EMQN best practice guidelines for genetic testing in hereditary breast and ovarian cancer.

Hereditary Breast and Ovarian Cancer (HBOC) is a genetic condition associated with increased risk of cancers. The past decade has brought about significant changes to hereditary breast and ovarian cancer (HBOC) diagnostic testing with new treatments, testing methods and strategies, and evolving information on genetic associations. These best practice guidelines have been produced to assist clinical laboratories in effectively addressing the complexities of HBOC testing, while taking into account advancements since the last guidelines were published in 2007. These guidelines summarise cancer risk data from recent studies for the most commonly tested high and moderate risk HBOC genes for laboratories to refer to as a guide. Furthermore, recommendations are provided for somatic and germline testing services with regards to clinical referral, laboratory analyses, variant interpretation, and reporting. The guidelines present recommendations where 'must' is assigned to advocate that the recommendation is essential; and 'should' is assigned to advocate that the recommendation is highly advised but may not be universally applicable. Recommendations are presented in the form of shaded italicised statements throughout the document, and in the form of a table in supplementary materials (Table S4). Finally, for the purposes of encouraging standardisation and aiding implementation of recommendations, example report wording covering the essential points to be included is provided for the most common HBOC referral and reporting scenarios. These guidelines are aimed primarily at genomic scientists working in diagnostic testing laboratories.

Recommendations for laboratory workflow that better support centralised amalgamation of genomic variant data: findings from CanVIG-UK national molecular laboratory survey.

BACKGROUND: National and international amalgamation of genomic data offers opportunity for research and audit, including analyses enabling improved classification of variants of uncertain significance. Review of individual-level data from National Health Service (NHS) testing of cancer susceptibility genes (2002-2023) submitted to the National Disease Registration Service revealed heterogeneity across participating laboratories regarding (1) the structure, quality and completeness of submitted data, and (2) the ease with which that data could be assembled locally for submission. METHODS: In May 2023, we undertook a closed online survey of 51 clinical scientists who provided consensus responses representing all 17 of 17 NHS molecular genetic laboratories in England and Wales which undertake NHS diagnostic analyses of cancer susceptibility genes. The survey included 18 questions relating to 'next-generation sequencing workflow' (11), 'variant classification' (3) and 'phenotypical context' (4). RESULTS: Widely differing processes were reported for transfer of variant data into their local LIMS (Laboratory Information Management System), for the formatting in which the variants are stored in the LIMS and which classes of variants are retained in the local LIMS. Differing local provisions and workflow for variant classifications were also reported, including the resources provided and the mechanisms by which classifications are stored. CONCLUSION: The survey responses illustrate heterogeneous laboratory workflow for preparation of genomic variant data from local LIMS for centralised submission. Workflow is often labour-intensive and inefficient, involving multiple manual steps which introduce opportunities for error. These survey findings and adoption of the concomitant recommendations may support improvement in laboratory dataflows, better facilitating submission of data for central amalgamation.

Secondary (additional) findings from the 100,000 Genomes Project: Disease manifestation, health care outcomes, and costs of disclosure.

PURPOSE: The UK 100,000 Genomes Project offered participants screening for additional findings (AFs) in genes associated with familial hypercholesterolemia (FH) or hereditary cancer syndromes including breast/ovarian cancer (HBOC), Lynch, familial adenomatous polyposis, MYH-associated polyposis, multiple endocrine neoplasia (MEN), and von Hippel-Lindau. Here, we report disclosure processes, manifestation of AF-related disease, outcomes, and costs. METHODS: An observational study in an area representing one-fifth of England. RESULTS: Data were collected from 89 adult AF recipients. At disclosure, among 57 recipients of a cancer-predisposition-associated AF and 32 recipients of an FH-associated AF, 35% and 88%, respectively, had personal and/or family history evidence of AF-related disease. During post-disclosure investigations, 4 cancer-AF recipients had evidence of disease, including 1 medullary thyroid cancer. Six women with an HBOC AF, 3 women with a Lynch syndrome AF, and 2 individuals with a MEN AF elected for risk-reducing surgery. New hyperlipidemia diagnoses were made in 6 FH-AF recipients and treatment (re-)initiated for 7 with prior hyperlipidemia. Generating and disclosing AFs in this region cost £1.4m; £8680 per clinically significant AF. CONCLUSION: Generation and disclosure of AFs identifies individuals with and without personal or familial evidence of disease and prompts appropriate clinical interventions. Results can inform policy toward secondary findings.

