| 1. |
- Gemmell, Neil J., et al.
(author)
-
The tuatara genome reveals ancient features of amniote evolution
- 2020
-
In: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 584:7821, s. 403-409
-
Journal article (peer-reviewed)abstract
- The tuatara (Sphenodon punctatus)—the only living member of the reptilian order Rhynchocephalia (Sphenodontia), once widespread across Gondwana1,2—is an iconic species that is endemic to New Zealand2,3. A key link to the now-extinct stem reptiles (from which dinosaurs, modern reptiles, birds and mammals evolved), the tuatara provides key insights into the ancestral amniotes2,4. Here we analyse the genome of the tuatara, which—at approximately 5 Gb—is among the largest of the vertebrate genomes yet assembled. Our analyses of this genome, along with comparisons with other vertebrate genomes, reinforce the uniqueness of the tuatara. Phylogenetic analyses indicate that the tuatara lineage diverged from that of snakes and lizards around 250 million years ago. This lineage also shows moderate rates of molecular evolution, with instances of punctuated evolution. Our genome sequence analysis identifies expansions of proteins, non-protein-coding RNA families and repeat elements, the latter of which show an amalgam of reptilian and mammalian features. The sequencing of the tuatara genome provides a valuable resource for deep comparative analyses of tetrapods, as well as for tuatara biology and conservation. Our study also provides important insights into both the technical challenges and the cultural obligations that are associated with genome sequencing.
|
|
| 2. |
- Karawita, Anjana C., et al.
(author)
-
The swan genome and transcriptome, it is not all black and white
- 2023
-
In: Genome Biology. - : BioMed Central (BMC). - 1465-6906 .- 1474-760X. ; 24:1
-
Journal article (peer-reviewed)abstract
- BackgroundThe Australian black swan (Cygnus atratus) is an iconic species with contrasting plumage to that of the closely related northern hemisphere white swans. The relative geographic isolation of the black swan may have resulted in a limited immune repertoire and increased susceptibility to infectious diseases, notably infectious diseases from which Australia has been largely shielded. Unlike mallard ducks and the mute swan (Cygnus olor), the black swan is extremely sensitive to highly pathogenic avian influenza. Understanding this susceptibility has been impaired by the absence of any available swan genome and transcriptome information.ResultsHere, we generate the first chromosome-length black and mute swan genomes annotated with transcriptome data, all using long-read based pipelines generated for vertebrate species. We use these genomes and transcriptomes to show that unlike other wild waterfowl, black swans lack an expanded immune gene repertoire, lack a key viral pattern-recognition receptor in endothelial cells and mount a poorly controlled inflammatory response to highly pathogenic avian influenza. We also implicate genetic differences in SLC45A2 gene in the iconic plumage of the black swan.ConclusionTogether, these data suggest that the immune system of the black swan is such that should any avian viral infection become established in its native habitat, the black swan would be in a significant peril.
|
|
| 3. |
- Aken, Bronwen L., et al.
(author)
-
The Ensembl gene annotation system
- 2016
-
In: Database. - : Oxford University Press (OUP). - 1758-0463.
-
Journal article (peer-reviewed)abstract
- The Ensembl gene annotation system has been used to annotate over 70 different vertebrate species across a wide range of genome projects. Furthermore, it generates the automatic alignment-based annotation for the human and mouse GENCODE gene sets. The system is based on the alignment of biological sequences, including cDNAs, proteins and RNA-seq reads, to the target genome in order to construct candidate transcript models. Careful assessment and filtering of these candidate transcripts ultimately leads to the final gene set, which is made available on the Ensembl website. Here, we describe the annotation process in detail.
|
|
| 4. |
- Dussex, Nicolas, et al.
(author)
-
Population genomics of the critically endangered kākāpō
- 2021
-
In: Cell Genomics. - : Elsevier BV. - 2666-979X. ; 1:1
-
Journal article (peer-reviewed)abstract
- Summary The kākāpō is a flightless parrot endemic to New Zealand. Once common in the archipelago, only 201 individuals remain today, most of them descending from an isolated island population. We report the first genome-wide analyses of the species, including a high-quality genome assembly for kākāpō, one of the first chromosome-level reference genomes sequenced by the Vertebrate Genomes Project (VGP). We also sequenced and analyzed 35 modern genomes from the sole surviving island population and 14 genomes from the extinct mainland population. While theory suggests that such a small population is likely to have accumulated deleterious mutations through genetic drift, our analyses on the impact of the long-term small population size in kākāpō indicate that present-day island kākāpō have a reduced number of harmful mutations compared to mainland individuals. We hypothesize that this reduced mutational load is due to the island population having been subjected to a combination of genetic drift and purging of deleterious mutations, through increased inbreeding and purifying selection, since its isolation from the mainland ∼10,000 years ago. Our results provide evidence that small populations can survive even when isolated for hundreds of generations. This work provides key insights into kākāpō breeding and recovery and more generally into the application of genetic tools in conservation efforts for endangered species.
|
|
| 5. |
- Uebbing, Severin, et al.
