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Here the Human Pangenome Reference Consortium presents a first draft of the human pangenome reference. The pangenome contains 47 phased, diploid assemblies from a cohort of genetically diverse individuals1. These assemblies cover more than 99% of the expected sequence in each genome and are more than 99% accurate at the structural and base pair levels. Based on alignments of the assemblies, we generate a draft pangenome that captures known variants and haplotypes and reveals new alleles at structurally complex loci. We also add 119 million base pairs of euchromatic polymorphic sequences and 1,115 gene duplications relative to the existing reference GRCh38. Roughly 90 million of the additional base pairs are derived from structural variation. Using our draft pangenome to analyse short-read data reduced small variant discovery errors by 34% and increased the number of structural variants detected per haplotype by 104% compared with GRCh38-based workflows, which enabled the typing of the vast majority of structural variant alleles per sample.

To better understand the pattern of primate genome structural variation, we sequenced and assembled using multiple long-read sequencing technologies the genomes of eight nonhuman primate species, including New World monkeys (owl monkey and marmoset), Old World monkey (macaque), Asian apes (orangutan and gibbon), and African ape lineages (gorilla, bonobo, and chimpanzee). Compared to the human genome, we identified 1,338,997 lineage-specific fixed structural variants (SVs) disrupting 1,561 protein-coding genes and 136,932 regulatory elements, including the most complete set of human-specific fixed differences. Across 50 million years of primate evolution, we estimate that 819.47 Mbp or ~27% of the genome has been affected by SVs based on analysis of these primate lineages. We identify 1,607 structurally divergent regions (SDRs) wherein recurrent structural variation contributes to creating SV hotspots where genes are recurrently lost (CARDs,ABCD7,OLAH) and new lineage-specific genes are generated (e.g.,CKAP2,NEK5) and have become targets of rapid chromosomal diversification and positive selection (e.g.,RGPDs). High-fidelity long-read sequencing has made these dynamic regions of the genome accessible for sequence-level analyses within and between primate species for the first time.

Studies of de novo mutation (DNM) have typically excluded some of the most repetitive and complex regions of the genome because these regions cannot be unambiguously mapped with short-read sequencing data. To better understand the genome-wide pattern of DNM, we generated long-read sequence data from an autism parent-child quad with an affected female where no pathogenic variant had been discovered in short-read Illumina sequence data. We deeply sequenced all four individuals by using three sequencing platforms (Illumina, Oxford Nanopore, and Pacific Biosciences) and three complementary technologies (Strand-seq, optical mapping, and 10X Genomics). Using long-read sequencing, we initially discovered and validated 171 DNMs across two children—a 20% increase in the number of de novo single-nucleotide variants (SNVs) and indels when compared to short-read callsets. The number of DNMs further increased by 5% when considering a more complete human reference (T2T-CHM13) because of the recovery of events in regions absent from GRCh38 (e.g., three DNMs in heterochromatic satellites). In total, we validated 195 de novo germline mutations and 23 potential post-zygotic mosaic mutations across both children; the overall true substitution rate based on this integrated callset is at least 1.41 × 10(−8) substitutions per nucleotide per generation. We also identified six de novo insertions and deletions in tandem repeats, two of which represent structural variants. We demonstrate that long-read sequencing and assembly, especially when combined with a more complete reference genome, increases the number of DNMs by >25% compared to previous studies, providing a more complete catalog of DNM compared to short-read data alone.

The human Y chromosome has been notoriously difficult to sequence and assemble because of its complex repeat structure including long palindromes, tandem repeats, and segmental duplications. As a result, more than half of the Y chromosome is missing from the GRCh38 reference sequence and it remains the last human chromosome to be finished. Here, the Telomere-to-Telomere (T2T) consortium presents the complete 62,460,029 base pair sequence of a human Y chromosome from the HG002 genome (T2T-Y) that corrects multiple errors in GRCh38-Y and adds over 30 million base pairs of sequence to the reference, revealing the complete ampliconic structures ofTSPY, DAZ, andRBMY; 42 additional protein-coding genes, mostly from theTSPYgene family; and an alternating pattern of human satellite 1 and 3 blocks in the heterochromatic Yq12 region. We have combined T2T-Y with a prior assembly of the CHM13 genome and mapped available population variation, clinical variants, and functional genomics data to produce a complete and comprehensive reference sequence for all 24 human chromosomes.