Impact of Residual Lesion Severity on Neurodevelopmental Outcomes Following Congenital Heart Surgery in Infancy and Childhood.

Children with congenital heart disease are at increased risk of neurodevelopmental delay throughout their lifespan. This risk is exacerbated following congenital heart surgery (CHS) in infancy. However, there are few modifiable risk factors for postoperative neurodevelopmental delay. In this study, we assessed the Residual Lesion Score (RLS), a quality assessment metric that evaluates residual lesion severity following CHS, as a predictor of neurodevelopmental delay. This was a single-center, retrospective review of patients who underwent CHS from 01/2011 to 03/2021 and post-discharge neurodevelopmental evaluation from 12 to 42 months of age using the Bayley Scales of Infant Development, 3rd Edition (BSID-III). RLS was assigned per published criteria: RLS 1, no residua; RLS 2, minor residua; and RLS 3, major residua or pre-discharge reintervention. Associations between RLS and BSID-III scores, as well as trends in neurodevelopmental outcomes over time, were evaluated. Of 517 patients with median age at neurodevelopmental testing of 20.0 (IQR 18.0-22.7) months, 304 (58.8%), 146 (28.2%), and 67 (13.0%) were RLS 1, 2, and 3, respectively. RLS 3 patients had significantly lower scaled scores in the cognitive, receptive, and expressive communication, and fine and gross motor domains, compared with RLS 1 patients. Multivariable models accounted for 21.5%-31.5% of the variation in the scaled scores, with RLS explaining 1.4-7.3% of the variation. In a subgroup analysis, RLS 3 patients demonstrated relatively fewer gains in cognitive, expressive communication, and gross motor scores over time (all p < 0.05). In conclusion, RLS 3 patients are at increased risk for neurodevelopmental delay, warranting closer follow-up and greater developmental support for cognitive, language, and motor skills soon after surgery.

Developmental Care for Hospitalized Infants With Complex Congenital Heart Disease: A Science Advisory From the American Heart Association.

Developmental disorders, disabilities, and delays are a common outcome for individuals with complex congenital heart disease, yet targeting early factors influencing these conditions after birth and during the neonatal hospitalization for cardiac surgery remains a critical need. The purpose of this science advisory is to (1) describe the burden of developmental disorders, disabilities, and delays for infants with complex congenital heart disease, (2) define the potential health and neurodevelopmental benefits of developmental care for infants with complex congenital heart disease, and (3) identify critical gaps in research aimed at evaluating developmental care interventions to improve neurodevelopmental outcomes in complex congenital heart disease. This call to action targets research scientists, clinicians, policymakers, government agencies, advocacy groups, and health care organization leadership to support funding and hospital-based infrastructure for developmental care in the complex congenital heart disease population. Prioritization of research on and implementation of developmental care interventions in this population should be a major focus in the next decade.

UK recommendations for SDHA germline genetic testing and surveillance in clinical practice.

SDHA pathogenic germline variants (PGVs) are identified in up to 10% of patients with paraganglioma and phaeochromocytoma and up to 30% with wild-type gastrointestinal stromal tumours. Most SDHA PGV carriers present with an apparently sporadic tumour, but often the pathogenic variant has been inherited from parent who has the variant, but has not developed any clinical features. Studies of SDHA PGV carriers suggest that lifetime penetrance for SDHA-associated tumours is low, particularly when identified outside the context of a family history. Current recommended surveillance for SDHA PGV carriers follows an intensive protocol. With increasing implementation of tumour and germline large panel and whole-genome sequencing, it is likely more SDHA PGV carriers will be identified in patients with tumours not strongly associated with SDHA, or outside the context of a strong family history. This creates a complex situation about what to recommend in clinical practice considering low penetrance for tumour development, surveillance burden and patient anxiety. An expert SDHA working group was formed to discuss and consider this situation. This paper outlines the recommendations from this working group for testing and management of SDHA PGV carriers in clinical practice.

