through these extensive studies where neo-Darwinian principles can be inferred to play roles throughout neoplastic transformation. The cells promoted during cancer development exhibit cancer hallmarks combined with the related enabling characteristics as outlined by Hanahan and Weinberg, analogous to natural selection and survival of the fittest. Selection of driver mutations that inactivate proteins encoded by tumor suppressor genes differs in profound ways from mutations that activate tumor promoter proteins. In most cases, the later stages of cancer development are characterized by sudden, extensive damage to chromosomes in a process that is not Darwinian in nature. Nevertheless, cells that survive these cataclysmic events remain subject to Darwinian selection promoting clones exhibiting the greatest rates of progression. Duplications of chromosomal segments containing oncogenes, deletions of segments harboring tumor suppressor genes, or distinctive chromosomal rearrangements are often found in cells progressing into later stages of cancer. In summary, the technological developments in genome sequencing since the start of the century have given us clear insights into genomic alterations promoting tumor progression where neo-Darwinian mechanisms of clonal selection can be inferred to play a primary role.

Clinical features and genetic analysis of two fetuses with ring chromosome 21 mosaicism

To investigate the perinatal clinical phenotype and genetic characteristics of two fetuses with ring chromosome 21 mosaicisms. Two fetuses who were diagnosed at the Xiamen Maternal and Child Health Care Hospital in November 2021 were selected as the study subjects. Clinical data of the two fetuses were collected. Conventional G-banded karyotyping and chromosomal microarray analysis (CMA) were carried out for the fetuses and their parents. Prenatal ultrasonography of fetus 1 has revealed absence of nasal bone, ventricular septal defect, persistent left superior vena cava, and mild tricuspid regurgitation. Chromosomal karyotyping was 46,X?,dic r(21;21)(p12q22;q22p12)[41]/45,X?,-21[9]. CMA has revealed a 30.00 Mb quadruplication at 21q11.2q22.3 and a 3.00 Mb deletion at 21q22.3. For fetus 2, ultrasonography has revealed pointed echo of the nasal bone. The fetus was found to have a karyotype of 46,X?,r(21)(p12q22)[83]/45,X?,-21[14]/46,X?,dic r(21;21)(p12q22;q22p12)[3]. CMA has revealed a 5.10 Mb quadruplication at 21q22.12q22.3 and a 2.30 Mb deletion at 21q22.3. The perinatal phenotype of the two fetuses with ring chromosome 21 mosaicisms is related to the duplication of chromosomal segments near the breakpoints of the chromosomal deletions. The combined chromosomal karyotyping and CMA has enabled prenatal diagnosis and genetic counseling for these families.

Clonal reproduction of Moniliophthora roreri and the emergence of unique lineages with distinct genomes during range expansion.

The basidiomycete Moniliophthora roreri causes frosty pod rot of cacao (Theobroma cacao) in the western hemisphere. Moniliophthora roreri is considered asexual and haploid throughout its hemibiotrophic life cycle. To understand the processes driving genome modification, using long-read sequencing technology, we sequenced and assembled 5 high-quality M. roreri genomes out of a collection of 99 isolates collected throughout the pathogen's range. We obtained chromosome-scale assemblies composed of 11 scaffolds. We used short-read technology to sequence the genomes of 22 similarly chosen isolates. Alignments among the 5 reference assemblies revealed inversions, translocations, and duplications between and within scaffolds. Isolates at the front of the pathogens' expanding range tend to share lineage-specific structural variants, as confirmed by short-read sequencing. We identified, for the first time, 3 new mating type A locus alleles (5 in total) and 1 new potential mating type B locus allele (3 in total). Currently, only 2 mating type combinations, A1B1 and A2B2, are known to exist outside of Colombia. A systematic survey of the M. roreri transcriptome across 2 isolates identified an expanded candidate effector pool and provided evidence that effector candidate genes unique to the Moniliophthoras are preferentially expressed during the biotrophic phase of disease. Notably, M. roreri isolates in Costa Rica carry a chromosome segment duplication that has doubled the associated gene complement and includes secreted proteins and candidate effectors. Clonal reproduction of the haploid M. roreri genome has allowed lineages with unique genome structures and compositions to dominate as it expands its range, displaying a significant founder effect.

