Single-cell genomics meets human genetics.

Single-cell genomic technologies are revealing the cellular composition, identities and states in tissues at unprecedented resolution. They have now scaled to the point that it is possible to query samples at the population level, across thousands of individuals. Combining single-cell information with genotype data at this scale provides opportunities to link genetic variation to the cellular processes underpinning key aspects of human biology and disease. This strategy has potential implications for disease diagnosis, risk prediction and development of therapeutic solutions. But, effectively integrating large-scale single-cell genomic data, genetic variation and additional phenotypic data will require advances in data generation and analysis methods. As single-cell genetics begins to emerge as a field in its own right, we review its current state and the challenges and opportunities ahead.

CellRegMap: a statistical framework for mapping context-specific regulatory variants using scRNA-seq.

Single-cell RNA sequencing (scRNA-seq) enables characterizing the cellular heterogeneity in human tissues. Recent technological advances have enabled the first population-scale scRNA-seq studies in hundreds of individuals, allowing to assay genetic effects with single-cell resolution. However, existing strategies to analyze these data remain based on principles established for the genetic analysis of bulk RNA-seq. In particular, current methods depend on a priori definitions of discrete cell types, and hence cannot assess allelic effects across subtle cell types and cell states. To address this, we propose the Cell Regulatory Map (CellRegMap), a statistical framework to test for and quantify genetic effects on gene expression in individual cells. CellRegMap provides a principled approach to identify and characterize genotype-context interactions of known eQTL variants using scRNA-seq data. This model-based approach resolves allelic effects across cellular contexts of different granularity, including genetic effects specific to cell subtypes and continuous cell transitions. We validate CellRegMap using simulated data and apply it to previously identified eQTL from two recent studies of differentiating iPSCs, where we uncover hundreds of eQTL displaying heterogeneity of genetic effects across cellular contexts. Finally, we identify fine-grained genetic regulation in neuronal subtypes for eQTL that are colocalized with human disease variants.

Management of Terminal Osseous Overgrowth of the Humerus With Simple Resection and Osteocartilaginous Grafts.

BACKGROUND: Osseous overgrowth is a common complication in children after humeral transcortical amputation. Capping tibial overgrowth with the proximal fibula has been shown to be the most effective treatment. However, best treatment practices are not clear for the humerus. We compared patients treated surgically for humeral osseous overgrowth with simple resection or autologous osteocartilaginous graft to determine if this treatment were as effective in the humerus as it has been in the tibia. METHODS: A retrospective review of humeral amputees from 1987 to 2011 at a pediatric hospital was performed. Patients with 2 years follow-up who underwent surgical treatment for established humeral overgrowth were included. Patients initially managed with simple resection were compared with those managed with autologous osteocartilaginous grafts. Descriptive statistics were calculated for demographic and outcome variables. T tests and χ tests were used to compare differences between groups. RESULTS: Eighteen humeri in 16 patients met inclusion criteria. Mean age at surgery was 8.3 (2.6 to 13.6) years and mean follow-up was 6.3 (1.5 to 10.4) years. Thirteen humeri underwent simple resection, with recurrent overgrowth in 9, and revision surgery in 8 at a mean 2.6 years. Five humeri were primarily managed with autologous osteocartilaginous grafts. Two developed non-overgrowth-related complications at 1 and 42 months. Including revision procedures after simple resection, 10 humeri were managed with autologous osteocartilaginous grafts. Thirty percent (3/10) required revision surgery; however, there were no cases of recurrent overgrowth. χ comparison showed lower rates of complications (P=0.004) and reoperation (P=0.012) with capping as compared with simple resection. CONCLUSIONS: Autologous osteocartilaginous capping of the humerus has a significantly lower rate of complications and reoperation compared with simple resection. However, the capping procedure has the potential for other complications related to difficulty with graft fixation. Surgeons should be aware that the outcomes are not as consistent as when the technique is applied to osseous overgrowth of the tibia and anticipate the possibilities of hardware prominence and difficulty with fixation. LEVEL OF EVIDENCE: Level 3-therapeutic-retrospective comparative.