The divergence of chimpanzee and bonobo provides one of the few examples of recent hominid speciation1,2. Here we describe a fully annotated, high-quality bonobo genome assembly, which was constructed without guidance from reference genomes by applying a multiplatform genomics approach. We generate a bonobo genome assembly in which more than 98% of genes are completely annotated and 99% of the gaps are closed, including the resolution of about half of the segmental duplications and almost all of the full-length mobile elements. We compare the bonobo genome to those of other great apes1,3–5 and identify more than 5,569 fixed structural variants that specifically distinguish the bonobo and chimpanzee lineages. We focus on genes that have been lost, changed in structure or expanded in the last few million years of bonobo evolution. We produce a high-resolution map of incomplete lineage sorting and estimate that around 5.1% of the human genome is genetically closer to chimpanzee or bonobo and that more than 36.5% of the genome shows incomplete lineage sorting if we consider a deeper phylogeny including gorilla and orangutan. We also show that 26% of the segments of incomplete lineage sorting between human and chimpanzee or human and bonobo are non-randomly distributed and that genes within these clustered segments show significant excess of amino acid replacement compared to the rest of the genome., A high-quality bonobo genome assembly provides insights into incomplete lineage sorting in hominids and its relevance to gene evolution and the genetic relationship among living hominids.

Despite their importance in disease and evolution, highly identical segmental duplications (SDs) are among the last regions of the human reference genome (GRCh38) to be fully sequenced. Using a complete telomere-to-telomere human genome (T2T-CHM13), we present a comprehensive view of human SD organization. SDs account for nearly one-third of the additional sequence, increasing the genome-wide estimate from 5.4 to 7.0% [218 million base pairs (Mbp)]. An analysis of 268 human genomes shows that 91% of the previously unresolved T2T-CHM13 SD sequence (68.3 Mbp) better represents human copy number variation. Comparing long-read assemblies from human ( n = 12) and nonhuman primate ( n = 5) genomes, we systematically reconstruct the evolution and structural haplotype diversity of biomedically relevant and duplicated genes. This analysis reveals patterns of structural heterozygosity and evolutionary differences in SD organization between humans and other primates.

TRP channel-associated factor 1/2 (TCAF1/TCAF2) proteins antagonistically regulate the cold-sensor protein TRPM8 in multiple human tissues. Understanding their significance has been complicated given the locus spans a gap-ridden region with complex segmental duplications in GRCh38. Using long-read sequencing, we sequence-resolve the locus, annotate full-length TCAF models in primate genomes, and show substantial human-specific TCAF copy number variation. We identify two human super haplogroups, H4 and H5, and establish that TCAF duplications originated ~1.7 million years ago but diversified only in Homo sapiens by recurrent structural mutations. Conversely, in all archaic-hominin samples the fixation for a specific H4 haplotype without duplication is likely due to positive selection. Here, our results of TCAF copy number expansion, selection signals in hominins, and differential TCAF2 expression between haplogroups and high TCAF2 and TRPM8 expression in liver and prostate in modern-day humans imply TCAF diversification among hominins potentially in response to cold or dietary adaptations., Duplications of gene segments can allow novel physiological adaptations to evolve. A detailed analysis of the TCAF gene family in primates and archaic humans suggest rapid duplication and diversification in this gene family is associated with cold or dietary adaptations.

Despite widespread clinical genetic testing, many individuals with suspected genetic conditions lack a precise diagnosis, limiting their opportunity to take advantage of state-of-the-art treatments. In some cases, testing reveals difficult-to-evaluate structural differences, candidate variants that do not fully explain the phenotype, single pathogenic variants in recessive disorders, or no variants in genes of interest. Thus, there is a need for better tools to identify a precise genetic diagnosis in individuals when conventional testing approaches have been exhausted. We performed targeted long-read sequencing (T-LRS) using adaptive sampling on the Oxford Nanopore platform on 40 individuals, 10 of whom lacked a complete molecular diagnosis. We computationally targeted up to 151 Mbp of sequence per individual and searched for pathogenic substitutions, structural variants, and methylation differences using a single data source. We detected all genomic aberrations-including single-nucleotide variants, copy number changes, repeat expansions, and methylation differences-identified by prior clinical testing. In 8/8 individuals with complex structural rearrangements, T-LRS enabled more precise resolution of the mutation, leading to changes in clinical management in one case. In ten individuals with suspected Mendelian conditions lacking a precise genetic diagnosis, T-LRS identified pathogenic or likely pathogenic variants in six and variants of uncertain significance in two others. T-LRS accurately identifies pathogenic structural variants, resolves complex rearrangements, and identifies Mendelian variants not detected by other technologies. T-LRS represents an efficient and cost-effective strategy to evaluate high-priority genes and regions or complex clinical testing results.