Does chromosome 16p12.1-p12.2 harbor a novel gene for essential tremor? (P5-11.012)

<h3>Objective:</h3> To describe a patient with de novo duplication of 16p12.1-p12.2 associated with severe action tremor and developmental delay, and genetic analysis of candidate genes within the duplicated chromosomal segment. <h3>Background:</h3> A family history of essential tremor (ET) can be found in 30–80% of all affected patients, suggesting a strong genetic contribution to its etiology. However, discovery of disease-causing genes has been largely elusive. Candidate genes can be identified using linkage analysis, whole exome or genome sequencing, and genetic association studies. Detection of genomic rearrangements with gene dosage changes in tremor patients provides another unique opportunity to identify additional candidate genes. <h3>Design/Methods:</h3> Case report and genetic analysis of the candidate chromosomal region. Chromosomal microarray analysis was performed in patient and both parents. We designed PCR primers for all coding exons of selected candidate genes. We included 75 unrelated probands from kindreds with familiar ET. Candidate genes were sequenced in all ET controls. <h3>Results:</h3> The proband is a 20-year-old female with significant developmental delay who developed progressive tremor at age of 15 years. Her tremor was a moderate to severe 4–5 Hz postural and action distal tremor, not present at rest, minimally responsive to propranolol. Additional examination revealed diffusely brisk reflexes with positive Hoffman and cross adductor sign, and upgoing toes. MRI brain did not show evidence of hypomyelination. She underwent chromosomal microarray analysis that identified duplications 12p13.33 and 16p12.2-p12.1. Chromosome 12p duplication was also detected in her father. Duplication of 12p was considered nonpathogenic and duplication 16p was <i>de novo</i>. The duplicated segment on chromosome 16p contained eight genes and six were considered possible candidate for tremor: <i>UQCRC2</i>, <i>CDR2</i>, <i>EEF2K</i>, <i>POLR3A</i>, <i>LOG23117</i>, and c16orf65. No putative deleterious mutations have been identified in ET controls. <h3>Conclusions:</h3> We report identification and genetic analysis of six novel candidate genes on chromosome 16p12.1-p12.2 that may be associated with ET. <b>Disclosure:</b> Dr. D’Aguiar Rosa has nothing to disclose. Dr. Yousaf has nothing to disclose. Dr. Hedera has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alexion. Dr. Hedera has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Abbvie. Dr. Hedera has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for University of Louisville.

Genome wide noninvasive prenatal testing detects microduplication of the distal end of chromosome 15 in a fetus: a case report

BackgroundNoninvasive prenatal testing (NIPT) is the most recent modality widely used in prenatal diagnostics. Commercially available NIPT has high sensitivity and specificity for the common fetal chromosomal aneuploidies. As future advancements in NIPT sequencing technology are becoming promising and more reliable, the ability to detect beyond aneuploidies and to expand detection of submicroscopic genomic alterations, as well as single-gene disorders might become possible.Case presentationHere we present a case of a 34-year-old pregnant woman, G2P1, who had NIPT screening which detected a terminal microduplication of 10.34 Mb on the long arm of chromosome 15 (15q26.1q26.3). Subsequent prenatal diagnostic testing including karyotype, microarray and fluorescence in situ hybridization (FISH) analyses were performed. Microarray testing confirmed and particularized a copy number gain of 10.66 Mb of the distal end of the long arm of chromosome 15. The G-banding cytogenetic studies yielded results consistent with unbalanced translocation between chromosome 15 and 18. To further characterize the abnormality involving the long arm of chromosome 18 and to map the genomic location of the duplicated 15q more precisely, FISH analysis using specific sub-telomeric probes was performed. FISH analysis confirmed that the extra duplicated segment of chromosome 15 is translocated onto the distal end of the long arm of chromosome 18 at band 18q23. Parental karyotype and FISH studies were performed to see if this unbalanced rearrangement was inherited from a healthy balanced translocation carrier versus being a de novo finding. Parental chromosomal analysis provided no evidence of a rearrangement between chromosome 15 and chromosome 18. The final fetal karyotype was reported as 46,XX,der(18)t(15;18)(q26.2;q23)dn.ConclusionsIn this case study, the microduplication of fetal chromosome 15q26.1q26.3 was accurately detected using NIPT. Our results suggest that further refinements in NIPT have the potential to evolve to a powerful and efficient screening method, which might be used to detect a broad range of chromosomal imbalances. Since microduplications and microdeletions are a potential reportable result with NIPT, this must be included in pre-test counseling. Prenatal diagnostic testing of such findings is strongly recommended.