A Practical Approach to Determining the Center of the Femoral Head in Subluxated and Dislocated Hips.

BACKGROUND: Mistaking the ossific nucleus as the surrogate for the center of the femoral head affects treatment decisions in hip dysplasia. Previous studies of ossific nucleus position within the femoral head have been qualitative, or, have not included both subluxated and dislocated hips. The purpose of this study was, first, to determine the most accurate radiographic landmark to define the center of the immature femoral head in hip dysplasia, and, second, to quantitatively analyze the position of the ossific nucleus relative to the center of the femoral head. METHODS: The center of the femoral head was determined from hip arthrograms for 19 consecutive patients with untreated hip dysplasia. Three radiographic proxies for the center were defined on each film: (1) the center of the proximal physis; (2) the center of the ossific nucleus; and (3) a modification of Mose's concentric circles. Each point was compared with the true center of the head on an arthrogram. RESULTS: Nineteen patients of an average age of 35.5 months (range, 9 to 76 mo) yielded 22 dysplastic hips. Modified Mose circle was the most accurate technique. In subluxated hips, the center of the femoral physis was equally accurate. The ossific nucleus was the poorest estimation of the center of the femoral head. All of the ossific nuclei were located cephalad and lateral to the center of the femoral head as determined on arthrogram. CONCLUSIONS: The modified Mose technique is the most accurate technique for determining the center of the femoral head. In subluxated hips, the center of the physis is a practical, equivalent, technique. The ossific nucleus is a poor proxy for the center of the head in hip dysplasia. CLINICAL RELEVANCE: A modification of Mose's technique is the most accurate assessment of the center of the femoral head in both subluxated and dislocated hips. The center of the physis is a practical, reliable, surrogate for the center of the head in subluxated hips without requiring an arthrogram.

Does pediatric body mass index affect surgical outcomes of lower-extremity external fixation?

BACKGROUND: Obese patients are highly prevalent in the pediatric orthopaedic surgeon's practice and obesity is an increasing issue in the United States. Increased body mass index (BMI) has been associated with increased complications in pediatric orthopaedic patients, but no study has looked specifically at external fixation. The purpose of this study was to determine whether obesity is a risk factor for increased complications in lower-extremity procedures requiring external fixation. METHODS: A retrospective chart review was conducted of pediatric patients who underwent external fixation as definitive operative treatment for any condition at a tertiary care hospital over a 15-year period. Patients were grouped into normal weight, overweight, and obese based on Centers for Disease Control definitions. All orthopaedic complications were recorded. RESULTS: A total of 208 patients with a mean age of 11.2 years were identified. Ninety-four children were obese at the 95th percentile BMI or higher, 22 were overweight and 93 were normal weight. External fixation was applied to the tibia in 82 cases, to the femur in 77 and to both in 49. Mean duration of fixation was 160 days (range, 31 to 570 d) and patients were followed for a mean of 3.9 years (range, 1.0 to 12.0 y). There was no statistically significant difference in the rate of complications between the 3 groups (P=0.61). In the obese group complications occurred in 68.1% versus 66.7% in the overweight group and 61.3% in normal weight. CONCLUSIONS: In the setting of external fixator use for lower-extremity pathology in pediatric patients, there is no association between an increase in complications and obesity as defined by BMI. Complication rates are high when external fixation is utilized for the lower extremity, however, patients and families should not be counseled that increased BMI will add to the burden of orthopaedic complications in this situation. LEVEL OF EVIDENCE: Level II-prognostic.

Evidence into practice: pediatric orthopaedic surgeon use of removable splints for common pediatric fractures.