A high-quality rhesus macaque genome Genome technology has improved substantially since the first full organismal genomes were generated. Applying new technology, Warren et al. refined the genome of the rhesus macaque, a model nonhuman primate. Long-read technology and other recent advances in sequencing technology were applied to generate a genome with far fewer gaps and helped to refine the locations and numbers of repetitive elements. Furthermore, the authors performed resequencing among populations to identify the genetic variability of the rhesus macaque. Thus, a previously incomplete and inaccurate set of sequence information is now fully resolved, improving gene mapping for biomedical and comparative genetic studies. Science , this issue p. eabc6617

Long-read and strand-specific sequencing technologies together facilitate the de novo assembly of high-quality haplotype-resolved human genomes without parent–child trio data. We present 64 assembled haplotypes from 32 diverse human genomes. These highly contiguous haplotype assemblies (average contig N50: 26 Mbp) integrate all forms of genetic variation across even complex loci such as the major histocompatibility complex. We focus on 107,590 structural variants (SVs), of which 68% are inaccessible by short-read sequencing. We identify new SV hotspots (spanning megabases of gene-rich sequence), characterize 130 of the most active mobile element source elements, and find that 63% of all SVs arise by homology-mediated mechanisms—a twofold increase from previous studies. Our resource now enables reliable graph-based genotyping from short reads of up to 50,340 SVs, resulting in the identification of 1,525 expression quantitative trait loci (SV-eQTLs) as well as SV candidates for adaptive selection within the human population.

Resolving genomic structural variationMany human genomes have been reported using short-read technology, but it is difficult to resolve structural variants (SVs) using these data. These genomes thus lack comprehensive comparisons among individuals and populations. Ebertet al.used long-read structural variation calling across 64 human genomes representing diverse populations and developed new methods for variant discovery. This approach allowed the authors to increase the number of confirmed SVs and to describe the patterns of variation across populations. From this dataset, they identified quantitative trait loci affected by these SVs and determined how they may affect gene expression and potentially explain genome-wide association study hits. This information provides insights into patterns of normal human genetic variation and generates reference genomes that better represent the diversity of our species.Science, this issue p.eabf7117

BACKGROUNDDespite widespread availability of clinical genetic testing, many individuals with suspected genetic conditions do not have a precise diagnosis. This limits their opportunity to take advantage of state-of-the-art treatments. In such instances, testing sometimes reveals difficult-to-evaluate complex structural differences, candidate variants that do not fully explain the phenotype, single pathogenic variants in recessive disorders, or no variants in specific genes of interest. Thus, there is a need for better tools to identify a precise genetic diagnosis in individuals when conventional testing approaches have been exhausted.METHODSTargeted long-read sequencing (T-LRS) was performed on 33 individuals using Read Until on the Oxford Nanopore platform. This method allowed us to computationally target up to 100 Mbp of sequence per experiment, resulting in an average of 20x coverage of target regions, a 500% increase over background. We analyzed patient DNA for pathogenic substitutions, structural variants, and methylation differences using a single data source.RESULTSThe effectiveness of T-LRS was validated by detecting all genomic aberrations, including single-nucleotide variants, copy number changes, repeat expansions, and methylation differences, previously identified by prior clinical testing. In 6/7 individuals who had complex structural rearrangements, T-LRS enabled more precise resolution of the mutation, which led, in one case, to a change in clinical management. In nine individuals with suspected Mendelian conditions who lacked a precise genetic diagnosis, T-LRS identified pathogenic or likely pathogenic variants in five and variants of uncertain significance in two others.CONCLUSIONST-LRS can accurately predict pathogenic copy number variants and triplet repeat expansions, resolve complex rearrangements, and identify single-nucleotide variants not detected by other technologies, including short-read sequencing. T-LRS represents an efficient and cost-effective strategy to evaluate high-priority candidate genes and regions or to further evaluate complex clinical testing results. The application of T-LRS will likely increase the diagnostic rate of rare disorders.

