Pilocytic astrocytomas are the most common pediatric brain tumors, typically presenting as low-grade neoplasms. We report two cases of pilocytic astrocytoma with atypical tumor progression. Case 1 involves a 12-yr-old boy with an unresectable suprasellar tumor, negative for BRAF rearrangement but harboring a BRAF p.V600E mutation. He experienced tumor size reduction and stable disease following dabrafenib treatment. Case 2 describes a 6-yr-old boy with a thalamic tumor that underwent multiple resections, with no actionable driver detected using targeted next-generation sequencing. Whole-genome and RNA-seq analysis identified an internal tandem duplication in FGFR1 and RAS pathway activation. Future management options include FGFR1 inhibitors. These cases demonstrate the importance of escalating molecular diagnostics for pediatric brain cancer, advocating for early reflexing to integrative whole-genome sequencing and transcriptomic profiling when targeted panels are uninformative. Identifying molecular drivers can significantly impact treatment decisions and improve patient outcomes.

Affibody molecules are small (6-kDa) affinity proteins generated by directed evolution for specific binding to various target molecules. The first step in this workflow involves the generation of an affibody library, which can then be used for biopanning using multiple display methods. This protocol describes selection from affibody libraries using display on Staphylococcus carnosus. Display of affibodies on staphylococci is very efficient and straightforward because of the single cell membrane and the use of a construct with a constitutive promoter. The workflow involves display of affibody libraries on the surface of S. carnosus cells, followed by screening and selection of binders using fluorescence-activated cell sorting (FACS). The transformation of DNA libraries into S. carnosus is less efficient and more complicated than for Escherichia coli. Because of this, staphylococcal display is suitable for affinity maturation or other protein-engineering efforts that are not dependent on very high diversity, and thus magnetic-activated cell sorting (MACS) is often not required before FACS. However, MACS is an option, and MACS procedures used for E. coli can easily be adapted for use in S. carnosus if needed.

Affibody molecules are small (6-kDa) affinity proteins generated by directed evolution for specific binding to various target molecules. The first step in this workflow involves the generation of an affibody library, which can then be used for selection via multiple display methods. This protocol describes selection from affibody libraries by Escherichia coli cell surface display. With this method, high-diversity libraries of 10¹¹ can be displayed on the cell surface. The method involves two steps for selection of binders from high-diversity libraries: magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS). MACS is used first to enrich the library in target-binding clones and to decrease diversity to a size that can be effectively screened and sorted in the flow cytometer in a reasonable time (typically <10⁷ cells). The protocol is based on methodology using an AIDA-I autotransporter for display on the outer membrane, but the general procedures can also be adjusted and used for other types of autotransporters or alternative E. coli display methods.

Affibody molecules are small (6-kDa) affinity proteins generated by directed evolution for specific binding to various target molecules. The first step in this workflow involves the generation of an affibody library. This is then followed by amplification of the library, which can then be used for biopanning using multiple methods. This protocol describes amplification of affibody libraries, followed by biopanning using phage display and analysis of the selection output. The general procedure is mainly for selection of first-generation affibody molecules from large naive (unbiased) libraries, typically yielding affibody hits with affinities in the low nanomolar range. For selection from affinity maturation libraries with the aim of isolating variants of even higher affinities, the procedure is similar, but parameters such as target concentration and washing are adjusted to achieve the proper stringency.

Affibody molecules are small (6-kDa) affinity proteins folded in a three-helical bundle and generated by directed evolution for specific binding to various target molecules. The most advanced affibody molecules are currently tested in the clinic, and data from more than 300 subjects show excellent activity and safety profiles. The generation of affibody molecules against a particular target starts with the generation of an affibody library, which can then be used for panning using multiple methods and selection systems. This protocol describes the molecular cloning of DNA-encoded affibody libraries to a display vector of choice, for either phage, Escherichia coli, or Staphylococcus carnosus display. The DNA library can come from different sources, such as error-prone polymerase chain reaction (PCR), molecular shuffling of mutations from previous selections, or, more commonly, from DNA synthesis using various methods. Restriction enzyme-based subcloning is the most common strategy for affibody libraries of higher diversity (e.g., >10⁷ variants) and is described here.