OBJECTIVES: Removable splints when compared with circumferential casts in randomized trials have been shown to be a safe and cost-effective method of managing many common minor distal radius and fibular fractures. This study estimated the extent to which this evidence is being implemented in clinical practice, and determined the perceived barriers to the adoption of this evidence. METHODS: A cross-sectional survey of practicing orthopaedic surgeon members of the Pediatric Orthopedic Surgeons of North America (POSNA) was conducted, using a 22-item online questionnaire, and distributed using a modified Dillman technique. Survey questions were derived from and validated by literature review, expert opinion, and pilot-testing on the targeted sample before implementation. RESULTS: Of the 826 eligible participants, 558 (67.6%) responded to the survey. Of these, 505 (90.5%) had completed a fellowship in pediatric orthopaedics, 335 (60.0%) worked in a university-affiliated setting, and 377 (67.6%) had been in practice for <20 years. Only 158/543 [29.1%; 95% confidence interval (CI), 25.28, 32.92] reported using a removable splint to treat buckle fractures of the distal radius; 32 (5.9%; 95% CI, 3.9, 7.9) and 8 (1.5%; 95% CI, 0.5, 2.5) would use such splints for minimally displaced greenstick and transverse fractures of the distal radius, respectively. For distal fibular avulsion fractures, 122 (22.5%; 95% CI, 19.0, 26.0) would use a removable splint; 57 (10.5%; 95% CI, 7.9, 13.1) and 28 (5.6%; 95% CI, 3.7, 7.5) would do so for nondisplaced Salter-Harris I and II fractures of the distal fibula, respectively. The most commonly reported perceived barriers to application of a removable device were concerns about patient compliance, potential complications, and possible medicolegal implications. CONCLUSIONS: Only a relatively small proportion of practicing POSNA use such splints for minor distal radius and distal fibular fractures. These data support the need for implementation of knowledge translation strategies (eg, education) targeted at all the stakeholders to encourage pediatric orthopaedic surgeons to change practice in keeping with the best evidence for these common and stable injuries. LEVEL OF EVIDENCE: Level II.

Evidence into practice: emergency physician management of common pediatric fractures.

OBJECTIVES: Randomized trials have shown that removable immobilization devices are at least as good as circumferential casts for the management of common specific types of pediatric wrist and ankle fractures. Our main objective was to determine the proportion of emergency physicians who prescribe removable devices for distal radius buckle fractures and/or nondisplaced distal fibular Salter-Harris I fractures. We also examined follow-up referral patterns for these injuries. METHODS: This was an online survey of members of 2 national emergency physician associations in Canada: Pediatric Emergency Research Canada and the Canadian Association of Emergency Physicians. RESULTS: Of the 849 eligible participants, 447 responded to the survey, yielding an aggregate response rate of 52.7%. Organization-specific response rates were 169 (70.4%) of 240 for the Pediatric Emergency Research Canada and 278 (45.6%) of 609 for the Canadian Association of Emergency Physicians. Overall, 263 of 416 (63.2%; 95% confidence interval [CI], 58.6-67.8) of emergency physicians treat buckle fractures of the distal radius with a removable splint and refer 212 of 398 (53.3%; 95% CI, 48.4-58.2) of these injuries to the primary care physician for follow-up. For Salter-Harris I fractures of the distal fibula, emergency physicians treat 201 of 416 (48.3%; 95% CI, 43.5-53.1) with a removable ankle support and refer 94 of 398 (23.6%; 95% CI, 19.4-27.8) to the primary care physician for follow-up. CONCLUSIONS: At least 50% of the surveyed Canadian emergency physicians treat distal radius buckle fractures and/or Salter-Harris I fibular fractures with a removable immobilization device, and the primary care physician follow-up of these injuries occur with some regularity for both these injuries.

Palliative use of non-invasive ventilation in end-of-life patients with solid tumours: a randomised feasibility trial.