Genome-Wide Analysis of the Protein Phosphatase 2C Genes in Tomato

The plant protein phosphatase 2C (PP2C) plays an irreplaceable role in phytohormone signaling, developmental processes, and manifold stresses. However, information about the PP2C gene family in tomato (Solanum lycopersicum) is relatively restricted. In this study, a genome-wide investigation of the SlPP2C gene family was performed. A total of 92 SlPP2C genes were identified, they were distributed on 11 chromosomes, and all the SlPP2C proteins have the type 2C phosphatase domains. Based on phylogenetic analysis of PP2C genes in Arabidopsis, rice, and tomato, SlPP2C genes were divided into eight groups, designated A–H, which is also supported by the analyses of gene structures and protein motifs. Gene duplication analysis revealed that the duplication of whole genome and chromosome segments was the main cause of SLPP2Cs expansion. A total of 26 cis-elements related to stress, hormones, and development were identified in the 3 kb upstream region of these SlPP2C genes. Expression profile analysis revealed that the SlPP2C genes display diverse expression patterns in various tomato tissues. Furthermore, we investigated the expression patterns of SlPP2C genes in response to Ralstonia solanacearum infection. RNA-seq and qRT-PCR data reveal that nine SlPP2Cs are correlated with R. solanacearum. The above evidence hinted that SlPP2C genes play multiple roles in tomato and may contribute to tomato resistance to bacterial wilt. This study obtained here will give an impetus to the understanding of the potential function of SlPP2Cs and lay a solid foundation for tomato breeding and transgenic resistance to plant pathogens.

Genetic analysis of a family with 9q34.3 microdeletion and microduplication caused by abnormal chromosome balance structure

To perform prenatal diagnosis, pedigree analysis, and genetic counseling of a pregnant woman who gave birth to a child with Kleefstra syndrome. Karyotype analysis, chromosomal microarray analysis (CMA), multiplex ligation-dependent probe amplification (MLPA) and fluorescence in situ hybridization (FISH) were used of peripheral blood and amniotic fluid to find causes. Recurrence risk assessment was performed later. The amniotic fluid sample showed a 9q34.3 microduplication of arr (hg19) 9q34.3 (140 168 806-141 020 389)× 3, which overlapped the 9q34.3 microdeletion region of proband. The pregnant woman was detected with a balanced translocation of ish, t(9;17)(9q34.3; qter) (9p+; 17p+,9q+, 17q+). No other abnormal results were found in the family. Offspring who share the same chromosome segment deletion or duplication are always from parent who carries balanced chromosomal structural aberration.

Chromosome 9p terminal deletion in nine Egyptian patients and narrowing of the critical region for trigonocephaly.