The positional preference of an animal can be very informative regarding the choices it makes about how to interact with its environment. The fruit fly Drosophila melanogaster has been used as a robust system for examining neurobiological mechanisms underlying behavior. Fruit fly positional preference can be gathered from TriKinetics Drosophila activity monitors (DAMs), which contain four infrared beams, allowing for tracking the position of individual flies along the length of a tube. Here, we describe a method for using DAM5Ms to examine food preference. Specifically, we show an example in which circadian changes in food preference are compared between different Drosophila species. More information about the evolution of behavior can be gathered by measuring feeding preference relative to time of day. Noni, fruit from Morinda citrifolia, contains octanoic acid, a chemical toxic to many species of Drosophila. D. melanogaster and D. simulans, both food generalists, show high sensitivity to octanoic acid, whereas D. sechellia, a specialist, can tolerate high concentrations. When two different food substrates are provided at each end of a tube, food preference can be inferred at various times of the day, using the sleep and circadian analysis MATLAB program (SCAMP) to extract and analyze positional data from DAM5Ms. Data gathered from these analyses can be used to compare avoidance or attraction to nutrients, tastants, or odors between species and genotypes or after specific different treatments. Additionally, such data can be examined as a function of time of day.

Sleep is a fundamental feature of life for virtually all multicellular animals, but many questions remain about how sleep is regulated by circadian rhythms, homeostatic sleep drive that builds up with wakefulness, and modifying factors such as hunger or social interactions, as well as about the biological functions of sleep. Substantial headway has been made in the study of both circadian rhythms and sleep in the fruit fly Drosophila melanogaster, much of it through studies of individual fly activity using Drosophila activity monitors (DAMs). Here, we describe approaches for the activation of specific neurons of interest using optogenetics (involving genetic modifications that allow for light-based neuronal activation) and thermogenetics (involving genetic modifications that allow for temperature-based neuronal activation) so that researchers can evaluate the roles of those neurons in controlling rest and activity behavior. In this protocol, we describe how to set up a rig for simultaneous optogenetic or thermogenetic stimulation and activity monitoring for analysis of sleep and circadian rhythms in Drosophila, how to raise appropriate flies, and how to perform the experiment. This protocol will allow researchers to assess the causative role in the regulation of sleep and activity rhythms of any genetically tractable subset of cells.

Affibody molecules are small, robust, and versatile affinity proteins currently being explored for therapeutic, diagnostic, and biotechnological applications. Surface-exposed residues on the affibody scaffold are randomized to create large affibody libraries from which novel binding specificities to virtually any protein target can be generated using combinatorial protein engineering. Affibody molecules have the potential to complement—or even surpass—current antibody-based technologies, exhibiting multiple desirable properties, such as high stability, affinity, and specificity, efficient tissue penetration, and straightforward modular extension of functional domains. It has been shown in both preclinical and clinical studies that affibody molecules are safe, efficacious, and valuable alternatives to antibodies for specific targeting in the context of in vivo diagnostics and therapy. Here, we provide a general background of affibody molecules, give examples of reported applications, and briefly summarize the methodology for affibody generation.

BackgroundDuring the COVID-19 pandemic, global trends of reduced healthcare-seeking behaviour were observed. This raises concerns about the consequences of healthcare avoidance for population health.AimTo determine the association between healthcare avoidance during the early stages of the COVID-19 pandemic and all-cause mortality.Design and settingThis was a 32-month follow-up within the population-based Rotterdam Study, after sending a COVID-19 questionnaire at the onset of the pandemic in April 2020 to all communty dwelling participants (n = 6241/8732, response rate 71.5%).MethodCox proportional hazards models assessed the risk of all-cause mortality among respondents who avoided health care because of the COVID-19 pandemic. Mortality status was collected through municipality registries and medical records.ResultsOf 5656 respondents, one-fifth avoided health care because of the COVID-19 pandemic (n = 1143). Compared with non-avoiders, those who avoided health care more often reported symptoms of depression (n = 357, 31.2% versus n = 554, 12.3%) and anxiety (n = 340, 29.7% versus n = 549, 12.2%), and more often rated their health as poor to fair (n = 336, 29.4% versus n = 457, 10.1%) . Those who avoided health care had an increased adjusted risk of all-cause mortality (hazard ratio [HR] 1.30, 95% confidence interval [CI] = 1.01 to 1.67), which remained nearly identical after adjustment for history of any non-communicable disease (HR 1.20, 95% CI = 0.93 to 1.54). However, this association attenuated after additional adjustment for mental and physical self-perceived health factors (HR 0.93, 95% CI = 0.71 to 1.20).ConclusionThis study found an increased risk of all-cause mortality among individuals who avoided health care during COVID-19. These individuals were characterised by poor mental and physical self-perceived health. Therefore, interventions should be targeted to these vulnerable individuals to safeguard their access to primary and specialist care to limit health disparities, inside and beyond healthcare crises.