Germline mismatch repair (MMR) gene analyses from English NHS regional molecular genomics laboratories 1996-2020: development of a national resource of patient-level genomics laboratory records.

OBJECTIVE: To describe national patterns of National Health Service (NHS) analysis of mismatch repair (MMR) genes in England using individual-level data submitted to the National Disease Registration Service (NDRS) by the NHS regional molecular genetics laboratories. DESIGN: Laboratories submitted individual-level patient data to NDRS against a prescribed data model, including (1) patient identifiers, (2) test episode data, (3) per-gene results and (4) detected sequence variants. Individualised per-laboratory algorithms were designed and applied in NDRS to extract and map the data to the common data model. Laboratory-level MMR activity audit data from the Clinical Molecular Genetics Society/Association of Clinical Genomic Science were used to assess early years' missing data. RESULTS: Individual-level data from patients undergoing NHS MMR germline genetic testing were submitted from all 13 English laboratories performing MMR analyses, comprising in total 16 722 patients (9649 full-gene, 7073 targeted), with the earliest submission from 2000. The NDRS dataset is estimated to comprise >60% of NHS MMR analyses performed since inception of NHS MMR analysis, with complete national data for full-gene analyses for 2016 onwards. Out of 9649 full-gene tests, 2724 had an abnormal result, approximately 70% of which were (likely) pathogenic. Data linkage to the National Cancer Registry demonstrated colorectal cancer was the most frequent cancer type in which full-gene analysis was performed. CONCLUSION: The NDRS MMR dataset is a unique national pan-laboratory amalgamation of individual-level clinical and genomic patient data with pseudonymised identifiers enabling linkage to other national datasets. This growing resource will enable longitudinal research and can form the basis of a live national genomic disease registry.

Design and methods for the training in exercise activities and motion for growth (TEAM 4 growth) trial: A randomized controlled trial.

BACKGROUND: Growth is often impaired in infants with congenital heart disease. Poor growth has been associated with worse neurodevelopment, abnormal behavioral state, and longer time to hospital discharge. Nutritional interventions, drug therapy, and surgical palliation have varying degrees of success enhancing growth. Passive range of motion (PROM) improves somatic growth in preterm infants and is safe and feasible in infants with hypoplastic left heart syndrome (HLHS), after their first palliative surgery (Norwood procedure). METHODS: This multicenter, Phase III randomized control trial of a 21-day PROM exercise or standard of care evaluates growth in infants with HLHS after the Norwood procedure. Growth (weight-, height- and head circumference-for-age z-scores) will be compared at 4 months of age or at the pre-superior cavopulmonary connection evaluation visit, whichever comes first. Secondary outcomes include neonatal neurobehavioral patterns, neurodevelopmental assessment, and bone mineral density. Eligibility include diagnosis of HLHS or other single right ventricle anomaly, birth at ≥37 weeks gestation and Norwood procedure at <30 days of age, and family consent. Infants with known chromosomal or recognizable phenotypic syndromes associated with growth failure, listed for transplant, or expected to be discharged within 14 days of screening are excluded. CONCLUSIONS: The TEAM 4 Growth trial will make an important contribution to understanding the role of PROM on growth, neurobehavior, neurodevelopment, and BMD in infants with complex cardiac anomalies, who are at high risk for growth failure and developmental concerns.

Developmental Care Practice and Documentation Variability in the Cardiac ICU.