BACKGROUND: Despite best-possible medical management, many patients with end-stage cancer experience breathlessness, especially towards the end of their lives. We assessed the acceptability and effectiveness of non-invasive mechanical ventilation (NIV) versus oxygen therapy in decreasing dyspnoea and the amount of opiates needed. METHODS: In this randomised feasibility study, we recruited patients from seven centres in Italy, Spain, and Taiwan, who had solid tumours and acute respiratory failure and had a life expectancy of less than 6 months. We randomly allocated patients to receive either NIV (using the Pressure Support mode and scheduled on patients' request and mask comfort) or oxygen therapy (using a Venturi or a reservoir mask). We used a computer-generated sequence for randomisation, stratified on the basis of patients' hypercapnic status (PaCO2 >45 mm Hg or PaCO2 ≤45 mm Hg), and assigned treatment allocation using opaque, sealed envelopes. Patients in both groups were given sufficient subcutaneous morphine to reduce their dyspnoea score by at least one point on the Borg scale. Our primary endpoints were to assess the acceptability of NIV used solely as a palliative measure and to assess its effectiveness in reducing dyspnoea and the amount of opiates needed compared with oxygen therapy. Analysis was done by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00533143. FINDINGS: We recruited patients between Jan 15, 2008, and March 9, 2011. Of 234 patients eligible for recruitment, we randomly allocated 200 (85%) to treatment: 99 to NIV and 101 to oxygen. 11 (11%) patients in the NIV group discontinued treatment; no patients in the oxygen group discontinued treatment. Dyspnoea decreased more rapidly in the NIV group compared with the oxygen group (average change in Borg scale -0·58, 95% CI -0·92 to -0·23, p=0·0012), with most benefit seen after the first hour of treatment and in hypercapnic patients. The total dose of morphine during the first 48 h was lower in the NIV group than it was in the oxygen group (26·9 mg [37·3] for NIV vs 59·4 mg [SD 67·1] for oxygen; mean difference -32·4 mg, 95% CI -47·5 to -17·4). Adverse events leading to NIV discontinuation were mainly related to mask intolerance and anxiety. Morphine was suspended because of severe vomiting and nausea (one patient in each group), sudden respiratory arrest (one patient in the NIV group), and myocardial infarction (one patient in the oxygen group). INTERPRETATION: Our findings suggest that NIV is more effective compared with oxygen in reducing dyspnoea and decreasing the doses of morphine needed in patients with end-stage cancer. Further studies are needed to confirm our findings and to assess the effectiveness of NIV on other outcomes such as survival. The use of NIV is, however, restricted to centres with NIV equipment, our findings are not generalisable to all cancer or palliative care units. FUNDING: None.

Integrating population genetics, stem cell biology and cellular genomics to study complex human diseases.

Human pluripotent stem (hPS) cells can, in theory, be differentiated into any cell type, making them a powerful in vitro model for human biology. Recent technological advances have facilitated large-scale hPS cell studies that allow investigation of the genetic regulation of molecular phenotypes and their contribution to high-order phenotypes such as human disease. Integrating hPS cells with single-cell sequencing makes identifying context-dependent genetic effects during cell development or upon experimental manipulation possible. Here we discuss how the intersection of stem cell biology, population genetics and cellular genomics can help resolve the functional consequences of human genetic variation. We examine the critical challenges of integrating these fields and approaches to scaling them cost-effectively and practically. We highlight two areas of human biology that can particularly benefit from population-scale hPS cell studies, elucidating mechanisms underlying complex disease risk loci and evaluating relationships between common genetic variation and pharmacotherapeutic phenotypes.

Early palliative care program in idiopathic pulmonary fibrosis patients favors at-home and hospice deaths, reduces unplanned medical visits, and prolongs survival: A pilot study.