BackgroundLong-term health conditions are major challenges for care systems. Social prescribing link workers have been introduced via primary care networks (PCNs) across England since 2019 to address the wider determinants of health by connecting individuals to activities, groups, or services within their local community.AimTo assess whether the rollout of social prescribing link workers was in areas with the highest need.Design and settingA retrospective study of social prescribing link workers in England from 2019 to 2023.MethodWorkforce, population, survey, and area-level data at the PCN-level from April 2020 to October 2023 were combined. Population need before the rollout of link workers was measured using reported lack of support from local services in the 2019 General Practice Patient Survey. To assess if rollout reflected need, linear regression was used to relate provision of link workers (measured by full-time equivalent [FTE] per 10 000 patients) in each quarter to population need for support.ResultsPopulations in urban, more deprived areas and with higher proportions of people from minority ethnic groups had the highest reported lack of support. Geographically these were in the North West and London. Initially, there was no association between need and provision; then from July 2022, this became negative and significant. By October 2023, a 10-percentage point higher need for support was associated with a 0.035 (95% confidence interval = −0.634 to −0.066) lower FTE per 10 000 patients.ConclusionRollout of link workers has not been sufficiently targeted at areas with the highest need. Future deployments should be targeted at those areas.

BackgroundAttention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder, for which there are effective pharmacological treatments that improve symptoms and reduce complications. Guidelines published by the National Institute for Health and Care Excellence recommend that primary care practitioners prescribe medication for adult ADHD under shared-care agreements with Adult Mental Health Services (AMHS). However, provision remains uneven, with some practitioners reporting a lack of support.AimThis study aimed to describe elements of support, and their availability/use, in primary care prescribing for adult ADHD medication in England to improve access for this underserved population and inform service improvement.Design and settingCross-sectional surveys were used to elicit data from commissioners, health professionals (HPs), and people with lived experience of ADHD (LE) across England about elements supporting pharmacological treatment of ADHD in primary care.MethodThree interlinked cross-sectional surveys were used to ask every integrated care board in England (commissioners), along with convenience samples of HPs and LEs, about prescribing rates, AMHS availability, wait times, and shared-care agreement protocols/policies for the pharmacological treatment of ADHD in primary care. Descriptive analyses, percentages, and confidence intervals were used to summarise responses by stakeholder group. Variations in reported provision and practice were explored and displayed visually using mapping software.ResultsData from 782 responders (42 commissioners, 331 HPs, 409 LEs) revealed differences in reported provision by stakeholder group, including for prescribing (95% of HPs versus 64% of LEs). In all, >40% of responders reported extended AMHS wait times of ≥2 years. There was some variability by NHS region – for example, London had the lowest reported extended wait time (25%), while East of England had the highest (55%).ConclusionElements supporting appropriate shared-care prescribing of ADHD medication via primary care are not universally available in England. Coordinated approaches are needed to address these gaps.

BackgroundCOVID-19 pandemic restrictions may have influenced behaviours related to weight.AimTo describe patterns of weight change among adults living in England with type 2 diabetes (T2D) and/or hypertension during the pandemic.Design and settingAn observational cohort study using the routinely collected health data of approximately 40% of adults living in England, accessed through the OpenSAFELY service inside TPP.MethodClinical and sociodemographic characteristics associated with rapid weight gain (>0.5 kg/m2/year) were investigated using multivariable logistic regression.ResultsData were extracted on adults with T2D (n = 1 231 455, 43.9% female, and 76.0% White British) or hypertension (n = 3 558 405, 49.7% female, and 84.3% White British). Adults with T2D lost weight overall (median δ = −0.1 kg/m2/year [interquartile range {IQR} −0.7–0.4]). However, rapid weight gain was common (20.7%) and associated with the following: sex (male versus female: adjusted odds ratio [aOR] 0.78 [95% confidence interval {CI} = 0.77 to 0.79]); age (older age reduced odds, for example, aged 60–69 years versus 18–29 years: aOR 0.66 [95% CI = 0.61 to 0.71]); deprivation (least deprived Index of Multiple Deprivation [IMD] quintile versus most deprived IMD quintile: aOR 0.87 [95% CI = 0.85 to 0.89]); White ethnicity (Black versus White: aOR 0.95 [95% CI = 0.92 to 0.98]); mental health conditions (for example, depression: aOR 1.13 [95% CI = 1.12 to 1.15]); and diabetes treatment (non-insulin treatment versus no pharmacological treatment: aOR 0.68 [95% CI = 0.67 to 0.69]). Adults with hypertension maintained stable weight overall (median δ = 0.0 kg/m2/year [IQR −0.6–0.5]); however, rapid weight gain was common (24.7%) and associated with similar characteristics as in T2D.ConclusionAmong adults living in England with T2D and/or hypertension, rapid pandemic weight gain was more common among females, younger adults, those living in more deprived areas, and those with mental health conditions.

