Early Fetal Brain Development Research Articles

Cerebral palsy in children: A clinical practice review

Cerebral palsy is a disorder characterized by abnormal tone, posture, and movement. In clinical practice, it is often useful to approach cerebral palsy based on the predominant motor system findings – spastic hemiplegia, spastic diplegia, spastic quadriplegia, extrapyramidal or dyskinetic, and ataxic. The prevalence of cerebral palsy is between 1.5 and 3 per 1,000 live births with higher percentage of cases in low to middle income countries and geographic regions. Pre-term birth and low birthweight are recognized as the most frequent risk factors for cerebral palsy; other risk factors include hypoxic-ischemic encephalopathy, maternal infections, and multiple gestation. In most cases of cerebral palsy, the initial injury to the brain occurs during early fetal brain development. Intracerebral hemorrhage and periventricular leukomalacia are the main pathologic findings found in preterm infants who develop spastic cerebral palsy. The diagnosis of cerebral palsy is primarily based on clinical findings. Early recognition of infants at risk for cerebral palsy as well as those with cerebral palsy is possible based on a combination of clinical history, use of standardized neuromotor assessment and findings on magnetic resonance imaging; however, in clinical practice, cerebral palsy is more reliably diagnosed by 2 years of age. Magnetic resonance imaging scan is indicated to delineate the extent of brain lesions and to identify congenital brain malformations. Genetic testing and tests for inborn errors of metabolism are indicated to identify specific disorders, especially treatable disorders. Because cerebral palsy is associated with multiple associated and secondary medical conditions, its management requires a sustained and consistent collaboration among multiple disciplines and specialties. With appropriate support, most children with cerebral palsy grow up to be adults with good functional abilities.

In Vitro and In Vivo Supplementation with Curcumin Promotes Hippocampal Neuronal Synapses Development in Rats by Inhibiting GSK-3β and Activating β-catenin.

The human fetal thyroid gland is not capable of producing thyroid hormones independently until 20 weeks of gestation, and if maternal thyroid hormone synthesis is inadequate in early pregnancy, fetal brain and nerve development may be affected by maternal hypothyroidism. Curcumin, which is isolated from turmeric (Curcuma longa), has been shown to be effective in repairing neurological disorders and is effective in relieving nerve damage when consumed over a long period of time. In this experiment, we investigated the effect of curcumin supplementation on synaptic development of rat hippocampal neurons. A cell model of oxidative damage and a young rat model of hypothyroidism were constructed, and model cells and rats were treated with triiodothyronine (T3), tetraiodothyronine (T4), and curcumin, respectively. Damage of nerve cells and animal brain tissues was examined, and the effect of curcumin in alleviating the blocked neurodevelopment was investigated. Further modulation of GSK-3β/β-catenin was performed to investigate the mechanism of action of curcumin. Ultimately, we found that T3-, T4-, and curcumin-treated model cells and young rats had increased numbers of synapses and good neurodevelopment. At the same time, we found that curcumin inhibited the production of GSK-3β and Axin to activate β-catenin. The inhibition of β-catenin weakened the therapeutic effect of curcumin, and the differences between the indicators and the model group disappeared. Both cellular and animal experiments supported that curcumin effectively alleviated the oxidative cell damage caused by thyroxine deficiency and activated the synaptogenic ability of nerve synapses by inhibiting GSK-3β and protecting β-catenin activity.

Large-scale organoid study suggests effects of trisomy 21 on early fetal neurodevelopment are more subtle than variability between isogenic lines and experiments.