OBJECTIVES: Describe variability in developmental care practices, as documented in the electronic health record, for infants undergoing congenital heart surgery. DESIGN: Multicenter, retrospective, cohort study. SETTING: Six pediatric cardiac centers. PATIENTS: One hundred eighty-two infants undergoing one of three index operations: Norwood palliation, aortic arch reconstruction with ventricular septal defect closure, or arterial switch. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Core domains of developmental care encompassing pain assessment, feeding, infant holding, caregiver involvement, therapy, and psychosocial services were reviewed. Practices varied across individuals, institutions, and the hospital stay. At five of six sites, greater than 90% of individuals had physical or occupational therapy services as part of their care, but the day of first evaluation ranged from day of admission to postoperative day 28. Similar patterns were seen in feeding team and social work involvement. Consistent documentation of developmental care was dependent on the domain and site. Of the total days reviewed (n = 1,192), pain scores were documented in 95%. In those same days, documentation of whether or not a patient was out of the crib to be held varied by site from 11% to 93%. Type of oral feeding, breast versus bottle, was documented on the day prior to discharge 48% of the time. CONCLUSIONS: There are significant, quantifiable variations in documented developmental care practices at both the individual and site level. More reliable documentation of developmental care practices is required to associate these variables with later outcomes and investigate disparities in individualized developmental care practices.

Uterine leiomyomatosis in adolescents and young adults (AYAs) may represent a narrow phenotypic variant of FH tumour predisposition syndrome.

FH Tumour Predisposition Syndrome, also known as Hereditary Leiomyomatosis and renal cell cancer (HLRCC), or Reed Syndrome, is an autosomal dominant condition clinically characterized by multiple cutaneous leiomyomas, multiple early-onset uterine leiomyomas and early-onset renal cell cancer. Here we report a young female with FH Tumour Predisposition Syndrome with no clinical features except early-onset uterine leiomyomas. Whilst there is a significant history of uterine leiomyomas in her family, there is no history of cutaneous leiomyomas or renal cell cancer (RCC). Uterine leiomyomatosis in young adults may represent a narrow phenotypic variant of FH Tumour Predisposition Syndrome. It is important that young women who present with multiple leiomyomata or leiomyomata with atypical features are referred for molecular genetic testing.

Quantifying evidence toward pathogenicity for rare phenotypes: The case of succinate dehydrogenase genes, SDHB and SDHD.

PURPOSE: The weight of the evidence to attach to observation of a novel rare missense variant in SDHB or SDHD in individuals with the rare neuroendocrine tumors, pheochromocytomas and paragangliomas (PCC/PGL), is uncertain. METHODS: We compared the frequency of SDHB and SDHD very rare missense variants (VRMVs) in 6328 and 5847 cases of PCC/PGL, respectively, with that of population controls to generate a pan-gene VRMV likelihood ratio (LR). Via windowing analysis, we measured regional enrichments of VRMVs to calculate the domain-specific VRMV-LR (DS-VRMV-LR). We also calculated subphenotypic LRs for variant pathogenicity for various clinical, histologic, and molecular features. RESULTS: We estimated the pan-gene VRMV-LR to be 76.2 (54.8-105.9) for SDHB and 14.8 (8.7-25.0) for SDHD. Clustering analysis revealed an SDHB enriched region (ɑɑ 177-260, P = .001) for which the DS-VRMV-LR was 127.2 (64.9-249.4) and an SDHD enriched region (ɑɑ 70-114, P = .000003) for which the DS-VRMV-LR was 33.9 (14.8-77.8). Subphenotypic LRs exceeded 6 for invasive disease (SDHB), head-and-neck disease (SDHD), multiple tumors (SDHD), family history of PCC/PGL, loss of SDHB staining on immunohistochemistry, and succinate-to-fumarate ratio >97 (SDHB, SDHD). CONCLUSION: Using methodology generalizable to other gene-phenotype dyads, the LRs relating to rarity and phenotypic specificity for a single observation in PCC/PGL of a SDHB/SDHD VRMV can afford substantial evidence toward pathogenicity.

Neurological features in infants with congenital heart disease.