BackgroundOrlistat is recommended as an adjunct to diet and exercise for weight loss in the treatment of type 2 diabetes mellitus (T2DM).AimTo explore associations between patient characteristics and orlistat prescribing, and to determine associations of orlistat with weight loss in T2DM and prediabetes.Design and settingCohort study using anonymised health records from a UK database of general practice.MethodThe UK Clinical Practice Research Datalink (CPRD) Aurum database was searched to compile a cohort of patients aged ≥18 years, first diagnosed with T2DM or prediabetes in 2016 or 2017. Once the data had been collated, multivariable logistic regression models were used to determine associations with starting orlistat and stopping it early (<12 weeks of prescriptions) and orlistat’s associations with weight loss in those who had not been prescribed second-line antidiabetic medications.ResultsOut of 100 552 patients with incident T2DM or prediabetes, 655 (0.8%) patients with T2DM and 128 (0.7%) patients with prediabetes were prescribed orlistat. Younger people, females, those in areas of deprivation, current smokers, those coprescribed metformin, and those recorded as having hypertension were statistically significantly more likely to be prescribed orlistat; higher baseline glycated haemoglobin levels were associated with early stopping. In comparison with patients not on orlistat, those who continued using it for ≥12 weeks were more likely to lose ≥5% weight (adjusted odds ratio [AOR] 1.69, 95% confidence interval [CI] = 1.07 to 2.67) but those who stopped orlistat early were less likely to lose ≥5% weight (AOR 0.56, 95% CI = 0.29 to 1.09).ConclusionOrlistat was significantly associated with weight loss in patients with T2DM and prediabetes when taken for at least 12 weeks; however, it was infrequently prescribed and often taken for <12 weeks. Orlistat may be a useful adjunct to lifestyle modifications for patients with T2DM and prediabetes, but barriers to continued use means it may not be effective for everyone in managing weight loss.

BackgroundMost people with type 2 diabetes receive treatment in primary care by GPs who are not specialised in diabetes. Thus, it is important to uncover the most essential information needs regarding type 2 diabetes in general practice.AimTo identify information needs related to type 2 diabetes for GPs.Design and settingSystematic review focused on literature relating to Western countries.MethodMEDLINE, Embase, PsycInfo and CINAHL were searched from inception to January 2024. Two researchers conducted the selection process, and citation searches were performed to identify any relevant articles missed by the database search. Quality appraisal was conducted with the Mixed Methods Appraisal Tool. Meaning units were coded individually, grouped into categories, and then studies were summarised within the context of these categories using narrative synthesis. An evidence map was created to highlight research gaps.ResultsThirty-nine included studies revealed eight main categories and 36 subcategories of information needs. Categories were organised into a comprehensive hierarchical model of information needs, suggesting ‘Knowledge of guidelines’ and ‘Reasons for referral’ as general information needs alongside more specific needs on ‘Medication’, ‘Management’, ‘Complications’, ‘Diagnosis’, ‘Risk factors’, and ‘Screening for diabetes’. The evidence map provides readers with the opportunity to explore the characteristics of the included studies in detail.ConclusionThis systematic review provides GPs, policymakers, and researchers with a hierarchical model of information and educational needs for GPs, and an evidence map showing gaps in the current literature. Information needs about clinical guidelines and reasons for referral to specialised care overlapped with needs for more specific information.