(author)
-
Divergence in gene expression within and between two closely related flycatcher species
- 2016
-
In: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 25:9, s. 2015-2028
-
Journal article (peer-reviewed)abstract
- Relatively little is known about the character of gene expression evolution as species diverge. It is for instance unclear if gene expression generally evolves in a clock-like manner (by stabilizing selection or neutral evolution) or if there are frequent episodes of directional selection. To gain insights into the evolutionary divergence of gene expression, we sequenced and compared the transcriptomes of multiple organs from population samples of collared (Ficedula albicollis) and pied flycatchers (F. hypoleuca), two species which diverged less than one million years ago. Ordination analysis separated samples by organ rather than by species. Organs differed in their degrees of expression variance within species and expression divergence between species. Variance was negatively correlated with expression breadth and protein interactivity, suggesting that pleiotropic constraints reduce gene expression variance within species. Variance was correlated with between-species divergence, consistent with a pattern expected from stabilizing selection and neutral evolution. Using an expression PST approach, we identified genes differentially expressed between species and found 16 genes uniquely expressed in one of the species. For one of these, DPP7, uniquely expressed in collared flycatcher, the absence of expression in pied flycatcher could be associated with a ≈ 20 kb deletion including 11 out of 13 exons. This study of a young vertebrate speciation model system expands our knowledge of how gene expression evolves as natural populations become reproductively isolated.
|
|
| 6. |
- Dar, Pe'er, et al.
(author)
-
Cell-free DNA screening for prenatal detection of 22q11.2 deletion syndrome.
- 2022
-
In: American journal of obstetrics and gynecology. - : Elsevier BV. - 1097-6868 .- 0002-9378. ; 227:1
-
Journal article (peer-reviewed)abstract
- Prenatal screening has historically focused primarily on detection of fetal aneuploidies. Cell-free DNA (cfDNA) now enables noninvasive screening for subchromosomal copy number variants, including 22q11.2 deletion syndrome (22q11.2DS or DiGeorge syndrome), which is the most common microdeletion and a leading cause of congenital heart defects and neurodevelopmental delay. Although smaller studies have demonstrated the feasibility of screening for 22q11.2DS, large cohort studies with postnatal confirmatory testing to assess test performance have not been reported.To assess the performance of SNP-based cfDNA prenatal screening for detection of 22q11.2DS.Patients who had SNP-based cfDNA prenatal screening for 22q11.2DS were prospectively enrolled at 21 centers in 6 countries. Prenatal or newborn DNA samples were requested in all cases for genetic confirmation with chromosomal microarray. The primary outcome was sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of cfDNA for detection of all deletions, including the classical deletion and nested deletions that are ≥500kb, in the 22q11.2 low copy repeat A-D region. Secondary outcomes included the prevalence of 22q11.2DS and performance of an updated cfDNA algorithm that was evaluated blinded to pregnancy outcome.Of 20,887 women enrolled, genetic outcome was available in 18,289 (87.6%). Twelve 22q11.2DS cases were confirmed in the cohort, including five (41.7%) nested deletions, yielding a prevalence of 1:1524. In the total cohort, cfDNA reported 17,976 (98.3%) as low risk for 22q11.2DS and 38 (0.2%) as high-risk; 275 (1.5%) were non-reportable. Overall, 9 of 12 cases of 22q11.2 were detected, yielding a sensitivity of 75.0% (95% CI: 42.8, 94.5); specificity of 99.84% (95% CI: 99.77, 99.89); PPV of 23.7% (95% CI: 11.44, 40.24) and NPV of 99.98% (95% CI: 99.95, 100). None of the cases with a non-reportable result was diagnosed with 22q11.2DS. The updated algorithm detected 10/12 cases (83.3%; 95% CI: 51.6-97.9) with a lower false positive rate (0.05% vs. 0.16%, p<0.001) and a PPV of 52.6% (10/19; 95% CI 28.9-75.6).Noninvasive cfDNA prenatal screening for 22q11.2DS can detect most affected cases, including smaller nested deletions, with a low false positive rate.
|
|
| 7. |
- Dar, Pe'er, et al.