BackgroundThis study aimed to delineate the clinical phenotype of patients with 9p deletions, pinpoint the chromosomal breakpoints, and identify the critical region for trigonocephaly, which is a frequent finding in 9p terminal deletion.MethodsWe investigated a cohort of nine patients with chromosome 9p terminal deletions who all displayed developmental delay, intellectual disability, hypotonia, and dysmorphic features. Of them, eight had trigonocephaly, seven had brain anomalies, seven had autistic manifestations, seven had fair hair, and six had a congenital heart defect (CHD).ResultsKaryotyping revealed 9p terminal deletion in all patients, and patients 8 and 9 had additional duplication of other chromosomal segments. We used six bacterial artificial chromosome (BAC) clones that could identify the breakpoints at 17–20 Mb from the 9p terminus. Array CGH identified the precise extent of the deletion in six patients; the deleted regions ranged from 16 to 18.8 Mb in four patients, patient 8 had an 11.58 Mb deletion and patient 9 had a 2.3 Mb deletion.ConclusionThe gene deletion in the 9p24 region was insufficient to cause ambiguous genitalia because six of the nine patients had normal genitalia. We suggest that the critical region for trigonocephaly lies between 11,575 and 11,587 Mb from the chromosome 9p terminus. To the best of our knowledge, this is the minimal critical region reported for trigonocephaly in 9p deletion syndrome, and it warrants further delineation.

Genome-wide mining of wheat B-BOX zinc finger (BBX) gene family provides new insights into light stress responses

The B-BOX (BBX) proteins are an important class of zinc-finger transcription factors involved in the regulation of plant growth and development, and have been identified in many plant species. However, there is no systematic study of common wheat (Triticum aestivum L.) BBX genes. Through comprehensive bioinformatics analysis, we identified and characterised 96 BBX genes from wheat, and provided the genes with a unified nomenclature. We describe the chromosomal location, gene structure, conserved domains, phylogenetic relationships and promoter cis-elements of TaBBX family members. The expression patterns under different conditions, especially under different hormones and light–dark conditions, were studied in detail. According to the diversity of conserved domains, we divided TaBBX proteins into five subfamilies. Gene-duplication analysis showed that duplication of chromosome segments was the main reason for the expansion of the TaBBX gene family. Detecting the expression profiles of six TaBBX genes in different tissues by quantitative real-time PCR, we found that the six genes are regulated under light–dark treatment, and that some TaBBX genes (TaBBX2.11, TaBBX2.13, TaBBX2.15 and TaBBX3.10) are strongly induced by the plant hormones abscisic acid, indole-3-acetic acid and salicylic acid. Our analysis of wheat BBX genes at the genomic level will provide a solid foundation for further identifying the functions of specific genes in light stress responses.

CRISPR-PCDup: a novel approach for simultaneous segmental chromosomal duplication in Saccharomyces cerevisiae

In our previous study, a novel genome engineering technology, PCR-mediated chromosome duplication (PCDup), was developed in Saccharomyces cerevisiae that enabled the duplication of any desired chromosomal region, resulting in a segmental aneuploid. From one round of transformation, PCDup can duplicate a single chromosomal region efficiently. However, simultaneous duplication of multiple chromosomal regions is not possible using PCDup technology, which is a serious drawback. Sequential duplication is possible, but this approach requires significantly more time and effort. Because PCDup depends upon homologous recombination, we reasoned that it might be possible to simultaneously create duplications of multiple chromosomal regions if we could increase the frequency of these events. Double-strand breaks have been shown to increase the frequency of homologous recombination around the break point. Thus, we aimed to integrate the genome editing tool CRISPR/Cas9 system, which induces double-strand breaks, with our conventional PCDup. The new method, which we named CRISPR-PCDup increased the efficiency of a single duplication by up to 30 fold. CRISPR-PCDup enabled the simultaneous duplication of long chromosomal segments (160 kb and 200 kb regions). Moreover, we were also able to increase the length of the duplicated chromosome by up to at least 400 kb, whereas conventional PCDup can duplicate up to a maximum of 300 kb. Given the enhanced efficiency of chromosomal segmental duplication and the saving in both labor and time, we propose that CRISPR-PCDup will be an invaluable technology for generating novel yeast strains with desirable traits for specific industrial applications and for investigating genome function in segmental aneuploid.