TRP channel-associated factor 1/2 (TCAF1/TCAF2) proteins antagonistically regulate the cold-sensor protein TRPM8 in multiple human tissues. Understanding their significance has been complicated given the locus spans a gap-ridden region with complex segmental duplications in GRCh38. Using long-read sequencing, we sequence-resolve the locus, annotate full-length TCAF models in human and nonhuman primate genomes, and show substantial human-specific TCAF copy number variation. We identify two human super haplogroups, H4 and H5, and establish that TCAF duplications originated ~1.7 million years ago but diversified only in Homo sapiens by recurrent structural mutations that altered TCAF copy number and regulation. Conversely, in all archaic-hominin samples the fixation for a specific H4 haplotype without duplication is likely due to positive selection. The significant, positive effect of H4 on TCAF2 expression in modern-day humans with candidate associations for hypothyroidism, nerve compression, and diabetes suggests TCAF diversification among hominins potentially in response to cold or dietary adaptations.

Adaptive archaic hominin genes As they migrated out of Africa and into Europe and Asia, anatomically modern humans interbred with archaic hominins, such as Neanderthals and Denisovans. The result of this genetic introgression on the recipient populations has been of considerable interest, especially in cases of selection for specific archaic genetic variants. Hsieh et al. characterized adaptive structural variants and copy number variants that are likely targets of positive selection in Melanesians. Focusing on population-specific regions of the genome that carry duplicated genes and show an excess of amino acid replacements provides evidence for one of the mechanisms by which genetic novelty can arise and result in differentiation between human genomes. Science , this issue p. eaax2083

Investigation of the genetic lesions underlying classical Hodgkin lymphoma (CHL) has been challenging due to the rarity of Hodgkin and Reed-Sternberg (HRS) cells, the pathognomonic neoplastic cells of CHL. In an effort to catalog more comprehensively recurrent copy number alterations occurring during oncogenesis, we investigated somatic alterations involved in CHL using whole-genome sequencing-mediated copy number analysis of purified HRS cells. We performed low-coverage sequencing of small numbers of intact HRS cells and paired non-neoplastic B lymphocytes isolated by flow cytometric cell sorting from 19 primary cases, as well as two commonly used HRS-derived cell lines (KM-H2 and L1236). We found that HRS cells contain strikingly fewer copy number abnormalities than CHL cell lines. A subset of cases displayed nonintegral chromosomal copy number states, suggesting internal heterogeneity within the HRS cell population. Recurrent somatic copy number alterations involving known factors in CHL pathogenesis were identified (REL, the PD-1 pathway, and TNFAIP3). In eight cases (42%) we observed recurrent copy number loss of chr1:2,352,236-4,574,271, a region containing the candidate tumor suppressor TNFRSF14. Using flow cytometry, we demonstrated reduced TNFRSF14 expression in HRS cells from 5 of 22 additional cases (23%) and in two of three CHL cell lines. These studies suggest that TNFRSF14 dysregulation may contribute to the pathobiology of CHL in a subset of cases.

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous, autosomal-recessive disorder, characterized by oto-sino-pulmonary disease and situs abnormalities. PCD-causing mutations have been identified in 20 genes, but collectively they account for only ∼65% of all PCDs. To identify mutations in additional genes that cause PCD, we performed exome sequencing on three unrelated probands with ciliary outer and inner dynein arm (ODA+IDA) defects. Mutations in SPAG1 were identified in one family with three affected siblings. Further screening of SPAG1 in 98 unrelated affected individuals (62 with ODA+IDA defects, 35 with ODA defects, 1 without available ciliary ultrastructure) revealed biallelic loss-of-function mutations in 11 additional individuals (including one sib-pair). All 14 affected individuals with SPAG1 mutations had a characteristic PCD phenotype, including 8 with situs abnormalities. Additionally, all individuals with mutations who had defined ciliary ultrastructure had ODA+IDA defects. SPAG1 was present in human airway epithelial cell lysates but was not present in isolated axonemes, and immunofluorescence staining showed an absence of ODA and IDA proteins in cilia from an affected individual, thus indicating that SPAG1 probably plays a role in the cytoplasmic assembly and/or trafficking of the axonemal dynein arms. Zebrafish morpholino studies of spag1 produced cilia-related phenotypes previously reported for PCD-causing mutations in genes encoding cytoplasmic proteins. Together, these results demonstrate that mutations in SPAG1 cause PCD with ciliary ODA+IDA defects and that exome sequencing is useful to identify genetic causes of heterogeneous recessive disorders.