(author)
-
Cell-free DNA screening for trisomies 21, 18 and 13 in pregnancies at low and high risk for aneuploidy with genetic confirmation
- 2022
-
In: American journal of obstetrics and gynecology. - : Elsevier BV. - 1097-6868 .- 0002-9378. ; 227:2
-
Journal article (peer-reviewed)abstract
- Cell-free DNA (cfDNA) non-invasive prenatal screening for trisomy (T) 21, 18, and 13 has been rapidly adopted into clinical practice. However, prior studies are limited by lack of follow up genetic testing to confirm outcomes and accurately assess test performance, particularly in women at low-risk for aneuploidy.To compare the performance of cfDNA screening for T21, T18 and T13 between women at low and high-risk for aneuploidy in a large, prospective cohort with genetic confirmation of results.A multicenter prospective observational study at 21 centers in 6 countries. Women who had SNP-based cfDNA screening for T21, T18 and T13 were enrolled. Genetic confirmation was obtained from prenatal or newborn DNA samples. Test performance and test failure (no-call) rates were assessed for the cohort and women with low and high prior risk for aneuploidy were compared. An updated cfDNA algorithm, blinded to pregnancy outcome, was also assessed.20,194 were enrolled at median gestational age of 12.6 weeks (IQR:11.6, 13.9). Genetic outcomes were confirmed in 17,851 (88.4%): 13,043 (73.1%) low-risk and 4,808 (26.9%) high-risk for aneuploidy. Overall, 133 trisomies were diagnosed (100 T21; 18 T18; 15 T13). cfDNA screen positive rate was lower in low- vs. high-risk (0.27% vs. 2.2%, p<0.0001). Sensitivity and specificity were similar between groups. The positive predictive value (PPV) for the low and high-risk groups was 85.7% vs. 97.5%, p=0.058 for T21; 50.0% vs. 81.3%, p=0.283 for T18; and 62.5% vs. 83.3, p=0.58 for T13, respectively. Overall, 602 (3.4%) patients had no-call result after the first draw and 287 (1.61%) after including cases with a second draw. Trisomy rate was higher in the 287 with no-call results than patients with a result on a first draw (2.8% vs. 0.7%, p=0.001). The updated algorithm showed similar sensitivity and specificity to the study algorhitm with a lower no-call rate.In women at low-risk for aneuploidy, SNP-based cfDNA has high sensitivity and specificity, PPV of 85.7% for T21 and 74.3% for the three common trisomies. Patients who receive a no-call result are at increased risk of aneuploidy and require additional investigation.
|
|
| 8. |
- Martin, Kimberly, et al.
(author)
-
Impact of high-risk prenatal screening results for 22q11.2 deletion syndrome on obstetric and neonatal management: Secondary analysis from the SMART study
- 2023
-
In: Prenatal Diagnosis. - 0197-3851 .- 1097-0223. ; 43:13, s. 1574-1580
-
Journal article (peer-reviewed)abstract
- Objective: One goal of prenatal genetic screening is to optimize perinatal care and improve infant outcomes. We sought to determine whether high-risk cfDNA screening for 22q11.2 deletion syndrome (22q11.2DS) affected prenatal or neonatal management. Methods: This was a secondary analysis from the SMART study. Patients with high-risk cfDNA results for 22q11.2DS were compared with the low-risk cohort for pregnancy characteristics and obstetrical management. To assess differences in neonatal care, we compared high-risk neonates without prenatal genetic confirmation with a 1:1 matched low-risk cohort. Results: Of 18,020 eligible participants enrolled between 2015 and 2019, 38 (0.21%) were high-risk and 17,982 (99.79%) were low-risk for 22q11.2DS by cfDNA screening. High-risk participants had more prenatal diagnostic testing (55.3%; 21/38 vs. 2.0%; 352/17,982, p<0.001) and fetal echocardiography (76.9%; 10/13 vs. 19.6%; 10/51, p<0.001). High-risk newborns without prenatal diagnostic testing had higher rates of neonatal genetic testing (46.2%; 6/13 vs. 0%; 0/51, P<0.001), echocardiography (30.8%; 4/13 vs. 4.0%; 2/50, p=0.013), evaluation of calcium levels (46.2%; 6/13 vs. 4.1%; 2/49, P<0.001) and lymphocyte count (53.8%; 7/13 vs. 15.7%; 8/51, p=0.008). Conclusions: High-risk screening results for 22q11.2DS were associated with higher rates of prenatal and neonatal diagnostic genetic testing and other 22q11.2DS-specific evaluations. However, these interventions were not universally performed, and >50% of high-risk infants were discharged without genetic testing, representing possible missed opportunities to improve outcomes for affected individuals.
|
|
| 9. |
- Martin, Kimberly, et al.
(author)
-
Performance of prenatal cfDNA screening for sex chromosomes.