This study examines cortical organoids generated from a panel of isogenic trisomic and disomic iPSC lines (subclones) as a model of early fetal brain development in Down syndrome (DS). An initial experiment comparing organoids from one trisomic and one disomic line showed many genome-wide transcriptomic differences and modest differences in cell-type proportions, suggesting there may be a neurodevelopmental phenotype that is due to trisomy of chr21. To better control for multiple sources of variation, we undertook a highly robust study of ∼1,200 organoids using an expanded panel of six all-isogenic lines, three disomic, and three trisomic. The power of this experimental design was indicated by strong detection of the ∼1.5-fold difference in chr21 genes. However, the numerous expression differences in non-chr21 genes seen in the smaller experiment fell away, and the differences in cell-type representation between lines did not correlate with trisomy 21. Results suggest that the initial smaller experiment picked up differences between small organoid samples and individual isogenic lines, which "averaged out" in the larger panel of isogenic lines. Our results indicate that even when organoid and batch variability are better controlled for, variation between isogenic cell lines (even subclones) may obscure, or be conflated with, subtle neurodevelopmental phenotypes that may be present in ∼2nd trimester DS brain development. Interestingly, despite this variability between organoid batches and lines, and the "fetal stage" of these organoids, an increase in secreted Aβ40 peptide levels-an Alzheimer-related cellular phenotype-was more strongly associated with trisomy 21 status than were neurodevelopmental shifts in cell-type composition.

Alzheimer's disease like neuropathology in Down syndrome cortical organoids.

Introduction: Down syndrome (DS) is a genetic disorder with an extra copy of chromosome 21 and DS remains one of the most common causes of intellectual disabilities in humans. All DS patients have Alzheimer's disease (AD)-like neuropathological changes including accumulation of plaques and tangles by their 40s, much earlier than the onset of such neuropathological changes in AD patients. Due to the lack of human samples and appropriate techniques, our understanding of DS neuropathology during brain development or before the clinical onset of the disease remains largely unexplored at the cellular and molecular levels. Methods: We used induced pluripotent stem cell (iPSC) and iPSC-derived 3D cortical organoids to model Alzheimer's disease in Down syndrome and explore the earliest cellular and molecular changes during DS fetal brain development. Results: We report that DS iPSCs have a decreased growth rate than control iPSCs due to a decreased cell proliferation. DS iPSC-derived cortical organoids have a much higher immunoreactivity of amyloid beta (Aß) antibodies and a significantly higher amount of amyloid plaques than control organoids. Although Elisa results did not detect a difference of Aß40 and Aß42 level between the two groups, the ratio of Aß42/Aß40 in the detergent-insoluble fraction of DS organoids was significantly higher than control organoids. Furthermore, an increased Tau phosphorylation (pTau S396) in DS organoids was confirmed by immunostaining and Western blot. Elisa data demonstrated that the ratio of insoluble Tau/total Tau in DS organoids was significantly higher than control organoids. Conclusion: DS iPSC-derived cortical organoids mimic AD-like pathophysiologyical phenotype in vitro, including abnormal Aß and insoluble Tau accumulation. The molecular neuropathologic signature of AD is present in DS much earlier than predicted, even in early fetal brain development, illustrating the notion that brain organoids maybe a good model to study early neurodegenerative conditions.

Microglia homeostasis mediated by epigenetic ARID1A regulates neural progenitor cells response and leads to autism-like behaviors.

Microglia are resident macrophages of the central nervous system that selectively emerge in embryonic cortical proliferative zones and regulate neurogenesis by altering molecular and phenotypic states. Despite their important roles in inflammatory phagocytosis and neurodegenerative diseases, microglial homeostasis during early brain development has not been fully elucidated. Here, we demonstrate a notable interplay between microglial homeostasis and neural progenitor cell signal transduction during embryonic neurogenesis. ARID1A, an epigenetic subunit of the SWI/SNF chromatin-remodeling complex, disrupts genome-wide H3K9me3 occupancy in microglia and changes the epigenetic chromatin landscape of regulatory elements that influence the switching of microglial states. Perturbation of microglial homeostasis impairs the release of PRG3, which regulates neural progenitor cell self-renewal and differentiation during embryonic development. Furthermore, the loss of microglia-driven PRG3 alters the downstream cascade of the Wnt/β-catenin signaling pathway through its interaction with the neural progenitor receptor LRP6, which leads to misplaced regulation in neuronal development and causes autism-like behaviors at later stages. Thus, during early fetal brain development, microglia progress toward a more homeostatic competent phenotype, which might render neural progenitor cells respond to environmental cross-talk perturbations.

Epigenomic programming in early fetal brain development.

