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At least 271 records · Page 15Linked to original sources

Human neural stem cells: a new tool for studying cortical development in Down's syndrome.

The clinical characteristics of Down's syndrome (DS), or trisomy 21, are caused by errors that occur during development. In addition to mental retardation, DS individuals have craniofacial abnormalities, clinical defects of the heart, gut and immune system, as well as predisposition to certain diseases, such as leukemias and Alzheimer's disease. To explain the developmental mechanisms that cause these traits, it is necessary to look at how developmental processes in DS compare to normal development. The neurological characteristics of DS are established during the prenatal and early postnatal period in humans, when the bulk of brain development occurs. Mouse models of DS have provided a useful way of studying DS neural development. However, there are clearly significant differences between rodent and human biology that may not be reflected in mouse models. Recent advances in stem cell biology now allow the generation of human neural tissue in the culture dish (Ostenfeld & Svendsen 2003). Stem cells offer a novel model system to study alterations in neuron development in developmental disorders such as DS.

Animals↗

Optokinetic nystagmus in normal and visually deprived children: implications for cortical development.

Ten years ago we proposed that the limitations on young infants' vision might be caused by an immature Y-pathway through the cortex, while their abilities might be mediated by an X-pathway to the cortex and by Y- and/or W-pathways to the superior colliculus and pretectum (Maurer & Lewis, 1979). Although that explanation was too simple overall, it fits well with what is known about asymmetrical optokinetic nystagmus, viz. the difficulty in eliciting OKN to patterns moving from the nasal field toward the temporal field. In this paper, we describe the development of symmetrical OKN, its alteration by early deprivation from cataract, and its physiological basis. We then suggest that, for primates, an explanation based on projections through the magnocellular versus parvocellular layers of the lateral geniculate nucleus may be more appropriate than one based on X-, Y-, and W-cells.

Animals↗

Cyclooxygenase-2-selective inhibitors impair glomerulogenesis and renal cortical development.

BACKGROUND: Antenatal exposure to nonsteroidal anti-inflammatory drugs (NSAIDs) has been associated with renal dysgenesis in humans. METHODS: These studies characterized cyclooxygenase-2 (COX-2) versus COX-1-selective inhibition on nephrogenesis in the rodent using histomorphometry, immunohistology, and in situ hybridization. RESULTS: Administration of a COX-2-selective inhibitor (SC58236), started during pregnancy until weaning, significantly impaired development of the renal cortex and reduced glomerular diameter in both mice and rats. An identical phenotype was demonstrated in COX-2 -/- mice. In contrast to its effects on the developing kidney, a COX-2 inhibitor had no effect on glomerular volume in adult mice. This effect was specific for COX-2 because maternal administration of a COX-1-selective inhibitor (SC58560) did not affect renal development despite significantly inhibiting gastric mucosal prostaglandin E2 (PGE2) synthesis in pups. The expression of COX-2 immunoreactivity peaked in the first postnatal week and was localized to S-shaped bodies and the macula densa in the cortex. Treatment with a COX-2 inhibitor during this period (from postnatal day 0 to day 21) severely reduced glomerular diameter, whereas treatment limited to pregnancy did not affect glomerular size. CONCLUSION: These data demonstrate an important role for COX-2 activity in nephrogenesis in the rodent, and define a specific time period of susceptibility to these effects.

Animals↗

Microlissencephaly: a heterogeneous malformation of cortical development.

We report the neonatal courses, early postnatal development, and neuroimaging findings of 17 patients with marked microcephaly and simplified cerebral gyral patterns, a condition that we call microlissencephaly. Retrospective analyses of the clinicoradiologic features of these patients allowed segregation of the patients into 5 distinct groups with varying outcomes. The apparent discreteness of these groups suggests multiple etiologies of this malformation, although there appears to be a strong genetic component with probable autosomal recessive inheritance. Utilizing the neonatal course and neuroradiologic features of these infants allows classification of specific subsets, which may be useful to predict outcome.

Cerebral Cortex↗

A classification scheme for malformations of cortical development.

Malformations of the cerebral cortex are being recognized more frequently as a cause of epilepsy, developmental delay, neurological deficits, and mental retardation. Nonetheless, a standard nomenclature and classification system of these malformations, based upon state-of-the art knowledge derived from genetics, embryology, imaging, and pathology, has not been devised. In this manuscript, we propose such a classification system. Moreover, we have constructed the system such that both the framework and the classifications themselves are flexible and can be adapted as our knowledge of the embryology, genetics, imaging, and pathology of these disorders advances. We believe that the use of this classification system will help both clinicians and researchers to understand and think about these disorders and their causes better. In turn, we hope that this improved understanding will lead to further refinements in classification, to advances in our knowledge and, ultimately, to improvements in therapy.

Brain Damage, Chronic↗

Lissencephaly and other malformations of cortical development: 1995 update.

