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541 result(s) for "Chow, William"
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Genomics of cold adaptations in the Antarctic notothenioid fish radiation
Numerous novel adaptations characterise the radiation of notothenioids, the dominant fish group in the freezing seas of the Southern Ocean. To improve understanding of the evolution of this iconic fish group, here we generate and analyse new genome assemblies for 24 species covering all major subgroups of the radiation, including five long-read assemblies. We present a new estimate for the onset of the radiation at 10.7 million years ago, based on a time-calibrated phylogeny derived from genome-wide sequence data. We identify a two-fold variation in genome size, driven by expansion of multiple transposable element families, and use the long-read data to reconstruct two evolutionarily important, highly repetitive gene family loci. First, we present the most complete reconstruction to date of the antifreeze glycoprotein gene family, whose emergence enabled survival in sub-zero temperatures, showing the expansion of the antifreeze gene locus from the ancestral to the derived state. Second, we trace the loss of haemoglobin genes in icefishes, the only vertebrates lacking functional haemoglobins, through complete reconstruction of the two haemoglobin gene clusters across notothenioid families. Both the haemoglobin and antifreeze genomic loci are characterised by multiple transposon expansions that may have driven the evolutionary history of these genes. The notothenioid radiation is a remarkable group of fish adapted to life in the icy waters of the Southern Ocean. This study investigates the evolutionary history of this group and the basis of their adaption to cold environments through genomic analysis of 24 new genome assemblies.
A New Chicken Genome Assembly Provides Insight into Avian Genome Structure
The importance of the Gallus gallus (chicken) as a model organism and agricultural animal merits a continuation of sequence assembly improvement efforts. We present a new version of the chicken genome assembly (Gallus_gallus-5.0; GCA_000002315.3), built from combined long single molecule sequencing technology, finished BACs, and improved physical maps. In overall assembled bases, we see a gain of 183 Mb, including 16.4 Mb in placed chromosomes with a corresponding gain in the percentage of intact repeat elements characterized. Of the 1.21 Gb genome, we include three previously missing autosomes, GGA30, 31, and 33, and improve sequence contig length 10-fold over the previous Gallus_gallus-4.0. Despite the significant base representation improvements made, 138 Mb of sequence is not yet located to chromosomes. When annotated for gene content, Gallus_gallus-5.0 shows an increase of 4679 annotated genes (2768 noncoding and 1911 protein-coding) over those in Gallus_gallus-4.0. We also revisited the question of what genes are missing in the avian lineage, as assessed by the highest quality avian genome assembly to date, and found that a large fraction of the original set of missing genes are still absent in sequenced bird species. Finally, our new data support a detailed map of MHC-B, encompassing two segments: one with a highly stable gene copy number and another in which the gene copy number is highly variable. The chicken model has been a critical resource for many other fields of study, and this new reference assembly will substantially further these efforts.
Advances in the Repurposing and Blood–Brain Barrier Penetrance of Drugs in Pediatric Brain Tumors
Central nervous system (CNS) tumors are the leading cause of cancer-related mortality in children, with prognosis remaining dismal for some of these malignancies. Though the past two decades have seen advancements in surgery, radiation, and targeted therapy, major unresolved hurdles continue to undermine the therapeutic efficacy. These include challenges in suboptimal drug delivery through the blood–brain barrier (BBB), marked intra-tumoral molecular heterogeneity, and the elusive tumor microenvironment. Drug repurposing or re-tasking FDA-approved drugs with evidence of penetration into the CNS, using newer methods of intracranial drug delivery facilitating optimal drug exposure, has been an area of intense research. This could be a valuable tool, as most of these agents have already gone through the lengthy process of drug development and the evaluation of safety risks and the optimal pharmacokinetic profile. They can now be used and tested in clinics with an accelerated and different approach. Conclusions: The next-generation therapeutic strategy should prioritize repurposing oncologic and non-oncologic drugs that have been used for other indication, and have demonstrated robust preclinical activity against pediatric brain tumors. In combination with novel drug delivery techniques, these drugs could hold significant therapeutic promise in pediatric neurooncology.