BACKGROUND: Idiopathic Pulmonary Fibrosis (IPF) is a lethal disease; most patients die in hospitals because palliative care (PC) is not wildly and early available. We aimed to determine the impact of an early PC program in IPF patients on place of death, emergency department (ED) admission, unplanned medical visits and survival before and after its implementation at our clinic. METHODS: IPF patients from our ILD clinic who died between January 1st, 2018 and December 31th, 2023 were included in the analysis. Primary outcomes were location of death, number of ED access and unplanned medical visits; secondary outcomes was survival from diagnosis. RESULTS: A total of 46 decedents between 2018 and 2023 were analysed: (median age 71,5 ± 5,5 years, 89 % male): 26 died before the implementation of the early PC program and 20 after. Through χ2 test, location of death resulted significantly different in the two groups, showing the capacity of early PC to favor at home or in hospice death (p = 0,02); similarly, the number of unplanned visits was significantly lower (p = 0,03). Finally, survival was significantly lower in patients not receiving the early PC program (p = 0,01). CONCLUSION: The availability of an early PC program since the diagnosis significantly reduced both the death rate in hospital settings, favoring dying in hospice or at home, and the number of unplanned medical visits. Furthermore, IPF patients receiving early PC showed a longer survival than those who did not.

Efficient and accurate mixed model association tool for single-cell eQTL analysis.

Understanding the genetic basis of gene expression can help us understand the molecular underpinnings of human traits and disease. Expression quantitative trait locus (eQTL) mapping can help in studying this relationship but have been shown to be very cell-type specific, motivating the use of single-cell RNA sequencing and single-cell eQTLs to obtain a more granular view of genetic regulation. Current methods for single-cell eQTL mapping either rely on the "pseudobulk" approach and traditional pipelines for bulk transcriptomics or do not scale well to large datasets. Here, we propose SAIGE-QTL, a robust and scalable tool that can directly map eQTLs using single-cell profiles without needing aggregation at the pseudobulk level. Additionally, SAIGE-QTL allows for testing the effects of less frequent/rare genetic variation through set-based tests, which is traditionally excluded from eQTL mapping studies. We evaluate the performance of SAIGE-QTL on both real and simulated data and demonstrate the improved power for eQTL mapping over existing pipelines.

Effects of 24/7 palliative care consultation availability on the use of emergency department and emergency medical services resources from non-oncological patients: a before-and-after observational cohort study.

OBJECTIVES: The non-oncological population is relatively under-represented among end-of-life (EOL) patients managed by palliative care (PC) services, and the effects of different PC delivery models are understudied in this population.This retrospective observational study on routinely collected data aimed at evaluating the effects of the extension from workday-only to 24/7 mixed hands-on and advisory home PC service on emergency department (ED) access and emergency medical services (EMS) interventions needed by non-oncological patients during their last 90 days of life, and their probability to die in hospital. METHODS: A before-and-after design was adopted comparing preimplementation and postimplementation periods (2018-2019 and 2021-22).We used a difference-in-differences approach to estimate changes in ED access and EMS intervention rates in the postintervention period through binomial negative regression. The oncological population, always exposed to 24/7 PC, was used as a control. A robust Poisson regression model was adopted to investigate the differences regarding hospital mortality. The analyses were adjusted for age, sex and disease grouping by the system involved. Results were reported as incidence rate ratios (IRRs) and ORs. RESULTS: A total of 2831 patients were enrolled in the final analysis.After the implementation of 24/7 home PC, both ED admissions (IRR=0.390, p<0.001) and EMS interventions (IRR=0.413, p<0.001) dropped, as well as the probability to die in hospital (OR=0.321, p<0.001). CONCLUSIONS: The adoption of a 24/7 mixed hands-on and advisory model of home PC could have relevant effects in terms of ED access and EMS use by non-oncological EOL patients under PC. TRIAL REGISRATION NUMBER: NCT05640076.

Gartland type I supracondylar humerus fractures in children: is splint immobilization enough?

