MKL1 deficiency results in a severe neutrophil motility defect due to impaired actin polymerization.

Megakaryoblastic leukemia 1 (MKL1) promotes the regulation of essential cell processes, including actin cytoskeletal dynamics, by coactivating serum response factor. Recently, the first human with MKL1 deficiency, leading to a novel primary immunodeficiency, was identified. We report a second family with 2 siblings with a homozygous frameshift mutation in MKL1. The index case died as an infant from progressive and severe pneumonia caused by Pseudomonas aeruginosa and poor wound healing. The younger sibling was preemptively transplanted shortly after birth. The immunodeficiency was marked by a pronounced actin polymerization defect and a strongly reduced motility and chemotactic response by MKL1-deficient neutrophils. In addition to the lack of MKL1, subsequent proteomic and transcriptomic analyses of patient neutrophils revealed actin and several actin-related proteins to be downregulated, confirming a role for MKL1 as a transcriptional coregulator. Degranulation was enhanced upon suboptimal neutrophil activation, whereas production of reactive oxygen species was normal. Neutrophil adhesion was intact but without proper spreading. The latter could explain the observed failure in firm adherence and transendothelial migration under flow conditions. No apparent defect in phagocytosis or bacterial killing was found. Also, monocyte-derived macrophages showed intact phagocytosis, and lymphocyte counts and proliferative capacity were normal. Nonhematopoietic primary fibroblasts demonstrated defective differentiation into myofibroblasts but normal migration and F-actin content, most likely as a result of compensatory mechanisms of MKL2, which is not expressed in neutrophils. Our findings extend current insight into the severe immune dysfunction in MKL1 deficiency, with cytoskeletal dysfunction and defective extravasation of neutrophils as the most prominent features.

Recently Registered Midazolam Doses for Preterm Neonates Do Not Lead to Equal Exposure: A Population Pharmacokinetic Model.

Although midazolam is a frequently used sedative in neonatal intensive care units, its use in preterm neonates has been off-label. Recently, a new dosing advice for midazolam for sedation on intensive care units has been included in the label (0.03 mg/[kg·h] for preterm neonates <32 weeks and 0.06 mg/[kg·h] for neonates >32 weeks). Concentration-time data of a prospective multicenter study (29 patients, median gestational age 26.7 [range 24.0-31.1 weeks]) were combined with previously published data (26 patients, median gestational age 28.1 [range 26.3-33.6 weeks]), and a population pharmacokinetic model describing the maturation of midazolam pharmacokinetics was developed in NONMEM 7.3. Clearance was 73.7 mL/h for a neonate weighing 1.1 kg and changed nonlinearly with body weight (exponent 1.69). Volume of distribution increased linearly with body weight and was 1.03 L for a neonate weighing 1.1 kg. Simulations of the newly registered dosing show considerable differences in steady-state concentrations in preterm neonates. To reach similar steady-state concentrations of 400 µg/mL (±100 µg/mL), a dose of 0.03 mg/(kg·h) is adequate for neonates ≥1 kg and ≤2 kg but would have to be reduced to 0.02 mg/(kg·h) (-33%) in neonates <1 kg and increased to 0.04 mg/(kg·h) (+33%) in neonates weighing >2 kg and ≤2.5 kg. The impact of the observed differences in exposure is difficult to assess because no target concentrations have yet been defined for midazolam, but the current analysis shows that one should be cautious in giving dosage advice based on historical data with a lack of reliable pharmacokinetic and effect data.

AGORA, a data- and biobank for birth defects and childhood cancer.

BACKGROUND: Research regarding the etiology of birth defects and childhood cancer is essential to develop preventive measures, but often requires large study populations. Therefore, we established the AGORA data- and biobank in the Netherlands. In this study, we describe its rationale, design, and ongoing data collection. METHODS: Children diagnosed with and/or treated for a structural birth defect or childhood cancer and their parents are invited to participate in the AGORA data- and biobank. Controls are recruited through random sampling from municipal registries. The parents receive questionnaires about demographics, family and pregnancy history, health status, prescribed medication, lifestyle, and occupational exposures before and during the index pregnancy. In addition, blood or saliva is collected from children and parents, while medical records are reviewed for diagnostic information. RESULTS: So far, we have collected data from over 6,860 families (3,747 birth defects, 905 childhood cancers, and 2,208 controls). The types of birth defects vary widely and comprise malformations of the digestive, respiratory, and urogenital tracts as well as facial, cardiovascular, kidney, skeletal, and central nervous system anomalies. The most frequently occurring childhood cancer types are acute lymphatic leukemia, Hodgkin and non-Hodgkin lymphoma, Wilms' tumor, and brain and spinal cord tumors. Our genetic and/or epidemiologic studies have been focused on hypospadias, anorectal malformations, congenital anomalies of the kidney and urinary tract (CAKUT), and orofacial clefts. CONCLUSION: The large AGORA data- and biobank offers great opportunities for investigating genetic and nongenetic risk factors for disorders in children and is open to collaborative initiatives. Birth Defects Research (Part A) 106:675-684, 2016. © 2016 Wiley Periodicals, Inc.

