Marmosets as model systems for the study of Alzheimer's disease and related dementias: substantiation of physiological Tau 3R and 4R isoform expression and phosphorylation.

INTRODUCTION: Marmosets have been shown to spontaneously develop pathological hallmarks of Alzheimer's disease (AD) during advanced age, including amyloid-beta plaques, positioning them as a model system to overcome the rodent-to-human translational gap for AD. However, Tau expression in the marmoset brain has been understudied. METHODS: To comprehensively investigate Tau isoform expression in marmosets, brain tissue from eight unrelated marmosets across various ages was evaluated and compared to human postmortem AD tissue. Microtubule-associated protein tau ( MAPT ) mRNA expression and splicing were confirmed by RT-PCR. Tau isoforms in the marmoset brain were examined by western blot, mass spectrometry, immunofluorescence, and immunohistochemical staining. Synaptic Tau expression was analyzed from crude synaptosome extractions. RESULTS: 3R and 4R Tau isoforms are expressed in marmoset brains at both transcript and protein levels across ages. Results from western blot analysis were confirmed by mass spectrometry, which revealed that Tau peptides in marmoset corresponded to the 3R and 4R peptides in the human AD brain. 3R Tau was primarily enriched in neonate brains, and 4R enhanced in adult and aged brains. Tau was widely distributed in neurons with localization in the soma and synaptic regions. Phosphorylation residues were observed on Thr-181, Thr-217, and Thr-231, Ser202/Thr205, Ser396/Ser404. Paired helical filament (PHF)-like aggregates were also detected in aged marmosets. DISCUSSION: Our results confirm the expression of both 3R and 4R Tau isoforms and important phosphorylation residues in the marmoset brain. These data emphasize the significance of marmosets with natural expression of AD-related hallmarks as important translational models for the study of AD.

Early molecular events of autosomal-dominant Alzheimer's disease in marmosets with PSEN1 mutations.

INTRODUCTION: Fundamental questions remain about the key mechanisms that initiate Alzheimer's disease (AD) and the factors that promote its progression. Here we report the successful generation of the first genetically engineered marmosets that carry knock-in (KI) point mutations in the presenilin 1 (PSEN1) gene that can be studied from birth throughout lifespan. METHODS: CRISPR/Cas9 was used to generate marmosets with C410Y or A426P point mutations in PSEN1. Founders and their germline offspring are comprehensively studied longitudinally using non-invasive measures including behavior, biomarkers, neuroimaging, and multiomics signatures. RESULTS: Prior to adulthood, increases in plasma amyloid beta were observed in PSEN1 mutation carriers relative to non-carriers. Analysis of brain revealed alterations in several enzyme-substrate interactions within the gamma secretase complex prior to adulthood. DISCUSSION: Marmosets carrying KI point mutations in PSEN1 provide the opportunity to study the earliest primate-specific mechanisms that contribute to the molecular and cellular root causes of AD onset and progression. HIGHLIGHTS: We report the successful generation of genetically engineered marmosets harboring knock-in point mutations in the PSEN1 gene. PSEN1 marmosets and their germline offspring recapitulate the early emergence of AD-related biomarkers. Studies as early in life as possible in PSEN1 marmosets will enable the identification of primate-specific mechanisms that drive disease progression.

Bridging the rodent to human translational gap: Marmosets as model systems for the study of Alzheimer's disease.