Haplotype-resolved whole-genome sequencing of the HeLa CCL-2 strain shows that HeLa is relatively stable in terms of point variation; integration of several data sets reveals strong, haplotype-specific activation of the proto-oncogene MYC by the human papilloma virus type 18 genome, and enables the relationship between gene dosage and expression to be examined. The first genomic characterization of the HeLa cancer cell line, the longest-serving and arguably most commonly used human cell line in biomedical research, reveals a genome that is surprisingly stable with respect to both point-mutation and copy-number alterations. The point-mutation rate may be no higher than the somatic mutation rate of normal tissue, and very few copy-number alterations distinguish the genomes of different HeLa strains that were split from one another in the mid-1950s. The authors examine the relationship between gene dosage and expression by integrating several data sets, including those from the ENCODE project, and find strong activation of the MYC proto-oncogene by the human papilloma virus type 18 (HPV-18) integration at chromosome 8q24.21. The HeLa cell line was established in 1951 from cervical cancer cells taken from a patient, Henrietta Lacks. This was the first successful attempt to immortalize human-derived cells in vitro1. The robust growth and unrestricted distribution of HeLa cells resulted in its broad adoption—both intentionally and through widespread cross-contamination2—and for the past 60 years it has served a role analogous to that of a model organism3. The cumulative impact of the HeLa cell line on research is demonstrated by its occurrence in more than 74,000 PubMed abstracts (approximately 0.3%). The genomic architecture of HeLa remains largely unexplored beyond its karyotype4, partly because like many cancers, its extensive aneuploidy renders such analyses challenging. We carried out haplotype-resolved whole-genome sequencing5 of the HeLa CCL-2 strain, examined point- and indel-mutation variations, mapped copy-number variations and loss of heterozygosity regions, and phased variants across full chromosome arms. We also investigated variation and copy-number profiles for HeLa S3 and eight additional strains. We find that HeLa is relatively stable in terms of point variation, with few new mutations accumulating after early passaging. Haplotype resolution facilitated reconstruction of an amplified, highly rearranged region of chromosome 8q24.21 at which integration of the human papilloma virus type 18 (HPV-18) genome occurred and that is likely to be the event that initiated tumorigenesis. We combined these maps with RNA-seq6 and ENCODE Project7 data sets to phase the HeLa epigenome. This revealed strong, haplotype-specific activation of the proto-oncogene MYC by the integrated HPV-18 genome approximately 500 kilobases upstream, and enabled global analyses of the relationship between gene dosage and expression. These data provide an extensively phased, high-quality reference genome for past and future experiments relying on HeLa, and demonstrate the value of haplotype resolution for characterizing cancer genomes and epigenomes.

Analysis of cell-free fetal DNA in maternal plasma holds promise for the development of noninvasive prenatal genetic diagnostics. Previous studies have been restricted to detection of fetal trisomies, to specific paternally inherited mutations, or to genotyping common polymorphisms using material obtained invasively, for example, through chorionic villus sampling. Here, we combine genome sequencing of two parents, genome-wide maternal haplotyping, and deep sequencing of maternal plasma DNA to noninvasively determine the genome sequence of a human fetus at 18.5 weeks of gestation. Inheritance was predicted at 2.8 × 10(6) parental heterozygous sites with 98.1% accuracy. Furthermore, 39 of 44 de novo point mutations in the fetal genome were detected, albeit with limited specificity. Subsampling these data and analyzing a second family trio by the same approach indicate that parental haplotype blocks of ~300 kilo-base pairs combined with shallow sequencing of maternal plasma DNA is sufficient to substantially determine the inherited complement of a fetal genome. However, ultradeep sequencing of maternal plasma DNA is necessary for the practical detection of fetal de novo mutations genome-wide. Although technical and analytical challenges remain, we anticipate that noninvasive analysis of inherited variation and de novo mutations in fetal genomes will facilitate prenatal diagnosis of both recessive and dominant Mendelian disorders.