Neuronal migration disorders are a group of malformations of the brain which primarily affect development of the cerebral cortex. The best known of these is lissencephaly (smooth brain). Most types result from incomplete neuronal migration to the cortex during the third and fourth months of gestation. In this review, we describe and illustrate the different types of neuronal migration disorders. We also review the many different genetic syndromes associated with neuronal migration disorders. Over 25 syndromes with lissencephaly or other neuronal migration disorders have been described. Among them are syndromes with several different patterns of inheritance including chromosomal or new mutation autosomal dominant, autosomal recessive, X-linked and unknown. Genetic counseling thus differs greatly between syndromes. The genes responsible for several of the lissencephaly syndromes have been mapped. X-linked lissencephaly has tentatively been mapped to chromosome Xq22 based on observation of a single X-autosomal translocation in a girl. Both Miller-Dieker syndrome and isolated lissencephaly sequence (in many patients) were mapped to chromosome 17p13.3 by detection of deletions and other structural chromosome rearrangements. Fukuyama congenital muscular dystrophy was mapped to chromosome 9q31-33 by homozygosity mapping.

Abnormalities, Multiple↗

Reelin, integrin and DAB1 interactions during embryonic cerebral cortical development.

Extracellular matrix-like molecule reelin and cell surface adhesion receptors such as alpha3beta1 integrin can regulate neuronal migration and position in the developing cerebral cortex. Here we show that alpha3beta1 integrin binds to the N-terminal region of reelin, a site distinct from the region of reelin shown to associate with other reelin receptors such as VLDLR/ApoER2. Furthermore, Dab1, a member of the reelin signaling pathway, can complex with the cytoplasmic region of beta1 integrin in a reelin-dependent manner. Thus, alpha3beta1 integrin-reelin interactions may contribute to appropriate neuronal placement in the developing cerebral cortex.

Animals↗

P-GAP-43 is enriched in horizontal cell divisions throughout rat cortical development.

Asymmetric cell divisions are correlated to neurogenesis in the mammalian cortex and occur often with a horizontal orientation of cell division. However, the molecular mechanisms of spindle orientation or asymmetric cell divisions are not well understood in the developing mammalian central nervous system. Here we show a new molecular marker for horizontally dividing precursors in the mammalian telencephalon. The antibody 2G12 directed against phosphorylated serine of growth associated protein 43 (GAP-43) labels postmitotic neurons and a subset of cells in mitoses in the developing rat telencephalon. 2G12 immunoreactivity was found at a high frequency in mitotic cells dividing parallel to the ventricular surface throughout neurogenesis (embryonic day 13-17) in the cerebral cortex and ganglionic eminence. Interestingly, we detected the same predominance of 2G12 immunoreactivity in horizontally dividing cells in the subventricular zone, the second proliferative layer that has recently been involved in the generation of neurons. Moreover, 2G12 immunostaining is no longer detectable in mitotic cells of the ventricular zones at E21, the onset of gliogenesis in rat telencephalon. These data imply GAP-43 phosphorylation in the phase of neuronal commitment during M-phase and present to our knowledge the first molecular correlate to horizontally dividing precursors in mammalian neurogenesis.

Aging↗

Cellular patterns of transcription factor expression in developing cortical interneurons.

Most gamma-aminobutyric acidergic interneurons in the neocortex and hippocampus are derived from subpallial progenitors in the medial ganglionic eminence and migrate tangentially to the pallium, where they differentiate into a diverse set of neuronal subtypes. Toward elucidating the mechanisms underlying the generation of interneuron diversity, we have studied in mice the expression patterns in differentiating and mature neocortical interneurons of 8 transcription factors, including 6 homeobox (Dlx1, Dlx2, Dlx5, Arx, Lhx6, Cux2), 1 basic helix-loop-helix, (NPAS1), and 1 bZIP (MafB). Their patterns of expression change during interneuron differentiation and show distinct distributions within interneuron subpopulations in adult neocortex. This study is a first step to define the combinatorial codes of transcription factors that participate in regulating the specification and function of cortical interneuron subtypes.

Aging↗

Enhancement of auditory cortical development by musical experience in children.

Auditory evoked potentials (AEPs) express the development of mature synaptic connections in the upper neocortical laminae known to occur between 4 and 15 years of age. AEPs evoked by piano, violin, and pure tones were measured twice in a group of 4- to 5-year-old children enrolled in Suzuki music lessons and in non-musician controls. P1 was larger in the Suzuki pupils for all tones whereas P2 was enhanced specifically for the instrument of practice (piano or violin). AEPs observed for the instrument of practice were comparable to those of non-musician children about 3 years older in chronological age. The findings set into relief a general process by which the neocortical synaptic matrix is shaped by an accumulation of specific auditory experiences.

Acoustic Stimulation↗