Introduction: Our limited understanding of the mechanisms that trigger the emergence of Alzheimer's disease (AD) has contributed to the lack of interventions that stop, prevent, or fully treat this disease. We believe that the development of a non-human primate model of AD will be an essential step toward overcoming limitations of other model systems and is crucial for investigating primate-specific mechanisms underlying the cellular and molecular root causes of the pathogenesis and progression of AD. Methods: A new consortium has been established with funding support from the National Institute on Aging aimed at the generation, characterization, and validation of Marmosets As Research Models of AD (MARMO-AD). This consortium will study gene-edited marmoset models carrying genetic risk for AD and wild-type genetically diverse aging marmosets from birth throughout their lifespan, using non-invasive longitudinal assessments. These include characterizing the genetic, molecular, functional, behavioral, cognitive, and pathological features of aging and AD. Results: The consortium successfully generated viable founders carrying PSEN1 mutations in C410Y and A426P using CRISPR/Cas9 approaches, with germline transmission demonstrated in the C410Y line. Longitudinal characterization of these models, their germline offspring, and normal aging outbred marmosets is ongoing. All data and resources from this consortium will be shared with the greater AD research community. Discussion: By establishing marmoset models of AD, we will be able to investigate primate-specific cellular and molecular root causes that underlie the pathogenesis and progression of AD, overcome limitations of other model organisms, and support future translational studies to accelerate the pace of bringing therapies to patients.

Measurement of symphysis fundal height for gestational age estimation in low-to-middle-income countries: A systematic review and meta-analysis.

In low- and middle-income countries (LMIC), measurement of symphysis fundal height (SFH) is often the only available method of estimating gestational age (GA) in pregnancy. This systematic review aims to summarize methods of SFH measurement and assess the accuracy of SFH for the purpose of GA estimation. We searched PubMed, EMBASE, Cochrane, Web of Science, POPLINE, and WHO Global Health Libraries from January 1980 through November 2021. For SFH accuracy, we pooled the variance of the mean difference between GA confirmed by ultrasound versus SFH. Of 1,003 studies identified, 37 studies were included. Nineteen different SFH measurement techniques and 13 SFH-to-GA conversion methods were identified. In pooled analysis of five studies (n = 5838 pregnancies), 71% (95% CI: 66-77%) of pregnancies dated by SFH were within ±14 days of ultrasound confirmed dating. Using the 1 cm SFH = 1wk assumption, SFH underestimated GA compared with ultrasound-confirmed GA (mean bias: -14.0 days) with poor accuracy (95% limits of agreement [LOA]: ±42.8 days; n = 3 studies, 2447 pregnancies). Statistical modeling of three serial SFH measurements performed better, but accuracy was still poor (95% LOA ±33 days; n = 4 studies, 4391 pregnancies). In conclusion, there is wide variation in SFH measurement and SFH-to-GA conversion techniques. SFH is inaccurate for estimating GA and should not be used for GA dating. Increasing access to quality ultrasonography early in pregnancy should be prioritized to improve gestational age assessment in LMIC.

Mapping inequalities in exclusive breastfeeding in low- and middle-income countries, 2000-2018.

Exclusive breastfeeding (EBF)-giving infants only breast-milk for the first 6 months of life-is a component of optimal breastfeeding practices effective in preventing child morbidity and mortality. EBF practices are known to vary by population and comparable subnational estimates of prevalence and progress across low- and middle-income countries (LMICs) are required for planning policy and interventions. Here we present a geospatial analysis of EBF prevalence estimates from 2000 to 2018 across 94 LMICs mapped to policy-relevant administrative units (for example, districts), quantify subnational inequalities and their changes over time, and estimate probabilities of meeting the World Health Organization's Global Nutrition Target (WHO GNT) of ≥70% EBF prevalence by 2030. While six LMICs are projected to meet the WHO GNT of ≥70% EBF prevalence at a national scale, only three are predicted to meet the target in all their district-level units by 2030.

Oral rehydration therapies in Senegal, Mali, and Sierra Leone: a spatial analysis of changes over time and implications for policy.