Aim:To provide a comprehensive understanding of gene regulatory networks in the developing human brain and a foundation for interpreting pathogenic deregulation.Materials & methods:We generated reference epigenomes and transcriptomes of dissected brain regions and primary neural progenitor cells (NPCs) derived from cortical and ganglionic eminence tissues of four normal human fetuses.Results:Integration of these data across developmental stages revealed a directional increase in active regulatory states, transcription factor activities and gene transcription with developmental stage. Consistent with differences in their biology, NPCs derived from cortical and ganglionic eminence regions contained common, region specific, and gestational week specific regulatory states.Conclusion:We provide a high-resolution regulatory network for NPCs from different brain regions as a comprehensive reference for future studies.

O11.1. MULTIPLE GENOMIC MEASURES OF SCHIZOPHRENIA RISK ARE RELATED TO CORTICAL THICKNESS IN TYPICALLY DEVELOPING YOUTH AND YOUNG ADULTS

BackgroundThe incidence of psychotic disorders increases in adolescence and young adulthood. Transition to a psychotic disorder is associated with atypical development of brain structures, specifically protracted developmental course. It is unknown how polygenic risk for schizophrenia and gene expression profiles of schizophrenia risk genes affect typical brain development. The goal of the current study is to examine relationships multiple genomic measures associated with schizophrenia risk and structural neuroimaging measures thickness in typically developing youth.MethodsWe combined structural neuroimaging and genetic data from three different cohorts of typically developing youth (N=994, 5–30 years old): the Philadelphia Neurodevelopmental Cohort, Pediatric Imaging Neurocognition and Genetics Study, and a locally collected sample at the University of Pittsburgh. All youth were free from psychiatric disorders and not taking psychiatric medications. We used Freesurfer to process the T1-weighted structural scans and calculate subcortical volumes, cortical thickness, and surface area measurements. After regressing out study, sex, ancestry eigenvectors, and grey matter signal-to-noise ratio, we ran principal components analysis on all neuroimaging measures (N=156). We calculated a schizophrenia polygenic risk score using genome-wide summary statistics from the Psychiatric Genome Consortium. Using a generalized linear model, each of the top five principal components was evaluated in relation to the risk score. We then used a computational method, Predixcan, to calculate expected gene expression profiles from the genotype data. We selected 125 genes that were associated with schizophrenia in a previous case-control comparison. Elastic net regression was used to determine significant associations between individual gene expression and the principal components.ResultsSchizophrenia polygenic risk was statistically associated with the 5th principal component (b=-0.10, p=0.001), which consisted of contributions from multiple measures of cortical thickness. Reduced cortical thickness in frontal and temporal regions was associated with increased genetic liability for schizophrenia. Increased cortical thickness in sensory-motor areas was associated with higher schizophrenia polygenic risk scores. This relationship remained when age was included as a predictor of interest and there were no statistically significant interactions between schizophrenia polygenic risk and age. Sixteen unique gene expression profiles were also associated with this principal component, significantly increasing the proportion of variance explained in this measure (from ~1% with the schizophrenia polygenic risk only to ~6% when including the additional gene expression measures). Many of the genes significantly associated with this principal component have important roles during early fetal brain development, including neuronal migration (e.g., SDCCAG8) and DNA repair (e.g., MLH1).DiscussionThese results suggest that that genetic risk for schizophrenia has a consistent influence on subtle, individual differences in a distinct spatial pattern of cortical thickness across typical development. This spatial pattern of cortical thickness is also associated with schizophrenia risk genes that have important functions during early brain development. Taken together, these findings suggest that increased genetic risk for schizophrenia is related to early subtle alterations during early brain development, setting up individuals with higher risk profiles to have a small biological vulnerability for later developing the illness.