A genomic basis of vocal rhythm in birds
Vocal rhythm plays a fundamental role in sexual selection and species recognition in birds, but little is known of its genetic basis due to the confounding effect of vocal learning in model systems. Uncovering its genetic basis could facilitate identifying genes potentially important in speciation. Here we investigate the genomic underpinnings of rhythm in vocal non-learning Pogoniulus tinkerbirds using 135 individual whole genomes distributed across a southern African hybrid zone. We find rhythm speed is associated with two genes that are also known to affect human speech, Neurexin-1 and Coenzyme Q8A. Models leveraging ancestry reveal these candidate loci also impact rhythmic stability, a trait linked with motor performance which is an indicator of quality. Character displacement in rhythmic stability suggests possible reinforcement against hybridization, supported by evidence of asymmetric assortative mating in the species producing faster, more stable rhythms. Because rhythm is omnipresent in animal communication, candidate genes identified here may shape vocal rhythm across birds and other vertebrates.
Showcasing diversity, equity, and inclusion in neurological surgery: a comparative analysis of neurological surgery residency program websites in the United States
Residency websites can often be crucial for influencing neurosurgery applicants’ first impressions of programs. This study explores the representation of diversity on neurological surgery residency program websites and evaluates the impact of Diversity, Equity, and Inclusion (DEI) statements. The websites of 117 neurological surgery residency programs were evaluated for the presence of 12 diversity and inclusion elements. Univariate analysis was conducted to determine significant differences in DEI scores between neurological surgery residency program websites. Program analysis revealed a mean diversity score of 7.9 out of a maximum score of 12, equating to the presence of 66% of possible DEI elements in our scoring system. Top-50 ranked programs (Doximity) exhibited a significantly higher mean diversity score (8.6 +/- 2.7) compared to those outside the top-50 (7.2 +/- 2.9) ( p  = 0.009). Accessibility of DEI content varied, with most program websites either having a direct link to a separate DEI webpage (41%) or lacking any DEI elements (42%). A secondary analysis found that the presence of a DEI statement on a program’s webpage was not significantly associated with Doximity ranking, NIH funding, geographic region, or hospital funding. However, programs with a DEI statement were significantly more likely to have various additional DEI elements ( p  < 0.001). While many neurological surgery residencies include elements of DEI on their websites, this is not currently a consistent practice across all programs. We advocate that these initiatives should be prominently featured on program websites to aid applicants in making informed decisions about their training journey.
The effects of macroprudential policy on Hong Kong’s housing market: a multivariate ordered probit-augmented vector autoregressive approach
This study evaluates the effects of macroprudential policy on Hong Kong’s housing market using a multivariate ordered probit-augmented vector autoregressive model (MOP-VAR). The proposed MOP-VAR extends the conventional dummy policy variable approach by allowing explicit measurement of time-varying policy intensities that underlie policy rules, and thus facilitates analyses of bilateral relationship between house prices and multiple policy instruments when endogeneity exits among the instruments’ intensities and prices. An impulse response analysis suggests that the dampening effect of macroprudential tightening is stronger and more instantaneous on transactions than on prices. The eventual outcome as indicated by conditional forecasts is dominated by a strong and prolonged own price response to house price shocks and other external developments that undermine the policy’s effectiveness. Moreover, over the long haul, a combination of a stamp duty and stress test tends to be more effective than restricting the loan-to-value ratio in triggering a trend reversal in house prices, despite the government’s preference for the latter. The out-of-sample probabilistic forecasts of policy changes are mostly consistent with the observable outcomes.