AIM: To report neurological examination findings at 5 to 12 months of age in infants with congenital heart disease (CHD) and to identify predictors of abnormal neurological examination. METHOD: This retrospective observational study included infants who required cardiac surgery at less than 3 months of age and underwent a standard neurological examination from a neurologist in the cardiac neurodevelopmental outpatient clinic between age 5 months and 12 months. Predictors for abnormal neurological examination (concerns on structured developmental history, demographic factors, medical history, and newborn neurodevelopmental assessment) were considered for multivariate regression. RESULTS: The sample included 127 infants (mean age 7mo 2wks), who underwent first cardiac surgery at 7 days (4-49 interquartile range [IQR]) of age and were seen for a neurological examination in the cardiac neurodevelopmental clinic. Neurological abnormalities were common; 88% of infants had an abnormal neurological examination in at least one domain assessed. The most common abnormalities were abnormal axial (48%) and extremity (44%) tone, mostly hypotonia. Abnormal neurological examination was associated with concerns on the concurrent structured developmental history, genetic condition, extracardiac anomaly, longer length of stay, more than one cardiac surgery, ongoing early intervention services, and abnormalities on newborn neurodevelopmental assessment. INTERPRETATION: Neurological examination abnormalities are common in infants with CHD after infant heart surgery, supporting the need for early and ongoing therapeutic developmental services and adherence to American Heart Association recommendations for developmental follow-up for children with CHD. What this paper adds Neurological examination abnormalities are common in infants who undergo open-heart surgery. Medical complications in infancy increase risk for neurological abnormalities. Family-reported concerns on structured developmental history may predict abnormal neurological examination at 5 to 12 months of age. Abnormal newborn neurodevelopmental assessment may predict abnormal neurological examination at 5 to 12 months of age.

Disruptions in the development of feeding for infants with congenital heart disease.

Congenital heart disease (CHD) is the most common birth defect for infants born in the United States, with approximately 36,000 affected infants born annually. While mortality rates for children with CHD have significantly declined, there is a growing population of individuals with CHD living into adulthood prompting the need to optimise long-term development and quality of life. For infants with CHD, pre- and post-surgery, there is an increased risk of developmental challenges and feeding difficulties. Feeding challenges carry profound implications for the quality of life for individuals with CHD and their families as they impact short- and long-term neurodevelopment related to growth and nutrition, sensory regulation, and social-emotional bonding with parents and other caregivers. Oral feeding challenges in children with CHD are often the result of medical complications, delayed transition to oral feeding, reduced stamina, oral feeding refusal, developmental delay, and consequences of the overwhelming intensive care unit (ICU) environment. This article aims to characterise the disruptions in feeding development for infants with CHD and describe neurodevelopmental factors that may contribute to short- and long-term oral feeding difficulties.

A Collaborative Learning Assessment of Developmental Care Practices for Infants in the Cardiac Intensive Care Unit.

OBJECTIVE: Assess differences in approaches to and provision of developmental care for infants undergoing surgery for congenital heart disease. STUDY DESIGN: A collaborative learning approach was used to stratify, assess, and compare individualized developmental care practices among multidisciplinary teams at 6 pediatric heart centers. Round robin site visits were completed with structured site visit goals and postvisit reporting. Practices of the hosting site were assessed by the visiting team and reviewed along with center self-assessments across specific domains including pain management, environment, cue-based care, and family based care coordination. RESULTS: Developmental care for infants in the cardiac intensive care unit (CICU) varies at both a center and individual level. Differences in care are primarily driven by variations in infrastructure and resources, composition of multidisciplinary teams, education of team members, and use of developmental care champions. Management of pain follows a protocol in most cardiac intensive care units, but the environment varies across centers, and the provision of cue-based infant care and family-based care coordination varies widely both within and across centers. The project led to proposed changes in clinical care and center infrastructure at each participating site. CONCLUSIONS: A collaborative learning design fostered rapid dissemination, comparison, and sharing of strategies to approach a complex multidisciplinary care paradigm. Our assessment of experiences revealed marked variability across and within centers. The collaborative findings were a first step toward strategies to quantify and measure developmental care practices in the cardiac intensive care unit to assess the association of complex inpatient practices with long-term neurodevelopmental outcomes.

