Expression of MAP1a and MAP1b in the ganglionic eminence and the internal capsule of the human fetal brain

Clinical neuropathology practice guide 5-2013: markers of neuronal maturation

This review surveys immunocytochemical and histochemical markers of neuronal lineage for application to tissue sections of fetal and neonatal brain. They determine maturation of individual nerve cells as the tissue progresses to mature architecture. From a developmental perspective, neuronal markers are all about timing. These diverse cellular labels may be classified in two ways: 1) time of onset of expression (early; intermediate; late); 2) labeling of subcellular structures or metabolic functions (nucleoproteins; synaptic vesicle proteins; enolases; cytoskeletal elements; calcium-binding; nucleic acids; mitochondria). Apart from these positive markers of maturation, other negative markers are expressed in primitive neuroepithelial cells and early stages of neuroblast maturation, but no longer are demonstrated after initial stages of maturation. These examinations are relevant for studies of normal neuroembryology at the cellular level. In fetal and perinatal neuropathology they provide control criteria for application to malformations of the brain, inborn metabolic disorders and acquired fetal insults in which neuroblastic maturation may be altered. Disorders, in which cells differentiate abnormally, as in tuberous sclerosis and hemimegalencephaly, pose another yet aspect of mixed cellular lineage. The measurement in living patients, especially neonates, of serum and CSF levels of enolases, chromogranins and S-100 proteins as biomarkers of brain damage may potentially be correlated with their corresponding tissue markers at autopsy in infants who do not survive. The neuropathological markers here described can be performed in ordinary hospital laboratories, not just research facilities, and offer another dimension of diagnostic precision in interpreting abnormally developed fetal and postnatal brains.

Cellular and molecular characterization of multipolar Map5-expressing cells: a subset of newly generated, stage-specific parenchymal cells in the mammalian central nervous system

Although extremely interesting in adult neuro-glio-genesis and promising as an endogenous source for repair, parenchymal progenitors remain largely obscure in their identity and physiology, due to a scarce availability of stage-specific markers. What appears difficult is the distinction between real cell populations and various differentiation stages of the same population. Here we focused on a subset of multipolar, polydendrocyte-like cells (mMap5 cells) expressing the microtubule associated protein 5 (Map5), which is known to be present in most neurons. We characterized the morphology, phenotype, regional distribution, proliferative dynamics, and stage-specific marker expression of these cells in the rabbit and mouse CNS, also assessing their existence in other mammalian species. mMap5 cells were never found to co-express the Ng2 antigen. They appear to be a population of glial cells sharing features but also differences with Ng2+progenitor cells. We show that mMap5 cells are newly generated, postmitotic parenchymal elements of the oligodendroglial lineage, thus being a stage-specific population of polydendrocytes. Finally, we report that the number of mMap5 cells, although reduced within the brain of adult/old animals, can increase in neurodegenerative and traumatic conditions.

Microtubule-associated protein 1B, a growth-associated and phosphorylated scaffold protein

Microtubule-associated protein 1B, MAP1B, is one of the major growth associated and cytoskeletal proteins in neuronal and glial cells. It is present as a full length protein or may be fragmented into a heavy chain and a light chain. It is essential to stabilize microtubules during the elongation of dendrites and neurites and is involved in the dynamics of morphological structures such as microtubules, microfilaments and growth cones. MAP1B function is modulated by phosphorylation and influences microtubule stability, microfilaments and growth cone motility. Considering its large size, several interactions with a variety of other proteins have been reported and there is increasing evidence that MAP1B plays a crucial role in the stability of the cytoskeleton and may have other cellular functions. Here we review molecular and functional aspects of this protein, evoke its role as a scaffold protein and have a look at several pathologies where the protein may be involved.

Exercise-induced gene expression changes in the rat spinal cord

There is growing evidence that exercise benefits recovery of neuromuscular function from spinal cord injury (SCI). However, the effect of exercise on gene expression in the spinal cord is poorly understood. We used oligonucleotide microarrays to compare thoracic and lumbar regions of spinal cord of either exercising (voluntary wheel running for 21 days) or sedentary rats. The expression data were filtered using statistical tests for significance, and K-means clustering was then used to segregate lists of significantly changed genes into sets based upon expression patterns across all experimental groups. Levels of brain-derived neurotrophic factor (BDNF) protein were also measured after voluntary exercise, across different regions of the spinal cord. BDNF mRNA increased with voluntary exercise, as has been previously shown for other forms of exercise, contributed to by increases in both exon I and exon III. The exercise-induced gene expression changes identified by microarray analysis are consistent with increases in pathways promoting neuronal health, signaling, remodeling, cellular transport, and development of oligodendrocytes. Taken together these data suggest cellular pathways through which exercise may promote recovery in the SCI population.

The ganglionic eminence--a putative intermediate target of amygdaloid connections

The superior part of the ganglionic eminence has been shown to act as an intermediate target for outgrowing axons of projections between the thalamus and the cerebral cortex. This study aims at investigating whether amygdaloid projections transiently contact the inferior portion of the human ganglionic eminence which directly borders upon the amygdala. Between 16 and 20 weeks of gestation a high number of small fiber bundles which were immunolabelled with anti-MAP1b and anti-SNAP-25 could be traced from the amygdala towards the mantle zone of the ganglionic eminence. These fiber bundles left a fiber system which coursed from the amygdala towards the entorhinal cortex. Within the mantle zone of the ganglionic eminence immunoreactive puncta indicative of fiber termination were observed. After 22 weeks of gestation the number of fibers entering the ganglionic eminence gradually decreased. These results provide the first evidence that the marginal zone of the inferior ganglionic eminence is likely to constitute an intermediate target for growing axons which belong the amygdaloid projection to the entorhinal cortex.

Ganglionic eminence of the human fetal brain--new vistas

This review deals with recent findings concerning the complex functions of the ganglionic eminence (GE), which represents a conspicuous domain of the telencephalic proliferative zone and persists nearly throughout fetal life. The GE not only contains precursor neurons of the basal ganglia, it also contributes significantly to the population of interneurons in the cerebral cortex and to a population of thalamic neurons. The latter migrate through a distinct transient structure, the gangliothalamic body (GTB). The GE also represents an intermediate target for growing thalamic axons (on their way to the cerebral cortex) and cortical axons (on their way to the thalamus). In developmental neuropathology the GE plays an important role in prematurely born infants. The pathogenesis of GE bleedings is discussed with regard to the abundant expression of interleukin-6 (IL-6) receptors on GE cells. The consequences of such bleedings are discussed in view of cellular responses, such as the induction of leukemia inhibitory factor (LIF) expression in GE cells after hemorrhage.