Evolutionary dynamics and impacts of chromosome regions carrying R-gene clusters in rice

To elucidate R-gene evolution, we compared the genomic compositions and structures of chromosome regions carrying R-gene clusters among cultivated and wild rice species. Map-based sequencing and gene annotation of orthologous genomic regions (1.2 to 1.9 Mb) close to the terminal end of the long arm of rice chromosome 11 revealed R-gene clusters within six cultivated and ancestral wild rice accessions. NBS-LRR R-genes were much more abundant in Asian cultivated rice (O. sativa L.) than in its ancestors, indicating that homologs of functional genes involved in the same pathway likely increase in number because of tandem duplication of chromosomal segments and were selected during cultivation. Phylogenetic analysis using amino acid sequences indicated that homologs of paired Pikm1–Pikm2 (NBS-LRR) genes conferring rice-blast resistance were likely conserved among all cultivated and wild rice species we examined, and the homolog of Xa3/Xa26 (LRR-RLK) conferring bacterial blight resistance was lacking only in Kasalath.

The Neurospora crassa Standard Oak Ridge Background Exhibits Atypically Efficient Meiotic Silencing by Unpaired DNA.

Meiotic silencing by unpaired DNA (MSUD), an RNAi-mediated gene silencing process, is efficient in crosses made in the Neurospora crassa standard Oak Ridge (OR) genetic background. However, MSUD was decidedly less efficient when the OR-derived MSUD testers were crossed with many wild-isolated strains (W), suggesting that either sequence heterozygosity in tester x W crosses suppresses MSUD, or that OR represents the MSUD-conducive extreme in the range of genetic variation in MSUD efficiency. Our results support the latter model. MSUD was less efficient in near-isogenic crosses made in the novel N. crassa B/S1 genetic background, and in N. tetrasperma strain 85. Possibly, in B/S1 and 85, additional regulatory cues, absent from OR, calibrate the MSUD response. A locus in distal chromosome 1R appears to underlie the OR vs. B/S1 difference. Repeat-induced point mutation (RIP) destroys duplicated genes by G:C to A:T mutation of duplicated DNA sequences. Chromosome segment duplications (Dps) dominantly suppress RIP, possibly by titrating out the RIP machinery. In Dp x N crosses, the Dp–borne genes cannot pair properly, hence efficient MSUD, as in OR, silences them and renders the crosses barren. We speculate that the increased productivity engendered by inefficient MSUD enables small duplications to escape RIP.

Genomic Organization of TBK1 Copy Number Variations in Glaucoma Patients.

Approximately 1% of normal tension glaucoma (NTG) cases are caused by TANK-binding kinase 1 (TBK1) gene duplications and triplications. However, the precise borders and orientation of these TBK1 gene copy number variations (CNVs) on chromosome 12 are unknown. We determined the exact borders of TBK1 CNVs and the orientation of duplicated or triplicated DNA segments in 5 NTG patients with different TBK1 mutations using whole-genome sequencing. Tandemly duplicated chromosome segments spanning the TBK1 gene were detected in 4 NTG patients, each with unique borders. Four of 5 CNVs had borders located within interspersed repetitive DNA sequences (Alu and long interspersed nuclear element-L1 elements), suggesting that mismatched homologous recombinations likely generated these CNVs. A fifth NTG patient had a complex rearrangement including triplication of a chromosome segment spanning the TBK1 gene. No specific mutation hotspots for TBK1 CNVs were detected, however, interspersed repetitive sequences (ie, Alu elements) were identified at the borders of TBK1 CNVs, which suggest that mismatch of these elements during meiosis may be the mechanism that generated TBK1 gene dosage mutations.

Identification and characterization of large DNA deletions affecting oil quality traits in soybean seeds through transcriptome sequencing analysis.