Neonatal glucocorticoid treatment: long-term effects on the hypothalamus-pituitary-adrenal axis, immune system, and problem behavior in 14-17 year old adolescents.

Neonatal glucocorticoid (GC) treatment is used to prevent bronchopulmonary dysplasia (BPD) in prematurely born babies. In the 1990s, treatment regimens with relatively high doses of dexamethasone (DEX) were common. As an alternative, hydrocortisone (HC) was used. Earlier, we compared long-term effects of both GCs in children aged 7-10 and detected adverse effects of neonatal DEX treatment, but not of HC, on a range of outcomes. The aim of the current cohort study was to investigate whether long-term effects of neonatal DEX were maintained and whether effects of HC remained absent at adolescent age (14-17years). We compared 71 DEX-treated and 67 HC-treated adolescents. In addition, 71 adolescents who were not neonatally treated with GCs participated. All were born <32weeks of gestation. DEX-treated girls showed increased adrenocorticotropic hormone (ACTH) and cortisol responses in the Trier Social Stress Test. The cortisol awakening response was lower in HC-treated participants compared to untreated participants. Negative feedback function of the HPA-axis in the dexamethasone suppression test did not differ between groups. In contrast to our observations at the age of 7-10years, we did not observe group differences in mitogen-induced cytokine production at the age of 14-17years. DEX-treated girls showed more social problems and anxious/depressed behavior than HC-treated girls. Untreated girls showed more problem behavior as well. In conclusion, our results suggest that, especially in girls, neonatal DEX has a programming effect on the HPA-axis and on the ability to adjust to the environment. The loss of group differences on immune system measures indicate that potentially negative effects detected at a younger age subsided.

Early life intervention with glucocorticoids has negative effects on motor development and neuropsychological function in 14-17 year-old adolescents.

OBJECTIVE: To reduce the risk of bronchopulmonary dysplasia, preterm infants receive neonatal treatment with glucocorticoids, mostly dexamethasone (DEX). Compared to current protocols, treatment regimens of the late 1980s - early 1990s prescribed high doses of DEX for an extensive period up to 6 weeks. Worldwide at least one million children have been treated with this dose regimen. Previous studies have shown adverse effects of neonatal treatment with the glucocorticoid dexamethasone (DEX) on outcome in children aged 7-10 years. On the other hand, treatment with another glucocorticoid, hydrocortisone (HC), was not related to adverse effects in childhood. In the current study we determined the consequences of early life intervention with DEX or HC in adolescents (age 14-17 years). Besides motor function and intellectual capacities, we also examined fundamental neuropsychological functions which have so far received little attention. METHODS: In an observational cohort study we compared 14-17 year-old adolescents who received DEX (.5 mg/kg/day tapering off to .1 mg/kg/day over 21 days, n=63), or HC (5 mg/kg/day tapering off to 1 mg/kg/day over 22 days, n=67), or did not receive neonatal glucocorticoids (untreated, n=71) after premature birth (gestational age<32 weeks). Because gestational age was shorter and duration of ventilation was longer in the DEX-treated group, all analyses were corrected for these potential confounders. Motor function, IQ, and neuropsychological functions were assessed. RESULTS: DEX-treated group participants scored lower on gross motor skill tasks than their HC-treated and untreated counterparts. A higher proportion of DEX-treated girls needed special education compared to the other groups. DEX-treated adolescents performed poorer on neuropsychological tasks measuring alertness, visuomotor coordination, and emotion recognition. The HC-treated group did not differ from the untreated group. CONCLUSIONS: Even after 14-17 years, neonatal treatment with .5 mg/kg/day DEX was associated with adverse effects on motor function, school level, and neuropsychological functions, whereas treatment with the clinically equally effective dose of 5 mg/kg/day HC was not. Potential physiological mechanisms underlying the differences in dexamethasone and hydrocortisone effects are discussed. Based on the current findings, we recommend early identification of neuropsychological deficits after DEX treatment in order to specify extra educational needs.