БОЛАЛАР ЦЕРЕБРАЛ ФАЛАЖЛИГИ: КЛИНИК ТАҲЛИЛ

Cerebral palsy (CP) is a disorder characterized by abnormal tone, posture and movement. The incidence of CP is 2–4 per 1,000 live births in the world. Prematurityand low birth weight are important risk factors for CP; however, multiple other factors have been associated with an increased risk for CP, including maternal infections and diseases, and abnormal birth process. In most cases of CP the initial injury to the brain occurs during early fetal brain development, later a brain area that is injured cannot function properly in the future. CP is classified clinically based on the predominant motor syndrome—spastic hemiplegia, spastic diplegia, spastic quadriplegia, ataxic and dyskinetic cerebral palsies. The diagnosis of CPis based on a combination of clinical history, use of standardized neuromotor assessment and findings on magnetic resonance imaging (MRI). If there is a suspicionof genetic or inborn metabolic disorders, screening tests should be provided additionally. Because CP is associated with multiple associated and secondary medical conditions, its management requires a multidisciplinary team approach

Cerebral palsy in children: a clinical overview.

Cerebral palsy (CP) is a disorder characterized by abnormal tone, posture and movement and clinically classified based on the predominant motor syndrome—spastic hemiplegia, spastic diplegia, spastic quadriplegia, and extrapyramidal or dyskinetic. The incidence of CP is 2–3 per 1,000 live births. Prematurity and low birthweight are important risk factors for CP; however, multiple other factors have been associated with an increased risk for CP, including maternal infections, and multiple gestation. In most cases of CP the initial injury to the brain occurs during early fetal brain development; intracerebral hemorrhage and periventricular leukomalacia are the main pathologic findings found in preterm infants who develop CP. The diagnosis of CP is primarily based on clinical findings. Early diagnosis is possible based on a combination of clinical history, use of standardized neuromotor assessment and findings on magnetic resonance imaging (MRI); however, in most clinical settings CP is more reliably recognized by 2 years of age. MRI scan is indicated to delineate the extent of brain lesions and to identify congenital brain malformations. Genetic tests and tests for inborn errors of metabolism are indicated based on clinical findings to identify specific disorders. Because CP is associated with multiple associated and secondary medical conditions, its management requires a multidisciplinary team approach. Most children with CP grow up to be productive adults.

Fetal de novo mutations and preterm birth.

Preterm birth (PTB) affects ~12% of pregnancies in the US. Despite its high mortality and morbidity, the molecular etiology underlying PTB has been unclear. Numerous studies have been devoted to identifying genetic factors in maternal and fetal genomes, but so far few genomic loci have been associated with PTB. By analyzing whole-genome sequencing data from 816 trio families, for the first time, we observed the role of fetal de novo mutations in PTB. We observed a significant increase in de novo mutation burden in PTB fetal genomes. Our genomic analyses further revealed that affected genes by PTB de novo mutations were dosage sensitive, intolerant to genomic deletions, and their mouse orthologs were likely developmentally essential. These genes were significantly involved in early fetal brain development, which was further supported by our analysis of copy number variants identified from an independent PTB cohort. Our study indicates a new mechanism in PTB occurrence independently contributed from fetal genomes, and thus opens a new avenue for future PTB research.

MECHANISMS IN ENDOCRINOLOGY: Neurodevelopmental disorders in children born to mothers with thyroid dysfunction: evidence of fetal programming?

Fetal programming is a long-standing, but still evolving, concept that links exposures during pregnancy to the later development of disease in the offspring. A fetal programming effect has been considered within different endocrine axes and in relation to different maternal endocrine diseases. In this critical review, we describe and discuss the hypothesis of fetal programming by maternal thyroid dysfunction in the context of fetal brain development and neurodevelopmental disorders in the offspring. Thyroid hormones are important regulators of early brain development, and evidence from experimental and observational human studies have demonstrated structural and functional abnormalities in the brain caused by the lack or excess of thyroid hormone during fetal brain development. The hypothesis that such abnormalities introduced during early fetal brain development increase susceptibility for the later onset of neurodevelopmental disorders in the offspring is biologically plausible. However, epidemiological studies on the association between maternal thyroid dysfunction and long-term child outcomes are observational in design, and are challenged by important methodological aspects.