- 2023
-
In: Genetics in medicine : official journal of the American College of Medical Genetics. - 1530-0366. ; 25:8
-
Journal article (peer-reviewed)abstract
- To assess the performance of cell-free DNA (cfDNA) screening to detect sex chromosome aneuploidies (SCA) in an unselected obstetrical population with genetic confirmation.This was a planned secondary analysis of the multicenter, prospective SMART study. Patients receiving cfDNA results for autosomal aneuploidies and who had confirmatory genetic results for the relevant sex chromosomal aneuploidies were included. Screening performance for SCAs, including monosomy X (MX) and the sex chromosome trisomies (SCTs; 47,XXX; 47,XXY; 47,XYY) was determined. Fetal sex concordance between cfDNA and genetic screening was also evaluated in euploid pregnancies.17,538 cases met inclusion criteria. Performance of cfDNA for MX, SCTs and fetal sex was determined in 17,297, 10,333 and 14,486 pregnancies, respectively. Sensitivity, specificity, and PPV of cfDNA were 83.3%, 99.9%, and 22.7% for MX, and 70.4%, 99.9%, and 82.6% for the combined SCTs. The accuracy of fetal sex prediction by cfDNA was 100%.Screening performance of cfDNA for SCAs is comparable to that reported in other studies. The PPV for the SCTs was similar to the autosomal trisomies, while the PPV for MX was substantially lower. No discordance in fetal sex was observed between cfDNA and postnatal genetic screening in euploid pregnancies. These data will assist interpretation and counseling for cfDNA results for sex chromosomes.
|
|
| 10. |
- Norton, Mary E, et al.
(author)
-
Obstetrical, perinatal and genetic outcomes associated with non-reportable prenatal cell free DNA screening results.
- 2023
-
In: American journal of obstetrics and gynecology. - : Elsevier BV. - 0002-9378 .- 1097-6868. ; 229:3
-
Journal article (peer-reviewed)abstract
- The clinical implications of non-reportable cfDNA screening results are uncertain, but this may reflect poor placental implantation in some cases and be associated with adverse obstetrical and perinatal outcomes.To assess the outcomes of pregnancies with non-reportable cell-free DNA (cfDNA) screening in a cohort of patients with complete genetic and obstetric outcomes.This was a prespecified secondary analysis of a multicenter prospective observational study of prenatal cfDNA screening for fetal aneuploidy and 22q11.2 deletion syndrome. Participants who underwent cfDNA screening from April 2015 through January 2019 were offered participation. Obstetric outcomes and neonatal genetic testing results were collected from 21 primary care and referral centers in the US, Europe, and Australia. The primary outcome was risk for adverse obstetrical and perinatal outcomes (aneuploidy, preterm birth (PTB) at <28, <34, and <37 weeks' gestation, preeclampsia, small for gestational age (SGA) or birthweight <10th percentile for gestational week, and a composite outcome that included PTB<37 weeks, preeclampsia, SGA, and stillbirth>20 weeks') after non-reportable cfDNA screening due to low fetal fraction or other causes. Multivariable analyses were performed, adjusting for variables known to be associated with obstetrical and perinatal outcomes, non-reportable results, or fetal fraction.In total, 25,199 pregnant individuals were screened, and 20,194 were enrolled. Genetic confirmation was missing in 1165 (5.8%), 1085 (5.4%) were lost to follow-up, and 93 (0.5%) withdrew; the final study cohort included 17,851 (88.4%) participants who had cfDNA, fetal or newborn genetic confirmatory testing, and obstetrical and perinatal outcomes collected. Results were non-reportable in 602 (3.4%). A sample was redrawn and testing again attempted in 427; in 112 (26.2%) results were again non-reportable. Non-reportable results were associated with higher BMI, chronic hypertension, later gestational age, lower fetal fraction, and Black race. Trisomy 13, 18, or 21 was confirmed in 1.6% with non-reportable tests vs. 0.7% with results (p=.013). PTB <28, 34, and 37 weeks, preeclampsia, and the composite outcome were higher after non-reportable results, and further increased with a second non-reportable test, while SGA was not increased. After adjustment for confounders, the aOR for aneuploidy was 2.2 (95% CI 1.1, 4.4) and 2.6 (95% CI 0.6, 10.8) and for the composite outcome was 1.5 (95% CI 1.2, 1.8) and 2.1 (95% CI 1.4, 3.2) after a first and second non-reportable test. In all, 94.9% of patients with non-reportable tests had a livebirth as compared to 98.8% with those with test results obtained (aOR for livebirth: 0.20 [95% CI 0.13-0.30]).Patients with non-reportable cfDNA results are at increased risk for a number of adverse outcomes, including aneuploidy as well as preeclampsia and preterm birth. They should be offered diagnostic genetic testing and clinicians should be aware of the increased risk of pregnancy complications.
|
|
