GAD isoforms exhibit distinct spatiotemporal expression patterns in the developing mouse lens: correlation with Dlx2 and Dlx5.

Gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter of the adult nervous system and its biosynthetic enzyme glutamic acid decarboxylase (GAD) are abundantly expressed in the embryonic nervous system and are involved in the modulation of cell proliferation, migration, and differentiation. Here we describe for the first time the expression of GABA and embryonic and adult GAD isoforms in the developing mouse lens. We show that the GAD isoforms are sequentially induced with specific spatiotemporal profiles: GAD65 and embryonic GAD isoforms prevail in primary fibers, while GAD67 is the predominant GAD expressed in the postnatal secondary fibers. This pattern correlates well with the expression of Dlx2 and Dlx5, known as upstream regulators of GAD. GABA and GAD are most abundant at the tips of elongating fibers and are absent from organelle-free cells, suggesting their involvement is primarily in shaping of the cytoskeleton during fiber elongation stages.     

远端同源异型盒2和叉头盒O3a在大鼠脑皮质发育过程中的分布与表达

目的 了目的 探讨远端同源异型盒2（Dlx2）和叉头盒O3a（FoxO3a）在SD大鼠脑皮质发育过程中的表达特点。 方法 应用Real-time PCR法检测Dlx2 mRNA和FoxO3a mRNA分别在受孕11d（E11）、E13、E15、E17、E19及生后1d（P1）的表达情况;应用免疫组织化学技术显示Dlx2和FoxO3a在E11、E13、E15、E17、E19及P1蛋白的表达情况。 结果 FoxO3a与Dlx2 mRNA在E11～P1均有表达,而FoxO3a mRNA表达高峰明显早于Dlx2 mRNA;Dlx2 mRNA表达在E15～E17时大幅度上升,而在此之后始终保持这一高水平的表达;Dlx2 mRNA与FoxO3a mRNA的表达在E15～P1呈现出一致的变化趋势;Dlx2基因在E19时出现mRNA水平的高表达而未见蛋白表达。 结论 Dlx2和FoxO3a基因在胚胎后期鼠脑皮质中均有表达,且其表达趋势具有一定的一致性;两基因的分布随皮质分层而改变。     

Differential expression of proteins of caspases and Bcl-2 families in the brain of mice

Apoptosis is an important process in the variety of different biological system including cell death and embryonic development. Inappropriate apoptosis is implicated in many human diseases such as Alzheimer's disease. Central component of the machinery of apoptosis program in neurons of patients with Alzheimer's disease includes proteins of caspases and Bcl-2 families. We examined whether endogenous protein levels of caspases and Bcl-2 families are expressed in a differential manner during the embryonic and postnatal development of BDF1 strain. Here, all four proteins with caspases-3, -9, Bcl-2 and Bax were highly expressed between embryonic day 19 and 1 week age of early postnatal development, but thereafter the expression dramatically declined. These patterns are needed to compare the proteins in the brains of APPsw-transgenic mice that are expected to be expressed highly in the brain of adult mice. Thus, the results are useful to understand fundamentally the mechanisms of the apoptotic changes during the embryonic and postnatal development of Alzheimer's model mice.     

Expression of opioid peptides and receptors in striatum and substantia nigra during rat brain development

We have used highly sensitive in situ hybridization to determine opioid receptor and peptide expression in embryonic and postnatal rat striatum, to follow the compartmentalization into patch and matrix structures, and have examined their developmental expression in the dopaminergic cell group of the substantia nigra (SN). Furthermore, opioid receptor binding sites were characterized in adjacent sections using highly selective ligands for the opioid receptor subtypes. The major findings of the study are: (1) striatal patches were first delineated by prodynorphin mRNA followed by mu opioid receptor mRNA expression at embryonic days 19 and 21, respectively; (2) in neonates, prodynorphin, mu and kappa opioid receptor mRNAs were transiently co-distributed within patches; (3) prodynorphin mRNA was co-expressed with mu but not kappa, receptor mRNA in neonatal patch neurons; (4) in the SN, kappa receptor and prodynorphin mRNAs were detected as early as embryonic days 15 and 19, respectively; (5) kappa receptor, but not prodynorphin, mRNA was expressed in dopaminergic neurons in the SN. The anatomical results are in agreement with the hypothesis that the endogenous opioid system has a trophic role during the development of striatal patch and matrix compartments and suggest the early regulation of dopamine release by kappa opioid receptors.     

Developmental expression and localization of glycogen synthase kinase-3β in rat brain

Glycogen synthase kinase (GSK)-3β is a protein kinase in the wingless/wnt pathway and as such is involved in the regulation of growth and development of the neural tissue in Drosophila and in vertebrates. This enzyme is also abundantly expressed in the mammal adult brain, where it might play a role in the regulation of several substrates. The expression and the neuroanatomical distribution of GSK-3β immunoreactivity in the rat brain from embryonic up to adult stages has been studied. GSK-3β was expressed in the developing brain with the highest expression observed from 18 days of embryonic life up to 10 days of postnatal life. Its expression decreased thereafter and was lowest in the adult. GSK-3β was strongly expressed in developing neurons but only weakly expressed in layers containing neuroblasts. In the adult and during development, GSK-3β was detected in the pericarya and proximal part of dendrites. In the embryo, an intense GSK-3β immunoreactivity was also observed in axonal tracts. This axonal immunoreactivity had markedly decreased by 10 days of postnatal life and was absent at 20 days of postnatal life and in the adult. No GSK-3β immunoreactivity was detected in astrocytes. The GSK-3β immunoreactivity was found in most brain regions, although significant local variations of GSK-3β expression were observed. The developmental evolution of GSK-3β compartmentalization in neurons parallels that of phosphorylated tau, a protein considered to be a physiological substrate for the kinase.     

Neurogenesis of the basal forebrain in euploid and trisomy 16 mice: an animal model for developmental disorders in Down syndrome

The neurogenesis and early histochemical differentiation of the basal forebrain in trisomy 16 fetal mice and their euploid littermates were examined by combining [3H]thymidine autoradiography with acetylcholinesterase histochemistry. Neurons of the basal forebrain were being born between embryonic day 11 and 15 in both chromosomally normal (euploid) and aneuploid mice. In euploid littermate controls, neurogenesis proceeded along a caudal to rostral gradient with the peak on embryonic day 11 for caudal portions and embryonic day 13 for rostral portions of the basal forebrain. In contrast, in trisomy 16 mice, rostral sections exhibited a peak of neurogenesis on embryonic day 11, 2 days earlier than in their euploid littermate controls. Hypocellularity of the basal forebrain region was noted in trisomy 16 mice; particularly dramatic was the reduction of the population of cells that expressed acetylcholinesterase. This reduction in cell number in the trisomics was not accompanied by a reduction in cell size or by a dramatic change in the distribution of residual neurons when compared to that of euploid littermate controls. Since trisomy 16 mice do not survive the perinatal period, we examined the pattern of acetylcholinesterase expression in normal C57B1/6J mice from embryonic day 16 to postnatal day 5 to determine the postnatal disposition of these neurons. Already at embryonic day 16, fibers staining for acetylcholinesterase penetrated the striatal anlage, in their course towards targets in the cerebral cortices. By postnatal day 5, the previously expansive distribution of basal forebrain neurons had become consolidated in a more ventral and rostral position by the extensive outgrowth of the striatal neurons, a pattern resembling that seen in adult animals.