OBJECTIVE: The primary objective of this study was to determine if Gartland type I supracondylar humerus (SCH) fractures undergo significant displacement resulting in a change in management when treated with a long-arm splint. Secondary objectives included measured changes at follow-up in displacement and/or angulation. METHODS: This was a retrospective review of children who presented with elbow injuries to a children's hospital. Patients were included if they were diagnosed with a Gartland type I SCH fracture, managed with a long-arm splint, and had at least 1 follow-up visit 2 to 3 weeks from the emergency department visit. The primary outcome was the proportion of cases that required the placement of a circumferential cast and/or an operative intervention. Secondary outcomes included the proportion of cases with significant changes in displacement on any view, Baumann or the lateral humerocapitellar angle, and/or category of position of anterior humeral line relative to capitellum. RESULTS: Of 804 elbow injuries that presented from 2003 to 2008, 53 patients met the inclusion criteria. The median age of the patients was 4.1 years (interquartile range, 3.4-6.1 years) years. Of the 53, there were no cases that required a change in management. One case had a change in the humerocapitellar angle, and another had a change of 1 category in position of the capitellum relative to the anterior humeral line. There were no other cases of significant changes in displacement or angulation. CONCLUSIONS: These data support that Gartland type I SCH fractures can be treated effectively with long-arm posterior splinting for the duration of therapy.

Computational principles and challenges in single-cell data integration.

The development of single-cell multimodal assays provides a powerful tool for investigating multiple dimensions of cellular heterogeneity, enabling new insights into development, tissue homeostasis and disease. A key challenge in the analysis of single-cell multimodal data is to devise appropriate strategies for tying together data across different modalities. The term 'data integration' has been used to describe this task, encompassing a broad collection of approaches ranging from batch correction of individual omics datasets to association of chromatin accessibility and genetic variation with transcription. Although existing integration strategies exploit similar mathematical ideas, they typically have distinct goals and rely on different principles and assumptions. Consequently, new definitions and concepts are needed to contextualize existing methods and to enable development of new methods.

Optimizing expression quantitative trait locus mapping workflows for single-cell studies.

BACKGROUND: Single-cell RNA sequencing (scRNA-seq) has enabled the unbiased, high-throughput quantification of gene expression specific to cell types and states. With the cost of scRNA-seq decreasing and techniques for sample multiplexing improving, population-scale scRNA-seq, and thus single-cell expression quantitative trait locus (sc-eQTL) mapping, is increasingly feasible. Mapping of sc-eQTL provides additional resolution to study the regulatory role of common genetic variants on gene expression across a plethora of cell types and states and promises to improve our understanding of genetic regulation across tissues in both health and disease. RESULTS: While previously established methods for bulk eQTL mapping can, in principle, be applied to sc-eQTL mapping, there are a number of open questions about how best to process scRNA-seq data and adapt bulk methods to optimize sc-eQTL mapping. Here, we evaluate the role of different normalization and aggregation strategies, covariate adjustment techniques, and multiple testing correction methods to establish best practice guidelines. We use both real and simulated datasets across single-cell technologies to systematically assess the impact of these different statistical approaches. CONCLUSION: We provide recommendations for future single-cell eQTL studies that can yield up to twice as many eQTL discoveries as default approaches ported from bulk studies.

Population-scale single-cell RNA-seq profiling across dopaminergic neuron differentiation.

Studying the function of common genetic variants in primary human tissues and during development is challenging. To address this, we use an efficient multiplexing strategy to differentiate 215 human induced pluripotent stem cell (iPSC) lines toward a midbrain neural fate, including dopaminergic neurons, and use single-cell RNA sequencing (scRNA-seq) to profile over 1 million cells across three differentiation time points. The proportion of neurons produced by each cell line is highly reproducible and is predictable by robust molecular markers expressed in pluripotent cells. Expression quantitative trait loci (eQTL) were characterized at different stages of neuronal development and in response to rotenone-induced oxidative stress. Of these, 1,284 eQTL colocalize with known neurological trait risk loci, and 46% are not found in the Genotype-Tissue Expression (GTEx) catalog. Our study illustrates how coupling scRNA-seq with long-term iPSC differentiation enables mechanistic studies of human trait-associated genetic variants in otherwise inaccessible cell states.

Single-cell meta-analysis of SARS-CoV-2 entry genes across tissues and demographics.