Traversing barriers – How thyroid hormones pass placental, blood-brain and blood-cerebrospinal fluid barriers

Thyroid hormone is essential for normal human fetal growth and brain development. As the fetal thyroid does not secrete thyroid hormones until about 18 weeks gestation, early fetal brain development depends on passage of maternal hormone across the placenta into the fetal circulation. To reach the fetal brain, maternally derived and endogenously produced thyroid hormone has to cross the blood-brain and blood-cerebrospinal fluid barriers. In this review we will discuss the complex biological barriers (involving membrane transporters, enzymes and distributor proteins) that must be overcome to ensure that the developing human brain has adequate exposure to thyroid hormone.

Early onset of inflammation during ontogeny of bipolar disorder: the NLRP2 inflammasome gene distinctly differentiates between patients and healthy controls in the transition between iPS cell and neural stem cell stages

Neuro-inflammation and neuronal communication are considered as mis-regulated processes in the aetiology and pathology of bipolar disorder (BD). Which and when specific signal pathways become abnormal during the ontogeny of bipolar disorder patients is unknown. To address this question, we applied induced pluripotent stem cell (iPSC) technology followed by cortical neural differentiation on adipocyte-derived cells from BD type I patients (with psychotic episodes in psychiatric history) and healthy volunteers (controls). RNA sequencing in iPSC and cortical neural stem cell (NSC) lines were used to examine alterations between the transcriptomes from BD I and control samples during transition from the pluripotent stage towards the neural developmental stage. At the iPSC stage, the most highly significant differentially expressed gene (DEG) was the NLRP2 inflammasome (P=2.66 × 10−10). Also among 42 DEGs at the NSC stage, NLRP2 showed the strongest statistical significance (P=3.07 × 10−19). In addition, we have also identified several cytoskeleton-associated genes as DEGs from the NSC stage, such as TMP2, TAGLN and ACTA2; the former two genes are recognised for the first time to be associated with BD. Our results also suggest that iPSC-derived BD-cortical NSCs carry several abnormalities in dopamine and GABA receptor canonical pathways, underlining that our in vitro BD model reflects pathology in the central nervous system. This would indicate that mis-regulated gene expression of inflammatory, neurotransmitter and cytoskeletal signalling occurs during early fetal brain development of BD I patients.

Comparative human and rat neurospheres reveal species differences in chemical effects on neurodevelopmental key events.

The developing brain is highly vulnerable to the adverse effects of chemicals, resulting in neurodevelopmental disorders in humans. Currently, animal experiments in the rat are the gold standard for developmental neurotoxicity (DNT) testing; however, these guideline studies are insufficient in terms of animal use, time and costs and bear the issue of species extrapolation. Therefore, the necessity for alternative methods that predict DNT of chemicals faster, cheaper and with a high predictivity for humans is internationally agreed on. In this respect, we developed an in vitro model for DNT key event screening, which is based on primary human and rat neural progenitor cells grown as neurospheres. They are able to mimic basic processes of early fetal brain development and enable an investigation of species differences between humans and rodents in corresponding cellular models. The goal of this study was to investigate to what extent human and rat neurospheres were able to correctly predict the DNT potential of a well-characterized training set of nine chemicals by investigating effects on progenitor cell proliferation, migration and neuronal differentiation in parallel to cell viability, and to compare these chemical responses between human and rat neurospheres. We demonstrate that (1) by correlating these human and rat in vitro results to existing in vivo data, human and rat neurospheres classified most compounds correctly and thus may serve as a valuable component of a modular DNT testing strategy and (2) human and rat neurospheres differed in their sensitivity to most chemicals, reflecting toxicodynamic species differences of chemicals.

Iodine Deficiency in Egyptian Autistic Children and Their Mothers: relation to Disease Severity

Introduction and Objectives Because autism may be a disease of early fetal brain development, maternal hypothyroxinemia (HT) in early pregnancy secondary to iodine deficiency (ID) may be related to etiology of autism. Aims to assess the iodine nutritional status in Egyptian autistic children and their mothers and its relationship with disease characteristics. Methods Fifty autistic children and their mothers were studied in comparison to 50 controls. All subjects were subjected to clinical evaluation, measurement of urinary iodine (UI), free triiodothyronine (fT3), free tetraiodothyronine (fT4) and thyroid-stimulating hormone (TSH) along with measurement of thyroid volume (TV). In addition, electroencephalography (EEG) and intelligence quotient (IQ) assessment were done for all autistic children. Results Of autistic children and their mothers, 54%and 58%, respectively, were iodine deficient. None of the control children or their mothers was iodine deficient. UI was lower among autistic patients (p Conclusions ID is prevalent in Egyptian autistic children and their mothers and was inversely related to disease severity and could be related to its etiology.