BackgroundIncident benzodiazepine prescriptions in primary care for anxiety decreased between 2003 and 2018. However, from 2008, incident prescribing of benzodiazepines for anxiety increased among those aged 18–34 years. There are increasing concerns around prescribing of benzodiazepines. Further, although guidelines state benzodiazepines should only be prescribed short term, in 2017, 44% of incident prescriptions were prescribed for longer than the recommended duration of 2–4 weeks.AimTo understand when and why GPs prescribe benzodiazepines for anxiety in young adults.Design and settingA qualitative study was undertaken using in-depth interviews with 17 GPs from 10 general practices in South West England.MethodInterviews were conducted by telephone or videocall. A topic guide was used to ensure consistency across interviews. Interviews were audio-recorded, transcribed verbatim, and data analysed using reflexive thematic analysis.ResultsGPs described caution in prescribing benzodiazepines for anxiety in young adults, but thought they had an important role in acute situations. GPs described caution in prescribing duration, but some thought longer-term prescriptions could be appropriate. In light of these views, some GPs questioned whether primary care needs to revisit how clinicians are using benzodiazepines. GPs perceived that some young adults requested benzodiazepines and suggested this might be because they wanted quick symptom relief. GPs noted that refusing to prescribe felt uncomfortable and that the number of young adults presenting to general practice, already dependent on benzodiazepines, had increased.ConclusionPatient-driven factors for prescribing benzodiazepines suggest there are current unmet treatment needs among young adults with anxiety. Given increases in prescribing in this age group, it may be timely to revisit the role of benzodiazepines in the management of people with anxiety in primary care.

BackgroundBetween 2003 and 2018, incident prescriptions of beta-blockers for anxiety increased substantially, particularly for young adults. National Institute for Health and Care Excellence guidance for anxiety does not recommend beta-blockers, probably due to a lack of evidence to support such use. Recent reports have highlighted the potential risks of beta-blockers.AimTo understand when and why GPs prescribe beta-blockers for people with anxiety.Design and settingIn-depth interviews with 17 GPs in Bristol and the surrounding areas.MethodInterviews were held by telephone or video call. A topic guide was used to ensure consistency across interviews. Interviews were audio-recorded, transcribed verbatim, and analysed thematically.ResultsMany GPs viewed beta-blockers as ‘low risk’, particularly for young adults. Some GPs viewed beta-blockers as an alternative to benzodiazepines, acting quickly and not leading to dependence. GPs reflected that some patients appeared to want an ‘immediate fix’ to their symptoms, which GPs thought beta-blockers could potentially offer. This is salient in light of substantial waiting lists for talking therapies and delays in antidepressants taking effect. GPs described how some patients seemed more willing to try beta-blockers than antidepressants, as patients did not perceive them as ‘mental health drugs’ and therefore viewed them as potentially more acceptable and less stigmatising. Further, GPs viewed beta-blockers as ‘patient-led’, with patients managing their own dose and frequency, without GP input.ConclusionMany GPs believe that beta-blockers have a role to play in the management of anxiety. Given recent increases in the prescribing of these drugs in primary care, there is a need to assess their safety and effectiveness as a treatment for people with anxiety disorders.

BackgroundThere has been significant investment in pharmacists working in UK general practice to improve the effective and safe use of medicines. However, evidence of how to optimise collaboration between GPs and pharmacists in the context of polypharmacy (multiple medication) is lacking.AimTo explore GP and pharmacist views and experiences of in-person, interprofessional collaborative discussions (IPCDs) as part of a complex intervention to optimise medication use for patients with polypharmacy in general practice.Design and settingA mixed-method process evaluation embedded within the Improving Medicines use in People with Polypharmacy in Primary Care (IMPPP) trial conducted in Bristol and the West Midlands, between February 2021 and September 2023.MethodAudio-recordings of IPCDs between GPs and pharmacists, along with individual semi-structured interviews to explore their reflections on these discussions, were used. All recordings were transcribed verbatim and analysed thematically.ResultsA total of 14 practices took part in the process evaluation from February 2022 to September 2023; 17 IPCD meetings were audio-recorded, discussing 30 patients (range 1–6 patients per meeting). In all, six GPs and 13 pharmacists were interviewed. The IPCD was highly valued by GPs and pharmacists who described benefits, including: strengthening their working relationship; gaining in confidence to manage more complex patients; and learning from each other. It was often challenging, however, to find time for the IPCDs.ConclusionThe model of IPCD used in this study provided protected time for GPs and pharmacists to work together to deliver whole-patient care, with both professions finding this beneficial. Protected time for interprofessional liaison and collaboration, and structured interventions may facilitate improved patient care.