Angiotensin-converting enzyme 2 (ACE2) and accessory proteases (TMPRSS2 and CTSL) are needed for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cellular entry, and their expression may shed light on viral tropism and impact across the body. We assessed the cell-type-specific expression of ACE2, TMPRSS2 and CTSL across 107 single-cell RNA-sequencing studies from different tissues. ACE2, TMPRSS2 and CTSL are coexpressed in specific subsets of respiratory epithelial cells in the nasal passages, airways and alveoli, and in cells from other organs associated with coronavirus disease 2019 (COVID-19) transmission or pathology. We performed a meta-analysis of 31 lung single-cell RNA-sequencing studies with 1,320,896 cells from 377 nasal, airway and lung parenchyma samples from 228 individuals. This revealed cell-type-specific associations of age, sex and smoking with expression levels of ACE2, TMPRSS2 and CTSL. Expression of entry factors increased with age and in males, including in airway secretory cells and alveolar type 2 cells. Expression programs shared by ACE2+TMPRSS2+ cells in nasal, lung and gut tissues included genes that may mediate viral entry, key immune functions and epithelial-macrophage cross-talk, such as genes involved in the interleukin-6, interleukin-1, tumor necrosis factor and complement pathways. Cell-type-specific expression patterns may contribute to the pathogenesis of COVID-19, and our work highlights putative molecular pathways for therapeutic intervention.

Static and dynamic gait parameters before and after multilevel soft tissue surgery in ambulating children with cerebral palsy.

BACKGROUND: Recent studies have questioned the efficacy of releasing hip flexion contractures and the resulting ankle position after tendoachilles lengthening in ambulating children with cerebral palsy (CP). METHODS: Twenty-three ambulatory children with CP underwent 96 soft tissue-lengthening procedures without bony surgery. Preoperative and postoperative clinical and computerized gait data were reviewed. RESULTS: Static contractures improved reliably, with improvements in all areas measured, including hip flexion contracture (14 degree improvement), hip abduction (19 degree improvement), popliteal angle (26 degree improvement), and ankle dorsiflexion (11 degree improvement). The changes in computerized gait data were less uniform. The knees showed significant benefits, as evidenced by improved maximal knee extension in stance phase (37.3 degree preop and 19.9 degree postop) and at initial contact (51.6 degree preop and 34.8 degree postop). At the hip, a statistically significant improvement was only seen in maximum hip extension in stance phase (minimum hip flexion), and the magnitude of this change was only 4.6 degree (15.3 to 10.7 degree). There were no significant changes at the pelvis. At the ankle, the tendency was toward calcaneal gait after Achilles tendon lengthening, with excessive dorsiflexion seen both in stance (17.3 degree) and at toe off (-6.9 degree). Tempero-spatial parameters showed improved stride length, but no significant changes in gait velocity or cadence. DISCUSSION: The persistence of crouch postoperatively, though improved, likely limited the potential changes in hip kinematics. As this study excluded patients undergoing osseous surgery, it is possible that lever arm dysfunction may have contributed to the ongoing crouch. The results of this study suggest that static contractures and knee kinematics improve reliably after soft tissue surgery in children with CP, but that caution must be exercised when considering heel cord lengthening in these children. LEVEL OF EVIDENCE: Therapeutic level II. See Instructions to Authors for a complete description of levels of evidence.

Publisher Correction: Single-cell RNA-sequencing of differentiating iPS cells reveals dynamic genetic effects on gene expression.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Single-cell RNA-sequencing of differentiating iPS cells reveals dynamic genetic effects on gene expression.

Recent developments in stem cell biology have enabled the study of cell fate decisions in early human development that are impossible to study in vivo. However, understanding how development varies across individuals and, in particular, the influence of common genetic variants during this process has not been characterised. Here, we exploit human iPS cell lines from 125 donors, a pooled experimental design, and single-cell RNA-sequencing to study population variation of endoderm differentiation. We identify molecular markers that are predictive of differentiation efficiency of individual lines, and utilise heterogeneity in the genetic background across individuals to map hundreds of expression quantitative trait loci that influence expression dynamically during differentiation and across cellular contexts.