Key messageIdentification and characterization of a 254-kb genomic deletion on a duplicated chromosome segment that resulted in a low level of palmitic acid in soybean seeds using transcriptome sequencing.A large number of soybean genotypes varying in seed oil composition and content have been identified. Understanding the molecular mechanisms underlying these variations is important for breeders to effectively utilize them as a genetic resource. Through design and application of a bioinformatics approach, we identified nine co-regulated gene clusters by comparing seed transcriptomes of nine soybean genotypes varying in oil composition and content. We demonstrated that four gene clusters in the genotypes M23, Jack and N0304-303-3 coincided with large-scale genome rearrangements. The co-regulated gene clusters in M23 and Jack mapped to a previously described 164-kb deletion and a copy number amplification of the Rhg1 locus, respectively. The coordinately down-regulated gene clusters in N0304-303-3 were caused by a 254-kb deletion containing 19 genes including a fatty acyl-ACP thioesterase B gene (FATB1a). This deletion was associated with reduced palmitic acid content in seeds and was the molecular cause of a previously reported nonfunctional FATB1a allele, fapnc. The M23 and N0304-304-3 deletions were located in duplicated genome segments retained from the Glycine-specific whole genome duplication that occurred 13 million years ago. The homoeologous genes in these duplicated regions shared a strong similarity in both their encoded protein sequences and transcript accumulation levels, suggesting that they may have conserved and important functions in seeds. The functional conservation of homoeologous genes may result in genetic redundancy and gene dosage effects for their associated seed traits, explaining why the large deletion did not cause lethal effects or completely eliminate palmitic acid in N0304-303-3.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-016-2725-z) contains supplementary material, which is available to authorized users.

The map-based genome sequence of Spirodela polyrhiza aligned with its chromosomes, a reference for karyotype evolution.

Duckweeds are aquatic monocotyledonous plants of potential economic interest with fast vegetative propagation, comprising 37 species with variable genome sizes (0.158-1.88Gbp). The genomic sequence of Spirodela polyrhiza, the smallest and the most ancient duckweed genome, needs to be aligned to its chromosomes as a reference and prerequisite to study the genome and karyotype evolution of other duckweed species. We selected physically mapped bacterial artificial chromosomes (BACs) containing Spirodela DNA inserts with little or no repetitive elements as probes for multicolor fluorescence insitu hybridization (mcFISH), using an optimized BAC pooling strategy, to validate its physical map and correlate it with its chromosome complement. By consecutive mcFISH analyses, we assigned the originally assembled 32 pseudomolecules (supercontigs) of the genomic sequences to the 20 chromosomes of S.polyrhiza. A Spirodela cytogenetic map containing 96 BAC markers with an average distance of 0.89Mbp was constructed. Using a cocktail of 41 BACs in three colors, all chromosome pairs could be individualized simultaneously. Seven ancestral blocks emerged from duplicated chromosome segments of 19 Spirodela chromosomes. The chromosomally integrated genome of S.polyrhiza and the established prerequisites for comparative chromosome painting enable future studies on the chromosome homoeology and karyotype evolution of duckweed species.

Populus endo-β-1,4-glucanases gene family: genomic organization, phylogenetic analysis, expression profiles and association mapping.

Extensive characterization of the poplar GH9 gene family provides new insights into GH9 function and evolution in woody species, and may drive novel progress for molecular breeding in trees. In higher plants, endo-β-1,4-glucanases (cellulases) belonging to the glycosyl hydrolase family 9 (GH9) have roles in cell wall synthesis, remodeling and degradation. To increase the understanding of the GH9 family in perennial woody species, we conducted an extensive characterization of the GH9 family in the model tree species, Populus. We characterized 25 putative GH9 members in Populus with three subclasses (A, B, and C), using structures and bioinformatic analysis. Phylogenetic analyses of 114 GH9s from plant (dicot, monocot, and conifer) and bacterial species (outgroup) demonstrated that plant GH9s are monophyletic with respect to bacteria GH9s. Three subclasses, A, B, and C, of plant GH9 are formed before the divergence of angiosperms and gymnosperms. Chromosomal localization and duplications of GH9s in the Populus genome showed that eight paralogous pairs remained in conserved positions on segmental duplicated blocks, suggesting duplication of chromosomal segments has contributed to the family expansion. By examining tissue-specific expression profiles for all 25 members, we found that GH9 members exhibited distinct but partially overlapping expression patterns, while certain members have higher transcript abundance in mature or developing xylem. Based on our understanding of intraspecific variation and linkage disequilibrium of two KORRIGANs (PtoKOR1 and PtoKOR2) in natural population of Populus tomentosa, two non-synonymous SNPs in PtoKOR1 associated with fiber width and holocellulose content were obtained. Characterizations of the poplar GH9 family provide new insights into GH9 function and evolution in woody species, and may drive novel progress for molecular breeding in trees.