Elevated fetal steroidogenic activity in autism

Autism affects males more than females, giving rise to the idea that the influence of steroid hormones on early fetal brain development may be one important early biological risk factor. Utilizing the Danish Historic Birth Cohort and Danish Psychiatric Central Register, we identified all amniotic fluid samples of males born between 1993 and 1999 who later received ICD-10 (International Classification of Diseases, 10th Revision) diagnoses of autism, Asperger syndrome or PDD-NOS (pervasive developmental disorder not otherwise specified) (n=128) compared with matched typically developing controls. Concentration levels of Δ4 sex steroids (progesterone, 17α-hydroxy-progesterone, androstenedione and testosterone) and cortisol were measured with liquid chromatography tandem mass spectrometry. All hormones were positively associated with each other and principal component analysis confirmed that one generalized latent steroidogenic factor was driving much of the variation in the data. The autism group showed elevations across all hormones on this latent generalized steroidogenic factor (Cohen's d=0.37, P=0.0009) and this elevation was uniform across ICD-10 diagnostic label. These results provide the first direct evidence of elevated fetal steroidogenic activity in autism. Such elevations may be important as epigenetic fetal programming mechanisms and may interact with other important pathophysiological factors in autism.

Iodine Deficiency in Egyptian Autistic Children and Their Mothers: Relation to Disease Severity

Because autism may be a disease of early fetal brain development, maternal hypothyroxinemia (HT) in early pregnancy secondary to iodine deficiency (ID) may be related to etiology of autism. The aim of the study was to assess the iodine nutritional status in Egyptian autistic children and their mothers and its relationship with disease characteristics. Fifty autistic children and their mothers were studied in comparison to 50 controls. All subjects were subjected to clinical evaluation, measurement of urinary iodine (UI), free triiodothyronine (fT3), free tetraiodothyronine (fT4) and thyroid-stimulating hormone (TSH) along with measurement of thyroid volume (TV). In addition, electroencephalography (EEG) and intelligence quotient (IQ) assessment were done for all autistic children. Of autistic children and their mothers, 54% and 58%, respectively, were iodine deficient. None of the control children or their mothers was iodine deficient. UI was lower among autistic patients (p <0.001) and their mothers (p <0.001). Childhood Autism Rating Scale (CARS) score correlated negatively with UI (r = -0.94, p <0.001). Positive correlations were detected between autistic patients and their mothers regarding UI (r = 0.88, p <0.001), fT3 (r = 0.79, p = 0.03), fT4 (r = 0.91, p <0.001) and TSH (r = 0.69, p = 0.04). Autism had a significant risk for association with each of low UI (OR: 9.5, 95% CI: 2.15-33.8, p = 0.02) and intake of noniodized salt (OR: 6.82, 95% CI = 1.36-34.27, p = 0.031). ID is prevalent in Egyptian autistic children and their mothers and was inversely related to disease severity and could be related to its etiology.

Neuroprotective peptide ADNF-9 in fetal brain of C57BL/6 mice exposed prenatally to alcohol