Neurodevelopmental assessment of infants with congenital heart disease in the early postoperative period.

OBJECTIVE: Mortality rates for children with congenital heart disease (CHD) have significantly declined, resulting in a growing population with associated neurodevelopmental disabilities. American Heart Association guidelines recommend systematic developmental screening for children with CHD. The present study describes results of inpatient newborn neurodevelopmental assessment of infants after open heart surgery. OUTCOME MEASURES: We evaluated the neurodevelopment of a convenience sample of high-risk infants following cardiac surgery but before hospital discharge using an adaptation of the Newborn Behavioral Observation. Factor analysis examined relationships among assessment items and consolidated them into domains of development. RESULTS: We assessed 237 infants at a median of 11 days (interquartile range [IQR]: 7-19 days) after cardiac surgery and median corrected age of 21 days (IQR: 13-33 days). Autonomic regulation was minimally stressed or well organized in 14% of infants. Upper and lower muscle tone was appropriate in 33% and 35%, respectively. Appropriate response to social stimulation ranged between 7% and 12% depending on task, and state regulation was well organized in 14%. The vast majority (87%) required enhanced examiner facilitation for participation. Factor analyses of assessment items aligned into four domains of development (autonomic, motor, oral motor, and attention organization). CONCLUSION: At discharge, postoperative infants with CHD had impairments in autonomic, motor, attention, and state regulation following cardiac surgery. Findings highlight the challenges faced by children with CHD relative to healthy peers, suggesting that neurodevelopmental follow-up and intervention should begin early in infancy.

Individualized Family-Centered Developmental Care: An Essential Model to Address the Unique Needs of Infants With Congenital Heart Disease.

BACKGROUND: Infants born with critical congenital heart disease (cCHD) who require surgical intervention in the newborn period are often hospitalized in a cardiac intensive care unit (CICU). Cardiac surgery and the CICU environment are traumatic to infants and their families. Infants are exposed to overwhelming stress, which can result in increased pain, physiologic instability, behavioral disorganization, disrupted attachment, and altered brain development. Individualized Family-centered Developmental Care (IFDC) is a model that can address the unique needs and developmental challenges of infants with cCHD. PURPOSE: The purpose of this article is to (1) clearly describe the uniqueness of the infant with cCHD, including the medical, neurological, and parental challenges, and (2) propose methods to apply IFDC to support recovery of infants with cCHD in the CICU. CONCLUSIONS: The experiences in the CICU shape the developing brain and alter recovery and healing, thus adversely impacting development. Individualized Family-centered Developmental Care is a promising model of care that nurses can integrate into the CICU to promote neuroprotection and development. Nurses can effectively integrate IFDC into the CICU by understanding the unique characteristics of infants with cCHD and applying IFDC interventions that include both maturity and recovery perspectives. CLINICAL IMPLICATIONS: The incorporation of IFDC interventions is essential for the infant with cCHD and should be a standard of care. Applying IFDC with a recovery perspective in all aspects of caregiving will provide opportunities for individualization of care and parent engagement, allowing infants in the CICU to recover from surgery while supporting both short- and long-term neurodevelopment.

Anal Intraepithelial Neoplasia from a Pathologists Point of View.

Anal squamous cell carcinoma is a relatively rare diagnosis, but its incidence has continued to rise. Anal squamous cell carcinoma and its precursor lesion, anal intraepithelial neoplasia (AIN), are human papillomavirus (HPV)-associated squamous neoplasias. High-risk HPV subtypes cause cellular proliferation in the anal transformation zone mucosa leading to similar dysplastic changes as seen in the cervix. Unified cytologic and histologic classification systems have emerged for all HPV-associated squamous lesions of the lower anogenital tract due to recent advancements in the understanding of these lesions. P16 immunohistochemical stain, a biomarker for HPV, is recommended in the diagnosis of HPV-associated lesions. The unity of terminology will aid in communication between pathologists and clinicians, ultimately leading to improved patient care.