BACKGROUND: Oral rehydration solution (ORS) is a simple intervention that can prevent childhood deaths from severe diarrhea and dehydration. In a previous study, we mapped the use of ORS treatment subnationally and found that ORS coverage increased over time, while the use of home-made alternatives or recommended home fluids (RHF) decreased, in many countries. These patterns were particularly striking within Senegal, Mali, and Sierra Leone. It was unclear, however, whether ORS replaced RHF in these locations or if children were left untreated, and if these patterns were associated with health policy changes. METHODS: We used a Bayesian geostatistical model and data from household surveys to map the percentage of children with diarrhea that received (1) any ORS, (2) only RHF, or (3) no oral rehydration treatment between 2000 and 2018. This approach allowed examination of whether RHF was replaced with ORS before and after interventions, policies, and external events that may have impacted healthcare access. RESULTS: We found that RHF was replaced with ORS in most Sierra Leone districts, except those most impacted by the Ebola outbreak. In addition, RHF was replaced in northern but not in southern Mali, and RHF was not replaced anywhere in Senegal. In Senegal, there was no statistical evidence that a national policy promoting ORS use was associated with increases in coverage. In Sierra Leone, ORS coverage increased following a national policy change that abolished health costs for children. CONCLUSIONS: Children in parts of Mali and Senegal have been left behind during ORS scale-up. Improved messaging on effective diarrhea treatment and/or increased ORS access such as through reducing treatment costs may be needed to prevent child deaths in these areas.

Mapping male circumcision for HIV prevention efforts in sub-Saharan Africa.

BACKGROUND: HIV remains the largest cause of disease burden among men and women of reproductive age in sub-Saharan Africa. Voluntary medical male circumcision (VMMC) reduces the risk of female-to-male transmission of HIV by 50-60%. The World Health Organization (WHO) and Joint United Nations Programme on HIV/AIDS (UNAIDS) identified 14 priority countries for VMMC campaigns and set a coverage goal of 80% for men ages 15-49. From 2008 to 2017, over 18 million VMMCs were reported in priority countries. Nonetheless, relatively little is known about local variation in male circumcision (MC) prevalence. METHODS: We analyzed geo-located MC prevalence data from 109 household surveys using a Bayesian geostatistical modeling framework to estimate adult MC prevalence and the number of circumcised and uncircumcised men aged 15-49 in 38 countries in sub-Saharan Africa at a 5 × 5-km resolution and among first administrative level (typically provinces or states) and second administrative level (typically districts or counties) units. RESULTS: We found striking within-country and between-country variation in MC prevalence; most (12 of 14) priority countries had more than a twofold difference between their first administrative level units with the highest and lowest estimated prevalence in 2017. Although estimated national MC prevalence increased in all priority countries with the onset of VMMC campaigns, seven priority countries contained both subnational areas where estimated MC prevalence increased and areas where estimated MC prevalence decreased after the initiation of VMMC campaigns. In 2017, only three priority countries (Ethiopia, Kenya, and Tanzania) were likely to have reached the MC coverage target of 80% at the national level, and no priority country was likely to have reached this goal in all subnational areas. CONCLUSIONS: Despite MC prevalence increases in all priority countries since the onset of VMMC campaigns in 2008, MC prevalence remains below the 80% coverage target in most subnational areas and is highly variable. These mapped results provide an actionable tool for understanding local needs and informing VMMC interventions for maximum impact in the continued effort towards ending the HIV epidemic in sub-Saharan Africa.

Prediction of gestational age with symphysis-fundal height and estimated uterine volume in a pregnancy cohort in Sylhet, Bangladesh.