BackgroundA derived peptide from activity-dependent neurotrophic factor (ADNF-9) has been shown to be neuroprotective in the fetal alcohol exposure model. We investigated the neuroprotective effects of ADNF-9 against alcohol-induced apoptosis using TUNEL staining. We further characterize in this study the proteomic architecture underlying the role of ADNF-9 against ethanol teratogenesis during early fetal brain development using liquid chromatography in conjunction with tandem mass spectrometry (LC-MS/MS).MethodsPregnant C57BL/6 mice were exposed from embryonic days 7-13 (E7-E13) to a 25% ethanol-derived calorie [25% EDC, Alcohol (ALC)] diet, a 25% EDC diet simultaneously administered i.p. ADNF-9 (ALC/ADNF-9), or a pair-fed (PF) liquid diet. At E13, fetal brains were collected from 5 dams from each group, weighed, and frozen for LC-MS/MS procedure. Other fetal brains were fixed for TUNEL staining.ResultsAdministration of ADNF-9 prevented alcohol-induced reduction in fetal brain weight and alcohol-induced increases in cell death. Moreover, individual fetal brains were analyzed by LC-MS/MS. Statistical differences in the amounts of proteins between the ALC and ALC/ADNF-9 groups resulted in a distinct data-clustering. Significant upregulation of several important proteins involved in brain development were found in the ALC/ADNF-9 group as compared to the ALC group.ConclusionThese findings provide information on potential mechanisms underlying the neuroprotective effects of ADNF-9 in the fetal alcohol exposure model.

Spatiotemporal Distribution of PAX6 and MEIS2 Expression and Total Cell Numbers in the Ganglionic Eminence in the Early Developing Human Forebrain

The development of the human neocortex is a complex and highly regulated process involving a time-related expression of many transcription factors including the homeobox genes Pax6 and Meis2. During early development, Pax6 is expressed in nuclei of radial glia cells in the neocortical proliferative zones and controls the differentiation and neurogenetic fate of these cells in the dorsal telencephalon in rodents. Animal studies on the Meis2 gene have revealed expression in the developing telencephalon and Meis2 is known to regulate the expression of Pax6 in the eye and pancreas. Because of this functional relation between Pax6 and Meis2, we studied the spatial and temporal expression of PAX6, and MEIS2 using a developmental series of human fetal brains at 7–19 postconceptional weeks with emphasis on the forebrain to investigate whether the two genes are expressed in the same regions and zones in the same time window. We demonstrate by in situ hybridization and immunohistochemistry that the two homeobox genes are expressed during early fetal brain development in humans. PAX6 mRNA and protein were located in the proliferative zones of the neocortex and in single cells in the cortical preplate at 7 fetal weeks and in the developing cortical plate from 8 or 9 to 19 fetal weeks. The expression of PAX6 expanded into the ganglionic eminence just prior to the stage at which a stereological estimation showed an exponential rise in total cell number in this area. The MEIS2 gene was also present in the proliferative zones of the human fetal neocortex and a higher expression of MEIS2 than PAX6 was observed in these areas at 9 fetal weeks. Further, MEIS2 was expressed at a very high level in the developing ganglionic eminence and at a more moderate level in the cortical plate.

Therapeutic Drug Monitoring During Pregnancy and Lactation: Thyroid Function Assessment in Pregnancy—Challenges and Solutions

The diagnosis and monitoring of thyroid disease necessitates the knowledge of thyroid pathophysiology and of the technical limitations of current thyroid-related biochemical tests. Thyroid disease diagnosis and monitoring are further complicated during pregnancy and lactation, due to pregnancy-related changes in thyroid hormone metabolism. Dramatic changes that occur in thyroxine and triiodothyronine ranges during pregnancy pose challenges for hypothyroid gravidas. Very early in pregnancy, levothyroxine replacement needs to be increased. Moreover, increases in thyroid hormone replacement need to be conducted individually and on a timely basis. For reasons that are still not entirely clear, although dependent in part on changes in thyroxine binding, free thyroxine (FT4) levels decrease as pregnancy progresses necessitating the use of trimester-specific reference intervals for appropriate replacement. Thyroxine binding protein levels vary by hormonal status, inheritance, and disease states and are higher in pregnancy; hence, FT4 assays became popular because they measure the unbound hormone. However, current FT4 immunoassays are estimate tests that do not reliably measure FT4 and are known to be sensitive to alterations in binding proteins and therefore are method-specific. The need to reliably identify hypothyroxinemic pregnant patients, especially in the first trimester, is of prime importance for early fetal brain development before the fetal thyroid functions. This article addresses 1) the current limitations of laboratory-free thyroxine immunoassay methodologies and especially during pregnancy; 2) trimester-specific reference intervals for thyroid function tests; and 3) the study of levothyroxine pharmacokinetics in pregnant and nonpregnant women.