Under the midnight sun: A case of actinic keratoses in an avid Inuit fisherman
We report the case of a 74-year-old Inuit man from Kangiqsualujjuaq, Quebec, with a 10-year history of persistent facial skin changes, reported as “dry skin.” Examination revealed violaceous scaly papules on sun-exposed areas that had sandpaper texture on palpation. The patient, with no significant medical history, spends extensive time outdoors in a subarctic environment. A diagnosis of actinic keratoses was made. This case highlights the need to recognize atypical presentations of actinic keratoses in patients with darker skin phototypes and high environmental ultraviolet exposure. Topical 5% fluorouracil was initiated.
Eczematous molluscum contagiosum masquerading as herpes simplex in an 8-year-old: A case report
Molluscum contagiosum is a common pediatric viral skin infection characterized by small, flesh-colored, umbilicated papules on the skin. Molluscum contagiosum lesions are typically benign and self-resolve, but they may trigger a surrounding eczematous dermatitis that may mimic other infections or an atopic dermatitis flare. We report a case of an 8-year-old boy with eczematous molluscum contagiosum whose eruption masqueraded as herpes simplex virus infection. The patient presented with a several week history of pruritic rash with bleeding and crusting, but careful examination revealed conventional umbilicated papules consistent with molluscum contagiosum. The dermatitis was managed with conservative skin care, low-potency corticosteroids, and topical antibiotics (for cracked skin/open sores). This case highlights the importance of recognizing molluscum dermatitis and distinguishing it from herpes simplex virus, atopic dermatitis flare, or bacterial infection to avoid unnecessary investigations or treatments.
A haplotype-resolved genome assembly of the Nile rat facilitates exploration of the genetic basis of diabetes
Background The Nile rat ( Avicanthis niloticus ) is an important animal model because of its robust diurnal rhythm, a cone-rich retina, and a propensity to develop diet-induced diabetes without chemical or genetic modifications. A closer similarity to humans in these aspects, compared to the widely used Mus musculus and Rattus norvegicus models, holds the promise of better translation of research findings to the clinic. Results We report a 2.5 Gb, chromosome-level reference genome assembly with fully resolved parental haplotypes, generated with the Vertebrate Genomes Project (VGP). The assembly is highly contiguous, with contig N50 of 11.1 Mb, scaffold N50 of 83 Mb, and 95.2% of the sequence assigned to chromosomes. We used a novel workflow to identify 3613 segmental duplications and quantify duplicated genes. Comparative analyses revealed unique genomic features of the Nile rat, including some that affect genes associated with type 2 diabetes and metabolic dysfunctions. We discuss 14 genes that are heterozygous in the Nile rat or highly diverged from the house mouse. Conclusions Our findings reflect the exceptional level of genomic resolution present in this assembly, which will greatly expand the potential of the Nile rat as a model organism.
Birth, expansion, and death of VCY-containing palindromes on the human Y chromosome
Background Large palindromes (inverted repeats) make up substantial proportions of mammalian sex chromosomes, often contain genes, and have high rates of structural variation arising via ectopic recombination. As a result, they underlie many genomic disorders. Maintenance of the palindromic structure by gene conversion between the arms has been documented, but over longer time periods, palindromes are remarkably labile. Mechanisms of origin and loss of palindromes have, however, received little attention. Results Here, we use fiber-FISH, 10x Genomics Linked-Read sequencing, and breakpoint PCR sequencing to characterize the structural variation of the P8 palindrome on the human Y chromosome, which contains two copies of the VCY ( Variable Charge Y ) gene. We find a deletion of almost an entire arm of the palindrome, leading to death of the palindrome, a size increase by recruitment of adjacent sequence, and other complex changes including the formation of an entire new palindrome nearby. Together, these changes are found in ~ 1% of men, and we can assign likely molecular mechanisms to these mutational events. As a result, healthy men can have 1–4 copies of VCY . Conclusions Gross changes, especially duplications, in palindrome structure can be relatively frequent and facilitate the evolution of sex chromosomes in humans, and potentially also in other mammalian species.