OBJECTIVE: To improve the accuracy of the prediction of gestational age (GA) before birth with the standardised measurement of symphysis-fundal height (SFH), estimation of uterine volume, and statistical modelling including maternal anthropometrics and other factors. DESIGN: Prospective pregnancy cohort study. SETTING: Rural communities in Sylhet, Bangladesh. PARTICIPANTS: 1516 women with singleton pregnancies with early pregnancy ultrasound dating (<20 weeks); 1486 completed follow-up. METHODS: SFH and abdominal girth were measured at subsequent antenatal care (ANC) visits by community health workers at 24 to 28, 32 to 36, and/or >37 weeks gestation. An estimated uterine volume (EUV) was calculated from these measures. Data on pregnancy characteristics and other maternal anthropometrics were also collected. PRIMARY OUTCOME MEASURE: GA at subsequent ANC visits, as defined by early ultrasound dating. RESULTS: 1486 (98%) women had at least one subsequent ANC visit, 1102 (74%) women had two subsequent ANC visits, and 748 (50%) had three visits. Using the common clinical practice of approximating the GA (in weeks) with the SFH measurement (cm), SFH systematically underestimated GA in late pregnancy (mean difference -4.4 weeks, 95% limits of agreement -12.5 to 3.7). For the classification of GA <28 weeks, SFH <26 cm had 85% sensitivity and 81% specificity; and for GA <34 weeks, SFH <29 cm had 83% sensitivity and 71% specificity. EUV had similar diagnostic accuracy. Despite rigorous statistical modelling of SFH, accounting for repeated longitudinal measurements and additional predictors, the best model without including a known last menstrual period predicted 95% of pregnancy dates within ±7.4 weeks of early ultrasound dating. CONCLUSIONS: We were unable to predict GA with a high degree of accuracy before birth using maternal anthropometric measures and other available maternal characteristics. Efforts to improve GA dating in low- and middle-income countries before birth should focus on increasing coverage and training of ultrasonography. TRIAL REGISTRATION NUMBER: NCT01572532.

Publisher Correction: Mapping exclusive breastfeeding in Africa between 2000 and 2017.

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

Mapping exclusive breastfeeding in Africa between 2000 and 2017.

Exclusive breastfeeding (EBF)-giving infants only breast-milk (and medications, oral rehydration salts and vitamins as needed) with no additional food or drink for their first six months of life-is one of the most effective strategies for preventing child mortality1-4. Despite these advantages, only 37% of infants under 6 months of age in Africa were exclusively breastfed in 20175, and the practice of EBF varies by population. Here, we present a fine-scale geospatial analysis of EBF prevalence and trends in 49 African countries from 2000-2017, providing policy-relevant administrative- and national-level estimates. Previous national-level analyses found that most countries will not meet the World Health Organization's Global Nutrition Target of 50% EBF prevalence by 20256. Our analyses show that even fewer will achieve this ambition in all subnational areas. Our estimates provide the ability to visualize subnational EBF variability and identify populations in need of additional breastfeeding support.

Development and evaluation of a mobile application for case management of small and sick newborns in Bangladesh.

BACKGROUND: In low-income settings, community health workers (CHWs) are frequently the first point of contact for newborns. Mobile technology may aid health workers in classifying illness and providing referral and management guidance for newborn care. This study evaluates the potential for mobile health technology to improve diagnosis and case management of newborns in Bangladesh. METHODS: A mobile application based on Bangladesh's Comprehensive Newborn Care Package national guidelines (mCNCP) was developed to aid CHWs in identifying and managing small and sick infants. After a 2-day training, CHWs assessed newborns at Sylhet Osmani Medical College Hospital and in the Projahnmo research site (Sylhet, Bangladesh) using either mCNCP or a comparable paper form (pCNCP), similar to standard IMCI-formatted paper forms. CHWs were randomized to conduct a block of ~ 6 newborn assessments starting with either mCNCP or pCNCP, then switched to the alternate method. Physicians using mCNCP served as gold standard assessors. CHW performance with mCNCP and pCNCP were compared using chi-squared tests of independence for equality of proportions, and logistic regressions clustered by CHW. RESULTS: Two hundred seven total CHW assessments were completed on 101 enrolled infants. mCNCP assessments were more often fully completed and completed faster than pCNCP assessments (100% vs 23.8%, p < 0.001; 17.5 vs 23.6 min; p < 0.001). mCNCP facilitated calculations of respiratory rate, temperature, and gestational age. CHWs using mCNCP were more likely to identify small newborns (Odds Ratio (OR): 20.8, Confidence Interval (CI): (7.1, 60.8), p < 0.001), and to correctly classify 7 out of 16 newborn conditions evaluated, including severe weight loss (OR: 13.1, CI: (4.6, 37.5), p < 0.001), poor movement (OR: 6.6, CI: (2.3, 19.3), p = 0.001), hypothermia (OR: 14.9, CI: (2.7, 82.2), p = 0.002), and feeding intolerance (OR: 2.1, CI: (1.3, 3.3), p = 0.003). CHWs with mCNCP were more likely to provide counseling as needed on 4 out of 7 case management recommendations evaluated, including kangaroo mother care. CONCLUSIONS: CHWs in rural Bangladesh with limited experience using tablets successfully used a mobile application for neonatal assessment after a two-day training. mCNCP may aid frontline health workers in Bangladesh to improve completion of neonatal assessment, classification of illnesses, and adherence to neonatal management guidelines.