We recently predicted the whole genome sequence of a human fetus using samples obtained non-invasively from the pregnant mother and the father. [Kitzman et al., 2012] This advance raises the possibility that it may soon be possible to perform genome-wide prenatal genetic testing without an invasive procedure early in pregnancy. Such a test would substantially broaden the scope of fetal genetic results that could be available prenatally. Non-invasive fetal genome sequencing (NIFGS) does not inherently raise new ethical issues, or those that cannot be addressed within the existing framework of medical bioethics. Indeed, many of the same issues have been raised by the introduction of other prenatal testing / screening technologies, now in wide use, and again more recently by the introduction of whole genome sequencing for clinical diagnosis. [Sayres et al., 2011, Schmitz et al., 2009, Ravitsky, 2009, Benn et al., 2009, Tabor et al., 2011, Berg et al., 2011] However, the ethical issues are, somewhat, magnified by the possibility of NIFGS and compounded by controversies surrounding elective pregnancy termination, rights of individuals with disabilities, and eugenics. Accordingly, the prospect of successful NIFGS, even on a research basis, is likely to generate considerable controversy and debate about the acceptability of developing such technologies, much less if and how they should be used. We view this response as very positive because it provides all stakeholders and the broader public in general with the opportunity to carefully consider and deliberate these issues in what we would hope is a thoughtful and balanced way. As NIFGS becomes technically tractable and increasingly cost-effective, and as an acceptable false positive/false negative profile is achieved, one population for which it might be of great benefit may be pregnant women who are currently offered invasive prenatal diagnostic testing. Such women are typically at risk for genetic conditions based on screening results or family history, and NIFGS would likely reduce if not eliminate adverse outcomes from invasive testing for most of these women. The expanded use of NIFGS would present several advantages and challenges. Broader use of NIFGS might lead to the greater detection of Mendelian disorders in families who would not otherwise have been offered prenatal testing, as well as families who might have refused invasive testing because of risks to the pregnancy and fetus. NIFGS could augment or even replace current approaches to neonatal screening as most such disorders are autosomal or X-linked recessive (e.g., hypothyroidism and congenital hearing loss are only sometimes Mendelian). Prenatal identification of disorders now found in neonatal screening would afford for earlier parental education, diminished false positives and the accompanying costs of retesting and parental anxiety and earlier therapeutic interventions. Earlier detection of such disorders would also foster improved prenatal care, pregnancy and delivery management and/or postnatal intervention. For example, 90% of genetic variants in SCNA1 that cause seizure disorders are de novo, and identification by NIFGS could allow for diagnosis before the onset of seizures and consideration of appropriate precautions and/or pharmacological treatment. [Marini et al., 20011] Similarly, 50% of mutations causing Multiple Endocrine Neoplasia 2B are spontaneous, and earlier identification of these mutations could prompt prophylactic thyroidectomy and improve outcomes. [Carlson et al., 1994] The availability of NIFGS could increase the utilization of prenatal testing, and in turn increase rates of elective termination, both for disorders for which testing is currently available and for the wide arrange of disorders and traits for which testing would be newly available. [Tischler et al., 2011] On the other hand, NIFGS might also make pregnancy termination safer, less costly, and less traumatic as it could be performed early in gestation. Broad use of NIFGS might result in increased societal pressure for pregnant women to undergo screening and terminate any fetus suspected to have a Mendelian condition. This could reverse important and continuing social progress towards civil rights and social support for people and families with disabilities. In addition, this societal pressure might threaten parental autonomy over reproductive decision-making. Broader use of NIFGS might also create or magnify social stigmas or inequities. NIFGS would likely remain expensive and may not be reimbursable by insurance in the short-term. This might exaggerate disparities between people who can easily afford access and those who cannot. If access is limited to those who can afford it, it is possible that a disproportionate number of lower income families could suffer from the higher rates of morbidity and mortality of invasive testing. In the extreme scenario, children with Mendelian conditions would be disproportionately born to lower income families that could not afford NIFGS. Such a disparity would likely further stigmatize many of these conditions and exaggerate existing disparities in access to healthcare and benefits for these populations. Another key issue raised by NIFGS is that it represents a substantially more comprehensive test for Mendelian disorders with a known cause, and will identify variants that are beyond the scope of conventional prenatal screening and diagnosis. Specifically, variants will be identified that indicate increased risk for developing adult onset conditions. This is not unique to NIFGS: in fact this is an ongoing challenge in pediatric clinical genetic testing. [Wilfond et al., 2009] Such information may be irrelevant or inappropriate to return for the benefit of the fetus/future child, but may have direct implications for the health of the parent, and therefore provide indirect benefit to any current or future children. However, if NIFGS is more broadly implemented, the scope of the results identified and the number of individuals affected may increase substantially. This will further overwhelm the existing infrastructure for providing genetic counseling. As with other applications of whole-genome sequencing, NIFGS will identify variants of ambiguous clinical utility in genes known to be associated with both pediatric and adult complex disease. For example, Kitzman et al. found a de novo novel missense variant in ACMSD, a gene in which common variants have been associated with Parkinson disease by genome-wide association. [Klitzman et al., 2012, International Parkinson Disease Genomics Consortium et al., 2011] This variant causes substitution of a highly conserved amino acid residue, but in the absence of compelling evidence of its role in Parkinson disease or other conditions, its detection is of limited clinical value. While this is no different than the challenge of interpreting WGS information in general, pregnancy might be a particularly vulnerable time in which to receive this information and parents might feel compelled to give more credence to the information than it warrants. There are several other important issues that require consideration. Will the non-invasive nature of this test, combined with the enhanced detection of Mendelian disorders, lead to a substantial increase in the number of women who consider prenatal diagnosis? How will the medical community meet the challenge of providing genetic counseling to address the complex nature of the information that may be identified? These concerns raise the possibility that some women may not be able to provide adequate informed consent, or may proceed with actions such as terminations without complete understanding of the test results or the prognosis for various rare Mendelian disorders. If NIFGS allows the creation of a record of a child’s whole genome prior to its birth, what should happen to that data? Should it be stored as part of the child’s medical record, with the possibility for future updating, analysis and mining for medically relevant information? Or should it be destroyed? Who should make this decision and have control over the data? As with many new technologies, NIFGS will be accompanied by many ethical and social challenges. We think that it is imperative that these questions and issues be discussed and addressed by a diverse group of stakeholders, as well as through collection of empirical data on stakeholder perspectives and concerns. Much can be learned from the history of the implementation of other prenatal testing approaches, such as amniocentesis and CVS, as well as the ongoing debates about pediatric genetic testing and return of results from whole genome sequencing. [Rapp, 2000]