Advanced fabrication of biosensor on detection of Glypican-1 using S-Acetylmercaptosuccinic anhydride (SAMSA) modification of antibody.

Glypican-1 (GPC-1) has been recognized as biomarker of pancreatic cancer. Quantification of GPC-1 level is also pivotal to breast cancer and prostate cancer's patients. We hereby report the first biosensor for GPC-1 detection. Instead of using crosslinking technique and surface immobilization of antibody, we applied a novel method for biosensor fabrication, using S-Acetylmercaptosuccinic anhydride (SAMSA) to modify the Anti-GPC-1 producing a thiol-linked Anti-GPC-1. The thiol-linked Anti-GPC-1 was then directly formed a single-layer antibody layer on the gold biosensor, minimizing the biosensor preparation steps significantly. Time of Flight Secondary Ions Mass Spectroscopy (TOF-SIMS) characterization verified the thiol-linked antibody layer and demonstrated a unique perspective for surface protein characterization. Differential pulse voltammetry (DPV) was applied to quantify GPC-1 antigen in undiluted human serum with a concentration range of 5,000 pg/µL to 100 pg/µL. The performance of this newly designed biosensor was also compared with modified self-assembled monolayer system fabricated biosensor, demonstrating the high-sensitivity and high-reproducibility of the SAMSA modified antibody based biosensor. This simple fabrication method can also expand to detection of other biomolecules. The simplified operation process shows great potential in clinical application development.

Deriving Dorsal Spinal Sensory Interneurons from Human Pluripotent Stem Cells.

Cellular replacement therapies for neurological conditions use human embryonic stem cell (hESC)- or induced pluripotent stem cell (hiPSC)-derived neurons to replace damaged or diseased populations of neurons. For the spinal cord, significant progress has been made generating the in-vitro-derived motor neurons required to restore coordinated movement. However, there is as yet no protocol to generate in-vitro-derived sensory interneurons (INs), which permit perception of the environment. Here, we report on the development of a directed differentiation protocol to derive sensory INs for both hESCs and hiPSCs. Two developmentally relevant factors, retinoic acid in combination with bone morphogenetic protein 4, can be used to generate three classes of sensory INs: the proprioceptive dI1s, the dI2s, and mechanosensory dI3s. Critical to this protocol is the competence state of the neural progenitors, which changes over time. This protocol will facilitate developing cellular replacement therapies to reestablish sensory connections in injured patients.

Netrin1 establishes multiple boundaries for axon growth in the developing spinal cord.

The canonical model for netrin1 function proposed that it acted as a long-range chemotropic axon guidance cue. In the developing spinal cord, floor-plate (FP)-derived netrin1 was thought to act as a diffusible attractant to draw commissural axons to the ventral midline. However, our recent studies have shown that netrin1 is dispensable in the FP for axon guidance. We have rather found that netrin1 acts locally: netrin1 is produced by neural progenitor cells (NPCs) in the ventricular zone (VZ), and deposited on the pial surface as a haptotactic adhesive substrate that guides Dcc+ axon growth. Here, we further demonstrate that this netrin1 pial-substrate has an early role orienting pioneering spinal axons, directing them to extend ventrally. However, as development proceeds, commissural axons choose to grow around a boundary of netrin1 expressing cells in VZ, instead of continuing to extend alongside the netrin1 pial-substrate in the ventral spinal cord. This observation suggests netrin1 may supply a more complex activity than pure adhesion, with netrin1-expressing cells also supplying a growth boundary for axons. Supporting this possibility, we have observed that additional domains of netrin1 expression arise adjacent to the dorsal root entry zone (DREZ) in E12.5 mice that are also required to sculpt axonal growth. Together, our studies suggest that netrin1 provides "hederal" boundaries: a local growth substrate that promotes axon extension, while also preventing local innervation of netrin1-expressing domains.