Mapping HIV prevalence in sub-Saharan Africa between 2000 and 2017.

HIV/AIDS is a leading cause of disease burden in sub-Saharan Africa. Existing evidence has demonstrated that there is substantial local variation in the prevalence of HIV; however, subnational variation has not been investigated at a high spatial resolution across the continent. Here we explore within-country variation at a 5 × 5-km resolution in sub-Saharan Africa by estimating the prevalence of HIV among adults (aged 15-49 years) and the corresponding number of people living with HIV from 2000 to 2017. Our analysis reveals substantial within-country variation in the prevalence of HIV throughout sub-Saharan Africa and local differences in both the direction and rate of change in HIV prevalence between 2000 and 2017, highlighting the degree to which important local differences are masked when examining trends at the country level. These fine-scale estimates of HIV prevalence across space and time provide an important tool for precisely targeting the interventions that are necessary to bringing HIV infections under control in sub-Saharan Africa.

A Novel Icterometer for Hyperbilirubinemia Screening in Low-Resource Settings.

BACKGROUND: Severe neonatal hyperbilirubinemia (>20 mg/dL) affects ∼1 million infants annually. Improved jaundice screening in low-income countries is needed to prevent bilirubin encephalopathy and mortality. METHODS: The Bili-ruler is an icterometer for the assessment of neonatal jaundice that was designed by using advanced digital color processing. A total of 790 newborns were enrolled in a validation study at Brigham and Women's Hospital (Boston) and Sylhet Osmani Medical College Hospital (Sylhet, Bangladesh). Independent Bili-ruler measurements were made and compared with reference standard transcutaneous bilirubin (TcB) and total serum bilirubin (TSB) concentrations. RESULTS: Bili-ruler scores on the nose were correlated with TcB and TSB levels (r = 0.76 and 0.78, respectively). The Bili-ruler distinguished different clinical thresholds of hyperbilirubinemia, defined by TcB, with high sensitivity and specificity (score ≥3.5: 90.1% [95% confidence interval (CI): 84.8%-95.4%] and 85.9% [95% CI: 83.2%-88.6%], respectively, for TcB ≥13 mg/dL). The Bili-ruler also performed reasonably well compared to TSB (score ≥3.5: sensitivity 84.5% [95% CI: 79.1%-90.3%] and specificity 83.2% [95% CI: 76.1%-90.3%] for TSB ≥11 mg/dL). Areas under the receiver operating characteristic curve for identifying TcB ≥11, ≥13, and ≥15 were 0.92, 0.93, and 0.94, respectively, and 0.90, 0.87, and 0.86 for identifying TSB ≥11, ≥13, and ≥15. Interrater reliability was high; 97% of scores by independent readers fell within 1 score of one another (N = 88). CONCLUSIONS: The Bili-ruler is a low-cost, noninvasive tool with high diagnostic accuracy for neonatal jaundice screening. This device may be used to improve referrals from community or peripheral health centers to higher-level facilities with capacity for bilirubin testing and/or phototherapy.

Alpha Oscillations Modulate Preparatory Activity in Marmoset Area 8Ad.