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous, autosomal-recessive disorder, characterized by oto-sino-pulmonary disease and situs abnormalities. PCD-causing mutations have been identified in 14 genes, but they collectively account for only ∼60% of all PCD. To identify mutations that cause PCD, we performed exome sequencing on six unrelated probands with ciliary outer dynein arm (ODA) defects. Mutations in CCDC114, an ortholog of the Chlamydomonas reinhardtii motility gene DCC2, were identified in a family with two affected siblings. Sanger sequencing of 67 additional individuals with PCD with ODA defects from 58 families revealed CCDC114 mutations in 4 individuals in 3 families. All 6 individuals with CCDC114 mutations had characteristic oto-sino-pulmonary disease, but none had situs abnormalities. In the remaining 5 individuals with PCD who underwent exome sequencing, we identified mutations in two genes (DNAI2, DNAH5) known to cause PCD, including an Ashkenazi Jewish founder mutation in DNAI2. These results revealed that mutations in CCDC114 are a cause of ciliary dysmotility and PCD and further demonstrate the utility of exome sequencing to identify genetic causes in heterogeneous recessive disorders.

Background Preimplantation genetic diagnosis (PGD) enables profiling of embryos for genetic disorders prior to implantation. The majority of PGD testing is restricted in the scope of variants assayed or by the availability of extended family members. While recent advances in single cell sequencing show promise, they remain limited by bias in DNA amplification and the rapid turnaround time (