In This Issue

see State-based surveillance for selected hemoglobinopathies Despite widespread newborn screening in the United States for sickle cell disease and thalassemia, there is no national system to monitor the health outcomes of individuals diagnosed with these disorders. To gain a better understanding of prevalence and treatment outcomes, the National Institutes of Health and the Centers for Disease Control and Prevention collaborated on a pilot surveillance system in six states, beginning in 2004. The Registry and Surveillance System for Hemoglobinopathies (RuSH) identified individuals using multiple data sources, including newborn screening records, emergency room records, and Medicaid claims. Researchers collected demographic data, clinical characteristics, and health care–utilization records. Although the program was designed to produce a standardized system, difficulties with access to records in some states made a standardized approach untenable. But it did become clear that creating a comprehensive picture required combining data from many sources because information for individuals found through one data source was not present in others. In addition, the various sources contained different types of information. The research team concluded that combining all these data yielded a more comprehensive picture of the number of individuals living with hemoglobinopathies, as well as how and where they receive health care. A follow-up project—the Public Health Research Epidemiology and Surveillance for Hemoglobinopathies (PHRESH), now being conducted in two of the RuSH states (California and Georgia)—is expected to validate and refine the data collected in RuSH. see Improved molecular diagnosis by the detection of exonic deletions with target gene capture and deep sequencing Copy-number variants (CNVs)—structural changes that result in deletion or duplication of chromosomal segments—are a significant contributor to inherited genetic disease. Currently, clinical testing for CNVs involves exon–targeted array comparative genomic hybridization or other methods involving stepwise probing of genomic regions of interest. But molecular diagnosis of human genetic diseases in clinical settings is rapidly moving toward massively parallel sequencing (MPS) technology. The ability to identify both single-nucleotide alterations and larger deletions and duplications using the same technology would greatly simplify and streamline the clinical workflow. Now, a team from Baylor College of Medicine, Houston, Texas, reports that it has taken a step in that direction using a method that analyzes copy number by comparing the number of sequencing reads of each exon of interest. Using previously collected clinical samples, the investigators correctly identified 11 samples with deletions. However, identification of duplications proved more problematic, with high false-positive rates. Similar to previous reports using sequence data, false-positive findings typically arose from areas of highly repetitive GC sequences. The authors concluded that, with further refinements to the methodology, point mutations and exonic deletions can be detected reliably using MPS.

Ethical and public policy challenges for pharmacogenomics

It is timely to consider the ethical and social questions raised by progress in pharmacogenomics, based on the current importance of pharmacogenomics for avoidance of predictable side effects of drugs, and for correct choice of medications in certain cancers. It has been proposed that the entire population be genotyped for drug-metabolizing enzyme polymorphisms, as a measure that would prevent many untoward and dangerous drug reactions. Pharmacologic treatment targeting based on genomics of disease can be expected to increase greatly in the coming years. Policy and ethical issues exist on consent for large-scale genomic pharmacogenomic data collection, public vs corporate ownership of genomic research results, testing efficacy and safety of drugs used for rare genomic indications, and accessibility of treatments based on costly research that is applicable to relatively few patients. In major psychiatric disorders and intellectual deficiency, rare and de novo deletion or duplication of chromosomal segments (copy number variation), in the aggregate, are common causes of increased risk. This implies that the policy problems of pharmacogenomics will be particularly important for the psychiatric disorders.