Cognitive control often requires suppression of prepotent stimulus-driven responses in favor of less potent alternatives. Suppression of prepotent saccades has been shown to require proactive inhibition in the frontoparietal saccade network. Electrophysiological evidence in macaque monkeys has revealed neural correlates of such inhibition in this network; however, the interlaminar instantiation of inhibitory processes remains poorly understood because these areas lie deep within sulci in macaques, rendering them inaccessible to laminar recordings. Here, we addressed this gap by exploiting the mostly lissencephalic cortex of the common marmoset (Callithrix jacchus). We inserted linear electrode arrays into areas 8Ad-the putative marmoset frontal eye field-and the lateral intraparietal area of two male marmosets and recorded neural activity during performance of a task comprised of alternating blocks of trials requiring a saccade either toward a large, high-luminance stimulus or the inhibition of this prepotent response in favor of a saccade toward a small, low-luminance stimulus. We observed prominent task-dependent activity in both alpha/gamma bands of the LFP and discharge rates of single neurons in area 8Ad during a prestimulus task epoch in which the animals had been instructed which of these two tasks to perform but before peripheral stimulus onset. These data are consistent with a model in which rhythmic alpha-band activity in deeper layers inhibits spiking in upper layers to support proactive inhibitory saccade control.SIGNIFICANCE STATEMENT Failures to inhibit automatic saccadic responses are a hallmark of many neuropsychiatric disorders, but how this process is implemented across the cortical layers in the frontoparietal saccade network remains unknown because many of the areas are inaccessible to laminar recordings in macaques. Here, we investigated laminar neural activity in marmoset monkeys, which have a smooth cortex. Monkeys were required either to generate or inhibit a prepotent saccade response. In area 8Ad, the putative frontal eye field in marmosets, rhythmic alpha-band activity (9-14 Hz) was higher in deeper layers and spiking activity was lower in upper layers when the animals were instructed to suppress a saccade toward a peripheral stimulus. Reduced alpha power during task preparation may be the underlying common neural basis of a saccade suppression deficit.

Methods for chair restraint and training of the common marmoset on oculomotor tasks.

The oculomotor system is the most thoroughly understood sensorimotor system in the brain, due in large part to electrophysiological studies carried out in macaque monkeys trained to perform oculomotor tasks. A disadvantage of the macaque model is that many cortical oculomotor areas of interest lie within sulci, making high-density array and laminar recordings impractical. Many techniques of molecular biology developed in rodents, such as optogenetic manipulation of neuronal subtypes, are also limited in this species. The common marmoset ( Callithrix jacchus) possesses a smooth cortex, allowing easy access to frontoparietal oculomotor areas, and may bridge the gap between systems neuroscience in macaques and molecular techniques. Techniques for restraint, training, and neural recording in these animals have been well developed in auditory neuroscience. Those for oculomotor neuroscience, however, remain at a relatively early stage. In this article we provide details of a custom-designed restraint chair for marmosets, a combination head restraint/recording chamber allowing access to cortical oculomotor areas and providing stability suitable for eye movement and neural recordings, as well as a training protocol for oculomotor tasks. We additionally report the results of a psychophysical study in marmosets trained to perform a saccade task using these methods, showing that, as in rhesus and humans, marmosets exhibit a "gap effect," a decrease in reaction time when the fixation stimulus is removed before the onset of a visual saccade target. These results are the first evidence of this effect in marmosets and support the common marmoset model for neurophysiological investigations of oculomotor control. NEW & NOTEWORTHY The ability to carry out neuronal recordings in behaving primates has provided a wealth of information regarding the neural circuits underlying the control of eye movements. Such studies require restraint of the animal within a primate chair, head fixation, methods of acclimating the animals to this restraint, and the use of operant conditioning methods for training on oculomotor tasks. In contrast to the macaque model, relatively few studies have reported in detail methods for use in the common marmoset. In this report we detail custom-designed equipment and methods by which we have used to successfully train head-restrained marmosets to perform basic oculomotor tasks.