PURPOSE

HIV pre-exposure prophylaxis (PrEP) may increase rates of bacterial sexually transmitted infections (STIs) among gay, bisexual, and other men who have sex with men (GBM) through risk compensation (eg, an increase in condomless sex or number of partners); however, longitudinal studies exploring the time-dependent nature of PrEP uptake and bacterial STIs are limited. We used marginal structural models to estimate the effect of PrEP uptake on STI incidence.

Patient expectations of receiving antibiotics for common symptoms can trigger unnecessary use. We conducted a survey (n = 564) between January 2020 to June 2021 in public and private primary care clinics in Texas to study the prevalence and predictors of patients’ antibiotic expectations for common symptoms/illnesses. We surveyed Black patients (33%) and Hispanic/Latine patients (47%), and over 93% expected to receive an antibiotic for at least 1 of the 5 pre-defined symptoms/illnesses. Public clinic patients were nearly twice as likely to expect antibiotics for sore throat, diarrhea, and cold/flu than private clinic patients. Lack of knowledge of potential risks of antibiotic use was associated with increased antibiotic expectations for diarrhea (odds ratio [OR] = 1.6; 95% CI, 1.1-2.4) and cold/flu symptoms (OR = 2.9; 95% CI, 2.0-4.4). Lower education and inadequate health literacy were predictors of antibiotic expectations for diarrhea. Future antibiotic stewardship interventions should tailor patient education materials to include information on antibiotic risks and guidance on appropriate antibiotic indications.

The aim of this work is to test whether the use of a transparent capsule affects the residual capsule weight after inhalation as a surrogate of the inhaled delivered dose for patients with non-reversible chronic airway disease. Researchers conducted an observational cross-sectional study with patients using a single-dose dry powder inhaler. The weight of the capsule was measured with a precision microbalance before and after inhalation. Ninety-one patients were included, of whom 63 (69.2%) used a transparent capsule. Inhalation with a transparent capsule achieved a weight decrease of 30.1% vs 8.6% for devices with an opaque capsule (P <0.001). These data reinforce the need to provide patients with mechanisms that verify the correct inhalation technique.

PURPOSE

Despite being key to better health outcomes for patients from racial and ethnic minority groups, the proportion of underrepresented in medicine (URiM) physicians remains low in the US health care system. This study linked a nationally representative sample of family physicians (FPs) with Medicaid claims data to explore the relative contributions to care of Medicaid populations by FP race and ethnicity.

PURPOSE

Currently, 40% of counties in the United States do not have an obstetrician or midwife, and in rural areas the likelihood of childbirth being attended to by a family medicine (FM) physician is increasing. We sought to characterize the effect of the FM presence on unit culture and a key perinatal quality metric in Iowa hospital intrapartum units.

BACKGROUND

For many patients with post–COVID-19 condition (long COVID), primary care is the first point of interaction with the health care system. In principle, primary care is well situated to manage long COVID. Beyond expressions of disempowerment, however, the patient’s perspective regarding the quality of long COVID care is lacking. Therefore, this study aimed to analyze the expectations and experiences of primary care patients seeking treatment for long COVID.

Comprehensive maps of neuronal connectivity provide a foundation for understanding the structure of neural circuits. In a circuit, neurons are diverse in morphology, electrophysiology, gene expression, activity, and other neuronal properties. Thus, constructing a comprehensive connectivity map requires associating various properties of neurons, including their connectivity, at cellular resolution. A commonly used approach is to use the gene expression profiles as an anchor to which all other neuronal properties are associated. Recent advances in genomics and anatomical techniques dramatically improved the ability to determine and associate the long-range projections of neurons with their gene expression profiles. These studies revealed unprecedented details of the gene–projection relationship, but also highlighted conceptual challenges in understanding this relationship. In this article, I delve into the findings and the challenges revealed by recent studies using state-of-the-art neuroanatomical and transcriptomic techniques. Building upon these insights, I propose an approach that focuses on understanding the gene–projection relationship through basic features in gene expression profiles and projections, respectively, that associate with underlying cellular processes. I then discuss how the developmental trajectories of projections and gene expression profiles create additional challenges and necessitate interrogating the gene–projection relationship across time. Finally, I explore complementary strategies that, together, can provide a comprehensive view of the gene–projection relationship.